INDtL."i ACUtrcULltiRAIJ

Rmr&A.B.CH LNSTITUTE, N li.W DELl;u

I:.h.F..U: (:lIP NLK-g·3 I.A.R.l.-1O.5.S5:-ISil6()

TECHNICAL PAPER. No. 8

THE HEIGHT OF MOUNT EVEREST .. A NEW DETERMINATION ( 1952-54 ) ..

By

8. l. Gulatee, M.A. (Cantab.), F.RJ.e.S., M.I.5. (India) Director, Geodetic and Research Branch, Survey of India

44622

11111111111111111111111111111111111 fAR!

" PUBLIflHED BY ORDER OIl'

THE SURVEYOR GENERAL OF INDlA

19&.1,

P1'ice Three Rupees O'f Five ShilUngs.

1.1\ Pf\N AU!{lL'(TLTl,[L\L

H EbEARCH lNb'I'l'l'u'l'E, NJi]\v D~~Ll[[.

I. .0\, R. I. 6.

\(l, Il'U- "l--I\ \.H{H-7 7 -:it-lll,flOI).

Corrections to Technical Paper No.8, The Height of 1'-1ount Everest" A New Determination (1952-54) "

Page i, Preface, pam 4, line .2.-

Aft,PI' 1954, add the following :-

"It aims at providing a clear preRcntation or Lhe i'lsnes involvetl ::mel no exhaustive bibliogl'l1phy of previous at,tempts at calcuhtLing this height, is given".

No.1, dated 23-6-fi/i.

Pa,ge 2, pa,1'(l 1, line 29.-

For' O· 05' substitute' () . 06 '.

No.2, dated 2,;-6-55.

Page 9, para B( b ), line 12.-

After the word l'cspeetivcly enter the following :-

"The heights obtained wel'e as follows :-

FrolU Ladnja T.S. " Ohatra v.s. " Dal'jeeling Ohservatory h.s.

No.3, dated 23-6-55.

Page M, para 8, line 2.-

Height in feet MiLYilm h.8. Laori Danda h.H.

10,948'7 11,878'0 10,946'5 11,875'8 10,951: 5 11,880' S"

For the words" Tavistock 'Theodolite" S~tb8tit7"te "Wild T 2 Theodo­lite" .

No.4, dated 23-;-6-55.

Page 13, pam 8, line 3.-

Fa!' the words "Geodetic Wild Theodolito" 8~tb8titute "Geodetic Tavistock Theodo1ite".

I.A. R

MUH'C

TECHNICAL PAPER No. 8

THE HEIGHT OF MOUNT EVEREST .. A NEW DETERMINATION (1952-54)"

By

B. L. Gulatee, M.A. (Cantab.). f.R.l.e.S., M.I.S. (India) Director, Geodetic and Research Branch, Survey of India

l'LTBLlSHEJ) BY ORDER OIl'

THf~ SURVEYOR GENERAL OF INDIA

19().J,

Prioe Three Rltpec8 or Five Shillings.

Mount, J~\l:l'Uflt is IU8[l,teLl U11 the Nepiil-1'ibo1, bUl'dl']' [mel is tIle Ill'ilia uf the U!'(:aL Himfda,ya,n range. It is U.lWllt. iO,OI)() flwt lliglwf than Kilimn,llj:Ll'U, Af'ri.urL\: highest !l1ul1l1l!a,itl, whose height ]J:b.S just beon l'tH\t;t.eJ:mine.cl pl'el;i;-;eiyl ~md (Wen t,hu highest peal::, uf .S.A. \vmIld mIlk :\::; its minul.' :'ii,(,ellites,

'rhe heighL of l\lollnt Enil'uc:t, iLceepted by tho 8111'\'0,)' of India i.s ::':H,on~ foet : Lhii:i 11.],::; enliul'ud rue 0\'(;1' i\ eonl:,ul'V anll tho In::;t digit. of:.l has int.rigued t.he e:ql('l't Hud the hy-man tdike <'fur a long tilll.~. f,eV(',l'id ot.her Yil.lnes sucb n~ :2H,i)i)O: 2!l,OSIJ, :.'iU-H allil :29, H!) h:wo been qnoted lOt' it from tillW to t.illlt: :\,IH[ wit.h the growillg entI1l1:;i:l,stll regiLl'Cling 1,11 HULLLoJ'S pert,(l,illing to j\lOIIIIL E~Vnl'e;ii!, (;['1'i-ILi11 hiLlf j,l'llths keep Oil gett,ing printeil 111 trho scmi-pnj)lIlaJ_' (HHl O\'Oll googl';'t,pliie(\,l and f,clentilin 1itcwil,tm'c. fi'0l' ill~,tanu::: in tho \v:d;:o of t!le. di.SiL:.,Ll'UlIS AS;';ll.m c)ltrLilquii,l;:e (If 1.\),)0, a, story 1'0111111 wille eircuial iun in U.S. A, L'Jm1; ll-JaunL ];~\,(\L'e.sj; was prl sited up and i,hiLt. t,lle geoJogi:-Jt:.; WI\\' cUllsiclel' its height to be ~D,20U feet. Simiiill'ly in the London 'Pilll.Cd (i)oCUlUiJCl' :3, I Di) 1 ), II, cOl'res]lClndent u.:-lke<t YOI' Lho 1110:,1) l'econt.ly dntw'lllined height of llIlHlllii l~j\'crGBl. lIe was Lold ill l'eply IJY a WiS('KLOl'O tlmt. :!\l J 1,10 feot, W1L;, the lll,test figUJ'(' f1'o111 revised COlnpntatiolls and "Until t,tl'. Shipton Dr SfHlle ut.hor (:iimbm' st-aIHL;-; gn,sping 011 the summit wit,h :t.tJ ,mel'oid in Iris ha,nilE;, this seoms to 1)('. t.he i;c'c:t, t.lw,j:, soicneo can do".

'ro dispel slIch popllla,!' fH'L'onOOllS imlH'es:,ions, the ~,utltor hrought; out; ~L Impe1'3 whieh ;;:we lm ;tppl'iLi:·ml of tllE\ IJcculiar dif[icnJi:.,ics associtLtecl with the cleLcl'ntillatioll of the heights (ll' loft.y ltlOlmt::Lin peed,s. Chleu­btiollS uf RUOIt heights is dcpenclont. on :.l. llmnbel' of iml)orUtnt f;U;i"'(ll'ii in n, fidel which is mainly t.be PI\_lSUl'Ve of RfH:~(JiaJif;ts. It wn,s (!~~pbilW(l in the a,blwo piLper tlw,t, IJO(JrLllSe of lad, Ill' proper 0 hsorvationaI rna,tori;!'] and gcoc\etie dnli;t the older calenbtioll of t,lle height o[ Mount l~vel'cst \vas entil't)ly iniLdcqwote and there W(u:J nrgcnt l1eeLl for scient,ille;tlly pL-mnocl olH,m'vntiollS t() this pea,k from mOlllltn.ini'l in N epEU ll.ot far :t'i'Olll it,

'I'hi:; papei' rbJOl'ibes in ele[,n,it the wUl'k rmclerLakell for this l)l]l'PO,'JC during t.lw yuan; Hlfi2, H)[j8 ;tolld HJ[)·t Vel',v crLl'oful pin,lliling wa.s re­quired to ensure 1m n,cl(Hpa.t;e nlllnher of oh.scl'v[diol1sJ hoo,1:ing in mind t.he (liflleultios (If tel'r'lLin nnel bcl;: (If tl'tt.ll8j) OJ.' t! :),nrl enllllllunicatioJl:3.

'J'he :fir:-;j', clCHi(lernJurn was to (,:it1'I'.v 1L -triangulation sories u.s eiose to t,ile V(;~tk a:~ l)os,,;iblo. Thi,; iN n, custly item n.nd would 111.1.\'0 been unjustiti-­Itble if e~Ll'l'iec1 OLLt so!dy for t.he purpo:se of det.ermining th{:~ height of the pottl;:, :U'ol't-.mvd;eiy a. ehain of millor tl'iallgula,tion W:LS run in Nepal in the yenr:'> 10-111-,17 to provide control for irrigation projects. This wa,s reinforced by B Ineasurecl bases imel :3 spirit-levelled connect,ions (J,nd the trif1ilgllhLtioll was extended to the north in 1£)52-53, so thltt. its mOBt northerly stations were ftt distlmces of 30 to ·10 miles from tho per~k (see (Ilmrt II). Mount Everest wr~8 ohsol'ved fl'om 8 statiOJ18 of this series mnging in height from 8()70 to 14762 foet ,md gren,t, earo was t,aken to f'HSU],(_\ trmt. the heights or thes(~ t.uke off stations 'were well fix(xl III tel'lns or spirili-levolling.

[ '~f'ho (·:dUllliltioll Ill' UH~ height. of Kilimalljul'Q', by IV. l" Dicb'Oll, ]']mpiro Hnrn'y Hevicw, :fa!l. JUti!, p. 201).

~ "l\Jmmt Eyel'e~t-[tr;. llf].)ne tlUll lv'ight", by n. L. Gulfltcc, StIl'voy of Illili!t, Tcehnicu.l PapGC Ko .. 1.

ii

The prc\'iuu;; attelnph:! to fix t,jw height of the pen'!c were also Imm· pored by coltlplete Jetek of geodetic dfllta. In 195:3-i)4, D, cOlllllrehensivo pl\)gmHlllle of plumh-line deflections and gravity obsorv((,tions wa.s 1}!ll'1'ied out tu delinc;:rte the gooidn,l rIse under Mount Everest" These Ob"'{ll'Vatiolls a.m unique in ml1,ny wnys ;Lllc] aro of gren,t, sigllificnneo for l'OY011ling the HHdl:mimn of eornpollflH,t.ion of till" int.erest.ing region.

Tope) j,rin,nglllation extending west. from Ihl'jneliug was e'1.l'rled (Jilt

i!y JHf\,~lSI'il. n, H. Cll1lgh, l), D. IIIrungnin, H. L. Shntllln nllrl N. N. DIU1wan during the yi'UI'B ]n·.!I;-i):~ (Cha['t. 11); the extension tl'inngnInHoll hy Capt. llf. M. Dal~kl (10;-;:1); \el'tiual anglo ul JNel'vat,iollfJ hy JHessl's. lit llL Ihiitn, n,nd.J. B. IvliLtllur ( UJ;j:2-iJ:~-f,4) ; [·lln plrnnll-linc) cleflcci"ioIl~ by Slid ,J. J\. I\Ld;}lUl' 1l']1cl the gl'HvimeLer Oll.'lmTa.t.iolls by 8hl'i A. N. nll,m:mn,Hw.n (]\HIJ). Nlnoh el'odib is due to the observe!',.;; 1'1)1' cG,J.'l'ying the '.vork to ,1 fHlC:C(1s[,ful fHll H~l IlSiOIl Hndm' (tl'duolts conclitiUIls, c.~peei[tlly as Llwy \\'('1'0 Jlut IH'11 oqlliFpell for dimbing on hi:~h lllolmtains.

Tlw :tuttIYiii::; (tlH1 l"8l111CiiClltr3 of nUl new (bhL haye entailed hw\,yy wOl'k iu whidl I havu l't'(~uixed mIlCh il:'46i;;tlltllCe fl'om Shl'i C. :no IVbdall and the f'tn.lf nl" Lho (;unt[lulillg Huc,tion at Dehm DUll. Tlw:,,~ are doseribed fnlly in this ]lit)lOi' «,}lIl art: cnmpil,recl in clctail with 1i1O earlifw nhs(1l"vati0l1:'4,

I'll(> 11I:W/ vallie o!Jtailll,d ie; ~D,O::l8 fm,j; wl.lkll, :it i:i hoped, i:o: lUlL

Jib-I,Y to be ill (q'I'UI" by more t.llUlI I U 1<'0"1'. It \'iill ..,('ITU 1111 ll"c,flll ]>lll'pUNP

to push the ucunnl,cy i'l!rLhel' by mU!"t' o!l;:;urvatiom; as tho seasomd fluetuation of,muw 011 tlw :'lummit eould weU be of this urder ofrnagnitndc. The older vnlue, of 2H,OO:J feet; was vI1gue [mel 'WH,S cornputed in [l, mosb incumplete umnnur, e.g., with a definil.el,Y wrong ynJne of refraclion [mel ·wi1.11 lW i'egal'd tll the datum fiurf<1,ee. It has always been sllspm::ted t;!mt. if; erretl on tlw modnrnJe side anel some onthru;ia,sts have l'egal'dA(1 the po:::.k to bu some :200 foet. higher tha.n the quoted value. rrhey will, no doubt., be dj,~no]Jpl)in(ed. The aecepkd vfdutl 29,002 feel! hns beou cl'it":ically !),ppraisod ill para f) /tnd it will he soon thaI; the illlplicntiol1H of thil., now' figure for height. are very different. from thORO of t,he old one a,ad the two are rually not. C01l1P[~1'iLble, The fo.ct that. they M'O !-;o clORO

together is duo to fi)rtuit.Ol1R e:tncelbtioll oHlw effeot,'l of cert.ain impol'tant ph:vsical factor;,; w'hich had boon lleglected in the P"(WiOI18 computat.ion.

Illy tlw,nks nrc dlw to Brigadier. G. Bomfo1'(1 for helpful dii'cnstJ:QllK both oTally and by correspondenco.

DERRA DUN: Daiecl 25th Oct. '54.

B. L. GULATEE, M,A. ( CANTAB. ),

F,R.I.O.S" M,I.S, (IN"DIA ), Director, Geodetic & BesCa?'ch B~·anch.

Page

Pl't'Ltce

Pam

1, :Heights of Hhnu]:tya;n ~:llOW l'011k8

2. Refradion

Datum

4, Heights of Observing 8tfttiOll:i

G. 01ltljn(~ of Ull) Nnw Metho(l ~)

6. Tl'iallgnltLtion nml Height DakL 3

7. Plumb-line Deflections and the Geoid n s. :Final Value of Height U;

H. AnalYfli:3 of tho older vn,lucB of 29,002 feet and ~m, 141 feel; for Mount J~lleresb 15

.111 10. Summary ,

Tahln J.

'rable 2.

Table a.

Tables

Height of Mount; ~jveres(" from ohservations from 'I t;he plains

Height of 'Monnli Everest; from ohservations from Dal'jeeling Hills

Deilections itncl Hayford Anomalies At cud,

'J~ablc '.1:. Vorl,ioal angles to MOUllii ]TIverest

Table o. Height of Mount :mvercst

Charts and Plates })ago

Air Photogmph of Mount Everest from the south-west Frontispie.ce.

Chitrt I Older Observations to high Himalayan Peaks. I.

Chart II Triangulation, Levolling and Deflection Data in N opal. 2

Chart III Triangular Misclosures in Height. 9

Chart IV Devi[LtioIl of the Vertical. 10

Obart V Geoid in NepaL. , 12

Chart VI Geoidal Section Ladnia-Mt. Everest. 18

Mvmensingh '" .

'rHE I-IEIGffT Ol~' IViOUN'T EV'ERES'I' BY

B. L. GULAl'EE, lVI.A. ( CANTAB. )i F.U.I.C.S., M.l.S. ( INDIA)

1. Heights of Hi1"l'ltiUayan Snow Peaks.--'l'lle NuJ'i It.j~n,st Longi­Ludiual 8erl(1,'1, 001'01'lu,(,; (L lilHXH' lii",bHllC') oJ' 'Lbunt 740 mile,~ fl_'l)lu t;}lI) Deh1'll, DUll lmK(~ till SOllCl.kll{)cli~ iJ,tSO ill ]3ihi1l', \Va.~; obtlOLycll in the yea.]'" .I t;f(i to 1851, with Lheodolitcs l'<tnging ill size from 15 inehc;; t,o ;W inches. 11. "',tS 'Yi'iu;iuctlly jllr.ellded bhltt; i·hi" ;mries Hlumld TUll <110n!]; the NepM lllUllllLu.im,L but 'im;l)ite of 1'1lpefLi;ci\l attempts the Ne}}iil GO\;~l'lllllGllij <liel nut. :wooed pcl'tnissiilll fot' Ob:;Ol'lT:t.l,ioHS 'llong t.i1i" route [tnd tlw phn Imd to 1)0 nlLel'ed, Al'I.N' crodsLIl!j the hills of (hl,l'hwiil, Llle tl'ilLl1gleS were mad.e (.ll P:LSc; t..ln:nllgll, the llml;ll.'inUH fund llllhealtihy 1,1',l,Ct.tl i"t the footi (II' Lho }litllr~li"yiL:-;_ 'UH' uOllu(;ry heing iiai, , tuwem rthollj, :.!I) tu iIi') fe.eL lllgh WUH' ll~~\(l tlJ ;;eeure ill(A't-vi,dhilit.y of l.>tit~l!ioll;;. CJhn,rC ( illus1il',L\Jll:'; how thu Himaby(w pe:1.l,s ill N('ll):U wen:! oiJsel'\'ed a~ illtorseetl~d points IlY HUn'{\\'UL'''; ill lS.i!l to I. ::;6ii 1'1'()1tl di;s["mt; low lying statiolls of IJtiH

"!:'rio,;. :ItOI' eOlll.pa,ri::;ull, thll modern sta.tions from 'which MOllnt E1vcr(\8t Jm:; hOWl Ob:')(')l'ved ;;W0 ,'l}lOWll in tho in::Jet.

'l'he heightt:! of the IIimiiitLYltIl peaks evokeil great int()l'o:,;jj itl tjhe Survey of India even in the eltrly (bys and in ;), circ,ml[Ll' i;;:;lU~cl to j.he CrolLt Trigollomet.l'ical Survey parties in, the held iu Ul,!5, tillO ~:illl'VeyOl' UelWl'iJ.l Sit· Alld1'e1V WlHlgh wrote "TJw .Iofty SHOW penks situctted Hlnth lA' NepiLi art) t,]w moc;t "tLtPt'lldollB pilllwcles of the glohe. Theil' height:; aad relative po;;itiulls shuuld fOTln pernUUlent ubjec:h: ill Ute geodetica,l opcmtions". His instructions to Nloholso.n in 1840, when lie wa,s observing :doug t,he NOl'th-I~!Lst Ijongitudina,l SerieiS, woro I. You Khould lw in tho observatory berOI'll sunrise ltnd all prepared to comHumeo horizontul auglu" as suon m: it, iH light. The vEll'tiefLl fLug;leil nmy he t.a.ken from s to 1 I) o'e]uc.k A.:\I.". It is ext.l'Glllely rliflienlt to get visibility in the fLftOl'll0()1l over such long rays ttnd the Itt::;!; rltmtence was u,dded 1".0 on:mro at lea~t ::lome oLservatiolUl being ta,lwll at othor times, so t,hat the opportunity to obscerve tho high peaks WEtS not ent,ir()ly lost.

When viewed ffom tihe plctius of Nepal. MOllnt Evel'el;j:" illspite of its t>owm'ing personalit.y, (loes not ttppoal' to ovel'-i;}utdow the al'raJY of' surrounding peaks. In faut" io;ome of the peaks, lln a,(;count of their llcitrne:oJS, give tho ilhlHlon IJf boing higher and when obsel'vatioutl were [,a.lwll to lVluuntJ level'ost, there novel' WitS the slightest suspicion tlmt, it WitS the highest 1llolmta.in in the world. The geneml belief' at the time wm; Llmt ,KanchelljungtL WHS tilE) world's loftiest pea.k. '1'110 obsorvcrs took n,n illllllen::ie number of lWl'illolltal and vertic,Ll augle::; to the snow pen.ks from the pl'ineilnti St.lLtiOIll) uf North-East Longit'Ullinal Sedes. They could not pom,ibJy d1800\'01' individuctl IOCltl lli.tmes from :,;uuh IOllg clist[tlle0S and quite .1 Humber of peak;:; were characterized by figures n.nd HOllmn mlmeI'u.!:,;. Mount Bvel'est was simply labelled 'b' by Arrnstl'Ollg, 'y' by WttUgh tLlld La.ne and 'h' by Nicholson. This WitH eh:;tugotl to pm~k XV at headq1U~l'tel'S hy Helmcssey.

A reference to some old ltli),llllSCl'ipts has revealed t.hat J'. W. Armstrong while ohserving the Gora, MeridiOlml Series h!td thrown it

single my to Mount ]~vel'est in 1847 from a dista,nOB of about 200 miles. The observation cOIlfJistec1 of a. single cletel'mina,t;ion of clistance and ,t vOl'timtl ml~le. The value of the height which he obtained was :,lH,7l)H foo,t.

J

It, was lclottjl' o~);,;\;'rvt)rl t'l'OiH the following ):lis: ",t,lttion:-l of tJlC l'LB, LOHgit,ndin,'!-l borie:; in J HHhiO :~,J[!'l'()l, Mir:dl}_)Ul', .Ja,njipati, .Lnclnin, Ilnrpul', lhml Millai (bee elm,rLs 1 & II ),

These are sta,tiol1R in the phtius nt, an iWentge height uf «,bout .:!:·w feet; <tbove llle!l.H i'Jca-h:l\'ol mId !'OWOl'S ( Itbout, 20 tu :l2 feeti high) Imd to be ImHt 011 t1wlll. !iO nmko them intcl'visible for t.rirmgllbttiou, Tho 8tn,jiiollS

weTO "tbont llU lllilcH away frum the mountain, Onc:e it WHS known that j,bis was the worlrl.'8 highest peak, gl'f!n,t pain;.; were tn,ken ove], the I'etluc:tioll ot' the (bta" In pa,rtieu\ar, a, lot of 'I,t.tenbion was paid t.o J'cfhwtiOll whi()h plays a ([omina.nt 1'010 when t.he: r(\,.)'s me .long.

No llun'o,j,ive nl'(:ollnl givillg dotails of I,he old height, compuiJ;Ltiol1s ul' ]\IOlllll Evel'ei'il, ilS fClltheuming, Ta,hlo 1 gives tL :,;.vllop~,is I)f [,he ohstJl'­v n,tiOlIK; t, 1)(\ heiglli,s C<lieu bted from paull :,; tn tinll ~Lre g(\'011 ill uolmnn n, tho nwan v:dnf.) being :W,U()~ reel" whieh i:,; the figuru adupted up to tho 111'1'soni; timo. This ktble has bnt~Ill:01npilpd fl'Olll the Ol'igillitl eomput,[1t:ion volullles.

It i::; on rec:ol'd UH),!; t:\il' Andn\w \Vaugh took obbol'lLte OilS61'Vl1t.ion:-; for d.etol'mining 1,11k: ClIl.'V:),tUI'O of the pn,t.h of n. m,Y of light; between it

number of peaks ill tht\ OU(,l'·1' Hi lllil la,ya, a,nd t.lw pla.im; of Beugal by llletLllH uf Himu1t:1I1I.'OU8 I'peipl'OCt11. obso].'\·n,i-,i()lIH, Tho c:()(\tIieient.s of reft'uo­

LiOH k were o)Jta.inc·(1 hy givillg dut'- weight t.u the llUllliJel' of ohseJ.'vntion:-; and t.ho lengU\ (Jf t.lw f,illefl .. From (:()IUIllll 10 ofl'n,ble 1, we sop t,ludi tile (;;.':,; :1l'(' given to G pInun:-; qf tLee.imnis ;tilt! :uc: difl'(\l'elli', ii)!' diilc]'(,]lt, :,t.n,Liom:, The IH.~sis for (,he derivltLion of so nln,n,\' 11(',r,j(,ions digit." is nowl1Om ,.,tn,tell but. it if; 1'()pl'(,slmt,(~tivo of t.,he tn'nds in t.hose dn,y:::, Adwtlly, t,he eOllncjlt of k 1'01' ~meh long l'lI,YR i:-; ('l'l'OneOllS and lI.Jt.h()uglt Wit;]l our present know­Icdg(\ WI.' Citll do much hett.er, flt.ill fut' such long 1'(l,Ys, t,}te uVH.lu;),t.ioll of l'ofl'H,et.iun i:-; even now subject to ('lJllsidel'u,hle lI11el·,rbtillt.,V, In n.n," (:rtso, tIl() tigllt'(,,, adupted for k ( ,07 t,u ,()~; ) wore vel.'y Illtwh ai, timli; ; Lhey should luwe heen of t"he ol'llcl' of I), Oi'i, No ,WOollnt·, WlL:-\ ULkcn of plumb­lim\ detlect,ioll;'; either, as i.dOt~:,; about; t.hem \wre ntUll11' vague in tho:·\t' Lime:,;, nor WtloS the neeet:lill11'Y infol'llw,1>ion lLvaila,hle 1'01' fixing the tlntulIl a,hove which the height w,ts l'eekOllmL

In the 80[l:';ons 1880-8~1 and 1 \)n~, ful't.lwl' ub;;el'vM,ions were t,n.lWIl frolll Si;o,Ltiol1ti in tho Dm'jeelilllj hills in L1w COlU'He of (jhe normal Stll'voy progntl1l111e, (See Tftble :2), These ::;tMioll:-l \Yem lLbo tou fm', being ltt ttll Iwcrn,ge distf~nee of DO miles from Mouut, L<]vcl'est., bnt they Imcl Llw adYiw.tage of being iti', ;t, hig'hol' ]tn'd, Atistlluillg n coefticient. ofl'eii:lwliioll of 0 '03, Burmrcl calclllttt.ecl the height OfJ\IOUllt BYol'es(, Ji:Olll thCflC obsel'vtt­ti01l8 ill 1 DOo and arrived ,d; the v(t,lne of :W, 1-4; I Jed';', [-Ie nJ;;o l'oeompl1Lu([ tho older 0 bSOl'Vnitiolls amI fixed Uw euellicient.s of l'efl'aet.i.on for t,iw \'t1l'ioUF>l'ltYs by trialltlld errol' in slloh a W<ty tlmt the lllC"tll result fJltlUC out to be :W,l·.J,l feet, Here ftga.in plHlllb,lhw dcfleetious WCl,\l aot ltWized (Hid t.his va.luc i:-; ttbo ctbm'C an undof1Jl.ed cln,tum, But.it ha,s !11it.1't),eted cCllIsidemble ,"ttent.iull ill recent yertl':'i. 'rhe Amorica.ns h;we lndlli::;IlO(l it. 011 Hwil' l1li1P~ Hnd slIch all emi.nent; lllOLUltnineel' as p, S, Smythe in hi::; book "n'IQ\llltains in Oo~our" pul>lbhecl in 104:0 mttcle ,t definit.e sliittcment, that the true height of Mount Everest wail 29,141 feet, He a,ttl'ihuted. the differtmoe from 21),0(12 feet to be due to the fact, thn,j-, "the Hutss of the Himalaya::; puts the hubble of [I, theodolite very slightly (JUt. of plumb to the eentre of the er,l'th" which of eOl1rse is not the true exphination,

l1ei'ol'e we describe the new obsel'V/1,t.iolls, it, would be well to recoullt. SOlUe of the fa.et.ol's which haNe <tn importa,nt bmtring on t,he problem of t,he determination of heighwof ina,eeessible pen,ks.

'-~-*~X~tili~t~h-~Ttil~:G~~g~~l;t;y a~('l~;logy'~Ttl;~-fri~niiG:;';;-~~[o~~;;t~0~;:,~;;i~-'iii~t:;;~lIY Col, ~, G, BlIrml'd lInd H, II, Hayden, Pm't I, 1007, P :.l6,

o 27

._ "--~ --­~---.~--~

" 783 I'1l1es)-62S • • 4 G.8< R. B. , ::: 15· _. 369'O/N. C. 5 ( Reg ..... 0.

t.)~JU °el_ __ . ____ _

------- NC"ULATION, "8° 0

<> 28

TRiA '. :,. , <.~ E1.:1 !::CrKJf-~ 8! D'.f- ,.c ~ DATA

d t the Survey 0 Printe a . (P.Z:.OJ. find ia Offices

Chart II

'n Birch Hill h.s, h s I ~. Obscrvatl-,ry ..

je.lms S (Destroyed) rjccling . Igor Hill n,,,,

2. H.efradion.--lt W!LN t'orLll:l.ed en~n ill Lhe e,triiest da,ys t.hat refraction was it mo."li', potent l~l,et.ol' in E'valuat,illg' the l18ight,<; of t.he hi,gh mOlmttl,in llea,ks as ohRervecl from long (listftncefJ and 1111lch effort Wlll'; expended in deriving t.lH\ apl:lrnpri,Li:c\" ullpfj:ieionts of rofrrLct.ion. :F\w l'iLyS of IIG miles or so, an (\l'I'0l' or 10-:1 in k produces an errol' of 11

font OJ' so in height Itlltl 111i8 if~ why ill t,ho 01r181' cOJ1l:rmtatiomi t,lw k's were, tcLkcIl to H plane;;: I)f ("ir'einHtiR, hOCHIISt\ jJI(~y C(ili1pntNl oiLeh del'ivatioll of height, to OIW plnce of decimid, No tmnprJ'[l,tnre and prcssure ohRer­vat.iolls weru tnke]) nm1 it is llot known how sncll n brgo numher of digitI' were sclo()ted""·possihly the ruling cnnsifieraLiull was thnt there fdlfluld be it good mCHRUl'O of a,g'I'e('lIWnt. betweell tile IwiglJl:s dnrived li.'om v,l,l'inns st.l~t.i()l1R. Tn the light. of model'll knowh~(lge we know now thai the eoefficit:~ni!R of l'pfl'a.cl,inn f),(loptml in t.he older eOJ1ij)llt.n,t.ioW'l Were grossly in error a.lHl t.he l't\slIH'R fl'OIll t,lm \rill'ions ;;;t.n.t.iOllR wm'e qnHe hrterogeneous lK'ing bllrdened wit.h varying HYR\:olllatie (:H'l'Ol·S.

'['he (;11l'v[I,hll'e of ;1 l'iLy of light [Hld CU1IN(~qllent.ly its l'ef'l'fLo[,ion deponds OIl t.f'm]K'I'[tture 'I', pl'(':,~lll'n l' and t('mJl(~l'Ht',nl'e gl'<\,di('nt f3 of t.he ltt,mospiteric layers t.hrongh wlrir:h it ray l)n.Sf'i!~S, iLlld iii changing all 1,110 tinw. '1'0 oht'ilin it- ;~C('nl'f"h)]V, OllS(·l'l'nt.iOJJs :fOI' ;1,i1' density a,re required ;1,11 a,l()ng the rH,y itt Ihe 'j.ime of ohKe!'va,bioll. This is 'nover fei1sihle in prnd,ic(~ [l,nd (,ed,ain l1KRlllllpliiollS Iw,ve 1;0 110 made, The fl"ilnpleRt method iR to [LSSllllW a vltlllO of' (Joefficient of fOrmCtion k iiw thc\ t'H,y n.na get. refraction from the formula Q = kX' where X is (,he length or t.lw l':Ly in Hong-ult1l' measure. This conCepti of Ie is, however, not valid for long l'<lYR WiUl their exi;l'mnii.ieR at very different. elevCl,tionfl. It, is only [Lpplicable t.o (1.11 innnitcsimn.1 pfl.lt of no )'ny, boing ilepolHlenl; on the values of {3, P and 'I' provfLiling there nnd those va,ry t,ln:onghout, tlw day.

Ail' huing compressible, has n. gl:C~lttier dew;iLy neal' the eal'Ul because of the grCfLter mr~sf'! above it. When it rises, it expn.ncls anrl is cooled without" t.ransfer of heal; ,11Hl t.hus change,'; of tempemt.nre enn ocenI' in an ascending or dcsccllCling m'LRS of nil' dne to different. pressures. Theory ShOWfl t.lmi; this dynamic cooling of dry ail' due to expa,nsioll is 5· 5°F'. per ] ,000 feet.. 'l'his i;; en,lied t.he AdiEtbntic LltPSc HrLt.e, The a,hove figure, however, if'! for dl'Y air; the presence of moisture has a consiclel'­[Lhl0 retarding eifeot, on the cooling and n good average vitlue is 3.2°]1. pel' 1,000 feoli. Mueh research (t,heoreticn.l a,nel pl'<lcticnl) has been carried out. on refraction since t.he beginning of this eeni;llI'Y uncI it ha,R been found i,hat the mn.jol' portion of t.he v(triation of refraction is caused by the la.l'ge diurnal fluetnat,ions of the telllpemtme gradient. In t.ho plaim1, the bpse rate may ehange by ~1S mnch fig :WO% in the con1'8e of n day and in the htyOl' close to the gronnd suri}le(JI, the extont of val'i11-tiOll call bc vm'y cOllsidomble. 'rho mode en pra,etice to overcome irregular effects of refract.ion is by seleeting a partieular time of observa­tioll, cnlIecl t.ho time of minimum refi:action. This hn.ppeug to he 11ear mid-day, ltS it iF; only at this time that variations in the iiemper<1turc gradient from day-to-clay are least. On this account, the normal recip­rocal vert.ical anglo observations 3,re confined to this t.ime in the l1S11i\,[ routine of topogmphical Sl11'veys and if t.he extremitim; of the my ttl'e not f1t. I'ory cliffel'ont elevtltiollS, Tofmetion is ItKRllmcd to ho the same at tho two onds.

The I:lllOW peaks of the Himalaya,s, however, present, one gl'ea,t, (lifficulty in t,\mt reciprocal obscrvatiom; are not, possible. Even with Ollr

present knowledge it, is not possible to give a. theoretieal fornlllht for refraction, which will bcnniverSftlly flrpplieable fora,JllcllgHlSofmys, beemLso int.ervening Ja'lil'IO rateR 111n,y he very different. from t,he necepted oner;.

ExpCl'iOllOO shows tlw,t; even JOt (1, tl'i<\,llgulat,joll serios wit.h compal'll,t,ively shori, sides, heights dod ved from l'OCiPl'OCfd oh:;ol'vatoions differ c:yst,em­n,t,ic:l.l]y a.ccol'fling 1,0 the square of t.he lengt,h of ['110 my, inclic:1t-,ing elo[~I'ly thai; tho ;1,('.j',nnJ 'hn1l1,pcl'atu1'0 grnclionJ,N nrc diffnront. from tho talmia(jed ones.

1'110 only pl'ae[',ica,l wny of uvel'OmnilH5 the uncertl1illLy of rofm,ct.ion in such H CMi~\ itS 10 obser\"(\ h~om high hills n'l(l,~:,\ t.o 010 peak: 'I'he clim'nnl v,n,riation of If~pse l'a,(;o is eOllltJ111'ativ!'lly sma,1I in this cap,e and it is Hot ;l,bsolutely essential 1.0 conlll1e 1',110 ObReTVati011fl to mid-day. '1'l1e va.lues of refraction f()!' tho various l'ayH in this vapor Imve heen mtlcu k~f;t'(l hy llsing the following [o1'n1\[1n, for the eoc:flioient of rofnwtion :-.

p k cccc [)0,00(' 'Fi ( (HH87 + f3 ), whore T if; in [I,bilolnte degreeH -u'

Iwd f3 is dogl'oes F Ifk'; f3 has boen lfl,ken ns :~. J0Ji' 11,000 n. >Fol' st.eOl) l'nys, like the ones 1:,0 l'vIount, :Everest., wher~ the tompul'a-

1:,n1'o amI pI'OSimre eOllrlitiol1s (~b the two ends nrc very diff(-~l'eni" it; nan he showll tlUtt a value of k perta.ining [;0 k1 l)oint, l/:Jl'cl up along 1,he my givrR fl, Yfll'y good ;l,ppruxima,tioll. It; will be Bhnwll in [~ htkt' section tlHtL the l'csult.ing [liTO!' in height, due to pl'ollfthle Hll0[,I1n.tinn", in f3 f,n' the ohservf),biom; 1111.('[01' disOlls:,ion, is negligihle.

3. Datum.--Tho heightH of points on [,he cnt!;]t l;(l ho eomlliL1'idJJe with one anot.her h.-wo to he recknnoc1 above t.he sn,mo l'(~fOl.·ene(:\ rml'faee. SElvel';1,l snch reference r:mrJn,ces are ava.ilahle some of vihieh arc 1'oal while others are ill1ttgiru\'l'Y. 'rwo of the most:. importltlli-, DIles arc th() reference spheroid of the country on which the trinngulat.iol1 is computed Hnd t.he m0(111 Rea-level Sllrfi1Ce (geoid). In Tmlia, the ht,itnde aud longitnde for mn,pping pnrposes are oOlnputed 011 :L tnlH NplwI'oirl ealled t.he Ev(~resli spheroi<l. 'rhe gooid j8, however, noli n 1',1'110, mat.hematical sur'fM:0, on MlCount of the irregular distl'ilmtioll of bncl iLnfl Gon. One (ja.n cOllsistently work on eHhoT snrfaeo, i.e., one can q uoto either SpllOl'oi!lnl 01' geoidn,l heights ptovjllerl one does flO llilifonnly. Tl1el'(~ n,1'o, howey(;1', cCl't(Lin pros [mel COBS regarding t,he choice of the l'oferenec sllrface whieh need elmifying at t.he outset,. 'l'lw int.emet-.ion lJetween t.hese two smJac:m; involves Romo n.hstl'nse cnl1onp!.innf': a,nd ('.ven i,lip f\XP(~rt'R hnvp i,l'ippnd over it in t.he pnst.

The geoid, a.lLhough irregular, hns iLil rtetm\,l physical existenee and the surveyor's 01' engineer's level [I,ii efteh seUing selis iiiself parallel to it.. Rtal'ting with tho mean sea-level at, n, glVPll 001101tal obsnl'vntory, <t geodetic S111'VeyOl' Can 1;1'II,CO the geoid in grEmi, detr1il wit,hin the limits of observational and il1Btl'Ument;[I,l orrors. The reference spheroid, on the other Imml, hfts a 1l1ythic[I,1 exiflt.ence n.ncl r:a,ll only he located hy meam; of the geoid with the help of geodet.ic and ast.ronomical ObSOI'VfttiOllB.

-While it. is the only suitftble surface for reekolling In,t.iLucleH (1lHllongit.ncloR, iii is not so suit.a.ble as n height dntulll. Its ndoption would lead io nun­uniformity, as clifft\nmt (lollnt,rie::; mw very rUff'erent spheroidR ,\.:oJ theil' fig1l1'es of the eal't,h.

Our pl'odecessors in tho In,st century knew levelling a,urI 80 wero able to obtain geoidnl heightfl thereby. In tl10 plain'" by [;h0 mc[tfitll'C­

mont. of vertieo,l n,ngles they were (Llso getting geoida.l heights, nit-hough they wem often lma.wal'O of it. They wore not able to oh(,~dn heights above the Jilvel'cst spheroid, as tJwy hwked the infol'mation regarding the separation of the gooid from t.he sphel'oicl. In En,et;, Hw'( quite often eonfused the two surfa,ces. .

,. "Groilesy" hy G. Romfol'd, p. Hill.

5

In the phtius, till" nse of geoid l],!l dn,tllm rllll'faee fm' height offers no l)ftl'ticular difiicuHy. I.evelling l,vit:b suit,thle cOl'1'ectiollS can be 111ade k, give the geoiclal height dil'cet.- The llswl.l method mnp!oyed is that of verticnl angles. Tile height8 gi.ven hy thi.s method Ilre vngne fLnd further cOl1sideratioilR arc nOCOf,8m'Y to l'Odll(;e t]wm eiLlIer to the geoid or to the spheroid. The Cheodolito when leve1ied, c1ethW8 the geoichtl 110l'mn,J and sn the ohRul'vec1 \·C'i'l·ien.1 :tngles nro l't'iLHy geoidnL fj.llgles. '1'he usual height fornmh employed in trin,ngul:11,ion 1ll[1kef> t'-Wl) (lraHtic f1ss1llnpU.ons, viz :---

( (( ) tlw,t, the obsel'ved anglo;:; n;re sphel:Oid<d, ,Hu1 ( b ) that the geoid iH a, Rphel'o.

It, eaTl be proved that, with conditions :if; they exisi; in nat.urc, reeipl'ocnl vert,ieal lmgLe obSOl'\rnt,iol1s in 110l'llud LopogJ';1,phical i;rirmgu­l,tLiol1 give gooll orthonlet·de gooic!n.l height,,, inrJl)ito of i·he appnrently Cl'I'oncnns ttRRll111pLioml illvolved in tho eUlurJld.a(,[(JIW, ]'01' longer raYH MI [t,re met with in goo(ll,tie tl'iiLllgubLinll, tho preciHioll of heights bl~c'omuH If'RS IWlI 1'01' high Himii,byan peaks, WIWl'Cl l'(leiproonl o'bslll'V[l,I,i()lIfl arc 110t.

l'ea,sihle, the litigonmnekiea.l mot-hud' giv('~, }lOOI' geoidnl heights. Beneo, t;lw older dete1'Hlimtt.i()Hs of high Hima,hyn,n pea.kii wel'e \'lenJc To get heights of SItch peaks wit,h iLny degree of a,ct:1ll'H.oy l'eqllil'08 qllii,e difl0ront cr)Jlsidorntions i1S will he seen latel'. n iH important to l'Oalize i,fmt. spheroidn,l heights can only be ohtained from triftllgul:Ltioll if evel'Y ohs(ll'vec1 angle is (loI'l'oeted for deHnDt.iolls of 1118 }Jlmnh-line and this h:tR 11ev('1' heen done.

The geoid;)'l height or high lllount,(\,in ]le~tkB eMl only he derived VilL the l'cfcrenee 81)heroid nsnd fmd this l1.ecessitn,tcs t,httt, t.he tela-t,ion hetwoen the two HUl'faees shonk! he known VOl'Y ll.Ccul't1tely.

Thn fnll speeificn,t.ion (Jf ii, 1'0fo1'e11(:('. 8phel'oid involves ;) qUfl,ntitil~f;

(fl, Il, 1)0' go, No) at, t.he rl",tJum selcei-.ed HS bIte ()rigin of tl'jn,ngnhtion, where ft, b denote tho Homl-D,xes, '1)0' go the pluml)-lillc c1e:flectiOl18 :.lld No the separat,ion be{;ween (he geoid and t,110 sphel'oid. In India, j-,he lUef; ( <., h ) of the ]ijvel'osl; 8pheroir] which i8 still in nse for nnpping, W(;l'e det.ormined in lsao and the dn1;mn chosen wn,s Knlianpul'. In t.he 18GO'R, when ohsel'Vn.t.ionfl to Mounj-, F!v(west were t.n,ken, ideaK f~bot\li sneh concepts fLS plumb-Ii ne deflections and l'Ofel'CllCe spheroids were rather va,gue nnd lloi; much n,tt.ention -\'1[1,['1 devoted to 'tJo, go, No. In fltct, the meiwlll'c(l haRn-Hnes in t.hose dttys were reduced to geoid. iLRBuming ii', to coineirle, wit·h spheroid evorywhere. As geodetic Imowltxlge pro­gresRcd, it heC:lL11lC imperative '[;0 nllocate n, value to No. It. was defined 1;0 1)0 zero n,t, Kn,lifinpul' in H)2(j llRing t,he criterion t.lu.t thi8 choice nutde the mmm height of tho gooid iLbove the spheroid under the ten Indian baRes i-,hnt had been mmtsured np to t.hn,t time to be zoro. The year 1921) hrought ahout, Ute advent of the IIlt.()rn~tt.ional spheroicl, which is I. eonsi­dorahle improvem.ont 011 the Everest, spheroid. ]l'Ol' nil scientific st,udies of t,he geoid, this iR t.he spheroid now used in India. It WlLS defined to he :n feet above the geoid a.t ](a,JifLllpUl' in 1927 and the relation between the above two spheroidR in IndiA. ha.s been shown gra.phically hy tho nuthorl. rt- is only when the concept of snch H, l'eferenee spheroid is introduced to sm've IMl nn intermodiary t,lm!; tho prohlem of heights of high Himalayan peaks take!') Oll a eoherent form. ']'ho old.or figures of 29,002 fAet and 2n,141 foot; qnot,od foJ' 1",ho height:. of Mount lijvel'cst. are rather vague in I',hat t.hey do not, refer to any defined dn.tnm.

l "Tho separation bolwcen difforcnt, Allh(;l'OhlR ", hy n, IJ, Gll1ntce, Sllrvey of Judin., (i ofJ[1etic lkport., 11131·, CIlIIptel' VIII.

4. Heights of ObsenTing Stations.--'I'lw tnJ)Je below giveH the lwights uf t,)le Ij ,~latjrm" from whieh J\[ount RVBrm;l was ob;:.;orve(l in 18J!J-GO :---

H(eju'ht lI£wd ill - 1- . j I' J -, i -J" 'f~' It

,.., - j -to' --- : J- ('11-( 11-]l1l )11,",](\( i - )ne]'ellee o ( CUHlI)1] "l, WIle; I '- - :

, I -.~----.. -- ,,--.-.--~~. ~-~-"-i

feet fl'cl I

.Ta,I'DI 'I'.R. ~:n ~:!n ~ll

Tvlil'Jlfqml' T.8. ~;J4 ~+ii 9

.lrLnjipati 'I'.N. ~t13 :.!5i) 8

Ladnin. TB. :21·2, :z:~:i 7

Harptn' 'r.s. ~:Ul JIO 7

_Minai 1'.8. ")'J- :t.'lH !) I ..:.'.)J _,

C'nImnu ~ gives the heights lIsed in the older compnbtions an([ eolunm :1, the present :wcnptecl lwight.s after iI,cljufJtment to spirit-level va,lues. H will be seen thnt t-.lw meaH height of the ohserdng st.ations has ehnnged hy about 8 feeL. As It result. of this the height; of Mount; 'Everest-, waH ehange:d to 28, fl9J feet, on the cha.rtil of trianglllat,ion in hhe General Reporjjs ff)]' t.he veal'S 1802 t,o 1 n03. In 100:J, the old value of ZI),002 was l'c8tored as it W[\8 rea,lized correotly tba.t the change was prematme in that any new value would be burdened by mueh largf'l' errOl'E{'.

The values of the stal'tiug statiolls of 1880 obseJ'ntj,iOtls lta.ve also undergone c}u1;ngCiJ ns n l'cslIl1· of later spil'it-Icvellnd connections ItS tIll' following table will ilhuw ;--

tltl1t,ion I -------.. ~- "--~+

Sl1bel'kum h.s.

Tiger Hill h.s.

SI1l1dakplm h.N.

Phltli'tt h.s.

Senchal h.::;.

Year of obsel'vatioll

18XI

1880

188B

IHO:!

W02

Height. fL(jCepted in I Present, ILceepted oldor eomput.n,i-.iOl1fl i vn,lnes

I

fed. feet

I I,i\-i I

H.:')07

I 1, H20 L 1,H15

11,811\ 11,708

8,IJHH S,584

In order t.o ILvoic! n,ny nncertainl-,y on this account, special Cltre waH taken to provide an rulequat,e !lumher of spil'it-Jevt,lled conneotioml in the llew triangulations whieh have bepn used t.o provide st.n.tiom-l of obRervatioll for the new work.

5. Outline of the New Method.----The three nutin SOUTcefl of un­certainty in the older determinat.ion are-( a ) refrn.ction, (b) neglect. of deflections and ( c ) non-specifica.tion of the datum surface. ---_---_.----_.- . -----,------ -- ---' .. _-,-------- _---_ --... -,--~---

" .. A sketch of the Geogl'al)hy lind Geology of the Himii!nYIl l\i~I~;;t;i;;-~~~dTIIJCt;-;l;; Col. S. G. BUl'mrd. fllHl H. H. HIl.~'den, Part, 1, Hl07, pp 21i-27. .

"

Thu diagram hdow illm:j,rah)s holV UWHC' ha.ve bl'(~n (i\'orcome 111

Uw lWW 1llJlt.}lOcl.

-80 rnlles- -

Mt. Everest E

G

International ----------·-r.I~I~~s~Dh~e~ro~i~d~·II

- -30 miles - -

EverlOst'. Spheroid

LB dellotus t.lw oruHH-:-;oe\,ioll uf Lill' topogmphy [Jut,ween Ln.duin, ( In,titude 26° 23' 50'" :$2, longitude Stl" :~7' 15'" (lei ), ,t point in t,he pll1ins of :Bilti'u' [tild .Muunt, EVereHl.; A is ,t Htltt.iOll ,Lbout 12,00U feet high at iI, distanee of ao milcH ( say) from Everest,. The sect,ions of tho !.reoid, [utCl'lln,t;iOlml Hphel'oid and Evel'l\:-lt spheroid between t,he;;o points ,LTC

f11so shown in Lhe din,gmm. Our objeetin\ is to geL Ee: the height. of t,ho POlLk ab()\'o the geoid and

t.hi" can be done vin, the inh,l'tllOdial'Y or the Inte1'lHttional or EYoroflt spheroids. For our l'eduot.ioll:'3, we heLVe U1WSOll t.he fonner. If N1 , 1\1'0 (lenote the geoida,ll'i"(~fl unde]' A and:E respectively, we have EO = AG1 + ( EI --_ All) - (No -_. N J ). TIll' spheroida,l height difference (EI-­All) i:> detOl'lllined by vertioal :tngle UbSE'l'Va,tiol1:'3 ( correetcd for plumb­line uoHect,iollS) which ~Ll'e buruenod \vith l'efmet.ioll. In the filde!' observa,tiollS AE wa,rl of t.ho urder of lUI) miles (met in such ,L (:<lse l'cfw,ct.ion produccr-; illl iU:-lup0l'ilblc dil1iculty. It is sl.!bjel't t,o brge diuJ.'na.J \f,wicLtiOJl tLnt! its computation from theoretirml c(Jllsidcl'at.iolls, oan be in errol' by consiclentble <.\,1l1.0nnt.:-l even if t.Ile observations are confined to the timo of minimum rofhwtioll. In the present work, the vertical angles to Everest f\,l'C bkon from a. number of high peaks ( t.ypified by A ), distant about :~5 miles from the IJeltk. 'J.'hese stat.ions t11'O connected to the main G.T. serieN (N.R ]~ongitudilla,1 Series) by i1 short.-sided tria.ngulation. :Refhwt.ion at t.hese altitudes, being neither so hugo nor so erra,tie fLS in Lhe low lying plains, elHl be tackled much more sllcoessfully. The C01'­

met-ion to height; due to refhtction is only one-tenth of that of the eaTlier observations. At such high level:;;, the outsttlucling items that have to be J'ockoned with arc plumh"lilH~ deficetions a.nd geoid; el'l'Ol'S due to 1'C­fraction are seconda,ry, pl'ovided there are no gra.zing rays.

It ulight, ue melltiune(l Mutt the height of Mount Kilinumja,l'o ( HI,::I1U fuci;), the highe:'lli mounta,in iu .Afl.'ief~ htLS 1'ooent,ly been l'edeLel'mined1•

IJ, \Va:,; possihle fol' the obsul'vol';> to geL to the llloullt,uin top with their theodolites mlll to carry out rceipl'ocml observations. No accoltut Wets

taken of the plumb-line deflections, as .KiliuIHnjn,ro is noli f\llOh a. large um88. n i:-; oil iLceonnt of Lho gmgn,nGlIalllUHSs of t.he JTIvel'e::;t, pnxLuciug exceptiolHLlly hTgC deflectiolls etuel defol'm:ttion (,I' sClklevel allll Ule f<wt tiJ.a,L lW obst.'rn~LiOlml work is possible OIl its rmmmit tlmt Sf) nUI,ny rl\iine­trWl d~s h,"v(~ to be [,akon into aceount,.

H- e,Lll iJu ~llUwn t.hat iillO "I'dinm,v tl'igOHOlllUt:.t'il,;d (:omllntt~t,i\)llfl of l'euiprocnl l'n,yc; oj' 1), shol'L-siclccl tl'iangnlnLioll gil'tl 11, goud value of tlte geoirlaJ lwigilt,S. Tho ,~()(li.(lnl h.oigllt j\GJ of il is tltllS pl'oeisoly knowll.

l'lw ciol'l'ying UUli ut' slwl'li-;.;icled t,l·i.mgulitl,iull dose hi the 1Iu,1].;: is Lims an illlJlol·tn,nt tiLop fm.'wl1l'd. Nut. uiLly (Iou": :it, do aw,\y wi1ih Lhn llla,jUl' ll11c('rk~illlly due tu refead,iull bnt iti :dso gives good geoid.,i. h(:'igilL::; fur U~l"ul'l'at,iun ::;t-ntion" withuLlt! worrying about cleHuetion::;.

Tile ostim1ttiull of (No .-- Nl ), tilt) HlIlolllalowl rise of t,110 geuid ill 1,lw Jast! ;{5 mile::;, 1m,., tu De lnlsee! on dHe:~ pl'uvided by doiloetion a.nd gnw.it,.}' ulmel'vM,iollC>. DoHec:li.ioll ohsone,\,Liulls h(we been c,H'l'ie(l up to Nij,melw Ba-zii,l', :t diskLllee of ouly I. 8 mile;.; frotH IVlollJlt EVl1m'=it.

In Mle uhk.l' dc]'ivMiull of height:,;, noithel' the detl.cetiuHS HOi' t,hll l'uiatiou Lei;ween t.he geuid lUte[ t;he roi'erencll sphoruid" woro av:),ilttblc a,ud the derived heighLs did noli perta,in to any :,pecific Kul'iiwe, Its no ,t\:.eonllt, \Va,s tn,ken of these itl11Iui'ta,1l1', faetms.

6. Tdangulation and Height Data.---Chi1rt II Khows t,he Lriullg\l­h~l.ioll liKed for deriving the new v,due of the; heigh! of il,{ount ]<}vere8t. 'l'he v,H'ioUfl topugra,phiCltl Ll'it1ugulrt,1!ion" t'Ulan:Ltillg from the :-;t"Lt-i01l8 oi' the North-East Longituciiwll St'rj(:_\:'j were excent.ecL in the ,VOterK H)-1G--ti3 iA)

_Pl'ovicle cont,rol fol' irrigation projoets in eOllllectioll with t,he Kosi Dam. ITolll' Lttplace statiolls tMlcl three bu,se-lille,.; were intl'oduc:ed in t,he eireuiL Thaknrg(111j-Dnmcliillgi·-'1~01lgLu-S(lll(lrtkplll1-Gn,rhi-Chy,mltang-Telllkt~­Khiimtel ~ Meenn,Klii - Dllngrc -- Clmnt.itl'e - Sm.·uugn, - Lnclllia, 'l'hi::; cireuit; dosed 'with an error uf 1 in tho 5th pbeo nf log side, :,]" in [tZillluth, - 0" . 07 in ltttitude aud -- (J". II in longil,udu, which is vee)' ::;"ti::;i'ud,ory.

For the pllrpo,~e of pl.'oviding u1Holurvatioll fltcLtiollS to MOllnt, gvoretit. tLll extension triangulat,ion wal:) carried out in I !)G:.!-ti3, tltarting from [,Jw

sides. May5.m h.s.-LU:ori Dand,L h,N. and Aisyalukharlm h.s.-Uhhulyamu lUi. of the ahovu work This uxtellsiol\ Ll'hmgnltttioll provided eight KttLtiol1:, fl,!' height:,: nmgillg from 8,070 to 1<1,762 feet, from which verticltl ,:lingle" were obsel'Yed to i'lounb Evcrest in the yea,]'K J 952·-fi:l all(1 IHG3-5J.

( a ) Position oj .Monnt IEvercsl.-The old position of lVIount EVCl'OHL

was rather doubtfully fixed. It WetS observed from seven staMons of the North-EC1st LOllgitudimtl f:leries, but no two of them were incervisihle. The !Lugles lll~d to he declucecl thruugh reference stlLtions otJllel' tlmn tho observing stations with the help of [1zimuths computed from co-ordiru.tes. The original computed v:tlues of the posit,iol1 wore :--

Llttitudo Longitude

(l

':27 8H

, /I

5U 1G·748 58 05'852

1 Bmpira SlU'vey Review, JIlll. 1954, No. 01, Volume XII, p. 206.

86'30 27'r----45'

<;)."> 8 Il<I:)

, ,Pike Sub. + 2' 6 ISO h.s.

0,,9

30

. __ ._--_._-----_._---

8 +426·2

G

Chal'tp II!

._--,-------_._------------------

TRIANGULAR MISCLOSURES

IN

HEIGHT

Scale'l Inch to 4 Miles

Miles 5 4 3 :2 1 0 5 Miles cl·-~-·~--=IL-=··=-·~·t===~~r~-=--~---~I=·=---=-~t=====--=-.-=-======~~~===~

8

a too 27' 45'

'2. 7' . Rupakot h.s. '2. 7' 1~ ~-----------------------------------------~-----;~~------------------------------·~15' 86'30' 45' 87"00'

Reg,No. 376 D!N.C.'f.'>4(1'; 4 Mlles)-625. Printed at the Survey of India Officcs.(P.Z.O.).

'l'Jw eu-ul'llilllLLuH wero l'UUUII1PUtlid l.ll 1 DU:; ll~:illg dlO Itdj 11,;1;0\1

cu-ordiwLtoN 1)1:' tho ok:el'V.ltlg :.,Ii:L(jUll.~'1 m; durivucl 1'1.'\)lll Llw fJillllllii,LIWUHll

ndj U:,LlllUHt. of 1i1l0 Vrinoip(L] triangulatio!l of Illdill,. '['ItO lOIl,~!;iLl!d(1 Wi.L::!

a,bo bruught intu Lel'lm: oJ' Lho hd,OflL V,dlW uf Llw IU!l2;itudu of rlw IIL1I!m:, UlHmrvidiory. '1'he eO-()1'dill,Llio8 mluptucl WCll'll

La[;iliuc1o LUllgiLucle

Hi"·2:2 ;-{!) • ~Jl

Althu ugh Hut i Ill}lOl'liallL from [,\10 pUilll, of v low uf Iw.iglt I; {ll di{)l'tIli .. llaLi()jl, tho uu-urdiJl~I,\'Ufl uf l\iullnt, ]1;YL;rD6t lw,n: iJu{c'n l\)lixu{l frolll UU'l\O :-;liiLUO!H;, vill., BukllI' h.:>., UhhulyfLIl111 h.:'I. aIHl Upper Hu,uje, Il.il. during UJ;:;;3.

The l'O~:lllLc: of Lho ii\VU bl'iitiLg!C~; an) vory .lLuuul'danL, tll.O lllu;m v,duu iJeing

L,LtiLwle Longitude an .[il.

l\1.0UUii Everesti 1m,'! thuN [;(/ 1)0 ,.,hiflied hy ntHH11; ,.W fe(l~ ,,,oUUnVII,l'cl:;: nUll wm.,t,w,Lnb frum it,:-; lLr:,uoptelt plmition.

( Ii ) Heiuhls.-Jh·um a IJCl'llSld uf ChiLrt. H, it wuuld appeal' Llla,1, 1h0

LriituglllatioJl heights <urC) well cont.roJJed by :lpirlL-levol CUJllH1Ut.ioJl'l. The heights for bhe CDlllputa,tions of tho pl'csent 88l'iD;oJ t,Lko 011' from Diwnug,wj T.8. ( 72 J ), Ch"t.m V.8. ( 72 N ) fwd Dal'jeeliug OiJseI'Vl~toOl'Y 11.8. ( 78 A). Their i:ipirit-levolled height.:.; are as foUuws ;-

feeti iJiWtmgn,n,i 'f.S. 188' gil ClmtrH v.~. 371:)' UO Dfn'jeeling Obsol'vaLory h.:'I. 7, H4' Sf)

The height.s of lVIa.yUlll 11.:'1. and Laol'i D,Lm[;L 11.:0. WCI'U derivCll illciepellclollt,ly il.'om 3 routos,-frum Ladnilt T.S., ii.·um Cha,tl'H v,s. and frulll Di11'jeelillg Olx:crvH,tory h.8. l'lispuc:tiively. 'l'lw heightH derivod from these three routes h;wo been woiglltuct in tIm IJl'()pOl'tion uf 2, :~ and 1 respectively. Tho resul!i from Ch~tLl'a v,s. hn,B been givlIll the greatest, weight tW n pftl't from being shortest ill length, it, has the SlllfLllosi;

tl'il1nguhLl' mi8eio:-mres in heighti. The fin:Llly aecop1jcd vi1IucH of the heights of Mayi'i.m h.f:l. Mld LiWl'i llanda, il.ll. al'C as follows ;-

Height ill feet Mayiim h,8, 10,948 La,od DI1U(\,L It.s. 11,8'77

'rIw tl'i'l.JlgUictl' Illi:-;dosm:er'l ill hllight~: of tho main tLnlI extOllfJioll 1jrhmglllntiom.; (::;ee Chal'tj HI) m'o vcry SUU\,Ji nmging ouly fl'Olll I} t,o ,11.()ot and it, was not comiciel'ud wOl'Lhwltlle to i:"d:iu~t tho oxtonsion t.l'iallgulv..tioll lJ,)l t.he metjhod oj' loa:::\; SqU:LJ'BS.

The final V<.L!.lWH of the heights of the Evere:::t is obsel'ved al'O given below ;­

1.\ st,LtiollS frulll which Mount

. i\byalll lUl. Laod Dl1llCla h.s. Ai BYl11uldHLrka, 11.8. Clthulyfnnu h.8.

Height in feet 10,\.)-18 11,877

B, 67 0 10, lUO

:Pike I::)uh. h.B . 80][111114 h.B. Lower -n,allje 11.8. Upper Ranje h.s.

Height in feet 12,059 11,658 13,357 14,762

From tJle evidence of the tl'h1ngulu,1' miselosures it C,tll be safely inferred that theflO H,re eorrect tu vvilihin 2 or :3 feot.

7. Plumb~line Deflections and the Geoid.-'I'he rise of 'bhe geoid under the mighty range of t,he Himiila,yas h[lS been the subjeot of much

:.;pc()ulatiun. UW', II) CIl(' lJ(I,lluiLy uf ddluetlllll :tIld gn~v iCy dnt:t iH tItie] rogiull, no roli:~\)ll~ C:-;t,ilUitLO 1m:; MLl far been pos::;iblc.

By taking [t generalizod seCliioll of the iiopc)gmphy ()f [,he Himi:i,l:tyn,s and Tibet, Mader'" roekolloc1 that N (heighl; of the geoid) nllder llimitlayat; wonlll he 877 metros without isostitKY ntHl "1:0' 7 lllelil'OS wit,1t isostasy. He nlsu Cfltinmtocl that I,he uncumponsated geoid \voulcl rise by about BOO feot from the pln.inH to n, point uncler the BUlllllli(-, of tho Himi11a,Yi1s Mld CUlllpensa,ted geoid hy 120 feet. l\ittcier was not, COll­

eOl'llecl with MOllut, ]3; vereflt ill p:tl't.ieuLhl.' ,md hi" iiguros mm only be l'ogal'dorl a8 indicmtivo of LIt6 ordors of Ilta,\il1i[ude.

l>eHection ui>sel'vittiom; have ,IJCnll Uil,l'ried. Ollt clul'lwl' t.lln hLJ,(, :3 VI';),l','

iiO delineate the geoid ill t]ll\ 1V101lu(; li,;\Tcresl:. n,l'eiL. For thi:~ l)Il~'j)u"u, a 'lu-[, of 1l1.'epn,l'at,ol'Y work '.vas uoeos:,i1j'Y :for pl'ovicliilg a good ~t.al'tillg Im8ir:. 'I'll() existing geoidal :,;ect,ioll along liJte fooli-hill,; uf LIte Himi:'~byH'H frolll Dehm Dun 110 :Dal'jeeling Witlj very weak un (tcunllllL (If the piLllcity of prime vertical dctlectiol1fJ.

In IB5:2, tL dw,in of ast,roln,he ,,,LnliiollS ( eoverillg a liue/u' distnnee of about 300 miles) wa" cfljiabJi:,hetl ,1.1; a,lllJufj 1 ri-mile iut.erval a.long the Lower staliions of the NOl:th-l]il"lt Longilimlinal Series. These obscrva­LiollH provide i~ relia,hle I'[tJuo of the gooid,~i height, at La,clnia 'r.B. ( latitude 2()O ~i)' Gn"· ~l2, longitude SUo iJ7 ' Hi" 'IH ), ;, ]Joint, in. Mw pb1im; of Bihar. In H)Gll, WUl'k .n.ts oxLendml f['om 1.l,i" point, tu .Niimdw Brt>',u,I' (hUtude 27° 48' 4G"· 6, longiLnde SO" cU-l' J2"· 0 ) which iH clistmlt (lllly 18 miles from IVlount li:vel'es!;' The m::!.in eff'ml, WitS clireetod to ost:tLlish st,ations a,s fm' as possible (Liong the mOl'idifLll of BoO 40'. A number of nt,hol' Slll'I'OIUtdillg stf1t.iOllS l'lO1'O iLiso Ob',Ol'\'ccl to extend the Imowlodgo of tho geoid in this virgin region.

On account of the cos!, of t.1':l.11RPOl't-., cliffiwItiOll Ill' l'atilo11H, hok uf LJOllllllUniea,tions H,nd j)mwit.y of ~rigonon:wtrion,l ebbt to OioltabliKh pm,itiullH of st(ttions by resect,ioll, it wn,s not l}08Hible to 1mt in as dOllso a mesh ttK would have been do:;ira.ble lmd it was apprehundcd that the v[t,rintiollH of clefleetions ali sneh long inliervals might he too l'rl,ggccL ~() :IoIJuw of IUl 1l,(JUll­rate geL)itial se(Jtion boing dl'n,wn. But, the following will Hhow tIUdi the ch~ta obtu,ined is quite adequl1,te for pl'()lTiding l'elifLhle g(Joiclnl informH,tioll.

Ulmrt IV show:; the l'CNldt,lllg de,Hoot-iullS vect,ol'ially Ht, the Hiia,Lions ob­t'lol'vod. As expoctod, thUHO defiocti(J]Ui exhibit, :leveml POlll(,N or intil\l'eCiL. In t,he Ilil1ins, at [t disliltllCO of HG miles ['rom Mouni, IDvOl'OK!" t.he dufiect.iolls [t1'e northerly aml m~sterl'y but ;),1'0 of sm,dl Illltgnitudos. The llol'Ll10l'ly deflections inCl'fllLsc rapidly WI t.he fuul, uf the hills 18 l'c<telwd lLt. Olmutii,l'c ( height 2,615 feet, l1i"ta,llcO 7 0 mileH hum Mount ID VOl'ONt ). II'l'Olll Chmltal'o to the hill stntion of Mcmmshi ( 0,;118 footi ), thoro is n, doel'tmw of \)" in the meridional detlection (LIld <tYter (,lmL [-,here is ::~ stoMly inoroase of about 1" a mile till the ma,ximulll va,lne of 71" is nmehecl au ]~OWlll.· H.anje ( height 13,357 feet, clist,ance 30 miles fr0111 Mount mverest ), beyond which there is agl1ill a decreaso as wOllld be expeetm1. The 71/1 deflect,ion <tt, Lower H,a,uje is the bl'gest in the worl(l. 'Chis cleJIection is witih ref1peot tu the InternatiOl11tl spheroid. If Everest sph81'oid had boen e1lOsen itS

the reference surbco, it would Imvo boon grtmliel'.

The section Laclniit -Sal' llllgn,-Cllll, II titl'e-Dungre-MoolliLshi - Klmmtol­Rupakot-Aisyal ukIUtl'ka-Pa.ngu -Klliil'te-Cha unrikhark,t-Nu,mchc BlLZal' (sec

* .. Geoid ele vation due to masses of Himalayn.s & Tibet", by lIfl1lLElr. Gerl. Uoit. U)36 Voluille 4.6.

06

Chisankhu h.s.

Jaynagar~

Mirzapur T. S.~

Ladnia T. S. ~ Harpur T. S.~

Reg. No. 37.9 D/N.C.D.'54-775. 87

1111 Vi'"" Inc

Scale I: 1,000,000.

y'm h... 1 / Chainpur h.s.L

CHART IV

-_+---tW}-d Sanchal h.s.\, \

'\

NOTE. Deflections are shown to scale I Inch'" 50 seconds

(Meridian, r.v. & Resultants) thus .. " " .. " .. ~

Printed at the Survey of India. Offices, ( P. Z.o. ).

" ""

Ku rseong h. s.

Sillguri h.5.1

Dumdangi T. S. 6

6 Thakurganj T. s.

Lohiigara 1. S.

9 o 26,

88 30

11

Chart IT) is t"iJOut 100 miles long and fho avera,go interval be(;ween St,I1t.iOllS in its hilly portion is 10 to J 2 miles. It j~ not; si,l'ietily along a meridian, although vm'y ne;},riy NU.

The geoidnl rise nlong thi'l scej,iOIl W;LS c,trefuHy computed as follow,~: Although the eUl'n~i; (If oj)St1I'vo(L clefiontions 'woJ.'(:) f,1irly 8l11ooth, Olll' paNe experience shom; Lhnil, 10 rl'lil(\il is too long (1)11 interval fOl' mountainou,;; regions and that; iii i,~ ck\:"il'il,ble in ,;IIC,h easos (,0 l'eduGo the staLioll interva.l by deriving c1(;{hwtiollS [I,t; ."lomo intervoning strt1iiom, from UWorp.ticl1l eOl1sirlOl'fLtiollH. '['he Hn,yfol'tl c1efiooLioll nllon1nIie8 (''] - 'I)e, g '- gc) were cOlnpuliod f()l' t"w above :'1tll,tinn:,1 1)1l tho 11,'lSllmptioll or deptJl of eompcmsal,ion of 1 i:\· 7 kilollletres and :,ru shown in Ii'ig, 1 f),long wi_j,h t,he eUl'ves of observed rlPilt:~ej,il)ns. As Gxpecl,ucl, MlO anomaly curves [LJ'O mnch rmlooj,her 1;11:L11 the (17, g) CUi.'VOH. 1)oileotinn anomnJiof-l at (j intervening stnU()ll~, (K. 10\), K. 108, ])nugre h.B., :K. 18H, S. 130 i111(1

ChfLt1ial'pU h,s. ) wero road frum thn.',e ClU'VOS and ILLYCol'cl deflecti.ons wore also eomlmt.e(l for thom from whiuh vnJuoH of 1) a,ud. g wore deril'Eld. 'I'ho vnJllwfl at. theAo flt:1LiullFl h:we lJoen joined hy clotterl lines tmd it will be ,Iwon t,har, {hOBO vn,llIm pl'c)(ll1ee groa.(-,())· Hinnosity in t,he (leflection elll'VOH, hill, t.he,)' re!1upo t.he illtnl',,;\,llwfN.;e<m the Hbttjons to [btl ~werfLge of tlltliles, n.ncl i1 j,: IIOpod. t.hat, t.heir' inlroduntioll hns holped lin eliminate, to it great, extellf~, the Kyt-;jlml~ttjo en'orN in tho c:ompntaLiolls of the gooichLI rise. It; Ahould he no[,ed tha.t. this (levice to obtain deflectiolls itt,illt;erven~ iug stations b nut. vitiated by the inaccllracy of the maps Ol' by tho fact of Hayford's hypot.hesi::; not boing i.rue to na.t.nre.

As 1mfl boen explf~inocl befo1'o, a. knowledge of tho geoid between 1',1113 p1nins nnd the Htntio1l8 ('I'mn which Mount BVC1'esi; has boon observed i~ roally not; indisponsrthle for del'ivlllg tho height of ~~'IOUllt Everest. Tho very natLH'e of 0111' method ens me:, tlUtt the 1il'igonomotrical heights of OUl'

ObAC\l'vations wonld be geoiditl heights even though no a,ccnunt. was t.aken of tieflenl,ion (lOlTtlctionK. ThiFl depend:, on t.ho supposition tha,lj t.he dcflectiol1R V1LI'y l.ino:1l'ly beLween ncighbol1l'ing sta.t;iol1f:1 and m:e not hllJ'(lened wit.h large random ('1'1'0 I'S , To check this, the difference of height between Upper Ektujo all(l Itupa.ko(-. was compllted by t.wo met-hoc1R :- .

( (t ) ut,ilizing reeiprocal observntioJl8, diflpCl'Aing height. trhtnguln,r eno ['R tmd ignOl'i ng deflections n,lt.ogether ;

( b ) hy C(ll'l'ectillg ol)flol'vefl vel't.ieal ttngles for defleetions, compllj ing ,jphoroicbl heightr; and i;hen applying separation ))(\\'\VOA11 geoid nnrl Rphero]!l to get geoirlal heights.

The differencp of heigh 1.:-; het,wmm the t.wo meLhorb is only 2· fi feet in it diFfm'(lril,ird height·, of fl,2:i7 fmdj whieh is vory fHLt.isfacliory (LIHl shows j,lmli the (inflect-iollA ;:t,re lMlequaf;ely line~Ll'. Pnrt of the difference is accounted for by t.}10 faer, t.hiti; ( u ) was computed along one flank only, while ( n) wa" cnmpnt,ed by llsing it sorics of tri,tngles.

We now come to t,he ilnpOl'i;ant problem of estima,ting the anomalo11s ,l';ooi!ln.l rise bot-ween the ohservtttion Ht.a,tiollH a,11fl Monn.t I~verest.

A refel'en()(\ to :Fig. 1 shows t,lmt, tho mm_.idional a.nmnaly 'I) - 'f}o 1mB

nea.rly it. corml,H,nt valne of IG" in the hillyanlfL from CJhauLii.l'e to Kharte ann dwinrlleA down t.o zero M, Namche Ba,zal'. 'This is in tWOOI'd with what one would cxpeet. Theory f'ihows tlmt, fOl' a depth of compensation of 113·7 Inns" the effect of fJompensl1tion on the defiention shQnlc1 be practimtlly nil for (liRt,ltnCes up t.o 18 miles from tho pen.k and t,hl~ ohservec1 deflection 8}lOlllrl he nearly equaJ t.o the topographical! defiecj,ion, AI, It distmwe of ,

+10

ii) miles :from t,hl' peak, effect·, (If compml.Sntioll is VOl'Y lUfI/[,twin,l and is of com','Il) clopnlldmlL Oil j,lie (,Yjlle of (JompenfliLtiJlll aSimmoc1. Sinon 'l) is gl'orlter t,jmn 7/e, we ROO t1Utli the rogion iH 1l11ri [\1:· co Inpolls:1,tod , n, f~tot, which iH C:Cl!'l'obnl'atpd hy' tho gl'flovi('f dn.1:t.

" .c a; ~ +10 cO

.. '" ~ +' I: r:: E " I: ·c '" ;:l ,," ;;; ..

" Cl '" .<: oj II) ::;; :.: -'

lng. 1. DeHoet.ioll a.ncl Tk/led,ion Anoma.lies.

The oxt.l'apola,t.ion of iihe (1/ - 'l)c) nnd (g - ~e ) curves up to }\fount; I~vel'Cst eml, thnR, he cftrl'ied OU); wi(',h it cnnRidemhle lllO[WttrO of eert,a.:inty. 'Tbo extntp()htecl curve j" :-;llOwn by dotted lines and t.he values of YJ -- 'l)c, ~ - ee for Mouut E\'ol'cst, ,.rc ( + 1"· 2, + 1"· n). By eomputations, the lhyfnrd tIeHnet,ionR i1t Mounti JDvcre,qt are (.- 1:1", - 2") from 'which the <lefioc(,iol1R derived are (- L I" -8, - 0" -I ), TheRo CfLll bo utilizHtl for computing tho gooidal height of Mount Evnrost. An independ~nt motllO(l h\ to int,egmtu YJ-YJc o.,nd g-g(\ hetwoen Namcho Ba:i.al' and Mount BV(~r(}:3t n,nd tiO this value fLdd tho riRO (If tho isost[~tic geoid tlJ'\ d<n:ivod from mmt;idora.tiolt,; of topograI)hy. 'flw final value HlTivl)(l ati for tho geqirhl height of Monnt EV{)l"m;i, hy a conqidorlttion. of the twu mo'(:.hod" is H2' ~ foeti.

Table 3 gives t,11C deileet.ioL1s nt S(ifttioWl whieh h~we been utiilized to dl'[l,w fl, picture of the geoid in t.his n,reft. The mel'idiomtl COTlljHJrlllll(iS of the defied,ion IlfLve been corrected fm~ t.he normal enrva.tlll'o of the vmt.iO(l,l. The l'esliHing geoid iH HIWWll in Cbart V a,nd if:! helieved t,o be of fL high order of l1cenra.cy. The deflect.ion strdiollS lmve hAflll chosen n,t, str,tions

Bulikipur T.S.

-251 ---------------

Ladnia T.S.O

o HarpurT.S.

l'1i\~' AU! (1)

-. ---

G EOI D

IN

N EPA L 15'783 Miles. Scale I neh :: 10 Milos ~ +El() 5 O_~-.--_!k-==::=l .• Miles I~¢:""c!l!d

"'-"75

_. +10

:--- --- -- .....__ - --"-.....-..-- +60

""""-------~.-.--­-----------"-- -- --- ___ . -'- --- - ~-

+55

+50

+40

--------+35 -- ----- -- --- -- - -- +30

--~TS °ThakUrgani T.S.

jalpaiguri Long. s,O

o Ramganj T.S.

-10 ---- . 26·

8So o ( Z 0.). -

5 f I cia Offices P. . h Survey 0 " Printed alt e

+10

GEOIDAL SECTION

LADNIA - MT EVEREST Chart VI

Feet Mt. Everest r 30.000

If ~

II ~ "'" ~rv I ~~ 20.000

I \ ~~ /1 I It 15,000

~ I ~~ $7 1 g_ {;' J ! f=. '0000

Co I I I' ,

!~ I r lit

/

(c'1r. 1 L 5,000

I Feet ~ I lOOT

---11 +- 0 - - - 1 -i Feet

1 -'

i 75 j I j I 50 ~ ) ~1 I 25~1

Feet '_~ ___ --7""""=,,.L~.e::::::.:::::::=== ____ __:'i~O~9~m~i~ie~s ___ = __ ===::=:=====~-=-:-:-=--=-~-:_:-::_:Jjl ,,~l Cl 0 3 { t'on International Spheroid U as ~ d' Geoioo.\ SeC I -:; 'c CompenS:ice

-e~;~ __ ~ ~ Everest Spheroid j

-H L ~-HJ Feet (Scale 1 Inch to 15·783 Miles) Feet

Reg, NO,3!lOO/N.C.' 54(G, &> R. 8,)-625. Printed at the Su~"ey of India Offices. (P. Z. OJ,

] :l

or topogntphic~d t,riudlgnl:dlIHl n,[ul tlw:'iCl 01\,11 llU r05~H,['{led <:\:i 1ll1likd.y to he in orror by rnUl'e Ulan :1: 0"· L Tho pl'ohal,dc 0]'1\11' of the a~itl'l~lnmninaj btiLudes it" ± O"':L The (W01':L,S(O inL.~l'va] jx;Lwcen 11m f;[,a,l-,iomi i~, Ii Illite,:;

and t.he prolmhle error of i;lIC~ ,\!;coida,! r.bo I\) iiI iW fa,l' as ii, <1ep(q}(:\H on the 11lel'ic1ionrt] eompol1nnts of the duflc~{,Li{"I:;~ mm flU rOCkOllO(] 1'0 he :1:.: n· :l fcnt. Tho error of p01'sonal P(I1l11tion iu Ute nbli'1lle ]H1d,j(lH of t.he "r:el·ion 11Uty

lll'odncc an m'l'or of it foot, 01' HO anel ~:n migilL t',jw Ht'gleel, uJ blw rigift curvatnro correction to mel'i(iiorml do Acnt.inns. r!'ho lltHt bp beLwoc1n Namche Bar.al' nlld Mount. IDvon::~I) mny furtJIf)l' be in ereo]' by ± .} foot. Thc tot.nl pl'olmble error of the geoid :ill t.ho IVlnmti, 'jjjyorcf-it l'(~,!.!;ion can, t,llW';, he rockoll0(1 to be of tho order of 2 foet,.

Chart; VI Rhowillg t.he seetion alnllg the linc of gl'e;l,te:,t, Chttllge from I,adllin in the plainE: of 131h[\,]' [,0 MOlll)t RI/c'reHt is uniquo an(l or very great interost. The geoid shows an lnlprC(~odoiltcld riNG of 100 1(~Gt in n distance of 10\) miles.

COll1}mtil1tions show Hmt ·LllO LOIJogntphie geoid dne to visible masses woukl produco a riSfl of in:) fool,. rj'he n.etlml geoid tti~rplttys 1/:11'<1 of this lise indicating D, eOll.s:idora,ble lIummuo o[ eompensniion. 'f'o get an iden, (lHhe magniliulle of tho COnlp(:11um.t,ion, Fhyfol'd deilect.ionfl ,\yore compnted for these fltn,tions and IiaY[(l1'(l annmn,lioH vvem int,(lu:l'BJtecl for the section. 'rhe correspondin.g geoicJai. l'i;;n of I",ho cOJnpcns[bto(l geoid hetween thc two points is 31 foot •.

B01lh, the no,tu.l'a.l tbnd eompomutetl geoids follow tlw topography l1IHl in the higher hins there [tl'O incliea,tioJls of ft ccwtn,in ,1monnt of lllldol'­

compem:a;tion. G~mvit).Y obsoTvni,iom: ha.yo aINU heen 'trtken in t.his region and con Eir.lll. bhe above eoneluHioll.

8. Final Value of Height.-Vol'tien>l rmgle observat.ions to IVlonut Everost were ohserved wit.h 11 'J'avisi,oc:k tll(\odo]i(,(l in H)i}~-r;;1 a.nd with fI, Gcoclotie VviId t.heo<lolit,e in l\lf):~-rA. An nJmtl'i"d i~l given in Til,hle 4. A number of 80t8 were takon it1; o11.oh 8[:,iLtiou. They wore gonel'[!,lly very c.onsifltont, a,ml the 1nO[l.n of the viHioHs getr; on each c1f1Y wa" used for cltlenlating the hoighli. Column (i 8boW8 the nnmbel' of setA from which it would appea,l: tha,t, [1, suFfieiently hwgo l\lunber of ObHOl"..-at.inns s})reaQ ()Vel~ throe mont-hs in two different yearH hlL vo boe]) tn,ken 1icl get, n. reliable V [LIne 01:' height. AH n. rule, at, thot\o heights, diul'nn,] v(Lrbt.ion of refead,ion i~\ very small a,nd it is noli 8ssential to ndhol'Cl siorict,ly t;o ii1w t,in1O of minimum. l'efmetion. However, colum.n ;~ will Bhow tha,t, in the mai.n, ohsel'vatioIlA hnvo 1ee1l taken a1; tllifl time. vVii,h the d,vba derivcd in the pl'eVi011E\ ptWiLgl'fI,phs, iihe groun.d is now clen,lwl for n,rrivillg; ttl; t.he final value of height of Mount Evel'csJ"..

The geoidal heights as derived ii'om ca(:h sta.tion nrc given in ~eab]e 5. The various columns in t.his tiahle 111:0 self-explannt".Ol"Y. Culmun fj gives the sphel'OidrLl height; differonce between the FJtatioll of Ohflel'VatioH ftml Mount Everest a,nd column 7 the COl'reRpollcling geoidall'ise.

~rhe heights, as ijfLhula,ted in the Iftst. column, arc blU'clened with tho t()llowing errors ;_._

( (( ) Error in adoJlted geoicll11 height of obsorving stations. 1'hm18 lue well tied to Rpirit-leyellec1 heights and can 1)(\ in 01'1'01'

by 2 0)' :i feet a.t the 1l1os1;.

( b) Bl'l'ors in 8N the cstinmtecl geoidall'ise between tho stations and Monnt Evorest. 'rhis 011]1 v,ttftin it maximum of [j feet bnt sho[,ld he hott~r thnn thiB.

( c ) Errm'8 duo to estimo.iiecll'efmction.

No ohsel'vai,ioual chl,D, fm.' bp:':u l'[bi;0 QxiHl;s for the netmtl statiollH and the :celi.'action i",; computed on tho hypothofJis of sl1,[;u:nlJtod ndinJmtie JapR0 l'nbo of 3 '_'2°JI'/I))I)O feek }i"01' e:wh )'l1,Y, th':1 c:oeffieienf; of rofl'nc1iion iil <\omlll1t(1<i with this hpiiO 1'n,[;o fo1' liolll.}lm'al-,ur'e nlH1 Ill'CSSllrc'l nppropl'iai;c to n, point one-t.hil'd tho rlil'lkt,nc(l ll:long the line, '['he varirLtions in the lapse ral;o have, !wwevel', nn :irnpOl'til611t, offen!; on (illo l'OfL'[LOtioll. A refc<t'oneo to (;110 lLol'mn,1 u1mrtiH uf t,11o ]\'i:etool'ologie,11 Department show~; that; the iWOl'ago hp,se l'!;1,lie in the J'IIIOltll.!; ]JJV(ll'G.'it region agroos very

well wil;h the nbovo vitlne, The I'edicn,l iHlgle obsexwttiml" wel'e ttdwn during the mon1;lm of ])oceml)fft' to IVhbreh on sunny da,ys when thm'(l was no posJ-.;ibHiiiy of itWol':;:ion" Vf~J'il),1iio:n Ct1J1l. occur in. thjf:l 1!1pse rate clne to uhanging 111'eflf\lll'O mul n(ihel' l't1Jl1cn'lIlttl condit,ions, but it is l>elieved that tho clovin.tiorw from i;hi" ~1d()plied Inpso l'itte ;t1'(: never likely to be more than 20(10 :in om~ el:t,iO n,s the Oh'lOl'Vi~t.ion~ were ea;tried out ~L t.he time of minimulll l'o:fhtctioJl and tho Hnes W01'O wen den,r of' gnt7.es, A fluctuation of this [VIL\Olmt in t.he lapse l'<l,te would introclllce ~1n error of only :3 eXI in the adopted, value of k, whioh would prodn.ce an error of 1 Gmt, or so in height. over a my of :15 miles longth. '.I'ho error due to refraction may be emlNidm:ed as random for different stt1tiollS itnd of VOl'y stilihll ~11l10Ullt, Conflicloring thrht we luwe observations from Bight; stia1jiollS, Rpre:Ml over a pOI'iod of tInee lllonthg in two yeal'8, t,he et1'eet of l'efractioll Crl'Ol'H on the mean value should be quito negligible,

A perLlstLI of COlUlllll ( 8) show» t,hat the scatter of the derived values is only 16 feot, which is very stttisfa.ctory and hI compntible with the above remarks regarding the 01'ro1.·S due to different sources. In doriving tho finetl result, weights have to llO assigned to the values from the VflJriOUA

stations t,tldng into account the total number of obsernttions, tho number 01: days on which ohsel'vatiollt:'; have heon ma,cle u,nd the length of 1iho TloyH, It might, howev~r, l)e l)ointod out t1l11b rOlJoa1i 01JSOl:v,1tions on the Poa,ll\.O d,ay al'(-~ h(}avily eOtl'('11n,tocl t1ll(10von tho ob::IGTvat.ions on COHRocutivo days m:e cOt:l'elat,o(i to flome oxtent, 1)'01' i.nHtanco, it CotH

hal)l'OU tillEd; stlcceilf',ivo OlmOl'VH,ti.ons on. four cl[l,Ys m8.(10 during t,he timo of minimuTIl ]'(}fnLetion lllH,y cOlltlLin tho samo H'yf;tmU(1tic ftrrol', rnuwo ObR{ll'vations ean, thu~, he l'Elgn,nlod (1'\ (1 gOll.oml check nga,inRt. grO:'l::l

MeO!'R in the vortic[1,] angleR acoepted for computation,

Ail regards tuo longth of tho ray" it is ::-:t,ill opon to doubt whother tho weights should 1){) assigll<:Hl propol'til)ufl,l to ]'ociprom11 of tho Jongth of tIm ray or tho recipl'OCttl of tho sqm),f{l of tho longth of hllo my, Ii'ort.mHtt.nly tho :::eatter of tho ol)~orvntions is such tlw,t it cIl)es not lllu,lco much of t~ (lif'f(mmco wl1iehovm: fonn of woighting iR f1ci.opto(1.

Tho wliighted mOfLl1 valuo of the height of Monnii Evm'o,'lt workolli; to ho 2IJ,02B feet; with n prolmhlo orrol' of' ± 0' 8 {(let;. This proLmhlo ()l'l'OI' in clorivo<1, from ill1;Ol'nal ()vidflllOO alollo and i'l likoly t,o btl too sma.ll on account of tho pJ:l~SOlHlO of systnmaiiic errOl'S, BO(1l'illg ill mind j;Jm valious pmmihlo ROUl'ces of el'1'or, it is eonsiclol'Od that tho odds aro 20 j,o 1 !tgl1inRi; this vfLluH hoing ill 01'1'01' hy tl10l'O tlum 10 foot,

'L'h(l height has heen dotermined during the monthR of Deoem,ber to Ma,rch, 'l'his it:! the period when the amount of snow on t.ho {jOP is likely t.o ho least as the north-west wind is hi its full stride. 'Chore is heavy preeipita.tion of snow during the monsoon months--Juno to Soptomhor­n.nd, although thoro is no observational evidence t1Vaila.hle rnga,rding tho change of snow it,llnt the summit, it if> likely to be well over 10 feet,

It might, he of interest t() record hel'e that 1VIa,kfLln whioh l~i/:les from t,he main :-mowy l'a.nge ai; {l, di8!;!llWe oj' 12 ,mile:,>; j;o the east of M'ount

Jt~vm'o;·;(, h;l,:, ",btl bCl'11 I'U-UIJi'lW'ved fo1' huight.. 11'1'11]11 Uw j),j,l',ioIJtillg IliHr:, Lhi8 p(mk dUlnitl<\'LL)~l tho hntl::lC,tpo rat,hor i,han .I\it)unli Evuro::il' lJUc.nWl(1 ,ij-. i::; abo uti .12 wilo!> l1NU'ur.

It is supposed lio he the Hfbll higlteML in iillC\ lYudd ,·\.lltllw8 iJeen vel'y mueh in lihe neWH .lafiely, as a.n Ailleriean Jijxp(l(litloll lll;L(Le ,'L bid. til

(JonqllCl' it in 19M, for tho firClt Lime but; ha,d tu tm'u Imok duo t,o Imd weather and difficult terra,in.

Makillu was observed in 184l)-[iO frulll six low l:yiug st.a,L·ion.,> ill Ihe pta,ins, itti distu,nces of ~thout 110 miles from it. Lih:o l\'[ount Bvol'e:::b, its hoight was also eOlllpubecl with. ,b fa,alLy value uf lihe enet'ficienL of fefmer,ion and without proper cOllsiclel'<\'tiollS of drLtum ttllcl defleot,ion of the plumb-line and the vi~luo adoptoel was :27,7!Hl foot. In] Ui):!-[j:l, obscrvH,tiOl18 Wel'a tltken to this pet~k from live stn.Lion~ eLt distmwe;~ varying from :35 to 80 IDile.~. Tho vu,lue L'efHdtillg from thmm Obr-;Ol'Vibfiions lbfliel' taking due eount of the geoid unclel' l\{u,kiL!n is 27,8:H fnet. This is the value which will bo [tdopted for the future.

It; might be noted thaii ttlUwngh lihe FI.'OSOllii llbsOl'Vfbt,ions enabJe bIlo height of IVloUllt EVe1'0st to he clelierminocl wit.h no high degl'eo of precision, t.lll1Y do not, contribute to tho qne8Lion of the uplift of the Himahbyas. The question of the <.mount of erosion at the top of such high lulls a.lld the l>eCOnchtl'Y xlse to ttehieve isostasy must. st,ill rema,in a matLei' of specubtioll. Although tlto rock Sllllunit is subjecb tu violent seasonal winds, it is never brbl'e of snow fmd the el'oAion is not likely to be cOIlf3iderable.

9. Analysis of the older va.lues of 29,002 feet and 29,:1:41 feet for Mount Everest.--Thc ftbove two Hguros are BO well knowll tha.t to <1voicl

future misunc1erstmldingll regiu'ding them, it; is worJill\v'hile pnlit,ing down their oxact, signi£iea,llec. 2~I,002 feet, is tl, vague hdght, cl(1tonnil1t~(1 fl'om oH,rliol' computa.t;iOlU of 181)0 or fJO which C,111 be rockonod btl ho either 111:1

being above the geoid 01' above tho Evel'est ,':phel'oht so orientocl a,s to he tn,ngential to the geoid. in the plains soutih of Nepal. The datulll surfaec WH,g ignored during iliA fleri vation rmel tho cl)(,fficion t of l'efraut.ioll u~l}d \Va.., fHlulty. The reaSOll,il why it agroes IlO closely wiLl! the UO\V

value is due to alueky cLI,llcollation of error" ll.S the follovl'ing will show.

IDl'l'or in tIw assumed heights of the observing sta,tiolls raised the height hy 8 feet; the neglect of lilumb-linc deilecbiom; ma,de the heigllt lower by about 30 feet. Negleut of geoiual rise botween the plains of 'J3ihiLnmd MOlUlt IDvel'(:)st raised the hoighL by ll5 feei; OJ' [,;0 and takillg "LU exce8si vely h1rgo co(}fficiont or l'efl.'iwtioll lUttdo the height loweJ' by lLbout 120 feet. Jf t.he lar,t two SOLU'ces of errol' heLd uOlJ.spil'ed in the iJltl1le diTeetion, tillO derivecl height would have been in Cl'l'Dl' by over 200 feeb. It will be so en tIm(i bvo SOUl'COS uf erl.'Ol' made li111'l heights lower ~.ncl two higher, resultling in ll. lucky Ct1.ncella,tioll of enol's.

Of muoh greater interest ii~ the l'O~1S01l why Burrarcl, who wttS C(luipped wit,h much better informat.ion, went fLstr<Ly by f\, l1lUch grCl<tt(ll' t11nC)llllt

ill his eOllelusions. He was ono of tho most faillolls geodesist.s of his t,ime a,nd did Et lot of work on the determination of heights of lofty peaks.

In. his Hitnu,lrty,m Geogl.'<\,llhy*, ho gives an t),(j(\ouut of how in 1905 he derivccl the value 2H, HI feet for tho height of Mount Everest by utilizing the ln,tel' observf),t,ions of 1880 a,s \\'011. He was a.ble Lo effeet one

,~ "A sketch of tho Geogmphy 111ld Geology of t.hu Him(ilaya Mountaiu8 u,[ld 'ribet" hy Burrard, 11l1ydon & Heron ( W33 ). pp. 50-67. '

Ii.!

iUl.VOl'GallL illllH'()VUllI.uuL ill hila,!, [1(\ (:ullid Jlwko WlU uf 1.11.0 [;."tocll, kUl)\vludgo un j'nfl'ac,Liull. .H.o wa~; CUHlliu.ecl.t, lIdJd it 1m:·) of ton "0011 c;L,"Ced in Hovoral [lUbliuu,tiollk, Mw,t his Jigllru (If :'lD,lAL ruoL ww, much mom iLeclll'uJ,(3 HUHt :,W, oo::~ j(IO(-.. On page 07, 13 nl'l'iM'c1 COllUllellh; Llmli although 1; IIi:,; Jigul'O i:, by 110 lllonllH fin[l.l, .. Tho hui",!:ht, JU, 1-H lix)t, i.C; NLill prob:l,bly' t,oo sHmU, ,kj it, ]lUi-; yot, 1;0 ho cCIJ'l'lJ(~LOil {Ul' Lhe olfeub-l uf duvlaliiutlH of grn,viLy", He di;;li\lf;~e" Llii:~ C[lll1dLioll 'Lgil,in in deLu,il':' :in a later 11,\.[>01', and POillt.l-:l Oll(; t.he llifhcu\'lIy or lilllling c\, base roJ' height lllell,CmnIJ110n\j or the Hlllllt­In.yn,ll snow ],oid;;:H, Ulll'l'i1l'cl 111;.];:0:, n, fWl!lcLllloJlLal <tnei n, pOl'KiKton!, 01'1'01' uf pl'iuoiple in his iLl'glllllOU[S l'ugm.·ding elwico of datum, .He vi::nliLlizod Llw p()s:sibili t.y uf <tbnOl'lua! dtirl)l'Jn~i,(,ion of' Hua,-l(:)vul by n,s llllWh fl.f, 800 feet Ull.dOl' Tibet" but conLollclod Lhrl>i, this h(l,\lllO b0t~l'illg on tIte qLle~;ti(m of tho hoight:-', of IH~tLk'3 H,wl tlJ,Lt iilw SphOI'oid,ti lwighl;s were IL11

t.lmt wUllkl ho of iut.Lwi:'sL t.o tllC googmphet'8. III view 01' {he l'omitl'lm in .par;;~ 7, it would be itppnl'enli Lha,1i I,his is Hui; con·cct. Tho o8UIHn,l;ioll (It' ui}uiLLal rise bDl,\VUOll tho :,t;cLtions uf olmerv'Ltion [md Mount Evorost jll~l')lveH Ml extm Ktep but it, IUt8 iio be clono,

.Acliw.dly, BUl'J'ftl'c1'i-l figmo oj' :.lO,Ul feet. is eVOlllI1Ul'O vlLgno t.IULll the uarIim- dd,llt'llliwdjull, Although, l'ofmct.iotl JUtS bl10n treated lllm'O l'ntioually, hil-l vrdncs d~rived :fl'om s1iLLtii(llls in the plains ,11'e un l1ll Everest :·\]_)hol'oici, while theso dcrived from hilL st,Ltioll8 :t,ro cLiJove cliil'm'(\l1L lj~vero8t sphGl'Ili.(ls LiLllgmlti;LL to the geoid iLL t-,hUl,e sLrLbioll8,

Hf) visualizod OCU'l'octl'y t1ll1L MIG [Lppliuc1i.iou of delleeLium: would iUCl:0iLSC hi::; ftgmo of :W,14,1 foet, [bUd rocont OLlS{wvi),tioll.s show IIhat this illcmaso wonlcl he only aD foet, The cOHsidel'[I,tion of the geoidal riso, howevo[', which he ignored necessitate.:; n, diminution of over n, 100 feet, so (,h'Lt on t.he wholo (,he above figul'O wuuld he dOel'ettHocl.

10. Summary.---'_I:lm n.ow\y cte'Gul'rninlJd height, of Moun)i \'jvDres\, iB :29,(188 feef;, It is Imt LimeLy tlHLt, ttw elmUengo of itB h.eight dei;ol'lnin,t" tion should hayo been met :,hol'Liy a,ft.er its twtlml CO 11 (Illtlst. , 'I'hiK is the first timo MULt tho hoighL oJ' an impod. .. mt ilmUOlli:lsibJo poak lul,S honll (letel'miued by n, l'igorou8 todmiquo involving ;\, rela.tively complic,LLerl nexus of f;wts a,nel ielen,s. Geodetio ObdOl'Vat.iuflS had to be ciLl'l'ictl dU80 Lo the peak to get qultutita,tivo figlllTli' for tho dist,(nt,ion of tho ll1(~,LU sett-level Hnd the tilt of tho vertic:.L1 produced by the eol08::;us,

The new detenllluatioll :'ltandH in tL e1n,::.;s bv itHelf none[ iLg clm;e t\,gl'CO­

mont wit.h the older va.lue doos Iwt signify that; toiLe 1;\'[,1.01' Wil,S well &,1.01'­mineel. It is l'Oltlly due to the faet; that like ii, nut being cOlup,u'ocl WiUl like, Judged by modern ;c;tandtlol'ds, Ute u;bdiul' cleduel,ion of Lhe lwight of . . 'E J..' WiIS, [c l I 1 I I • I I lVlount 'verest vague III SIWCl'a l'o:,poe ,s, anl. WiLS lUl'C ellee! WLi,l :Ll'go el']'()l'" utl account, of negloc:t, or ineolllplete e0l18idul'at,iuu of' corLain phy:,;imtl factors, It, so ha,ppullec! (,hiLl; by ehnnoe, j,jw V1.LI'iOWj individwLl errors, nit-hough Inrge, have Leaded to ctLlleol DiLch oUter,

There 111'0 severn,] outsttLncliug peake! in the Himii,l,LYILIl mage --IQ, Kallchenjung1.1, N[mga :Pn.elmt, Dlutulagil'i, ete.-whieh also neo<l treatmont similar to t.lmt in t,his Pttl)Cll', Doubt st,ill remn,ilU-J whet.her IQ or IGmehen.iungu, should ocenpy t,he llex(~ III ace. Theil' ~~ccepted heights iue 28,250 foet. and 28,lJH font respcetiveJy iLud t.he <1Hfol'once is well within the m'l'o!'" uf olc1er determination. Some l'oceuli obscl'Va,tiolls hnove been li:tken to i{{mehenjungtt iLnd pl'e1iminary cmnpu­tations show that itR [Ldopterl heighL needs hWl'Oasing b'y GO f(:)e(, or so.

---" .. -- .... --.------.--~---.-.-.--.--.------ .~

" "The Place of l\IUllut Everest in lIi~tory" I,y Col. Sil' H. G. llul'l'nrd, Review, Septemher H)3,i, p, 41i6,

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G. & R.B.--P.O.-·.T.S. ~61-!l·8·fH-(l2fi Lib.

IMPERIAL AGRICULTURAL

H£SEARCH INSTITUTE, NEW DELHI.