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Part of a Letter from Mr. Stephen Gray, about a Way of Measuring the Heighth of theMercury in the Barometer More ExactlyAuthor(s): Stephen GraySource: Philosophical Transactions (1683-1775), Vol. 20 (1698), pp. 176-178Published by: The Royal SocietyStable URL: http://www.jstor.org/stable/102500 .
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This content downloaded from 194.29.185.71 on Fri, 16 May 2014 23:14:43 PMAll use subject to JSTOR Terms and Conditions
( r763
II. Part of a Letter fro Mr. Stephen Gray} abo«6t a ̂ 7 of MEa0xring tbe Height6 of thc RIercgry in tbe BJrometer wore exaSlg
-CN I N C E X fiw Mr. Dcrbam's Contrivance for meaZ 9 furing the Minute Variations of tlle Mercury in the Barometer, I have had fome Thoughes on that SubjedD X efReemed the Way he mentions (Nb. t3 7. of your PhilFJ<ophical GraafaSioas) with a toothed Ruler and Cir cle on thC Weather-Plate. very ingenious; yet I conceie ved'twtould be more accurate, if there were added fomewhat tO aEl(t the Eye in fetting the Indew tO the Surface of tlle Mercury. This put me upon thinking how to adapt a MicroScope to the Barometer, and tho' I could not, prerently, propore to my telf the moft con- ventent way to effed it; yee upon re-aSuming the(e Thougllts, I overcame tlle Difiiculty, as yoll will find by the DeNicriptiorl J hereirl give of a double MicroCcope9 furniflzed WItlI a Micrometer; by whicil the Mercury's Variations may be obScrved to the ThouSandth Part of an Ench.
A(Fig.6.)A long -fquareTable towards one End is treRed a Square Column, BB. Upon which there nides a Square Socket. C, From one Side whereof proceeds a crooked Arm, D E. At D there is a Screw-Hole to receive the Sct ew, and a.t E a Ring to fupport the Tube of the Mi croCcopes F. From the other Side the Socket, comes 2
Sllort Arm Gs, haVi!^?g a Screw Hole tO receive the long Screw I 1, wllofe lengtll may be about Sixor Seven [rs- CnEs: itS lower Endf by a fmall Hole in its Center, reRs on g1e Erld of a EmIl Screw, that comes through the Screw"Hole, in the /\rm H ; which is fixed on the back <^de of tEze (8n,lumn ; tllC per End of tlle Screw is filed
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( t77) IeSs than the Body of the Screwf and goes through the Genter of the Round Plate uZithout {haking; and to pre vent sits doing fo, either upwards or downutards, there is added a fpringing Plate N, which keeps tbe Shoulder of the Screw cloSe to the under &de ofthe Plate K; Qver this Plate there goes atl lndex 0, and o57er that an Handle Lt uporl the End ofthe Screw whicb comes through theCen ter of the Plate, which I (hould before have told yous is ris7ered to the Top of the Colutnn B B. The Teeth of tlle ssreY mTla be of that Sae, as tO have juR Ten in an Inch,The for& fide of thc Colum£l muR be disrided into Inches atld Tenths5 beginning about the HeigEit of the Secker H, wliere the lower end ofthe Screw reRs, and fo contxnue to tlle Top of the Column. The Limb of the Round Plate muR be divided into an Hundred Parts In tlle Facus of the EJ7e*(i1aSs of tlle MicroRcope is tixed an Hair, or very firle Silver TVire, i-n a Horizantal PoGtion.
I come now to {hew the Ute of-the tnlfl;rutuent com- bined W;tt1 tIae Barometer, tn which I llzallbe very briefX it5 U2 iing eafily apprenended by the D¢fcriprlon.
Take hold of t0e Handle, and, looRing through the MicrokopeX tutAn t0le SCreW ttll you haxte brough; the Ear to touch as it wtee the Surtace of the Mercury M r then i2Xve xv1zat DiviSons are cut on the Column, by the upper or und?r Ed tit the SockerX whirh are TerEths cif a.n Tnch. See likewiSe to what Pat¢ts the In dex potnts on t]e Limb or the Round Plate, svhich are TIundreds of a Tenthl or Thoufand Parts of arJ [nch; when you pfirce;ve th+o ^ Nfercury varled, ratE or d^preSs the %3ct%0p till t0t Hait be brougllt to its Surfawa as beSore ; then by (ubl}raAing the lelIer fr¢tz} t1;le great- ev of tlle TwcobServed Numbetso yon ws2! have the Va ttatson 1n tnchu$ and Thoufand [)artse
D d
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( T78 )
This InArument becomes a Micro£teter on the fame Principles, tho' I was obliged to alter its Struaure firom that uSed with the Telefcope, which utas firA invented 3by Mr. GaJ^saigx, improved by Mr. t0wxlyt artd defcribed by Dr. Hook, as appear.s by Mgmb. t5. and 29, of Mr. Oldeabgrg's PbiloJ<opbicaX tranfaaion$ ; to which Deb feription, it i did not acknowledge my felf beholsSen, were to do great InjuRice to the Authors of that excel er taxrention.
The lXhermemeter is capable of the -lIke Improveo ment, but then the Screw of the Mi£romerer muIl: be much longer, and the MicroScope will require a {onger Tube, to the End the Body of the Ob{erver be not tOO near the Thermometer, and by its warm EfEluvia decc;ve his Judgment in the Airi Temperature.
caatarrl/, May ^* x6p 8*
lV Part of a Letter from Dr. William Muf- grave, Fellow of tbe College of PbyJiciaSy and R. S. to Dr. Sloane s concerning the Caxre of the Necegay of Breatbing
OU know, how di5calt it has been thought} 1 to account for the principal Ufe of Refpiration-.
Nothing is more evident, thatl that breathing is, from the very Moment of our Births perpetuaIly neceI!ary to Li*; yet nothlng more in the Dar}sX than the true (:auSe and Reafon cfthat Necel1itzr.
Dr. [brnWox aSerts the chief LTfe of ReSpirationX to bnfi0 in rnaintasning a due hIotion- of the Blood.
0*R
( T78 )
This InArument becomes a Micro£teter on the fame Principles, tho' I was obliged to alter its Struaure firom that uSed with the Telefcope, which utas firA invented 3by Mr. GaJ^saigx, improved by Mr. t0wxlyt artd defcribed by Dr. Hook, as appear.s by Mgmb. t5. and 29, of Mr. Oldeabgrg's PbiloJ<opbicaX tranfaaion$ ; to which Deb feription, it i did not acknowledge my felf beholsSen, were to do great InjuRice to the Authors of that excel er taxrention.
The lXhermemeter is capable of the -lIke Improveo ment, but then the Screw of the Mi£romerer muIl: be much longer, and the MicroScope will require a {onger Tube, to the End the Body of the Ob{erver be not tOO near the Thermometer, and by its warm EfEluvia decc;ve his Judgment in the Airi Temperature.
caatarrl/, May ^* x6p 8*
lV Part of a Letter from Dr. William Muf- grave, Fellow of tbe College of PbyJiciaSy and R. S. to Dr. Sloane s concerning the Caxre of the Necegay of Breatbing
OU know, how di5calt it has been thought} 1 to account for the principal Ufe of Refpiration-.
Nothing is more evident, thatl that breathing is, from the very Moment of our Births perpetuaIly neceI!ary to Li*; yet nothlng more in the Dar}sX than the true (:auSe and Reafon cfthat Necel1itzr.
Dr. [brnWox aSerts the chief LTfe of ReSpirationX to bnfi0 in rnaintasning a due hIotion- of the Blood.
0*R
This content downloaded from 194.29.185.71 on Fri, 16 May 2014 23:14:43 PMAll use subject to JSTOR Terms and Conditions
