An Account of an Uncommon Phaenomenon in Dorsetshire: In a Letter from John Stephens,M. A. to Emanuel Mendes da Costa, F. R. S.Author(s): John StephensSource: Philosophical Transactions (1683-1775), Vol. 52 (1761 - 1762), pp. 119-123Published by: The Royal SocietyStable URL: http://www.jstor.org/stable/105599 .

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XXII. 24? Sccount of at gncommor Phno- genox ir Dorfet(liire: In a Letter fro lohn Stephens, M. H. to Emanuel Mendcs da CoPta, F. R. S.

S I 1t, Read April 9, /t S no eSay, howel7er imperfed) which

7 ^, tends to illuRratc the operations of natureX can be unacceptable to the learned, I took the liberty to addrefs myfelf to you, in Setting fortl the following {hort, but juIl account of a phaerlo menon obferved in our c)wn country, and, as far as I can recolle2, rlot hitherto defcribed.

In the month of AuguR I7sI, the air having been for fome time remarkably hot and dry, was change(l of a fudden by a heavy fall of raill, and a higll i:outll- wefc wind; the cliffs near Cllal mouth, in the wCitel n part of DorSetnlire, prefently after this alteration of the atmorpllereZ lDegan to fmoke, alld foon after they burned) witls a vifible though a fubtil flatlae, for Se- Yeral days isucceilvely; and continued to fluole, and femetimes to buln, at intervals, till tlle approacll (f winter: nay, ever Slace tllat time, - efpecially after any great fall of rain, tlaunder and ligIas:l-izgX or a l<;gh foutll-weIt wind (nthich drives the fea svitl <,reat violence againI:t the cliSs, a.ncl beats off large pieces of them), tlle cliH-s continue to fnoke, and iotnetines to burn with a vifible flanze; vllic1]5

sluring the fummer months, is frequently obSelved n tlle night-time. On examining thefe CliffS? ill tbe year I7vi9> I diScovereel a great quantity of pyr;tes

1'lOt

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[ I20 ]

not in any regtllar lltata, but interfperfed in large nzaXes through- the earth, and uthich proved to be martial; of marcafites, which yielded near one tenth part of conzmon fulphl3r; of cornua ammonis of dif: ferent fises, and other {hells, but of the bivalve claEs) wlzicll svere cruRed over, and as it were mineralized} svith the pyritical Inatter; of belmnites, alfo cru{ted over witll the like tzbftance: and the cliEs, for near two miles long, asld from the furfice, to 35 or qo feet deep even to the rocks at higlz-water mark, were orle bed of a dalk coloured loams Arongly cI-larged with bitunzen. Mereover, I foun-d alfo a dark coloured fubRance, rdcnlbling coal-cinder; fome of which being rwdcredX ax,d walhed in di ftilled rain-water, upc)n filtrating the water, alld eva- porating it Rowly to a pellicule, its lialts Ihoot into fine clyItals, and a}rpear to lJe no more than a mar- tial Yitrio\: one ounce of tl}is cinder-like fubItance yielv3s Dne drachm of falt. I gathered up about one hundred pounds weigllt of the dafferent kinds of tIlofe pyrita, marcaiitesa &c. whi£h srrere laid in a heapa expofed to tlle aJr, and every slay fprinkled with svater: the confequence saras, that, in about ten days time, they grew hot, fOOt1 after caught fire, burned for feveral llours, and fell into duR, Hence, there forc, it is inzagined, tl)at l:heSe martial and fulphurous foffills, by being expefed to the air and svet) by being agitated by tbe beating of tlle Sea, and, if I may ufc tlle expreilon, by being eleEtrified by the ftlbtil flanle of the lightning, ta-ise fire, which is ivoured -by the bituminous particles contained in the loan:l, and burIl till all their phlogiRon is confuxlled, and theirx iron, or martial earth;, is diffiolYed in ttle acid cf fxllphwur;

wliich

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which conRitutes tlle martial vitriol, found to be neat the one eighth part of this cincler-like matter.

When the cliffs were obServed to burn in the night-time, the flame was plainly perceived by a fpeEtator at a diRance, but, when he drew near to the place, feemingly on fire, he could perceive a finoke, but no flame. In the day-time, notlaing lDut a fInoke v;tas perceived, except the fun IBined, whvn the cliffs appeared, at a diIlance) as if they were co- rered with pieces of glafs, wllich refledced the funts meridional rays; but, upon drawing near to tbe places, whele thefe luminous appearances were per- ceived, they difappeared, and the cliffs feemed to lte covered with fmoke, which Itunk of a bituminous and fulphureous matter.

I have alfo been an eye-witnefs of the fame kind of flame arif1ng from the Lodes in Cornwall, efpe_ cially fuch, as contained a great quantity of mundic and martial pyrites. Three times I have feen this flame arife from the eartll in the night, and once in the middle of the day. In the night, a perfon, Ilanding at a little diIlance, would imagine, that the place was all on fire, and even on drawing ntar tlae fame, he perceives himfelf furrounded with flame but is not hurt; and in four or fiste minutes time, he pelceives this flarxle to dwcleaie, and fall into the eartil. In the day-titne, tlle flanle is of a different colour, and not much ulllilie the flatne, which a-riIEs from a fulnace. 1there are Severa1 mitzes dilcovctcd in tTlis county by tlefe mineral fires, where tlzXe were nO fymptoms of fecll mines before; but it ip generally obf>rved, tlwat they abound with marcafite and pyrites. Moreo^7er, tllefe mirleral flames, ariflng

YOL. LII R f;vin

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[ 122 } from igllited pyriuy are frequently difcovered in thc bottom of mines and coal-pits; and are oftep detri mental, and fometimes dePrraftive, to the miners; which mie the late learned Dr. Woodward, and othersX imagine} that they were sapours arlfing *om an abyEs

Frotn; what has been faid therefore, we may} in my humble opinion, draw the following concl;uEions.

I. That a11 fabterraneous firess even thofe of Hecla,: VeI;vius, and iEtna, together with t}iofe ob_ ferved in the mines and coal-pits, are cauSed by the he-at and fixing of pyrites and marca^stes.

. That the waters of our hot baths derive their heat from paSing over a bed of ignited pyrites. In- deed the folid contents of thofe waters do evidently prove this aINertion being nothing more than fuch parZ ticles of the pyrites as are foluble in water.

3. That thefe mirseral flam-es will be more or lefs fubtil, according tQ the minutenefs of the par- ticles of the combuRible matter, and- the quantity of phlogikon, which they contain.

4* That the convulfive mottons and tremblings of the eafh are cauSed by the heat of the burning pyrites expanding the air contained itl its bowels. This is clearly proved, by their caufing, immediatcly aficer, an eruption of the eaxth, which generally difcharges a dark coloured cinder--like and frothy matter. And,

5. That thoSe places, where the earth contains ie greateR quantity of pyrites and marcafites} will be moll liable to- thefe convulflve motions-and-tremP blings, no other natural caufevcontradiEtory.

However, I Shall, with great refipe&cf fubmit thefe obServati-orss to the confideratiosx Qf due Prefident and

Fellows

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[ 23 ] Fellfows of the Royal Soc-iety, to whom, Sir) if you will be fo kind as to communscate them, you will greatly oblige,

S I R, Your very humble fenant, &c

WoodRock-Streets r April4, I76X. . John Stepens.

XXIII. iqddutional Obyersvtions gpon J?me Plottes of white Gla80 fogrd a Hercula- neum: Ix a Lenter to Charles Morton, M. i:3. R. S. S. B y J. Nixon, i?. M. and F. R. S.

Dear Sir, Read April 9, T N a paper, wEsch I had the honour

1761- 1 to preSent to this learned Society about * two years ago, I offered my thoughts upon fome plates of white glaEs found in the ruins of Hercula_ neum. I now beg leave to add fome more obServa_ tions, with a view partly to explain and fupport what l then delivered, and partly to communicate I*uch new informations, as I have fince received, relating to the fame fubjeEt.

I obSerared +, upon the authorities produced by Monf. Renaudot +, tha$ glaEs plates we-re not applied

* Phil Tranf. Vol. t. Part I[. + Ibid. p, 602.

X Mem, de PAcad. des InfcriptVol. It

R 2 fot

[ 23 ] Fellfows of the Royal Soc-iety, to whom, Sir) if you will be fo kind as to communscate them, you will greatly oblige,

S I R, Your very humble fenant, &c

WoodRock-Streets r April4, I76X. . John Stepens.

XXIII. iqddutional Obyersvtions gpon J?me Plottes of white Gla80 fogrd a Hercula- neum: Ix a Lenter to Charles Morton, M. i:3. R. S. S. B y J. Nixon, i?. M. and F. R. S.

Dear Sir, Read April 9, T N a paper, wEsch I had the honour

1761- 1 to preSent to this learned Society about * two years ago, I offered my thoughts upon fome plates of white glaEs found in the ruins of Hercula_ neum. I now beg leave to add fome more obServa_ tions, with a view partly to explain and fupport what l then delivered, and partly to communicate I*uch new informations, as I have fince received, relating to the fame fubjeEt.

I obSerared +, upon the authorities produced by Monf. Renaudot +, tha$ glaEs plates we-re not applied

* Phil Tranf. Vol. t. Part I[. + Ibid. p, 602.

X Mem, de PAcad. des InfcriptVol. It

R 2 fot

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