Extract of Another Letter, from Mr. Hamilton, to Dr. Maty, on the Same SubjectAuthor(s): Mr. HamiltonSource: Philosophical Transactions (1683-1775), Vol. 61 (1771), pp. 48-50Published by: The Royal SocietyStable URL: http://www.jstor.org/stable/106071 .

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48 3

II. EJctraS of a?sother Letter, from Mr. Hamilton, to Dr. Maty, on tbe fiame SubjeS.

Wapless Marcll 5, 1 7 7 1.

Read May 3° C I NCE I had the pleafure of fending I771@ 3 you my letter, in wbich the nature of

the foil of more than twenty miles round this capital is defcribed; examining a deep hollow way cut by the rain waters into the outI1de cone of the So]faterra, I diScovered, that a great part of the cone of that ancient volcano has been calcined by the hot vapours above defcribed Pumice calcined feems to be the chief ingredient, of which Several fpecimens of (as I fuppofe) variegated uniform marble are compoSed, and the beautifill variegations in them nzay have probably been occafioned by the mineral vapours As eheSe fpecimens are now fent to the Royal Society, you will fee that thefe variegations are exadcly of the fame pattern and colours as are met in many marbles and flowered alabailersi and I cannot help thinking that they are marble or alabaflcer in its infant llate. What a proof we have here of the great changes the earth we inhabit is fubjedc to ! What is now the Solfaterra, we have every reaSon to fuppoSe, to have been originally throwrl llp by a fubterraneous explo- fion from the bottom of the fea. That it was long

I aa

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[ 4d9 ] an exilling volcano, is plain, from the ancient cur- rents of fava, that are llill to be traced from its crater ro the Sea, from the (Erata of pumice and erupteel matter, of which its cone, in common with thofe of all otller volcanos, is compofed, and fiom the teili motly of many ancient authors. Its cone in nzany parts has been calcined, and is-Rill ca]cining, lJy the hot vapours that are continually iffiuing forthtllrough its pores, and its nature is totally changed by this chemical procefs of nattlre ln the hollow eJayy where I nlade tlzefe renzarks, you fiee the different Ilrata of erupted rllattex, tllat :conlpoSe thv cone in lionze places perfe&]y calcincd, in others not, accord ing as the vapours have found means to infinuate themfelves more or lefs.

A hollow way calt by tIle rains on the lzack of the mountain, on which part of Naples is fituated, to- wards Capo di China, flacws that the mountain is cotnpoSed of llrata of eropted matter, among which are large maIXes of bitumen, in whicl] its former Rate of fluidity is very vifilble. Here it was I dif- covered that pumice Ilone is produced from bitu- men, which I believe has ncat yet been remarked. Some fpecimens Shew evideltly the gradual procefi from bitumen to pumice, and you will obServe that the cryRalline vitrifications, that are vifible in the bitumen, fuffer no alteration, but remain in the fatne Rate in the perfed} pumice as in the bitutnen.

In a piece of firatum, calcined from the .out- f1de of the Solfaterra, the form and texture of the pumice Itones is very diScernible. In feveral parts of the outf1de cone, this calcining operation is Rill carried on by the exhalation of conliant very hot

VOL. LXI. H and

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E sio ] and damp vapurs, impregnated with lts, fuiphurt alum, &c Where the above-tnentionedfvapours have not-operatd, the lirata Qf pumice and erupted maeterX that compoSe the cone of the Soliterra, are like thoSe of all the high grounds in its neigh- bourhood, which I fuppoIE to have been thrown up likewiCe by explofion. I have feen here, half of a large piece of lava perfedly calcined, whilli the sther half out of the reach of the vapours has been untouched; and in fome pieces the ceater feems tsy be already converted into true masble.

The variegated fpzecimens then, above deScribed, are nothing more than pumice and erupted mattera after having-been aEed upon in this manner by the hot Yapours; and if you confider the proceE, as I have traced it, fFom bitumen to pumice, and fFom pumice to marble, you will think with me that it is difficult to determine the primitive Rate o£ the many wonderful produEtions we fee in nature.

I fbund in the t of the mountain of Pau81ipe, a fFagment of lava: one fide I poliShed, to ffiew it to be true lava; the other ffiews the figns of the tu,fit, with which it is incorporated. It has evi- dently bcetl rounded by fEidion, and molt probably by rolling in the fia. Is it not natural then to ima- gine that there muR have been volcanoes near this fioot, long before the fbrmation Qf the mounuin of fiaufilipo > This little ffine may perhaps raiie in your mind fiuch reflitions, as it did in mine, relative to the great changes our globe fufErsX and ttne proba-* bility of its great antiquity

III J

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