EARTH A N D 



LAND S. 



25 



monly called rd^//^;?-j/?c?y^^, which Is a brown clayey tripoli ; and, sti^ata 



between th 



ilone and the above-mentioned fand-flone 



a 



flratum containing both mixed together. High on the fides of the 



hills towards the volcano, I found a whitiili, argillaceous fubfrance, 

 through which aqueous and fulphureous fleams, from the very 



ghbourhood of 



nually riling, and made 



the place intenfely hot : its tafte is flyptic, and I believe aluminous *. 

 Some native fulphur was to be {qqw in this earth, together with 



r 



feveral green Ipecks or marks of copper. Under thefe folfataras, 

 (whichj at each eruption from the volcano, emitted greater quanti- 



• 



of hot fleams) 



feveral hot well 



clofe 



the high-water 



mark, which, however, feem not to be in the leafl fulphureous. I 



E 



found 



* All the neighbourhood of the folfataras in Tanna contauis I'olcamc produftions. The 

 ftones near it are lavas ; the fand conlifts of volcanic afhcs, and the foil is clay mixed with 

 this fand. It is therefore beyond any doubt, that the clayey white fubftance, found in the 

 very fpiraculum, Is nothing but a new modification of the volcanic produ6iions. The firft 

 who ever had this idea, that clays are produced by an operation of the vitriolic acid upon vi- 

 trefcent or vitrified fubftances, is the ingenious Mr. Beaume^ vf\xo founded it oh a feries of 

 ■experiments. But the very firft, \^''ho applied this idea to the great operations of nature in 

 the folfataras, is Mr. Fcrhcr^ the moft intelligent, and mod accurate mineralogical writer of 



r 



this age, which may be fcen more at large in his xith letter, dated February 17, 1772, pub- 

 lilhed in his Travels through Italy ^ tranflatcd by Mr. Rafpe. Sir William Hamilton, that in- 

 defatigable obfervor of volcanos, had-already examined the folfatara in 1771 ; but he feems, 

 at that time, not to have had the leaft intimation of this rem*arkable procefs ; fince, in his 

 letter to Dr. Maty, dated March 5, 177 1, he calls the operation going forward at the folfa- 

 tara a calcination : and he mentions to have /ecu half of a large piece of lava perfectly cai.ciked, 

 Kvhiljl the other half out of the reach of the vapours^ has hccn untouched \ and in fome pieces ^ the ccn- 

 irefcc77is to le already converted into mv^ marble. Tkcfc whltifli' clays ?;;/V/7f, evenly their 



-appearance^ fays Mr. Fcrber, p, 16^, he inijl alien for liine-fl one \ no wonder, therefore, that 



thty {hould fuggefl the idea' of calcination and of true marble. 



