44© A Chemical Analyfn of Thru Species of Whinjlone, and Two of Lava, 



It foftens at 32 of Wedgwood, and does not lofe any weight in fires between 150 and 



169. After being boiled in muriatic acid, it left 68 parts /i^r ««^ undiflblved. Its fpe- 

 cific gravity is 2.823. 

 In 100 parts I found, 



Silex, ■ - - - . . - . 50.75 



Argil, - - - - r - . 17-50 



Oxydeofiron, - - - - - - 14.25 



Lime, .--. _. . lo 



Soda, about ■ - - - . - - 4 



Muriatic acid, about - - - - - - 1 



97-5° 

 In analyzing thefe two lavas, I examined the different folutions, with particular atten- 

 tion, for magnefia, and fulphuric acid ; but could not dete£t any traces of either of thefe 

 fubftances. 



The refults of thefe analyfes fliow, that whins, and a certain clafs of lavas, taken from 

 remote quarters of the globe, confifl: of the fame component elements, united in each, 

 nearly in the fame proportion. The only circumftance in which they materially differ, is 

 the lofs of fome volatile matter in the fire, which is peculiar to the whins alone. 



We need not be now furprifed at the fadls mentioned by Dolomieu, and others, of foda 

 being found about volcanos, or upon the furface of lavas; as it has thus been fhown to exift 

 in thefe fubftances in combination with their earthy bafes. 



The fa£l;s and experiments I am next to mentsQn will psove, that whins and lavas are 

 not the only ftones which contain foda ; and will even render it probable, that this alkali is 

 widely diffufed through mineral bodies, 



Soon after I firft difcovered it in whins, and had communicated the circumftance to Sir 

 James Hall, he fent me, from a high fandftone rock in his eftate, a quantity of the ftone 

 decompofed ; and informed me that there was a faline efflorefcence mixed with it, which 

 was coUedled along with the loofe matter, and which feemed, by the tafte, to be fea-falt. 

 The place has been long called by the common people the Salt Heugh. By fimply boiling 

 fome of the decompofed fandy part in water, and afterwards filtering and evaporating the 

 water, I obtained regular cryftals of fea fait, mixed with a fmall quantity of fulphate of 

 foda. 



Hence it appeared likely, that common fait would be found to be one of the component 

 parts of ordinary fandftone ftrata. To verify this important obfervation, I next examined 

 two hard and folid fpecimens, taken from fome depth below the furface, and perfectly free 

 from decompofition. The firft was broken from a quarry about two miles to the weftward 



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