Of WHINS ^ONE and LAVA. %$ 



in thefe (tones ; and their confiderable fufibility favoured the 

 fufpicion. 



Soon after thefe analyfes were made, I obferved another cir- 

 cumftance, which amounted to an abfolute proof of the whins 

 containing fomething of a faline nature, in combination with 

 their earthy bafes. Moft of the artificial cryftallites, made by 

 Sir James Hall, which I had always an opportunity of exa- 

 mining, threw out on their furfaces, two or three weeks after 

 their formation, a white efflorefcence, which had a Very fall 

 tafte. It was in too fmall quantity to be collected and exami- 

 ned ; but when warned off, it was often formed a fecond time. 



I was thus convinced of the exiftence of fome faline fub- 

 ftance in thefe bodies, and made different experiments with fe- 

 veral of them, in order to feparate it, and afcertain its nature ; 

 and foon found that it was foda. 



I shall next defcribe fome of the methods by which this al- 

 kali was moft eafily feparated from the earthy parts of the 

 Whins. 



Experiments to obtain the Soda, and determine its Quantity, 



Having broken fome of the bafalt of Staffa to fmall frag- 

 ments, I weighed 400 grains, and ground the whole with water 

 to an extremely fine powder, in a Wedgwood mortar. The 

 powder, and the water with which it had been ground, were 

 'then put into a fmall retort, and mixed with about 1200 grains 

 of fulphuric acid, which I had carefully diftilled for this ope- 

 ration. I placed the retort in the fand bath of a fmall furnace 

 which I ufe for analyfes, adapted a receiver, raifed the fire till 

 the acid began to diftill flowly, and carried on the diftillation 

 to drynefs. Water was then poured into the retort, and boiled, 

 the mixture thrown on a filter, and the undiffolved refiduum 

 fufficiently warned. This refiduum was njxt treated a fecond 



time 



