A Chem'cal Analyjis of Three Species qfWhinflont, and Two $f Lava. 411 



According to the refults of thefe different procefles, there are, in 100 parts of the bafalt 

 «fStafFa, 



Silex, - . _ - - . 48 



Argil, - - - - - - \6 



Oxyde of iron, ^ . . - • i5 



Lime, - - - . - . g 



Moifture, and other vol. matter, - . - . 5 



Soda, about - - - - - 4 



Muriatic acid, about - - - - i 



99 

 I have thus detailed exa£l:ly the various experiments performed in analyzing this fpecies. 

 As all the other whins, and the lavas, which follow, were analyzed in the fame manner, 

 and exhibited nearly the fame chemical properties, the refults only, in each example, fliall 

 be mentioned. 



ANALYSIS IL 



Whin of Salijbury Rock. 



The fpecimen employed was chofen from the fouth fide of the cragg, and was perfe£tly 

 hard and free from decompofition, as the particular fpot from which I broke it had been 

 quarried a fliort time before. 



A defcription of its external charaflers may be found in p. 54 of the 5th vol, of the 

 Tranfaftions of the Royal Society of Edinburgh, (or p. 15 of our prefent vol.) Its 

 powder is light greenifli grey ; but after being wet, acquires a dirty green colour. When 

 heated to rednefs, it becomes light brown. Though not attracted by the magnet in its 

 natural ftate, it becomes magnetic after being heated red hot. It does not effervefce with' 

 acids. When expofed to a low red heat for half an hour, whether in fragments or in pow- 

 der, it lofes ^percent, in weight. It foftens at 55 of Wedgwood. Its fpecific gravity 

 is 2.802. After being boiled, in the ftate of fine powder, in ten or twelve parts of 

 muriatic acid, the infoluble refiduum amounted to 65 per cent. 



I analyzed 200 grains of this whin, and found that it contained, in 100 parts, 

 Silex, - _ _ _ . _ 45 



. Argil, - - - _ , _ ig 



Oxyde of iron, - - - _ _ ly 



Lime, - - - , . . g 



Moifture, and other vol. matter, - - - 4 



Soda, about » - - . - - 3.^ 



Muriatic acid, about - - - - i 



98I;' 

 (To ie fsticludfd in tur ncaU) 



Fuftbtr 



