Of WHINSTONE and LAVA. 8i 



it became gelatinous ; and being evaporated to drynefs, and di- 

 luted again with water, i grain of filex was left. The remain- 

 ing folution produced, to the laft drop, cryftals of alum *. I 

 diflblved thefe cryftals in water, and precipitated the argil 

 by carbonate of ammonia. After being carefully waflied, 

 dried, and heated red hot a quarter of an hour, it weighed 12 

 grains. 



8. The brownifli matter, No. 6. infoluble in cauftic potafli, 

 feemed to be oxyd of iron; and after having been heated red hot, 

 weighed 24; grains. I powdered this mafs, and poured on it 

 fome acetous acid, in order to deted magnefia ; but nothing was 

 diflblved. It was next treated with nitric acid, which diflblved 

 the iron, but left 4 grains of filex. The iron being precipitated, 

 dried, and heated red hot, weighed 20 grains, and was magne- 

 tic. Sufpefting that fome argil might ftill be mixed with it, 

 from having efcaped the aflion of the cauftic potafli, I diflblved 

 5 grains in muriatic acid, and precipitated the iron by Pruflian 

 alkali. Having feparated the blue precipitate, I boiled the folu- 

 tion with carbonate of foda, and obtained i grain of argil. 

 Thefe 20 grains confifted, therefore, of 16 grains of iron, and 4 

 grains of argil. 



The remaining part of the iron was melted for an hour, with 

 ten times its weight of nitre, in order to detedl manganefe. The 

 mixture, howeven when cold, was not greenifli ; and water 

 made a colourlefs folution of the faline matter, which did not 

 become turbid, when expofed fome days to the adlion of the 

 air %. 



Part I. L 9. The 



* It therefore contained none of the 'earth which Vauquelin lately aifcovered, 

 and to which he has given the name of glucine. 



4" I THINK, however, it is probable, that this bafalt contained a fmall quantity of 

 tnanganefe, both from the browniih colour of the folution, No. i. and from the 

 green colour which the undiflblved refiduiiib gave, by fufion, with cauftic potafh. 



