( 5S ) 



we know that fufion readily follows, when 

 filex, alumine, and lime are mixed in the 

 proportion of 3, i and i. There was no 

 lava on which I made experiments, in which 

 I did not find thefe three kinds of earth ; 

 and though they might' not be combined 

 exadtly in this proportion, their combi- 

 nation was yet fuch as to render almoft 

 every lava fufible in the furnace. The lime, 

 which, in the dry way, ads as a flux to the 

 filex, is in a great degree diminifhed in the 

 decompofition of lavas, forming fulphate 

 of lime by its intimate union with the ful- 

 phuric acid ; and hence we have one im- 

 pediment to the fufibility of thefe lavas. 

 The diminution of the alumine, arifing from 

 its combination with the abovementioned 

 acid forming fulphate of alumine, which is 

 afterwards detached and carried away by 

 the rains ••'", will likewife be another obllacle; 



* To prevent any ambiguity, it may be proper to re- 

 peat what 1 have faid in Chap. II, that the pretended 

 tranfmutation of filex, or any other earth, into argil- 

 laceous earth, in the decompofition of lavas, has no 

 exiftence ; fince, in this c^ie, that earth likewife is di- 

 miniflied, from the caufes alleged above. 



E 4 to 



