46 EXPERIMENTS on WHINSTONE and LAVA. 



rafter of the refult was flony or vitreous, according to the 

 mode of its cooling. 



Some peculiar circumftances interrupted the profecution of 

 thefe experiments till laft winter, when I determined to refume 

 them. Deliberating on the fubftance moft proper to fubmit to 

 experiment on this occafion, I was decided by the advice of Dr 

 Hope *, well known by his difcovery of the Earth of Stron- 

 tites, to give the preference to whinftone. 



The term whinftone, as ufed in moft parts of Scotland, de- 

 notes a numerous clafs of (tones, diftinguifhed in other coun- 

 tries by the names of bafaltes, trap, wacken, grunftein and 

 porphyry. As they are, in my opinion, mere varieties of the 

 fame clafs, I conceive that they ought to be connected by fome 

 common name, and have made ufe of this, already familiar to 

 us, and which feems liable to no objection, fince it is not con- 

 fined to any particular fpecies f. 



The following experiments were performed with various kinds 

 of whinftone, and have likewife been extended to lava. To investi- 

 gate the relation between thefe two clafles of fubftances, feems, in 

 the prefent ftate of geology, an object of confiderable impor- 

 tance ; for they refemble each other in fo many refpects, that 

 we are naturally led to afcribe the formation of both to the 



fame 



* In the courfe of laft winter, when I firfl thought of refuming ray experiments, 

 1 propofed to this gentleman, that, in imitation of a practice, common in the 

 Academy of Sciences of Paris, we mould perform them in company. To this pro- 

 pofal he cheerfully agreed ; but, before any experiments had been begun, he found 

 himfelf fo much occupied by profeflional duties, that he could not beftow upon the 

 fubjecl: the time which it neceffarily required ; and we gave up the idea of working 

 in company. 



\ In character: fing the particular fpecimens, I have adopted, with fcarcely any 

 variation, defcriptions drawn up by Dr Kennedy, whofe name I fhall have occafion 

 frequently to mention in the courfe of this paper. In the employment of terms, 

 we have profited by the advice of Mr Deriabin, a gentleman well verfed in the 

 language of the Wernerian School. 



