46 EXPERIMENTS on TVHINSTONE and LAVA. 



ra(51cr of the refult was ftony or vitreous, according to the 

 mode of its cooling. 



Some peculiar circumftances interrupted the profecvition of 

 thefe experiments till laft winter, when I determined to refume 

 them. Deliberating on the fubilance mofl: 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 mod parts of Scotland, de- 

 notes a numerous clafs of flones, diftinguilhed in other coun- 

 tries by the names of bafaltes, trap, v^Mcken, griinftein and 

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

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

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

 us, and which feems liable to no obje(5lion, fince it is liot 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 invefti- 

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

 the prefent ftate of geology, an obje(5l of conliderable impor- 

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

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



fame 



» In llie courfc of laft winter, when I firft thouglit of refuming ray experiments, 

 1 propofed to this gentleman, that, in imitation of a praiStice, conrimon in the 

 Academy of Sciences of Paris, we fnould peiforni them in company. To this pro- 

 pofal he clieerfully agreed ; btit, before any experiments had been begun, he found 

 liimfelf fo much occupied by profeffional duties, that he could not bertow upon the 

 fubject the time which it neceffHrily required ; and we gave up the idea of working 

 in company. 



f Id charadlerifing the particular fpecimens, I have adopted, with fcarcely any 

 variation, defcriptions drawn up by Dr Kennedv, whofe name I ftiall have occafion 

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

 we have profited by the advice of Mr Dep.iabin, a gcntlernan well verfcd in the 

 language of the Wernerian School. 



