74 EXPERIMENTS on WHINSTONE and LAVA, 



the greateft diverfity. Some vertical ftreams muft have flowed 

 •while the mountain was yet low ; others may have found vent 

 at a low level; in both which cafes, the preffure would be 

 ieeble : whereas other ftreams, communicating with elevated 

 lateral eruptions, would fuftain, in their lower parts, the full re- 

 action of deep columns of liquid lava, and may be expected 

 to exhibit the effects of great preffure. Should any future tra- 

 veller be fortunate enough to meet with a nodule of calcareous 

 fpar in a lava, occupying the crevice of a mountain formed 

 by undoubted external eruptions, all that has been faid of the 

 effects of preffure would ceafe to be hypothetical, and this fun- 

 damental article of Dr Hutton's theory would be eftablifhed 

 beyond difpute. 



I have now examined the relation between whinftone and 

 lava in various points of view ; and the refult of the investi- 

 gation, by mowing the intimate connection between the two 

 claffes, tends ftrongly to confirm the ideas of Dr Hutton. I 

 flatter myfelf, likewife, that the experiments, independently of 

 the general views of geology, are of fome value, by account- 

 ing for the ftony character of lavas, and thus enabling us to di£- 

 penfe with the various myftical fuppofitions which have of late 

 perplexed the hiftory of volcanic phenomena. 



TABLE 



