EXPERIMENTS on WHINStONE and LAFA. 67 



ferences of refult we have obferved between the individuals of 



the fame clafs *. 



So clofe a refemblance affords a very ftrong prefumption 111 

 favour of Dr Hutton's fyftem, according to which both claffes 

 are fuppofed to have flowed by the aftion of heat ; but the cir- 

 cumftances under which they were expofed to this action being 

 materially different, we have reafon to look for indications of 

 that difference. Such are not wanting. 



Calcareous fpar frequently occurs in whinftone, either m 

 veins or in detached nodules, but is never found in lava, and 

 could not exift in a volcanic dream ; for heat, in fuch cir- 

 cumflances, would infalUbly drive off the carbonic acid, and 

 compel the lime to unite with the other component elements of 

 the mafs. In whinftone, which Dr Hutton fuppofes to have 

 flowed, at fome remote period, in crevices of the earth, at a great 

 depth below what was then its furface, the weight and ftrength 

 of the fuperincumbent mafs of ftrata f has been fufficient to 



I 2 refill 



« Though chemifts have hitherto overlooked, in their experiments, the mode 

 in which bodies were cooled after being reduced to a (late of fulion; yet many re- 

 fults, which we are now entitled to afcribe to (low cooling, have been occafionally 

 obferved. The flag of a furnace bears a ftrong refemblance to what we have call- 

 ed the liver cryftallite, and is probably formed in the fame manner. I have feen a 

 mafs poffefTing, in a great meafure, the ftony charader of whins and lavas, which 

 was produced in a lime-kiln by the fufion of an impure limeftone ; and Dr Beddoes 

 has obferved a cryftallized texture in the flags of fome iron furnaces. I am intormed, 

 that the celebrated Mr Klaproth has defcribed fome ftriking examples of cryftal- 

 lization after fufion, which he obtained in expofing various fubftances to the heat of 

 the porcelain furnace at Berlin. 



+ It may be aflied, what has become of this fuperincumbent mafs ; and by what 

 means it has been removed. Dr Hutton anfwers, that it has been gradually worn 

 away during an immenfe courfe of ages, by the adion of thofe caufes which conti- 

 nue, under our eyes, to corrode the furface of the globe : That the fohd parts, be- 

 ing conveyed to the bottom of the ocean, are there depofited in beds of fand and 

 gravel, which, in fome future revolution, being expofed to heat, may be again con- 



verted into ftony ftrata. 



X HE 



