EXPERIMENTS on WHINSTONE and LAVA. 45 



from the one to the other. He has fiilce expreffed the fame 

 fentiments in one of his late publications, (Theory of the Earth, 

 vol. I. p. 25 i.J, where he cenfures thofe who •' judge of the 

 " great operations of the mineral kingdom, from having kin- 

 " died a fire, and looked into the bottom of a little crucible." 



But, notwithstanding my veneration for Dr Hutton, I 

 could not help differing from him on this occafion : For, grant- 

 ing that thefe fubftances, when in fufion, were acted upon by a 

 heat of ever fo great intenfity, it is certain, neverthelefs, that 

 many of them rauft have congealed in moderate temperatures, 

 mice many are eafily fufible in our furnaces ; for it is impomble 

 that a fubflance mould congeal at a higher point than that at 

 which it may afterwards be melted. If, then, thefe phenomena 

 depend upon the circumflances of congelation, the imitation of 

 the natural procefs is an object which may be purfued with rations 

 al expectation of fuccefs ; and, could we fucceed in a few examples 

 on a fmall fcale, and with ealily fufible fubftances, we mould 

 be entitled to extend the theory, by analogy, to fuch as, by their 

 bulk, or by the refractory nature of their compofition, could 

 not be fubjected to our experiments. It is thus that the aflro* 

 nomer, by obferving the effects of gravitation on a little pendu- 

 lum, is enabled to eftimate the influence of that principle oa 

 the heavenly bodies, and thus to extend the range of accurate 

 fcience to the extreme limits of the folar fvflem. 



Encouraged by this reafoning, I began my projected feries 

 of experiments in the courfe of the fame year (1790), with very 

 promifing appearances of fuccefs. I found that I could com- 

 mand the refult which had occurred accidentally at the glafs- 

 houfe ; for, by means of flow cooling, I converted bottle glafs, 

 after fufion, into a flony fubflance, which again, by the ap- 

 plication of ftrong heat, and fubfequent rapid cooling, I reflo- 

 red to the ftate of perfect glafs. This operation I performed re- 

 peatedly with the fame fpecimen, fo as to afcertain that the cha- 

 racter,- 



