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ACTION OP HEAT MODIFIED 



and perfpicuity of whofe converfation formed a ftriking 

 contraft to the obfcurity of his writings. I was induced by 

 that charm, and by the numerous original fa£ls which his 

 fyftem had led him to obferve, to liften to his arguments, in 

 favour of opinions which 1 then looked upon as vifionary. I 

 thus derived from his converfation the fame advantage which 

 the world has lately done from the publication of Mr. Playfair's 

 llluftrations ; and, experienced the fame influence which is 

 now exerted by that work, on the minds of our moft eminent 

 men of fcience. 

 The author's After three years of alraoft daily warfare with Dr. Kutton, 



progrefs m^the ^ on the fubjed of his theory, I began to view his fundamental 

 principles with lefs and lefs repugnance. There is a period, 

 I believe, in all fcientific inveftigations, when the conjectures 

 of genius ceafe to appear extravagant; and when we balance 

 the fertility of a principle, in explaining the phenomena of 

 nature, againft its improbability as an hypothefis : The partial 

 view which we then obtain of truth, is perhaps the moft a(- 

 traflive of any, and moft powerfully ftimulales the exertions 

 of an adiive mind. The mift which obfcured fome obje6ls 

 diffipates by degrees, and allows ihem to appear in their 

 true colours; at the fame time, a difiant profptct opens to our 

 view, of fcenes unfafpe6ied before. 

 He propofes ex- Entering now ferioufly into the train of reafoning followed 

 perimental con- by D^, Hutton, I conceived that the chemical effects afcribed 

 * by him to compreffion, ought, in the firft place, to be invefti- 



^ated ; for, unlefs fome good reafon were given us for be- 

 lieving that heat would be modified by preflTure, in the manner 

 alledged, it would avail us little to know that they had a6led 

 together. He refted his belief of this influence on analogy ; 

 and on the fatisfadory folution of all the phenomena furniflied 

 by this fuppofition. It occurred to me, however, that this 

 principle was fufceptible of being eftabliflied in a direft man- 

 ner by experiment, and I urged him to make the attempt ; 

 but he always rejedied this propofal, on account of the im- 

 menCty of the natural agents, whofe operations he fuppofed 

 rejeftedby the ^^ ^'^ ^^^ beyond the reach of our imitation; and he feemed 

 l>oitor. to imagine, that any fuch attempt muft undoubtedly fail, and 



thus throw difcredit on opinions already fufficiently eftabliflied, 

 as he conceived, on other principles. I was far, however, 



from 



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