eHEMICAL THEOUt,' 1'61 



X. 



iFacts and Observations relating to the Theory of Heat, Light,, 

 and Combustion. By Mr. J. Arnold. 



To Mr. NICHOLSON, 

 SIR, 



JLT has been said, when a person begins to theorize, there; Dissertation oa 



is no absurdity which he may not mve credit to, and that ^^^ nature and 



, • • 11,-, . r.^, effects of heat, 



a professed theorist is much alhed to a madman. Ihis ap- ij^ht and com- 



ptars partly to be true, if we consider the numerous futile tastion. 

 hypotheses, on various subjects, which have each had its reign; 

 each has been supposed true, and each has deservedly fallen. 

 But when we observe farther into the matter, there is ample 

 room to suppose, that however wild the imaginations of cer- 

 tain persons may have been, yet from the exuberances of some, 

 the most important facts have been discovered. The accurate 

 attention of a person to the most trivial subject, has led to 

 Hie most important discovery : need I mention the circum- 

 stance which induced the great Newton to invent his most 

 just theory of gravitation : If common report be true, it was 

 the train of thought induced by seeing an apple * fall from a 

 tree. Lavoisier, by a proper train of thinking, discovered the 

 theory which would account for the phenomena of combus- , 

 tion : t and Copernicus, by attentive observation, wais led to 

 believe, that the earth was a globe ; J and, like the planets, 

 revolving round the sun. Even the publisher of a false theorj^ 

 has often gained himself a great degree of praise, as we see in 

 the cases of Stalil, Scheele, Dcs Cartes, &c. From this pre- * 

 face you may be led to think that I also am about to theorize 

 and yo,u may be induced to cry out, " delirat, delirat /" be 

 that us it may, I certainly a7n theorizing. 



Before I begin the more immediate subject of my hypothesis, 

 I sliall take a slight notice of the new-invented field itl v('hich 

 you and so many distinguished persons li-ave, and still c6iitinue ' 



* Newtonii opera omnia. ' • t Thompsoif. 



X Biographia Generalis. 



Vol . X I V .— J U A^ E , ] 8 0<5. Id : to 



