THE HISTORY OF A DOCTRINE. 



217 



physics tlie wrong in a multiplied form by generating an off- 

 spring especially inimical to true ideas about radiant heat, and 

 which is represented by a yet familiar term. I mean " caloric." 



This word is still used loosely as a synonym for heat, but has 

 quite ceased to be the very definite and technical term it once 

 was. To me it has been new to find that this so familiar word 

 " caloric/' so far as my limited search has gone, was apparently 

 coined only toward the last quarter of the last century. It is not 

 to be found in the earliest edition of Johnson's Dictionary, and, 

 as far as I can learn, appears first in the corresponding French 

 form in the works of Fourcroy. It expressed an idea which was 

 the natural sequence of the phlogiston theory, and which is an- 

 other illustration that the evil which such theories do lives after 

 them. 



" Caloric " first seemingly appears, then, as a new word coined 

 by the French chemists, and meant originally to signify the un- 

 known cause of the sensation heat, without any implication as to 

 its nature. But words, we know, though but wise men's counters, 

 are the money of fools ; and this one very soon came to commit 

 its users to an idea which was more likely to have had its origin 

 in the mind of a chemist at that time than of any other — the idea 

 of the cause of heat as a material ingredient of the hot body ; 

 something not, it is true, having weight, but which it would have 

 been only a slight extension of the conception to think might one 

 day be isolated by a higher chemical art, and exhibited in a tan- 

 gible form. 



We may desire to recognize the perverted truth which usually 

 underlies error, and gives it currency, and be willing to believe 

 that even " caloric " may have had some justification for its exist- 

 ence ; but this error certainly seems to have been almost alto- 

 gether pernicious for nearly the next eighty years, and down even 

 to our own time. With this conception as a guide to the philoso- 

 phers of the last years of the eighteenth century, it is not, at any 

 rate, surprising if we find that at the end of a hundred years from 

 Newton the crowd seems to be still going constantly further and 

 further away from its true goal. 



Although Provost gave us his most material contribution 

 about 1790, we have, it seems to me, on the whole, little to inter- 

 est us during that barren time in the history of radiant energy 

 called the eighteenth century — a century whose latter years are 

 given up, till near its very close, to bad a priori theories in our 

 subject, except in the work of two Americans ; for in the general 

 dearth, at this time, of experiments in radiant heat, it is a pleasure 

 to fancy Benjamin Franklin sitting down before the fire, with a 

 white stocking on one leg and a black one on the other, to see 

 which leg would burn first, and to recall again how Benjamin 



