42 Inquiry concerning the Nature of Pleat, 



by that means discovered that the whole of this black 

 substance, which had so completely covered the sides 

 of the instrument (a surface of polished brass = 50 

 superficial inches) that the metal did not shine through 

 it in any part, weighed no more than T ^ of a grain 

 Troy. 



How this very thin covering, which, if the specific 

 gravity of the black matter were only equal to that of 

 water, would amount to no more than ?-$- of an inch 

 in thickness, could expedite the cooling of the instru- 

 ment, in the manner it was found to do, is what still 

 remains to be shown ; but, before I proceed any farther 

 in these abstruse inquiries, I shall make a few observa- 

 tions relative to the results of the foregoing experi- 

 ments. 



Although we may with safety presume, that the ve- 

 locities with which the heat escaped through the sides of 

 the instruments * were nearly as the times inversely taken 

 up in cooling through the given interval of 10 degrees ; 

 yet, as. some heat must have made its way, in the course 

 of the experiment, through the ends of the instrument, 

 notwithstanding all the care that was taken to prevent 

 it by covering them up with warm clothing, it is 

 necessary, in order to be able to compare the results of 

 the preceding experiments in a satisfactory manner, to 



* I have found myself obliged in this, as in many other places, to make use of lan- 

 guage which is far from being as correct as I could wish. I do not believe that heat 

 ever makes its escape in the manner here indicated ; but I could not venture to use 

 uncommon expressions in pointing out the phenomena in question, however well 

 adapted such expressions might be to describe the events which really take place. If 

 it should be found that caloric, like phlogiston, is merely a creature of the imagination, 

 and has no real existence (which has ever appeared to me to be extremely probable), 

 in that case, it must be incorrect to speak of heat as making its escape out of one body, 

 and passing into another ; but how often are we obliged to use incorrect and figurative 

 language, in speaking of natural phenomena ! 



