60 Inquiry concerning the Nature of Heat, 



calorific rays which have long been known to proceed 

 from hot bodies. 



My first attempts, in these investigations, were to 

 ascertain the existence of those emanations universally, 

 and to discover what visible effects they might be made 

 to produce independently of concentration by means 

 of concave mirrors. 



Experiment No. 16. My two horizontal cylindrical 

 vessels of sheet brass (of the same form and dimen- 

 sions), having been made very clean and bright, were 

 fixed to their stands ; and, being elevated to a proper 

 height to be presented to the balls of the thermoscope, 

 were set down near that instrument (which was placed 

 on a table in a large quiet room), where they were suf- 

 fered to remain several hours, in order that the whole 

 of this apparatus might acquire precisely the same tem- 

 perature. 



Daylight was excluded by closing the window-shut- 

 ters ; and, in order that the thermoscope might not be 

 deranged by the calorific rays proceeding from the person 

 of the observer on his entering the room to complete 

 the intended experiments, screens were previously placed 

 before the instrument in such a manner that its balls 

 were completely defended from those rays. 



Things having been thus prepared, I entered the 

 room as gently as possible, in order not to put the air 

 of the room in motion, and, approaching the thermo- 

 scope, presented first one and then the other cylin- 

 drical vessel to one of the balls of the instrument; but 

 it was not in the least degree affected by them, the bub- 

 ble of spirit of wine remaining immovably in the same 

 place. 



Experiment No. 17. Having assured myself, by these 



