and the Mode of its Communication . 113 
before described instrument, which I have called a thermoscope, 
was to investigate the nature and properties of those emanations ; 
and to find out, if possible, whether they are not of the same 
nature as those 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. 
Exper. No. 16. My two horizontal cylindrical vessels, of sheet 
brass, (of the same form and dimensions,) 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 temperature. 
Day-light was excluded, by closing the window-shutters; 
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 thermoscope, presented first one, 
and then, the other cylindrical vessel, to one of the balls of the 
instrument ; but it was not in the least degree affected by them, 
MDCCCIV, O 
