104 Count Rumford’s Enquiry concerning the Nature of Heat, 
on both sides with gilt paper) serves for preventing one of the 
balls of the instrument from being affected by the calorific rays 
proceeding from a hot body which is presented to the opposite 
ball. 
Besides the circular screen represented in the figure, several 
other screens are used in making experiments ; for the instru- 
ment is so extremely sensible, that the naked hand presented to 
one of the balls, at the distance of several inches, puts the bubble 
in motion ; and it is affected very sensibly by the rays which 
proceed from the person who approaches it to make the experi- 
ments, unless care be taken, by the interposition of screens, to 
prevent those rays from falling on the balls. These screens can 
be best and most readily made, by providing light wooden 
frames, about 2 feet square, and half an inch in thickness, and 
covering them on both sides, first with thick cartridge paper, 
and then with what is called gilt paper ; the metallic substance 
(copper) with which one side of the paper is covered being on 
the outside. 
To support a moveable screen of this kind in a vertical posi- 
tion, it must of course be provided with a foot or stand. Those 
I use, are fastened to one side of a pillar of wood, by two screws; 
one of which passes through the centre of the screen, where 
the cross bars belonging to the frame of the screen meet; and 
the other through the middle of the piece of wood which forms 
the bottom of the screen. This pillar of wood, which is turned 
in a lathe, is i2-§- inches high, and is firmly fixed, at its lower 
end, in a piece of wood, 8 inches square, and 1 inch thick, which 
serves as a stand or foot, for supporting it. 
As, in making experiments with this thermoscope , it is fre- 
quently necessary to remove the hot bodies, that are presented 
