io6 Count Rumfori/s Enquiry concerning the Nature of Heat, 
which is fixed, is about i of an inch higher than the level 
of the upper surface of the sliders; in order that, when a ther- 
moscope longer than this fixed part is placed on it, the sliders 
may pass freely under its two projecting ends, without de- 
ranging it. 
It is evident, from this description, that, by placing the ther- 
moscope on the fixed part of the cover of the box, with its two 
balls in a line parallel to the axis of the box, and by placing the 
two hot bodies presented to the two balls of the instrument 
(elevated to a proper height) on stands set down on the sliders, 
an observer, by taking the two winches in his hands, keeping 
his eye fixed on the bubble, may, with the greatest facility, so 
regulate the distances of the hot bodies from their respective 
balls, that the bubble shall remain immoveable in its place. 
In order to be able to ascertain precisely the temperatures of 
the hot bodies presented to this instrument, and in order that 
their surfaces might be equal, two equal cylindrical vessels, of 
thin sheet brass, with oblique cylindrical necks, were provided, 
of the form represented in Figure 3. 
This cylindrical vessel, which is placed in a horizontal posi- 
tion, in brder that its flat bottom may be presented, in a vertical 
position, to one of the balls of the thermoscope, is so fixed to a 
wooden stand, of a peculiar construction, that it may be raised, 
or lowered, at pleasure. This is necessary, in order that its axis 
may be in the continuation of a line passing through the centres 
of the two balls of the thermoscope. 
This cylindrical vessel is 3 inches in diameter, and 4 inches 
in length ; and its oblique cylindrical neck is 0.86 of an inch in 
diameter, and 3.8 inches in length. 
The neck of tills vessel is inserted obliquely into its cylindrical 
