5 
of a new Pendulum. 
degree of cold, would bring down the point E so as to render 
ED shorter, just as much as the expansion of AB would raise 
up the rod ED, or as its contraction lower it. But if the mate- 
rials connecting the points A and E were less expansile and 
contractile by heat and cold, than the matter of the rods AB 
and CD, then upon the whole expanding, although the point E 
would be raised higher towards C, yet it would not be raised 
so high as the expansion of AB would raise the point C, and 
the whole rod CD. The same is true if the whole of them 
contract, but in an opposite direction. That is to say, the 
point E would not descend so far towards D, as the point C 
would descend towards D, and with it the whole rod CD ; by 
this means, although the part ED would not be always equal, 
yet it will be much more equal than if the point C were a 
fixed point, and not capable of being affected with the con- 
traction or expansion of the rod AB. 
If then the part of the rod CD, from opposite to the point 
E to D was a pendulum, it would not be always of the same 
length, but it would be more nearly so than a simple pendu- 
lum made of the same materials of which the rod CD consists; 
and it would be nearly of the same length as if the pendu- 
lum had been made of the materials which connect A and E. 
In order then to render ED always of an equal length, some 
other principle must be employed. Now let BA and CD con- 
sist of the same materials ; and the matter connecting A and 
E consist of a substance that expands by heat, and contracts 
by cold, less than the materials of which AB and CD are 
formed ; if the rod AB be brought down to H, and the fixed 
point be at H, and the points HE be connected together by 
the same materials which formerly connected the points AE 
