g Dr. Fordyce's Account 
in the rod EH, take a point K, equal in height with the points 
A D, and in the line AD which is parallel to the horizon, as it 
has already been taken in the construction ; then the rod AH 
shall expand, upon being heated, in perpendicular height more 
than the rod HK, and therefore the expansion of AH shall 
carry the point B, and in consequence the point C, higher 
than the expansion of the rod HK shall carry the point E ; 
but if the expansion of the rod AH be as great as the expan- 
sion of the whole rod HE, then the point C will be carried as 
much higher than the point E, as the point E is carried 
higher than it was before the heat was applied, and therefore 
the point E shall be at as great a distance from the point C, 
as it would have been if the materials connecting AE had been 
incapable of being altered by heat : and therefore if ED be a 
pendulum, it will be rendered of the same length. If then 
the rods AB, and CD, be of the same materials, and the sub- 
stance connecting A and E is capable of expanding and con- 
tracting less by heat than the matter of the rods AB and CD, 
then, by adding to the rod AB, a part AH, under the circum- 
stances already described, and making the fixed point at H, we 
can obtain a pendulum always of equal length ; or if the mate- 
rials of which the rod AB consists be capable of being expanded 
by heat as much as the materials of which CD consists, toge- 
ther with the expansion of the materials that connect A and E, 
in that case likewise the point C shall be carried as much 
higher than the point E, as it would be when they are ex- 
panded by heat, as if the materials connecting A and E had 
not been affected by heat at all. Or, lastly, if we take a rod 
GB of materials which expand much more than the expan- 
sion of the matter of the rod CD, and the connecting matter 
