C 2 3 
II. Account of anew Pendulum. By George Fordyce, M. D. 
F. R. S. ; being the Bakerian Lecture. 
Read November 7, 1793. 
Let AB and CD be two rods of any solid of the same species, 
and of a simple or uniform texture. Let these two rods be 
exactly of the same length ; let them be connected at the top 
with a rod BC, which is perfectly inflexible, let the angles 
ABC, and DCB, be both right angles, so that AB and DC 
shall be parallel to each other, and in the same plane ; let the 
rod AB be fixed at the point A, and perpendicular to the hori- 
zon : then the rod CD shall likewise be perpendicular to it, 
excepting for the curvature of the earth between B and C, 
which in a foot or two may be considered as nothing : let the 
rod CD be loose at the end D, so as to be capable of rising up 
or falling down ; in this case, if heat be applied equally to 
both rods, so as to expand them both, and lengthen them, the 
rod AB will raise up the rod BC, and lift up the rod DC; but 
the rod DC being equally lengthened by heat with the rod 
BA, the point D will be brought downwards by the lengthen- 
ing of the rod DC, as much as the point C is raised by the 
lengthening of the rod AB by the heat. In consequence, the 
rod DC will have its end D in a line exactly parallel to the ho- 
rizon, and cutting the end of the rod AB at A, as it did before 
the heat was applied ; and the same thing will be true if the 
