on the strength of materials. 135 
theory, which makes the comparative values as the breadths 
multiplied into the squares of the depths. The halves of the 
bars were tried, merely to keep up the analogy. The bar of 
4 inches deep, however, falls short of theory by 365 lbs. It 
is evident we cannot extend the system of deepening the bar 
much farther, nor does the theory exactly maintain in the 
case of the equilateral triangle by 243lbs. 
The diagonal position of the square bar, is actually worse 
than when laid on its side, contrary to many assertions. 
The same quantity of metal in the feather edged bar, wa| 
not so strong as in the 4 inch bar. 
The semi-elliptical bar, exceeded the 4 inch bar, although 
taken out of it. The parabolic bar came near it. 
The bar made fast at both ends, I suspect must have 
yielded, although the ends were made fast by iron straps. 
The experiments from Emerson, on solids of different forms 
might be made ; but the time and trouble these experiments 
have already cost, have compelled me to relinquish far- 
ther pursuits for the present. If, however, in the absence of 
better, they are worthy of the indulgence of the Royal Society, 
it will not only be a consolation to me that my labours merit 
t'heir attention, but a farther inducement to prosecute the 
investigation of useful facts, which, even in the present ad- 
vanced state of knowledge, will yet admit of addition. 
I am, with much respect, 
GEORGE RENNIE. 
Since my return to England, I find that a set of experi- 
ments have been undertaken by Mr. Peter Barlow, of the 
