126 
Mr. Rennie’s account of experiments 
The prisms usually assumed a curve similar to a curve of 
the third order, previous to breaking. 
The experiments on the different metals, give no satisfac- 
tory results. The difficulty consists in assigning a value to 
the different degrees of diminution. When compressed be- 
yond a certain thickness, the resistance becomes enormous. 
Experiments on the suspension of bars. 
The lever was used as in the former case, but the metals 
were held by nippers, as indicated in the drawing No. 2. 
They were made of wrought iron, and their ends adapted to 
receive the bars, which, by being tapered at both extremities, 
and increasing in diameter from the actual section (if I may 
so express it), and the jaws of the nippers being confined by 
a hoop, confined both. The bars, which were six inches 
long, and ^ square, were thus fairly and firmly grasped. 
April 30 th, 1817. 
lbs. 
No. 45 i inch, cast iron bar, horizontal 
46 ^ do. do. vertical 
47 £ do. cast steel previously tilted - 8391 
48 ^ do. blister steel, reduced per hammer 8322 
49 ^ do. shear steel, do. do. 
30 \ do. Swedish iron, do. do. 
51 5- do. English iron, do. do. 
7977 
45°4 
3492 
52 £ do. hard gun metal, mean of two trials 2273 
53 i do. wrought copper reduced per 
hammer 
54 ^ do, cast copper 
1192 
2112 
