on the strength of materials. 127 
No. 55 do. fine yellow brass - 1123 
56 i do. cast tin - 2 96 
57 f do. cast lead - - 1 14 
Remarks on the last experiments. 
The ratio of the repulsion of the horizontal cast cubes to 
the cohesion of horizontal cast bars, is 8.65 : 1 . 
The ratio of the vertical cast cubes to the cohesion of the 
vertical cast bars, is as 9.14 : 1. 
The average of the bars, compared with the cube, No. 16, 
is as 10.61 1 : 1. 
The other metals decrease in strength, from cast steel to 
cast lead. 
The stretching of all the wrought bars indicated heat. 
The fracture of the cast bars was attended with very little 
diminution of section, scarcely sensible. 
The experiment made by M. Prony, (which asserts, that 
by making a slight incision with the file, the resistance is 
diminished one half) was tried on a ~ inch bar of English 
iron ; the result was 292olbs., not a sixth part less. 
This single experiment, however, does not sufficiently 
disprove the authority of that able philosopher, for an incision 
is but a vague term. The incision I made might be about 
the 40th part of an inch. 
Experiments on the twist of ~ inch bars. 
To effect the operation of twisting off a bar, another appa- 
ratus was prepared : it consisted of a wrought iron lever two 
feet long, having an arched head about -g- of a circle, of 4 feet 
diameter, of which the lever represented the radius, the 
