Rules for ascertaining the Strength of Materials. 21 
but the bitterness has in a great degree given place to a coarse 
astringency. 
It is not improbable, that the bitterness produced in all the 
foregoing cases should be owing to the formation of the same 
bitter principle: and its constant conjunction with a vegetable 
acid, seems to show that there is some very intimate connexion 
between them, at present unknown, 
The preceding observations are offered as mere conjecture ; 
and I am fully sensible of what little consideration should be 
attached to them: they are not however entirely devoid of pro- 
bability. An hypothesis is below the dignity of a system which 
is founded on the indestructible basis of experiment: and even 
though it be supported by the coincidence of admitted facts, by 
direct analogies, and hy the correspondence of received opinions, 
. should nevertheless be the beginning and not the end of know- 
edge. 
a 
VI. Rules for ascertaining the Strength of Materials. 
To Mr. Tilloch. 
Sir, — Tae following rules for ascertaining the strength of 
materials are, I believe, new, and if you think them worthy of a 
place in your Magazine, the insertion of them will oblige 
Yours, &c. 
Tu Dy 
Sa 
Put f = the direct cohesive force of a square inch of the ma- 
terial ; 
b = the breadth; 
d = the depth, or the dimension. in the direction of the 
pressure ; and, 
L = the length. 
Then the lateral or transverse strength of a rectangular pris- 
matic beam or bar, is 
bd? 
“fi Z 
—Gr~ if supported at one end, by 
and — if supported at both ends. 
The lateral strength of a square beam or bar, when its dia- 
gonal is placed vertically, is 
eid if supported at one end, 
B3 and 
