1817.] Experiments on the Strength of Wood. 277 
259 367 AAO 
252°79 | 372-67 A440 
Experimented strength .. 129 193 
Heepwiar series... 2... 2006 128°28 | 13°51 
A piece of Dantzic oak two inches square, and projecting, like 
a beam, four feet from a wall, sustammed the mean weight of 
98.4. |b. hung on its extremity. The following rule will give how 
much the original piece would have borne, out of which the 25 
pieces of two inches square were cut. 
T=10 Loz. 1:0000000 
t = 2 Log. 03010300 
3°6939700 Log, 1°8444585 
Mean Exp, 30398 Log. 0°4828450 
0°3273035 Nat, N, 2°1247 
—— 
W. 984 Log. 1:9929951 
— Ib. T. Cwt. Ib. 
41176951 13°113 or 5 17 9 
— 
the calculated weight. But had the weight been calculated accord- 
ing to the cube of the thickness, it would have given 12300. ‘The 
mean weight which the 25 pieces of Dantzic oak actually bore was 
2459 ; then 12300 divided by 2459 leaves a quotient of 5°002; 5 
is the square root of 25, which proves that in this instance the 
strength of a piece of timber when divided into many pieces de- 
creases as the square root of the number into which it is divided, 
supposing each piece square and of the same size. The experi- 
ments also with the 25 pieces of pitch pine gave the quotient 
4°99)9, which is so near that it may be considered as 5. From 
these experiments are deduced the following practical conclusions, 
That in made and solid masts, or any other assemblage of pieces of 
wood, the pieces should be as few as possible. That in square 
beams the lateral strength is as the cubes of their breadth. That 
when the beam is not square, the strength is as the breadth multi- 
plied into the square of the depth. Prior to the wood breaking, the 
fibres on the upper side are stretched, and those on the under side 
compressed. On the weights being taken off, the wood did not 
recover its horizontal position ; and reversing the wood, it broke in 
the contrary direction with less weight. 
These facts respecting the decrease of the strength of timber by 
the compression of the fibres on one side, and their consequent 
elongation on the opposite, prove how destructive to the service is 
the bad practice of violently staying forward the lower masts of 
large ships. By this method, masts are often crippled prior to the 
vessels going to sea. ‘The mast is complained of, and rejected asa 
bad stick, replaced at the expense of several hundred pounds, and 
to the delay of the service. In the second set of experiments, the 
usual method of forming ship beams by splicing up and down is 
