1817.) Experiments on the Strength of Wood. 275 
of beams is increased or decreased by augmenting or diminishing 
their depth and breadth. Those already made did not satisfy my 
mind ; but should these appear to you likely to interest any of your 
readers, I beg you to insert them in the Annals, though accuracy 
is the only merit they can boast. 
The tables are divided into four columns: the first contains the 
weight employed to break the wood under trial, from 14 lb., 281b., 
avoirdupoise, and so on, to that which broke the wood: in the 
second column are the degrees and minutes, the timber bent by the 
application of the weights: in the third, the differences of the cur- 
vature of the pieces of wood : and the last column contains remarks, 
It is remarkable that in different parts of the same tree there is so 
great difference in the strength of the timber; for instance in the 
Dantzic oak, the strongest piece would sustain the mean weight of 
1361, lb., another piece of the same tree 76,3, lb., and another 
but 63,3, lb.: in this last piece, however, there was a shake or 
imperfection : the heart of the oak sustained the mean weight of 
84lb. The differences of the curvature are tolerably regular till 
loaded with more than half the greatest weight the piece would 
carry; then the curvature, though irregular, becomes greater than 
in proportion to the weight added. From these trials, the pitch 
pine appears the strongest wood; next to that, the English oak 
with straight and even fibres, as the experiments on the six pieces 
prove; then the English oak irregular and cross grained ; fourthly, 
the Riga fir; and, sixthly, the Dantzic oak. Thus the strength of 
pitch pine (by first experiment) is to the strength of 
English oak ....as 148-44 to 145°5, which is as 101 is to 99, 
(by second experiment) — 
English oak,... as 14844 to 128°66, which is as 15 is to 13 
| | as 148-44 to 116-01, which is as 83 is to 65 
Dantzic oak .. as 14844 to 98:4, which is as 86 is to 57 
and to the mean strength of 
English oak....as 148-44 to 137°08, which is as 13 is to 12. 
If the strength of the pitch pine be called 1000, the strength of 
the English oak by 
First experiment will be ............., 980 
Mecorid expertinent \.\. oo) 6: js sds soe »s- 867 
eee Oe the tw 58 EST -. 923 
Of the Riga fir...... « aia B avalalaiat PoROe 
Of the Dantzic oak ...... Fricae ote vetenGGS 
Call the mean strength of the English oak 1000; the strength of 
Riga fir will be 846; but the weight of the Riga fir is to that of 
the English oak as 659 to 1000. ‘Therefore the decrease of weight 
being in greater proportion than the increase of strength proves 
that in dry places it is better to use fir beams than oak, independently 
of the saving of expense. 
$ 2 
