162 Account of Experiments made 
Buffon, recorded in the Annals of the Academy of Sciences at 
Paris, in the years 1740.and 1741, were on a scale sufficiently 
large to justify every conclusion, hel he not omitted to ascertain 
the direct and absolute strength of the timber employed. It 
however appeared from his experiments, that the strength of the 
ligneous fibre is nearly in proportion to the specific gravity. 
Muschenbroeck, whose accuracy (it is said) entitled him to con- 
fidence, made a “imber of experiments on wood and iron, which 
by being tried on various specimens of the same materials, af- 
forded a mean result considerably higher than other previous au- 
thorities. Experiments have also been made by Mariotte, Va- 
rignon, Perronet, Ramus, Rondelet, Gauthey, Navier, Aubry and 
Texier de Norbeck, as also at the Ecole Polytechnique, under 
the direction of M. Prony. With such authorities before us, it 
might be deemed presumption in me, to offer you a communica- 
tion on a subject which had been previously treated of hy so 
many able men *. But whoever has had occasion to investigate 
the principles upon which any edifice is constructed, where the 
combination of its parts are more the result of uncertain rules 
than sound principle, will soon find how scanty is our knowledge 
on a subject so highly important. The desire of obtaining some 
approximation, which could only be accomplished by repeated 
trials on the substances themselves, induced me to undertake the 
following experiments. 
Description of the Apparatus. (Plate II.) 
A bar of the best English-iron, about ten feet long, was se- 
lected and formed into a lever (whose fulcrum is denoted by /). 
The hole was accurately bored, and the pin turned, which suf- 
fered it to move freely. The standard (A) was firmly secured by 
the nut (c) to a strong bed plate of cast iron, made firm to the 
* Tris true that the subject has been considered by many able philoso- 
phers, from Galileo down to the present period: but it is only lately that 
the proper object of attention has been ascertained ; or at least the results 
of their inquiries had not been brought forward in a practicable form. For 
when Dr. T. Young published his Lectures, there was little on the su! ject 
besides the intricate, and I may add unsatisfactory, investivations of Euler 
and Lagrange. As to the resistance to fracture, which with the greater 
part of inechanical writers is the only object attended &, itis of very in- 
ferior importance. 
The laws of flexure constitute the chief guide in the construction of 
buildings: and the intention uf these netes is to call the attention of ex- 
perimentalists to this part of the subject; and as itis probable the inge- 
nious author of the experiments now before me may be te mpted to resume 
his labours, I feel certain that he will not feel displeased to have his at- 
tention called to some inceresting points of inquiry, which he has either 
neglected to notice, or has not given to the public.—T. T. 
ground. . 
