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XXVI. Account of Experiments made on the Strength of Ma- 
terials. By Grorce Rennie jun. Esq. In a Letter to 
Tuomas Youne, M.D. For. Sec. R.S.* With Notes by 
Mr. T. TrEpGoLD. 
London, June 8, 1817. 
DEaR Sir,—Lw presenting you the result of the following ex- 
periments, [ trust I shall not ‘be considered as deviating from my 
subject, in taking a cursory view of the labours of others. ‘The 
knowledge of the properties of bodies which come more imme- 
_ diately under our observation, is so instrumental to the progress 
of science, that any approximation to it deserves our serious at- 
tention. The passage over a deep and rapid river, the construc- 
tion of a great and noble edifice, or the combination of a more 
complicated piece of mechanism, are arts so peculiarly subser- 
vient to the application of these principles, that we cannot be 
said to proceed with safety and certainty, until we have assigned 
their just limits. The vague results on which the more refined 
calculations of many of the most eminent writers are founded, 
have given rise to such a multiplicity of contradictory conclusions, 
that it is difficult to choose, or distinguish the real from that 
which is merely specious. The connexions are frequently so 
distant, that little reliance can be placed on them. The Royal 
Society appears to have instituted, at an early period, some ex- 
periments on this subject, but they have recorded little to aid us, 
Emerson, in his Mechanics, has laid down a number of rules 
and approximations. Professor Robison in his excellent treatise 
in the Encyclopedia Britannica; Banks on the Power of Ma- 
chines; Dr. Anderson of Glasgow; Colonel Beaufoy, &c. are 
those, amongst our countrymen, who have given the result of 
their experiments on wood and iron... The subject, however, 
appears to have excited considerable attention on the continent. 
A theory was published in the year 1638, by Galileo, on the re- 
sistance of solids, aud subsequently by many other philosophers. 
But however plausible these investigations appeared, they were 
more theoretical than practical, as will be seen in the sequel. 
It is only by deriving a theory from careful and well directed ex- 
periments, that practical results can be obtained. It would be 
useless to enumerate the labours of those philosophers, who in 
following, or varying from the steps of Galileo, have merely 
tended to obscure 4 subject respecting which they had no data 
to proceedupon. It is sufficient to enumerate the names of those 
who, in conjunction with our own countrymen, have added their 
labours to the little knowledge we possess. The experiments of 
* From the Transactions of the Royal Society for 1818, Part I. 
Vol. 53. No. 251. March 1819. L Buffon, 
