C “8 3 
VII. Account of experiments made on the strength of materials. 
By George Rennie, jun. Esq. In a Letter to Thomas 
Young, M. D. For. Sec. R. S. 
Read February X2th, 1818. 
dear sir, London, June 3, 1817. 
In presenting you the result of the following experiments, 
I 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 
immediately under our observation, is so instrumental to^the 
progress of science, that any approximation to it deserves our 
serious attention. The passage over a deep and rapid river, 
the construction of a great and noble edifice, or the combina- 
tion of a more complicated piece of mechanism, are arts so 
peculiarly subservient 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 multi- 
plicity of contradictory conclusions, that it is difficult to 
choose, or distinguish, the real from that which is merely 
specious. The connections are frequently so distant, that 
little reliance can be placed on them. The Royal Society 
appears to have instituted, at an early period, some experi- 
ments on this subject, but they have recorded little to aid us. 
Emerson, in his Mechanics, has laid down a number of rules, 
