Mr. Bevan's Experiments on the Modulus of Torsion. 1-23 



_ . ,„r J Modulus of Torsion. 



Species ot Wood. H^^ 



Plane sp. grav. -59 176 17 



Plum sp. grav. "79 23700 



Poplar sp. grav. -333 9473 



Satin-wood sp. grav. 1 -02 30000 



Sallow 18600 



Sycamore 22900 



Teak (old, and partially decayed) .... 16800 



Teak (African) 27300 



Walnut sp. grav. '572 19784 



I have observed in a great number of my experiments, that 

 the modulus of torsion bears a near relation to the weight of 

 the wood when dry, whatever may be the species ; and that 

 for practical purposes we may obtain the deflection (8) from 

 the specific gravity (s). Thus 



30000(/«s "~ ' 



1 Table of the Modulus of Torsion of Metals. 



Modulus of Torsion, 

 lbs. 



Iron, English (wrought) .. 1810000 



Iron, English (wrought) . . 174'0000 



Iron, thin hooping .... 1916000 



Steel 1984.000 



Steel 1648000 



Steel 1618000 



Iron cylinder 1910000 



Iron cylinder 1700000 



Iron square 1617000 



Iron square 1667000 



Iron square 1951000 



Mean of Iron and Steel 1779090 



Iron (Cast) 940000 



Iron (Cast) 963000 



Iron (Cast) ........ 952000 



Mean of cast-iron sp. grav. 7*163 951600 



Bell-metid sp. grav. 8-531 818000 



On comparing these niunbcrs with the modulus of elasticity 

 of the same substance, I find the modulus of torsion to be j'^th 

 of the modulus of elasticity in metallic substances. 



LXVI. On 



