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XXVI. On the Strength of Bone. By B. Bevan, Esq. 



To the Editor of the Philosophical Magazine and Journal. 

 Sir, 

 TN the lists published by various authors on the cohesive 

 ; strength of materials, the strength of bone has been much 

 underrated. In the Encyclopaedia Britannica it is quoted from 

 Muschenbroek's experiments to be 5,250 pounds per square 

 inch ; and I have observed this number copied into various 

 other books. But from experiments I have made with consi- 

 derable care, I find the strength much to exceed that now 

 stated, if the bone is sound and solid. There will always be 

 some variation in the results of experiments of this nature, 

 depending upon the quality of the substance, and also upon 

 the mode of conducting the experiment. I have tried the 

 bones of horses, oxen, and sheep, and find the strength of 

 cohesion per square inch to vary from 33,000 pounds to 

 42,500. One specimen of fresh mutton bone supported a 

 load in proportion to 40,000 pounds to the square inch for a 

 considerable time, without any visible injury to the bone, — or 

 nearly eight times the strength given by Muschenbroek. The 

 modulus of elasticity of beef bone I have found 2,320,000 

 pounds, and specific gravity of 2'08. A substance like bone, 

 so universally abounding, possessing such great strength, and 

 considerable flexibility, ought to be restored to its proper place 

 in the scale of bodies, applicable to so many purposes in the arts. 



Emerson has given the ratio of the strength of bone to ash 

 as 22 to 8 1 . Now by direct force applied to ash, its cohesion 

 appears to be 16,000 pounds to the square inch, making bone 

 upon the ratio above stated to be more than 41,000 pounds, 

 the correctness of which has been confirmed by my experi- 

 ments. 



I have been trying the cohesive force of various species of 

 wood, and find them generally to exceed the strength given 

 by Mr. Barlow in his treatise on the strength of timber. 



My apparatus is partly like that used by Mr. Barlow on the 

 direct cohesion ; but the mode of applying the load, instead of 

 adding large weights, is that of gradually advancing a given 

 weight along the arm of a lever, allowing the weight to rest 

 occasionally for several minutes, and sometimes for three or 

 four hours. By this machine I found that a good clear-grained 

 specimen of English oak supported a load in proportion to 

 19,800 pounds to the square inch, for several hours, having 

 left it at seven in the evening with that load suspended with- 

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