212 



REPORT 1842. 



given him every assistance his establishment afforded,), he (Mr. Hodgkinson) 

 had made a great many experiments upon wood, sandstones, marbles, glass, slate, 

 ivory, bone, &c, to ascertain the tensile, crushing, and transverse strength of 

 each ; also, as far as possible, the situation of the neutral line. He had sought 

 for these in thirteen kinds of timber, including oaks, pines, teak, &c. ; all the 

 different sorts of experiments were made, as far as possible, out of the same 

 specimen in each case. The wood was of good quality, and perfectly dry, having 

 been chosen for this purpose, and laid in a warm dry place for four years or 

 more. After describing the mode and character of his experiments on the va- 

 rious substances named above (specimens of which he produced), Mr. Hodg- 

 kinson gave the following summary of their comparative results on marbles 

 and stones of various degrees of hardness : — 



Description of Stone. 



Crushing 



force per 



square inch, 



called 1000. 



Tensile force 



per square 



inch. 



Transverse 

 strength of har 

 1 inch square, 

 and 1 foot long. 



Black marble 



Italian marble 



Rochdale flagstone 



High Moor stone 



Stone called Yorkshire flag 



Stone from Little Hulton, near"! 

 Bolton J 



Mean rates. . . . 



ioqp 



1000 

 1000 

 1000 

 1000 



1000 



14-3 



84 



104 



100 



70 



10-1 



10-6 



9-9 



9-5 



1000 



100 



9'8 



or calling the mean crushing strength per square inch, in the different articles 

 experimented upon, 1000, we have, — 



Crushing strength 1000. 



Tensile 

 strength. 



Transverse 

 strength. 



Ratio of mean 

 tensile to 

 crushing 

 strength. 



In timber 1000 



Cast iron 1000 



Glass (plate and crown) . . 1000 

 Stone and marble 1000 



1900 

 158 

 123 

 100 



85-1 

 19'8 

 10- 

 9-8 



lto 0*55 

 1 » 6-6 



1 » 7-8 

 1 „ 10-5, or, 



taking the hardest only, 8 - 9. 



The ratio of the crushing force to the transverse force i3 nearly the same in 

 glass, stone, and marble, including the hardest and the softest kinds. Hence, 

 if we know the transverse strength in any of these bodies, we may predict the 

 other ; and, as glass and the hardest stones resist crushing with from seven to 

 nine times the energy that they do being torn asunder, we may get an ap- 

 proximate value of the tensile force from the crushing force, or vice versa. 

 These results render it probable that the hardest bodies, whether cast-iron, 

 glass, stone, or marble, admit of certain atomic displacements, either in tear- 

 ing asunder or crushing ; these displacements being in a given ratio to each 

 other, or nearly so. In future calculations as to the strength of bodies, the 

 crushing strength ought to be made the fundamental datum, for the reasons 

 shown in this notice. The ratio of the transverse strength to the crushing 

 strength is greater in cast-iron than in glass, marble, and sandstones, arising 



