Proceedings of the British Association. 169 



results obtained on marbles and stones of various degrees of 

 hardness. 



Crushing force Tensile force Transverse strength 



Description of stone. per square inch per square of bar I inch square 



cailed 1000. inch. and 1 foot long. 



Black marble, . . 1000 .143 



Italian marble, . . 1000 . 84 



Rochdale flagstone, . 1000 . 104 



High Moor stone, . 1000 . 100 

 Stone called Yorkshire flag, 1000 



Stone from little Hulton, 1000 . 70 



Mean rates, . 1000 . 100 



10.1 



10.6 



9.9 



9.5 



8.8 



Or calling the mean crushing strength per square inch in the dif- 

 ferent articles experimented upon 1000, we have 



Ratio of mean 

 Crushing strength Tensile Transverse tensile to crush- 



1000. strength. strength. jng strength. 



In timber, . . 1000 1900 85.1 1 to 0.55 



Cast iron, . . 1000 158 19.8 1 " 6.6 



Glass, plate and crown, 1000 123 10. 1 " 7.8 



Stone and marble, 1000 100 9.8 1 " 10.5 



The ratio of the crushing force to the transverse force is 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 tearing 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 crush- 



i 



ing 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 from the ductility of that metal. 

 The necessity of enlarged inquiries in these matters will be seen, 

 when it is reflected that calculations of the tensile strength of 

 cast iron or marble or stones in general, made from the transverse 

 strength by the modes used by Tredgold, Navier and others, give 

 the tensile strength twice or three times as great as it ought to be. 



Vol. xliv, No. 1.— Oct.-Dec. 1842. 22 



