COMPABATIVE VALUE OF VABIOUS KINDS OF 8TONE. 



33 



On the durability of the specimens, I have made no further 

 inquiry than in regard to their power of resistance to strain. 

 Any addition would require a separate investigation into the 

 chemical constituents of the different specimens, and into 

 those changes to which stone of almost every description is 

 subjected when exposed to the action of the atmosphere. In 

 omitting this branch of the investigation I have not forgotten 

 its importance, but have very properly left its development 

 to abler hands. 



Before giving the results of the inquiry, I may observe 

 that a portion of the experiments were undertaken at the 

 request of Mr. E. W. Shaw, the surveyor of the borough of 

 Bradford, in Yorkshire, in order to ascertain the best and 

 strongest qualities of stone for paving the streets of that 

 town. The following tables give the result of the experi- 

 ments on fifteen specimens of Yorkshire sandstone, and on 

 some specimens from Wales and other places, as follow. 



Experiments to determine the force necessary to fracture, 

 and subsequently to crush, 2in. cubes of sandstone from the 

 Shipley quarries, Bradford. The pressure applied in the 

 direction of the cleavage. 



