31 



III. — On the Comparative Value of various kinds of 

 Stone, as Exhibited by their Powers of Resisting 

 Compression, 



By W. Fairbairn, F.R.S., &c. 



[ Rfd April 1st, 1856.] 



Our knowledge of the properties of stone, viewed as a building 

 material, is very imperfect, and our architects and stonemasons 

 have yet much to learn concerning the difference between one 

 kind of stone and another, both as regards their chemical 

 constitution, their durability, and their powers of resisting 

 compression. On this subject we have the experiments of 

 Gauthey, Rondelet and Rennie, which to some extent sup- 

 ply the deficiency and furnish data for the resistance to a 

 crushing force of a considerable variety of stone. These are, 

 however, to some extent inapplicable to the purposes for 

 which such data are required, and not finding them in exact 

 accordance with the results of some experiments recently 

 made, I have endeavoured to inquire into the causes of the 

 discrepancy, and to account for the difference. 



Stone is found in various forms and conditions, embedded 

 in and stratified under the earth's surface. That portion of 

 it which is used for building purposes, is a dense coherent 

 brittle substance, sometimes of a granulated, at others, of a 

 laminated structure. These qualities varying according to 

 its chemical constitution and the mode in which it has been 

 deposited. Sometimes the laminated and granular rocks 

 alternate with each other; at others, a rock of a mixed form 



