BRISTOIi BUILDING STONES. 



113 



due to tliem, and to Mr. F. W. Hardwick, Mr. W. E. 

 Kerslako, and Mr. A. E. Machott, for their aid in the inves- 

 tigation. 



All the experiments wore oarriod ont under the same 

 conditions, iron being the substance used between the jaws 

 of the machine and the test. . 



The details of the experiments are given with sutSciont 

 fulness in Tabic I. Table II. gives, not strict moans, but 



II. 



TABLE OF AVERAGE RESISTANCE. 



stone. 



Sizo oi Tost. 



Roaistanco 

 in tons. 



Resistance 

 in lbs. 



Tlcipht in foot 

 of column 2' 

 square which 

 will crush with 

 its own weight. 



Dundry . 

 Pennant 

 Draycott 

 Black Book . 

 Millstono Grit 

 Old Bed Sandstone 



Two-inch cube. 

 " 



3-3 

 21 



8 

 15 

 19 

 11 



7,392 

 47,040 

 17,920 

 33,()00 

 42,5()0 

 24,640 



2,112 

 10,357 

 4,032 

 7,200 

 9,516 

 6,037 



what seem to be the average resistances as the outcome of 

 the tests. In the last column I have given the height of a 

 column of the rock two inches squai'e, which would crush 

 at the base by its own weight. 



Comparison between tho results obtained with two-inch 

 cubes and prisms two inches square and three inches high, 

 give different results with different materials. With Dundry 

 stone the mean of four experiments (4-7) with cubes gives 

 .3-64 tons as the mean resistance to crushing, while tho mean 

 of throe experiments (14-16) with prisms gives 3'89 tons, — • 

 a sliglit advantage on the side of tho prism. On tho other 



