1884.] Determination of Pressures of Granular Substances. 227 



Let a = area of cell in feefe. 



d = diameter of inscribed circle in feet, 

 c = the constant determined by experiment. 

 w = weight of wheat in pounds per cubic foot. 

 j) — pressure upon the bottom of cell in pounds. 



If we apply this formula to the cell now under consideration, we 

 have — 



a X d X c X w=p } 



or 



f 122-8 ins. x l x 1 . 03 x 53 lbs 1 =46 . 56 lbs> 

 I 141 ins. J 



The actual pressure was ascertained by weighing to be 48 lbs., and 

 this was the total mean pressure upon the bottom of the cell, though 

 it was filled with wheat that weighed 202 - 8 lbs. I now know, and 

 will give the particulars later on, that if this cell had been lengthened 

 to 60 ft. or any other height, the pressure upon ths bottom would not 

 have exceeded 48 lbs. 



The investigations could not be considered conclusive if left at this 

 stage, since they in a remarkable manner appeared to be contradictory 

 to all our generally received knowledge of the laws governing the 

 flow and pressure of fluids. It was also reasonable to doubt their 

 reliability if applied on a large scale, notwithstanding their close 

 agreement with each other in all the experimental cells. Besides, 

 there was no evidence furnished by the experiments to show what 

 pressure the sides of the cells would have to sustain, although it 

 might be inferred that the side pressure upon a unit of surface, would 

 be less than that upon a similar unit of bottom surface, but how much 

 less, if any, was not indicated. I therefore decided to try the expe- 

 ments on a large scale, and to include in them determinations both 

 of the vertical and lateral pressures. These I now proceed to 

 describe. 



Mr. Paul, the well-known corn-merchant of Liverpool, at the sug- 

 gestion of Mr. Grayson, architect (both of whom took great interest 

 in the inquiry), placed at my disposal part of a warehouse at the 

 Duke's Dock, together with the use of grain, men, and machinery for 

 manipulating with. In one corner of the warehouse I constructed a 

 rectangular bin, two sides of which were formed with spruce deal 

 planks, 3 inches in thickness, placed on end, so that they were sup- 

 ported only at the level of each floor, and had a clear bearing in 

 the ground storey, of 9 ft. 3 ins. The other two sides of the bin 

 were the walls of the warehouse. On plan the bin measured inter- 

 nally 6 ft. 9 ins. by 6 ft. in., and 52 ft. 2 ins. in height, and it con- 

 tained when filled 2112 cubic feet of wheat, weighing 111,976 lbs. 



The weighing apparatus consisted of two graduated levers, one for 

 weighing the vertical, and the other for weighing the lateral pressures. 



