238 



Mr. I. Roberts. 



[Jan. 31, 



repose (about 30°) , and then passing through the mass of the wheat 

 towards the outlet. 



The flow of the wheat through an aperture, say of 80 square inches 

 area, can easily be stopped by a board held in the hand against it, 

 though the head may be 50 feet or more. 



These statements are not made by inference, for I have proved 

 their accuracy on several occasions. On one I placed some 1^-inch 

 cubes of wood, and a pound weight on the vortex column in a bin 

 containing wheat 37 ft. in height, and they passed through the body of 

 wheat and out at the bottom when 20 ft. of wheat still remained in 

 the bin. On another occasion, I am informed by a credible eye-witness, 

 that a cat passed through the mass of wheat by the vortex column and 

 came out alive and uninjured, through the aperture at the bottom of 

 the bin. The body of wheat through which it passed exceeded 20 ft. 

 in height. 



There is yet one question concerning the lateral pressure to be 

 considered, and that is : — If 43 lbs. equal the amount upon each 

 square foot uniformly from bottom to top in a bin which measures 

 6 ft. in. x 6 ft. 9 ins. x 45 ft. 6 ins., would it be exceeded in a bin 

 which measures, say 12 ft. in. X 12 ft. in. x 60 ft. in. ? In answer- 

 ing the question, it has already been shown that all lateral pressure 

 ceases at a height not exceeding two and a-half times the breadth of 

 the side (see Table IV), and therefore all lateral pressure would cease 

 in the bin assumed at the height of 30 ft. (12 ft. in. X 2^) ; and in 

 order to determine if the lateral pressure would be increased by 

 any increased breadth of the bin, I caused one to be constructed 

 within that already described, of the dimensions 3 ft. in. X 3 ft. in. 

 X 12 ft. in., and when it was filled with wheat the maximum dormant 

 pressure was 48'551bs. upon a square foot. This pressure was also 

 indicated when only 7 ft. of wheat was placed in the bin. 



This shows that within certain limits the lateral pressure is slightly 

 greater in the small bin than it is in the large one; and we may, 

 I think, in practice safely adopt 50 lbs. upon each square foot of side 

 as the constant for the lateral pressure of wheat. 



We shall now consider the pressure of peas. 



Those selected for the experiment were dry, hard, and round. 

 They weighed, when pressed into the measure, 54 lbs. per cubic foot, 

 and the determinations of the vertical and lateral pressures were 

 made precisely in the same manner, and with the same weighing- 

 machines and bin that were used in determining the pressures of 

 wheat. I need not, therefore, repeat any part of the descriptions 

 which have been already given, and will now discuss the tables which 

 embody the results obtained. They are numbered respectively VII, 

 VIII, IX, and X. 



Table VII shows the maximum dormant pressure upon the bottom 



