226 



Mr. I. Roberts. 



[Jan. 31, 



Table of the Results of Experiments made to ascertain the Vertical 

 Pressure of Wheat stored in Cells or Bins. 















a 





03 





© 



©" 



13 



a 







o 

 © 









o 



u 



•g'8 



o 



+3 



© 

 © 





3 



P" © 





Description of 



=4— t 



O 





O 

 ^2 







m 



© . 





=H 

 O 



cell. 







=4— 1 





C Oh 





+3 — 1 



© • 



Lengtl 

 side. 



Diame 

 inscri 



Area c 



K 



Heigh 

 mum 



Mean 

 botto 



Weigh 

 in eel 



Numb 

 made 





ins. 



ins. 



ins. 



ins. 



ins. 



lbs. 



lbs. 







7 



7 



49 



36 



11 



8-5 



46-8 



17 





4 



7 



41-57 



60 



12-5 



7 



70-2 



26 







12 



122-8 



60 



24 



48 



202-8 



18 





12 



20f 



374-11 



96 



36 



224 



1014 



19 



It will be observed that all pressure upon the bottom ceases in 

 each cell, at a point not exceeding in height two diameters of its 

 inscribed circle. In the 7-inch square cell, the pressure ceases at the 

 height of 11 inches. In the 7-inch hexagonal cell, it ceases at the 

 height of 12^ inches. In the 12-inch hexagonal cell, it ceases at the 

 height of 24 inches, and in the 20f -inch hexagonal cell, it ceases ab 

 the height of 36 inches. So the eighty trials which were made with 

 the four cells point clearly to one conclusion, namely, that in any cell 

 which has parallel sides, the pressure of wheat upon the bottom ceases 

 when it is charged up to twice the diameter of its inscribed circle. 



The weight of a cubic foot of wheat when filled loosely is 49 lbs., 

 and the weight when shaken and pressed into the measure is 53 lbs. 

 With these data, and those given in the foregoing Table, we may 

 determine the pressure-figure, or form, which the wheat assumes in 

 the cell. Let us take the 12-inch hexagonal cell as the type. Its 

 area is equal to 122-8 square inches. All pressure upon the bottom 

 ceased when the wheat was 24 inches in height, and the mean pressure 

 upon the bottom then was 48 lbs., which is very nearly the weight 

 of 1 cubic foot of wheat when loosely filled. Then 122*8 square 

 inches X 24 inches = 2947*2 cubic inches, but the pressure was only 

 equal to 1728 cubic inches of wheat (1 cubic foot) and, therefore, 

 the pressure-form must be some figure containing approximately 

 1728 cubic inches of wheat. We have three dimensions of the figure 

 ascertained by experiment, namely, the area of its base, its height, 

 and its cubical capacity, or, 122*8 ins. the base, 24 ins. the height, 

 and 1728 cubic inches the capacity. The figure that meets these 

 conditions is therefore parabolic, and I suggest the following formula 

 to determine its cubical capacity and pressure upon any given area: — 



