234 



Mr. I. Roberts. 



[Jan. 31, 



Table X. — Weighings of the Side or Lateral Pressures of Peas. 

 Size of the Aperture used =2 ft. iu. X 2 ft. in. =4 square feet. 





Peas 6 ft. high in bin. 



Peas 43 ft. 9 ins. high 

 in bin. 





Dormant 

 pressure 

 in lbs. 



Active 

 pressure 

 in lbs. 



Dormant 

 pressure 

 in lbs. 



Active 

 pressure 

 in lbs. 





97 



90 



67 



53 



121 

 118 



89 

 89 



Mean . . . 



93-5 



60 



119 5 



89 



In the experiments made with the model bins, which have been 

 already referred to, the bottom of the model was formed by a loose 

 board, which rested upon an ordinary weighing-machine, and it only 

 just touched the lower edges of the boards forming the sides. The 

 weights were removed a pound at a time off the machine, and the 

 pressure of the wheat was indicated by the bottom falling away, and 

 the wheat consequently running out ; but in the large bin the bottom 

 measured 6 ft. 9 ins. by 6 ft. in., and therefore it was not practicable 

 to weigh the whole of the pressure upon the bottom in the manner 

 adopted with the models. I therefore decided to weigh columns of 

 grain within the bin, having a base of 9 ft., 4ft., and 1 square foot 

 respectively. These columns were formed of the mass of the grain 

 contained within the bin, and being coincident with its centre, were 

 not subject to any friction against the sides, but only to the friction 

 amongst the particles of the grain. 



Referring now to Table I, it deals with a column of wheat having a 

 base area of 9 square feet. The mean dormant pressure when 6 ft. in 

 height was 1157 lbs. ; when 8 ft. in height it was 1159 lbs. ; when 



8 ft. 9 ins. in height it was 1146 lbs. ; and when 51 ft. 9 ins. in height 

 it was only 1172 - 67 lbs. One of the weighings at 6 ft. in height 

 showed the pressure to be 1202 lbs. ; but the greatest pressure indi- 

 cated with the height or head of 51 ft. 9 ins. was only 1191 lbs. 



The active pressure is in every case less at the height of 51 ft: 9 ins. 

 than it is at any height below that. At 6 ft. it reached 1034 lbs ; 

 but at 51 ft. 9 ins. it did not exceed 832 lbs. 



The actual weight of the column of wheat that indicated these 

 pressures was, in the case of 6 ft. in height, 2862 lbs. ( = 6ft. in. X 



9 ft. in. X 53 lbs.) ; and in the case of 51 ft. 9 ins. in height, 24,685 lbs. 

 = (9 ft. in. x 51 ft. 9 ins. x 53 lbs.) . 



