1884.} Determination of Pressures of Granular Substances. 235 



In Table II the column of wheat had a bottom area of 4 square 

 feet, and with the height of 51ft. 9 ins. would weigh 10,971 lbs.= 

 (4 ft. in. X 51 ft. 9 ins. X 53 lbs.) ; but the mean dormant pressure 

 upon the bottom was only 681*5 lbs., whilst at only 4ft. in height the 

 mean dormant pressure was 592 "5 lbs. 



The active pressure, as will be seen in this table also, is less when the 

 column of wheat is 51 ft. 9 ins. in height than it is at any lower level. 



In Table III the aperture had an area of 1 square foot, and the 

 column of wheat 51 ft. 9 ins. in height, indicated a mean dormant 

 pressure of 216 lbs., and in each weighing an active pressure of only 

 50 lbs., even at the height of 2 ft. 4 ins., this amount of active 

 pressure was indicated. The total weight of a column of wheat 

 1 foot square and 51 ft. 9 ins. in height would be 2742 lbs., but the 

 maximum dormant pressure did not exceed 229 lbs., and the active 

 pressure was only 50 lbs. If now we formulate the results obtained 

 and recorded in Tables I, II, and III in terms of those obtained by the 

 model bins already referred to, we have : — 



<x=area of column of wheat in square feet. 



d= diameter of inscribed circle in feet. 



c= constant determined by experiment. 



w — weight of wheat in pounds per cubic foot. 



■p = pressure upon the bottom. 



c is found to be variable within certain limits. With the aperture 

 of 9 square feet, according to Table I, it is 0'84. With the aperture 

 of 4 square feet, according to Table II, it is T66, and with the aper- 

 ture of 1 square foot, according to Table III, it is 4'32. 



It, therefore, appears that the apex of the paraboloid which repre- 

 sents the pressure upon 1 square foot area at the centre of a bin full of 

 wheat, is higher relatively with its inscribed circle, than it is relatively 

 with the inscribed circle which has its diameter equal to the bottom 

 of the bin. 



We shall now proceed to consider the lateral or side pressures, and 

 by referring to Tables IV, V, and YI, it will be seen that in each of 

 the weighings, irrespective of the height of the wheat in the bin, 

 there is a dormant and an active pressure both considerably less than 

 the corresponding vertical pressure. With the aperture of 9 square 

 feet the maximum dormant pressure of 385 lbs. was attained at the 

 height of 7 ft. 3 ins. above the lower edge of the aperture, and at the 

 height of 45 ft. 6 ins. the maximum pressure was 367 lbs. With 

 the aperture of 4 square feet the maximum dormant pressure was 

 238 lbs., at the height of 45 ft. and at the height of 6 ft. 9 ins. the 

 pressure reached 170 lbs. With the aperture of 1 square foot the 

 maximum dormant pressure at 44 ft. 6 ins. in height was 47 lbs. 



With the aperture of 2 ft. by 2 ft., and the wheat only 2 ft. in height, 

 that is to say, level with the top edge of the aperture, the dormant 



