18 Trans. Acad. Sci. of St. Louis. 



The sum of the 108 values for pressure on the front side, 

 each multiplied by the area to which it applies, viz.: -^ foot, 

 is 66.98 lbs. For the back side it is 51.76 lbs. The total 

 force to be applied at the center of pressure is therefore 

 118.7 lbs. 



For the location of the center of pressure, we have for the 

 front and back sides, respectively, 



^ ^ ^ Fl 169 « .o 

 ^•^"^^' E^= 6770 = '•''• 



Back, 541- ^-^ =2.47. 

 ' ^F ~ 51.8 



The center of pressure for the front side of the board is in 

 vertical row 7, and 0.02 feet from the middle line of the 

 board. For the back side it is in row 6, and 0.03 feet from 

 the middle line. These pressures would therefore practically 

 balance on the middle line. 



Summing the moments of the pressures with respect to the 

 upper edge of the board, the center of pressures is likewise 

 found to be below that edge a distance. 



For the front side 17.1 inches. 

 For the back side 18.6 inches. 



On the front side, the center of pressure is above the mid- 

 dle horizontal axis, a distance 0.9 inch, while for the back 

 side, the center of pressure is below that line by 0.6 inch. 



The resultant center of pressure is therefore slightly 

 above, but very near the center of the board. 



The completeness with which the indications of the col- 

 lector and gauge check against the spring balance, is 

 doubtless due in some degree to accident. It may be 

 worthy of remark that the first reduction gave for the 

 sum of the moments over the board a value 340 instead of 

 297 as before given. The reduction of all the original obser- 

 vations was then repeated, and the distributed pressures shown 

 in Fi<ys. 3 and 4 were carefully considered. There appeared 

 to be no justification of any change which could affect the 



