APPENDIX C. 



llo 



In addition to determining the position of the center of pressure for a square plane, 

 Kummer extended his experiments to the case of differentlj^ shaped rectangles, and his 

 results witli these are strikingly suggestive. It has been pointed out in cliapter VI that 

 above and below an angle of about 30° there is a reversal in the relative amounts of the 

 pressure on inclined rectanglar planes of different shapes; the tabulated results of Kummer 

 exhibit a similar reversal in the position of the center of pressure, of which the followino- 

 may be given as an example: 



Dkiancc of center of pressure from center of plane. 



For small angles the position of the center of pressure is further from the center of 

 figure in the 180 x 180 mm. plane than in the 90 x 180 mm. plane, wliile for 45° tliis 

 relation is reversed. It appears, therefore, that the reversal in the amount of pressui'e, 

 brought out in the experiments presented in this memoir, finds its counterpart in a corre- 

 sponding reversal in the position of the center of pressure exhibited in the work of Kummer. 

 It is believed that in this striking analogy may be found a key to the more complete 

 rational and deductive treatment of these inseparably related problems. 



