PLATE XI 
Fig. I—Measuring tray used in counting total number of balls delivered to the 
container on the balance arm during the 24-hour period. 
. Fig. 2.—Another view of the measuring tray looking vertically downward on the 
tray, showing the 6o° angle which the base makes with the graduated side. This 
tray contains 255 balls, as will be seen by reference to the graduations. 
