PLATE XI 



Fig. 1. — 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 dowTiward on the 

 tray, showing the 60° angle which the base makes with the graduated side. This 

 tray contains 255 balls, as will be seen by reference to the graduations. 



