MACHINE OPERATORS 
117 
This apparatus overcame, to a large extent, the difficul 
ties inherent in the Bogardus piece. In the first place, 
lt: was so constructed as to make possible a fairly ac 
curate performance. If the steel ball missed the slot and 
fell on the disk, it was prevented from falling off by a 
r aised rim. If the ball fell through the slot but missed 
the funnel, it was caught by a sort of apron which ex 
tended around the motor box. This apron was constructed 
at a pitch which quickly brought every steel ball to the 
feont of the machine into a little depression from which 
the operator had to pick it up. The apron was made of 
t'n, and was very noisy at the outset. However, it was 
later lined with heavy felt which subdued the noise very 
effectively. In the second place, this apparatus made it 
Possible to obtain an accurate score. Every successful 
at tempt of the operator to drop the ball through the fun- 
n el was recorded automatically, which meant, of course, 
that the failures were also registered. The latter was 
fecilitated by a Veeder star counter attached to one corner 
of the motor box in such a manner as to engage a pin pro 
jecting from the bottom of the revolving metal disk. This 
counter registered the revolutions of the disk and, at the 
Sa rne time, the number of opportunities for dropping the 
to the operator. The experimenter could there- 
his entire attention to the operator or person 
oeing tested. A third advantage was the ease with which 
the revolutions per minute of the disk could be governed 
fe contrast with the intricate and expensive control of the 
®°gardus apparatus. Fortunately, the range of the motor 
^as exactly suitable for this purpose. Moreover, extensive 
tr 'als showed that the disk would revolve at a constant 
s P e ed for eighteen minutes without the loss of a single 
Solution. After the eighteenth minute, the speed gradu- 
pus given 
fere devote