Oct. 18, 1915 
Automatic Transpiration Scale 
123 
Ball-dropping device. —The ball-dropping device used in our experi¬ 
ments is shown in fig. 12. A commercial telegraph sounder provides 
an efficient meehanism for actuating the valve. When the circuit is 
closed, the slide A moves in the direction of the arrow and releases the 
lowest ball in the tube. The remaining balls are prevented from pass¬ 
ing down the tube by the upper septum B, which moves into the tube as 
the lower septum C moves out. When the circuit is broken, a spring 
restores the valve mechanism to its original position and the reserve 
balls slide down the tube so as to rest against the lower septum. The 
mechanism is now in 
position to drop 
another ball as soon as 
the circuit is again 
closed. 
As the discharged 
ball leaves the valve it 
drops into the bal¬ 
anced receptacle D, 
which tips downward 
under the weight of the 
ball, closing the circuit 
of the recorder through 
the mercury cups E be¬ 
low. The ball in the 
meantime rolls into the 
funnel and is delivered 
into the ball receiver L 
suspended from the 
balance beam. With 
this arrangement no 
record is made unless 
the ball is actually re¬ 
ceived in D, and a second ball can not be recorded until the first has 
been delivered and D has returned to its initial position. In very gusty 
weather there is occasionally a fluttering of the valve A, two balls being 
dropped in rapid succession. The second ball simply shoots over D 
into the waste cup and is not recorded. 
The tube holding the reserve supply of balls (fig. 11) is of glass bent 
into the form of an open spiral, and is joined to the valve tube by a 
conical adapter. The diameter of the valve tube at the septa must be 
only slightly greater than the diameter of the balls to insure the valve's 
working properly, and the tube should taper gradually to this diameter. 
The distance between the adjacent faces of the two septa should also be 
equal to the diameter of the ball. Each septum when in its intercepting 
Fig. 9. —Copeland’s apparatus for recording transpiration in which 
the loss in weight through transpiration is counterbalanced by a 
change in position of a partially submerged float. 
