METHOD OF FALLING WEIGHT 2$ 



inertia of the revolving governor, but also the friction of the 

 lower points of the arms of the governor which rub against 

 a horizontal circular plate, not shown in the figure. In- 

 creasing inertia and friction both tend to slow down the 

 speed of the rotation of the vertical spindle on which the 

 rate of subsidence of the plant depends. A left-handed 

 turn of the adjusting screw S causes, on the other hand, a 

 continuous increase in the rate of subsidence. 



When the adjusting screw has been set at a particular 

 position, the balancing rate of subsidence of the plant 

 remains constant for many hours. The attainment of 



Fig. io. Record showing {a) condition of overbalance, and 

 (b) underbalance of growth. (Magnification 2000 times.) 



this constancy is a matter of fundamental importance in 

 accurate investigation by this method. 



The ease and exactitude of securing the balance are shown 

 in the records (fig. lo, a and h). In each of these the exact 

 balance is seen in the first part of the record at a definite 

 position of the adjusting screw. A slight turn of the screw 

 to the right reduced the rate of subsidence, resulting in the 

 upset of growth-balance upwards (fig. lo, a). A turn of 

 the screw in the opposite direction caused overbalance of 

 the growth-rate, the resulting curve being downwards 

 (fig. 10, b). 



Calibration. — This is effected as follows : the rate of 



