THE BALANCED CRESCOGRAPH 2oy 



weight W, in the place of coiled spring. The complete 

 apparatus is seen in figure 94. 



For purpose of simplicity of explanation, I assumed 

 the growth rate to have a definite value of r^^ inch per 

 second. But the rate varies widely in different plants and 

 even in the same plant at different days and seasons. In 

 practice the rate of growth for which compensation has 

 to be made varies from j^y^o ^^ 25~ooo~ iii^h, or from 0"17/x 

 to I'O/x per second. We have thus to secure some means of 

 continuous adjustment for growth, the rate of which could 

 be continuously varied from one to six times. This range 

 of adjustment I have been able to secure by the com- 

 pound method of frictional resistance and of centrifugal 

 governor. As regards frictional resistance the two pointed 

 ends of a hinged fork rub against a horizontal circular plate 

 not shown in the figure. By means of the screw head S, 

 the free ends of the fork spread out and the circumfer- 

 ence of the frictional circle continuously increased. The 

 centrifugal governor is also spread out by the action of 

 the adjusting screw. By the joint actions of the frictional 

 control and the centrifugal governor, the speed of rotation 

 can be continuously adjusted from 1 to 6 times. When the 

 adjusting screw is set in a particular position, the speed of 

 rotation, and therefore the rate of subsidence of plant-holder, 

 remains absolutely constant for several hours. The attain- 

 ment of this constancy is a matter of fundamental import- 

 ance, and it was only by the employment of the compound 

 system of regulation that I was able to secure it. 



The method of obtaining balance now becomes extremely 

 simple. Before starting the balancing movement by clock 

 regulation, the plant is made to record its magnified growth 

 by the Crescograph. The compensation is effected as 

 follows : the speed of the clockwork is at the beginning 

 adjusted at its lowest value, and the pressure of a button 



