A SIMPLIFIED I RECISION AUXANOMETER 
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/, the escapement wheel turns. At the end of one revolution the pin 
of the escapement wheel is again engaged by /. Foi each revolution 
of the escapement wheel the pinion wheel G turns sufficiently to lift the 
rack Fo.i mm. This upward movement of the rack causes the contact 
at D to open and the plant must grow o.i mm. before it will close 
again. Thus it will be seen that a record is made for each o.i mm. of 
growth, and from the chronograph records the rate of growth may be 
determined. 
It will be noticed that the circuit is closed at D but never broken 
there. The break is between H and J. This avoids arcing and the 
pitting of the terminals at D. It prevents sticking and actual falsi- 
fication of the record due to changes in the length of E. Making the 
break between H and J has another advantage: in setting up the 
instrument it is only necessary to attach the plant at C, and make the 
electrical connections. The escapement wheel is released and con- 
tinues to revolve until the rack F has lifted sufficiently to open D. 
The instrument then begins to record growth, no further adjustment 
being necessary. 
As the rack F moves up into the case the clock spring which actuates 
G unwinds. It is rewound by grasping the lower end of F and pulling 
it down. As the rack is 15 cm. long, 15 cm. of growth may be recorded 
at one winding. 
The expense of the experimental work on this machine has been 
borne by the L. E. Knott Apparatus Company of Boston and their 
mechanician, Mr. Browne, is to be credited with the development of 
the design so as to minimize the cost of manufacture. 
Harvard University, 
Laboratory of Plant Physiology 
