Frost: AUXANOMETER AND CONTINUOUS RECORDER. 183 



counter-weight on the wheel is made sufficient to keep taut 

 the thread which passes around the plant. 



As the plant increases in thickness the thread is unwound 

 from the pulley upon which it was previously wound; and as 

 this turns, and the teeth of the large wheel pass the ratchet, 

 the electric current is alternately opened and closed. 



In measuring growth in length the instrument is supported 

 above the plant and the thread passed from the growing part 

 to the small wheels. If the smallest wheel is used, during the 

 growth of a millimeter, 46 registrations are made, that is to 

 say one- forty- sixth of a mm. in length causes the circuit to be 

 closed, while the largest wheel registers a growth of one- 

 seventh of a millimeter. 



See Plate VIII. 



THE CONTINUOUS RECORDER. 



This part of the apparatus consists essentially of two rollers, 

 one of which is attached to a clock train, and as it revolves 

 winds upon itself a ribbon of paper on the other roller, 

 and an electro-magnet, to the armature of which is at- 

 tached a pen that presses against the paper on the second 

 roller. While the circuit remains open a continuous line is 

 traced near one edge of the paper ribbon. When the circuit is 

 closed the pen is drawn to the other side of the paper and the 

 length of the line traced there denotes directly the length of 

 time that the circuit is closed. 



The clock train is an eight day lever movement with strong 

 double springs. The case which is seven inches in diameter 

 is finished in brass, and is so attached to the base that it can be 

 easily removed. Projecting through the front of the case is 

 the pinion by which the rollers are turned. This pinion re- 

 volves once in twelve hours, carrying with it the roller 

 made of brass carefully turned and balanced. It is 

 slightly less than four inches in diameter; thus the paper 

 moves at a rate of one inch per hour. It has quarter inch 

 flanges, and an arrangement by which the end of the paper is 

 held in place. On the outer surface of this roller is a dial 

 plate with the lettering opposite to that on an ordinary clock. 

 Upon the support is a pointer. By means of this arrangement 

 the time indicated by the clock can be read within a few min- 

 utes. 



The second roller, with the exception of the dial, is exactly 

 similar to the first. Both are mounted on steel shafts, turned 



