100 



shoulders or pins on the record lever in the proper positions. 

 Such brief intervals are, however, hardly useful except in spe- 

 cial cases. 



The auxanometric lever should work easily and smoothly, 

 and truly in a vertical plane. This may be 

 accomplished in a manner devised by Pro- 

 fessor Herbert M. Richards, who kindly 

 allows me to incorporate the idea in this 

 paper. A U-shaped piece of metal is cut 

 out, and the ends of the legs are bent to a 

 J-form. These serve as beds for pieces of 

 capillary, or very heavy- walled, glass tub- 

 ing which function as "hole-jewels" for 

 the pivot of the recording lever. This 

 pivot may be made of a thinnish needle, 

 preferably a long one. Placing the "hole 

 jewels" on the pivot, they are bedded into 

 the J-shaped arms by means of shellac or, 

 better, sealing-wax, and adjusted so as to 

 give as little end-shake to the lever as will 

 allow it to work freely. The lever and its 

 support are then a simple piece of appa- 

 ratus which may be held in place by means 

 of a clamp. The clamp may be easily 

 improvised, a gravel-filled box or bottle 

 serving as a foot, or a retort stand may be 

 used. 



The recording pen is very satisfactory if 

 made of sheet celluloid, which may be ap- 

 propriately bent so as to scratch lightly on 

 smoked paper or mica, attached to the 

 lever actuated by the arm on the clock. 

 Mica is especially good because it does not warp if carefully 

 smoked and may be used in making sun-prints. The record 

 reproduced in the accompanying figure was made in such a way. 

 Some pieces of bent tin serve to make a holder for the recording 

 surface or it may be attached simply by thumb tacks. 



Fig. 3. Record of 

 growth of Vicia Faba 

 seedling. The dots op- 

 posite the marks indicate 

 six-hour intervals, begin- 

 ning at 6 p. M., May 14, 

 1903. The decrease and 

 irregularity in growth 

 after the first 24 hours 

 was due to unfavorable 

 conditions. 



