AUTOMATIC RECORD 



385 



plate has to be moved up and down by means of clockwork. 

 The recording plate has a movement from right to left, 

 and an oscillating movement up and down, at intervals of 

 2 minutes. The slope of the dotted record shows the rate 

 of natural torsion. An enhancement induced in the rate 



Fig. 218. Automatic Recorder of Torsion. 

 M, method of magnification; r, method of reduction. (See text.) 



causes an erection of the curve, while a diminution causes 



a flattening. If the natural torsion becomes reversed, the 



index I moves in clockwise direction, and the record is 



correspondingly reversed from an ascending to a descending 



curve. 



Method of reduction. — A continuous record for 24 hours 



was necessary for my investigation of the diurnal variation 



of torsional movement described in the next chapter. The 



total rotation during 24 hours was too great to be recorded 



2 c 



