SELF-RECORDING DYNAMOMETER. 



125 



es from one side to the other as the draught varies, but 

 not fast enough to allow any sudden motion. 



SELF-RECORDING DYNAMOMETER. 



A less simple but more perfect instrument is the Self- 

 recording Dynamometer, which marks accurately all 

 the vibrations on a sHp of paper while the plow is in 

 operation. A pencil is fixed to the index, and presses, 

 by means of a spring, against the paper, thus giving a 

 true register of the force exerted. To prevent the pen- 

 cil from constantly marking on the same line, the pa- 

 per is made to move slowly in a side direction, so that 

 all the vibrations are shown, as represented in Fig. 100, 



The markings of the Self-recording Dynamometer. 



and they may be accurately examined and read off at 

 leisure, a and b representing the forces of two different 

 plows, drawn through a single furrow across the field. 

 The motion of the paper is effected by being placed on 

 two rollers, one of which unwinds it from the other. 



