SELF-EECOKDING DYNAMOMETER. 



101 



An inconvenience occurs in the use of the instruments 

 now described from the rapid vibration of the index, re- 

 sulting from the quick changes in the force, partly from 

 inequalities in the soil, and partly from the unsteady mo- 

 tion of the horses. The vibration is sometimes so great 

 that the index can hardly be seen, rendering-it difficult to 

 measure the average force. This inconvenience has been 

 removed, in a great degree, by attaching to one end of 

 the index, E (fig. 110), a piston working in a cylinder filled 

 with oil, C ; this piston has a small hole through it, through 

 which the oil passes from one side to the other as the 

 draught varies, but not fast enough to allow any sudden 

 motion. 



SELF-EECOEDING DYXAMOMETEE. 



A less simple but more perfect instrument is the Self- 

 recording Dynamometer^ which marks accurately all the 



Fi'T. 111. 



The marldnss of the Self-recording Dynamometer. 



vibrations on a slip of paper while the plow is in opera- 

 tion. A pencil is fixed to the index, and presses, by means 

 of a spring, against the paper, thus giving a true register 



