100 



MECH.\JS1CS. 



with one hook attached to the plow and the other to the 

 whiffle-tree. The amount of force required to draw the plow 

 is accurately measured on the scale by the index or pointer,. 



Sometimes the motion of this index is multiplied, or 

 made greater and more easily seen, by means of a cog- 

 wheel and rack-work ; but this renders the instrument, at 

 the same time, more complex. 



Another form of this instrument is shown in fig. 109, 



Fig. 110. 



Elliptic Dynamometer, in compact /orm : S S, spring; F, cross-lever /or moving 



index. ^ 



where tlie ends of the oval spring, Q Q, are attached to 

 the plow and draught. The harder the force exerted by 

 the team, the closer together will the sides of tliis spring 

 be brought, causing the rod, E, to press against the index 

 or pointer, and showing the precise degree of force on the 

 circular scale. 



An improvement, by rendering the instrument more 

 compact, is shown in fig. 110, where S S is the spring, and 

 directly over it is the graduated scale. 



