126 MECHANICS. 



This roller is made to turn by means of a wheel run- 

 ning on the ground, which gives motion to the roller 

 through an endless chain, working a cog-wheel by 

 means of an endless screw. The cylindrical dynamom- 

 eter, shown in Fig. 101, is used for this purnose, length- 

 Fig. 101. wise upon which the two 

 rollers are placed for hold- 

 ing the paper. With this in- 

 strument a permanent reg- 

 ister might be made of the 

 Self-recording Dynamometer. forcc required for different 

 plows, the accuracy of which none could dispute. 



DYNAMOMETER FOR ROTARY MOTION. 



All these dynamometers apply only to simple, on- 

 ward draught, as in plowing, drawing wagons, harrow- 

 ing, &c. There is another, represented in Fig. 102, of 

 very ingenious but complex construction, which shows 

 the force required in working any rotary machine, such 

 as thrashers, straw-cutters, and mills, and showing,- at 

 the same time, the velocity, and recording the number 

 of revolutions made. 



The whole machine is supported by a cast-iron frame- 

 work, on four small wheels with flanges, like the 

 wheels of rail-cars, that it may be conveniently run up 

 on a temporary rail-way to the thrashing or other ma- 

 chine to be tried. 



The band- wheel, /, on the shaft, e, is connected with 

 the machine under trial, and the force is supposed, in 

 this instance, to be applied by hand to the handle, a, 

 on the fly-wheel. 



"When the fly-wheel is turned in the direction shown 



