ELECTRO-MOTIVE POWER. 



which is acted upon by the eccentric, and is thus allowed to 

 press against the axis y during half the revolution, and removed 

 from contact with it during the other half-revolution. When 

 the spring r' presses on the axis y the current is established ; 

 and when it is removed from it the current is suspended. 



It is evident that the action of this machine upon the lever 

 attached to the axis k is exactly similar to that of the foot on the 

 treddle of a lathe or a spinning- wheel ; and as in these cases, the 

 impelling force being "intermittent, the action is unequal, the 

 velocity being greater during the descending motion of the crank o 

 than during its ascending motion. Although the inertia of the 

 fly-wheel diminishes this inequality by absorbing a part of the 

 moving power in the descending motion, and restoring it to the 

 crank in the ascending motion, it cannot altogether efface it. 



Another electro-motive machine of M. Froment is represented 

 in elevation in fig. 4, and in plan in fig. 5. This machine has the 



advantage of producing a perfectly regular motion of rotation, 

 which itetains for several hours without sensible change. 



A drum, which revolves on a vertical axis x y, carries on its 

 circumference eight bars of soft iron a placed at equal distances 

 asunder. These bars are attracted laterally, and always in the 

 same direction, by the intermitting action of six electro-magnets 

 6, mounted" in a strong hexagonal frame of cast-iron, within 

 which the drum revolves. The intervals of action and suspension 

 200 



