CHAP. VII.] 



ELECTRO-MO TORS. 



659 



use of, winch was invented by a French engineer, M. Chenot, and 

 which has received the name of electric sorter. Fig. 429 gives a 

 general view of the apparatus. 



On the left is a hopper filled with the powdered mineral to be 

 sorted, and which drops down through the bottom of the hopper 

 on to a metallic sheet rolled round two cylinders ; from thence it is 

 carried beneath three vertical wheels provided with electro-magnets 

 attached to their circumference. These electro-magnets are con- 

 nected with a commutator fixed to the common axis of rotation. 

 When the motion brings this to 

 the lower part of the apparatus 

 they receive the current and be- 

 come active. The magnetic part 

 of the mineral only is attracted, 

 and remains in contact with the 

 electro-magnets until the moment 

 when the current, ceasing to excite 

 the latter, passes to the magnets, 

 which replace them. Then the 

 magnetic parts fall off, while 

 the non-magnetic fragments are 

 thrown out behind into a second 

 hopper. The sorting is thus 

 carried on continuously. 



Machines similar in principle 

 but having permanent magnets 

 are commonly employed for se- 

 parating iron and steel filings or 

 shavings from those of other metals in engineering workshops. 



A modified form of this machine has been designed by the same 

 inventor, in which the electro-magnets are fixed, and by means of a 

 revolving collector, the magnetic or attracted material is swept off 

 into a box placed for its reception. 



A French engineer, M. Achard, has conceived the idea of bor- 

 rowing from the active force of a train in motion the power 

 necessary for gradually pressing the blocks of the brakes against the 

 wheels of the carriages : and to put out of action the mechanism 

 which would act in this way, he makes use of the attraction of an 



u u 2 ' 



FIG. 430. -Achard's electric brake: mechanism 

 for throwing out of gear. 



