Electromagnetic Induction Machines. 445 



each other, for the reception of the same number of cores or 

 armatures, G^. The cores project about two inches through each 

 side of the disk, and are held firmly in their places by screws 

 tapped through its periphery. Around each inside face of the 

 circular framing, and concentric with the driving-shaft, sixteen 

 cylindrical electromagnets are fixed at the same angular distance 

 from each other and from the centre of the shaft as the iron cores 

 round the disk; the two circles of magnets consequently have 

 their poles opposite each other, with the disk and its circle of 

 iron cores revolving between them. The ends of the cores are 

 terminated with iron plates of a circular form, which answer the 

 double purpose of retaining the helices surrounding the cores in 

 their places, and overlapping for a short distance the spaces be- 

 tween the poles of the electromagnets. The closing of the mag- 

 netic circuits of the electromagnets and armatures for a short 

 distance, like the closing of the electric circuits for a brief in- 

 terval at the point of no current, has a marked influence on the 

 power of an electromagnetic induction machine, — both contri- 

 vances conspiring, simultaneously, to maintain the magnetic 

 intensity of the electromagnets during the rise and fall of the 

 magneto-electric waves transmitted through the helices. 



The cylindrical bar magnets are each coiled with 659 feet of 

 copper wire 0*075 of an inch in diameter, insulated with cotton ; 

 the helices are grouped together to form a fourfold circuit 2636 

 feet in length, and are joined up in such a manner that adjacent 

 magnets in each circle, as well as those directly opposite in both 

 circles, have north and south polarity in relation to each other. 

 A charge of permanent magnetism was imparted to the system 

 of electromagnets by the current from.; a separate electromag- 

 netic machine. 



The armatures, although formed of sixteen pieces of iron, are, 

 by projecting through both sides of the disk, thirty-two in num- 

 ber. The length of insulated wire on each armature is 1 16 feet ; 

 and the thickness is the same as that on the electromagnets. 

 These helices are divided into eight groups of four each, and 

 coupled up for an intensity of 4 x 464 feet. One of the groups 

 is used for producing the minor current for exciting the circle 

 of electromagnets, while the remaining groups are joined together 

 for a quantity of seven, and an intensity of four for the produc- 

 tion of the major current from the machine. The aggregate 

 weight 'of wire on the electromagnets is 356 lbs., and on the ar- 

 matures 26 lbs. The helices for exciting the electromagnets 

 are connected with the commutator H, while those producing 

 the major current are placed in connexion with the rings I, K, 

 or in place thereof with another commutator, according as the 

 alternating or the direct current from the machine is required. 



