270 



ELECTRIC LIGHTING, PROGRESS OF. 



ture-wire, and the oval figures the field-bob- 

 bins with their iron cores. One end of the ar- 

 mature zigzag is connected with a ring attached 

 directly to the axle, and the other with a similar 

 ring insulated from it. The current is taken 



FIG. 2. 



off by two rubbers. The field-magnets are ex- 

 cited by a small separate continuous-current 

 machine. The machine exhibited weighed but 

 1,175 pounds, and yet was able to support 300 

 Swan lamps, stated to be giving 20 candles 

 each, when driven at 2,000 revolutions per 

 minute. The armature-coil weighed but 18 

 pounds. An armature of this form has evi- 

 dently a good many advantages in practical 

 use, one of the chief of which is its little lia- 

 bility of becoming overheated. Its low first 

 cost is also a very important advantage over 



FIG. 3. 



the armatures of present machines, and will 

 secure it the preference in all those cases where 

 an alternating-current machine is desired. The 

 published descriptions of this machine do not 

 indicate the part Mr. Ferranti has taken in its 



production. The only novelty about it is the 

 armature, and that is the invention of Sir Will- 

 iam Thomson. 



The Gordon machine is chiefly remarkable 

 for being the largest dynamo yet constructed. 

 It is designed to supply 7,000 incandescent 

 lamps with adequate driving power, but it has 

 so far supplied only 1,300. The machine con- 

 sists essentially of a central. disk carrying elec- 

 tro-magnets, and revolving between sets of 

 similar electro-magnets on each side of it. The 

 rotating portion is the field, and the stationary 

 electro-magnets the armature. This latter con- 

 tains 128 coils, 64 on each side this being 

 twice as many as in the rotating part. The 

 object of this is to prevent the coils of the 

 fixed series acting detrimentally upon each 

 other by induction, a difficulty experienced in 

 a former machine of Mr. Gordon's, where the 

 coils in the moving and fixed part were equal. 

 The coils of the revolving magnets are excited 

 by a separate continuous-current machine, as is 

 the field of the Ferranti. The total weight of 

 the machine is 18 tons, that of the revolving 

 part being seven tons. Its diameter is eight 

 feet nine inches, and it is designed, when the 

 machine is giving its maximum current, to be 

 driven at 200 revolutions per minute. The 

 tests so far made show a very high efficiency, 

 and the alternating currents are found to work 

 well with the incandes- 

 cent lamps. Large as this 

 machine is, Mr. Gordon 

 regards it as a small af- 

 fair compared to what 

 should be used in supply- 

 ing lamps from a central 

 station, he having ex- 

 pressed himself as desir- 

 ous of constructing one 

 with the magnet -wheel 

 18 feet in diameter. The 

 engraving, Fig. 3, gives a 

 sufficiently clear repre- 

 sentation of this enor- 

 mous dynamo to render 

 any further description 

 unnecessary. 



The feature of the year 

 in incandescent electric 

 lighting was the starting 

 into operation of the first 

 Edison district in New 

 York city. While other 

 ; : inventors have either had 

 I no decided conviction as 

 ^ to the best way of sup- 

 ? plying incandescent light- 

 ing to the consumer, or 

 have not cared to ex- 

 press themselves on the 

 matter, Mr. Edison, from the outset of his ex- 

 periments, was convinced that the only prac- 

 ticable method was distribution direct from the 

 machine from large central stations, without 

 the interposition of intermediary apparatus, and 



