73 o THE POPULAR SCIENCE MONTHLY. 



coils in place. It has the mechanical advantage of presenting a 

 smooth exterior surface which can be turned true, and of holding 

 the winding in such a way that it can not become displaced, as is 

 possible with coils wound over the core and bound in place by a 

 wrapping of wire. Electrically it has the advantage of materially 

 diminishing the air gap the space between the face of the arma- 

 ture and the field poles and hence allowing the coils to move in 

 an intenser magnetic field. The armature core is carried by a 

 cast-iron spider weighing over fifteen tons which is keyed directly 

 to the shaft of the driving engine. The brush holders, of which 

 there are twelve sets, corresponding to the number of field poles, 

 are mounted upon a yoke supported at one side of the field mag- 

 net frame. They are moved into position by means of a shifting 

 gear operated by a hand wheel and are readily accessible from a 

 stairway passing over the shaft. The machine is designed to run 

 at seventy-five revolutions a minute and furnish a current under 

 a pressure of six hundred volts. It has an electrical capacity of 

 fifteen hundred kilowatts, and is claimed to have an efficiency of 

 ninety-six per cent. This ponderous machine was found to be 

 much too large and heavy to be shipped in its complete form, and 

 was accordingly forwarded from the factory in parts and assem- 

 bled upon its present foundation. 



An appreciation of its size and capacity may be gained by re- 

 membering what the standards of size were only ten years ago 

 when the Edison "Jumbo" was put to work in the first New 

 York Central station. This machine, which created a veritable 

 sensation at the Paris Exposition of 1881 on account of its im- 

 mense size, required only a hundred and twenty-five horse power 

 to drive it when working at its normal load. It had a capacity 

 of less than one hundred kilowatts, which is but a fifteenth of 

 that of the present " Jumbo," and weighed very much more in 

 proportion to its output. It is to be seen in the exhibit of the 

 General Electric Company, where it is rightly given a place of 

 honor as the precursor of the race of modern direct-connected 

 dynamos. 



While a motor car will answer admirably for the lighter forms 

 of electric traction, the invasion of the domain of the steam rail- 

 road, which electricians are already contemplating, will necessi- 

 tate the design and construction of special electric locomotives. 

 These have already been used quite largely in mine work, and a 

 number of electrical constructors have designed and built such 

 machines of moderate power, but the first one of any considerable 

 size and designed for high speed is one built at the Lynn shops 

 of the General Electric Company and shown in the Transporta- 

 tion Building at the Fair. It is a thirty-ton locomotive intended 

 for a normal speed of thirty miles per hour, and is of sufficient 



