134 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1907. 
degree its particular requirements because of the action of some 
foreign road. 
7. Extraordinary advances have been and are being made, and new 
discoveries are always possible. The limits of none of the systems 
now in use are clearly defined, and it would seem both natural and 
wise that the various manufacturing, technical, and inventive activi- 
ties should pursue every lead to its logical conclusion, for the best will 
be none too good. 
It is not my present intention to investigate railroad economics, nor 
to formulate any final conclusions in the matter of steam railway elec- 
trification, but rather briefly to analyze and make running comment 
upon various phases of the problem often discussed by engineers; to 
give some comparative facts as they have thus far developed; to 
describe sundry developments in electric locomotive construction; and 
to illustrate in some detail features specifically characteristic of the 
three typical initial equipments now commanding attention. 
Motor equipments.—In discussing the selection of any system, the 
first thing to investigate is the motor. In railway operation that 
which is to be replaced is a steam locomotive, in other words, a motor 
supplied by a local boiler, furnace, and coal bin; that which is pro- 
posed in its place is another motor, or group of motors supplied 
through a wire by bigger boilers, furnaces, and coal bins, or by 
energy from a water power. The working conductor, with every- 
thing connected to it in transmission or generation, although essen- 
tial, is tributary to the motor and its requirements. 
It is not sufficient that the source of power can be made of any 
desired size, although it is an essential feature; in any case such con- 
centrated generating equipment must supply a number of motors. 
What 7s essential, and in the last analysis vital, is that the new motor 
shall have not only certain mechanical advantages, to the extent of 
eliminating the evils of reciprocating parts, and reducing the cost of 
up-keep, but above all it must have capacity, measured not alone by 
drawbar pull or speed, but by both, and it must be of sustained char- 
acter; and to accomplish more than the steam locomotive, it must be 
greater than that of the latter. Such capacity should naturally be 
attained, first, by betterment of the individual motor or locomotive, 
and then, when this increase has reached its limit, by combining 
motors or locomotives under a common control by the multiple-unit 
Syotem. F* 2/ 451% 
Capacity being, therefore, the keynote of the equipment, I shall 
discuss at some length the characteristics of conductors and motors 
used with direct current and with alternating current. In so far as 
these comments relate to single-phase alternating-current operation, 
they will in some measure be based upon the only existing commer- 
cial development of this character now in the United States, that is, 
