186 SECTIONAL ADDRESSES. 
until 1885, and commutation in a reversible motor with copper brushes 
caused great trouble; armature construction and winding was in its 
infancy ; the suspension of the motor and the method of gearing it to the 
car axles were problems which were solved only after much experience. 
Rapid progress was made after about 1887, and the closing years of the 
century saw an enormous development, the elimination of horse tram-cars 
throughout the world and the electrification of a number of city and 
suburban railways. 
Of the various systems of collecting the current, only two have 
survived for street-cars, viz., the usual overhead wire and the exceptional 
underground conduit ; in the case of railways there is no necessity for a 
conduit and the conductor rail is carried on insulators above the ground- 
level. 
Although 500-volt D.C. supply has been standardised for street tram- 
ways, the relative merits of D.C. and A.C. for electric railways has been a 
burning topic for over twenty years, and is now perhaps more burning 
than ever. It is somewhat akin to the battle of the gauges in the early days 
of steam railways, for it involves in many cases the problem of through 
running, if not now, in the not very distant future. Although the three- 
phase system was successfully installed in Northern Italy, it has grave 
disadvantages, and the battle now is confined between direct current at 
an increased voltage of, say, 1,500 to 2,000 volts, and single-phase 
alternating current. In the latter case there is, moreover, a further 
question as to the best frequency to adopt, this being usually either 
25 or 162. The development of the A.C. commutator motor to the 
stage where it was applicable to traction took place during the first few 
years of this century, and, although in itself it is inferior to the D.C. motor, 
it introduces so many simplifications and economies in the transmission of 
the power from the generating station to the train that experts are very 
divided as to the relative merits of the two systems for main-line electrifi- 
cation. 
I can only just refer to the applications of electrical power to chemical 
and metallurgical processes. Some of these are purely electro-chemical, 
others are purely thermal, while in many processes the electric current 
performs the double function of melting and electrclysing. The possibility 
of electroplating was discovered as early as 1805, but the commercial 
application of electro-chemistry on a large scale was impossible before the 
development of the dynamo. Within the last thirty years the provision of 
an abundant supply of electrical power has led to the creation of enormous 
electro-chemical industries; I need only instance the production of 
aluminium, carborundum, and calcium carbide. These industries have 
usually been established near a hydro-electric plant and provide a load 
of very high load-factor. 
I turn now to what may be called both the earliest and the latest appli- 
cation of electricity; that is, its use for transmitting intelligence. One of the 
greatest factors in the development of our modern life has undoubtedly 
been the network of wires and cables which has spread over the whole 
earth, making possible an almost instantaneous transmission of intelligence 
and interchange of opinions. In the early days of electrical science the 
discovery of a new property of electricity was followed by attempts toutilise 
it for this purpose. As early as1746 there are records of the use of frictional 
