1918.] 
The N.Z. Journal of Science and Technology. 
323 
THE ELECTRIFICATION OF RAILWAYS IN NEW 
ZEALAND.* 
By E. Parry, Chief Electrical Engineer, Public Works Department. 
Argument. 
This paper is written with two objects : one is to remove misunderstand¬ 
ings which appear to exist regarding the relative merits of steam and 
electric haulage, and the other is to emphasize the importance of a com¬ 
prehensive system of electric-power supply in its bearing upon the subject 
of railway electrification. 
It must be recognized that the steam locomotive is the most economical 
means of haulage under normal conditions of easy grades and infrequent 
service. When the grades are severe, however, the average speed is 
reduced to a level much less than that imposed by other limiting features, 
the volume of traffic is restricted, and the economic limitations are soon 
reached. A higher speed demands an increased power, which can only be 
got by increasing the engine, boiler, and tender capacity, and as a result 
the dead load increases at the expense of the live load to such an extent 
as to become uneconomical. Electric haulage, on the other hand, is not 
subject to the same limitations as steam haulage, because the power is not 
generated on the locomotive itself. The locomotive merely converts electric 
power received from a stationary source to mechanical power for haulage, 
and, although the adhesion may be the same, a largely increased speed is 
obtainable, and the capacity for hauling and transporting goods is largely 
increased. The gain in speed is manifold : speed of movement is increased 
substantially, usually about twice; it is not necessary to stop for taking in 
water; the adhesion is usually greater and more uniform, and the rails do 
not become slippery in tunnels, as they do under steam-service conditions, 
owing to the deposit of moisture and soot from the locomotive. Smoke also 
interferes with the signal system where the tunnels are of any length, and 
even where ventilating-fans are in use a long period must often be allowed 
for the smoke to clear. 
The limits of steam haulage are also reached in suburban districts where 
rapid service and frequent stops become a necessity, and also where terminal 
stations are found too restricted for the increasing volume of traffic, or 
where the smoke nuisance becomes intolerable, or where it is desired to 
advance the terminal into the heart of a city such as New York or London, 
and where it must of necessity be constructed underground because of the 
prohibitive value of the surface. 
This aspect of the subject is one which is better understood than trunk¬ 
line electrification, and does not, therefore, need the same amount of dis¬ 
cussion as the latter, and the remainder of this discussion will be confined 
to the one aspect of main-line electrification. 
As soon as the limits of steam haulage have been reached on some 
critical section of the Main Trunk, say between Taumarunui and Taihape 
—that is to say, when no more traffic can be conducted over it in spite 
of the utmost possible improvements in track and locomotives, strengthening 
* Paper read at a meeting of the Technological Section of the Wellington Philo¬ 
sophical Society, 12th June, 1918. 
