1918.] The N.Z. Journal of Science and Technology. 
327 
used were of the Mallet type. Progress through the tunnel was slow and 
uncertain owing to the state of the rail. The fires on the locomotives 
were drawn and remade with special coal; the abrasion of the rails was 
excessive because of the liberal use of sand to maintain adhesion. The 
use of electricity in the tunnel has made a very much increased service 
possible because of the higher speed of the train through the tunnel and the 
possibility of applying the automatic block system to the tunnel. 
Another typical example is the Hoosac Tunnel on the Fitchbury divi¬ 
sion of the Boston and Maine. The tunnel is four miles and three-quarters 
long, and the grade only J per cent.; and although the limiting grades are 
on the outside of the tunnel, which place a limit upon the amount of load 
hauled, the obstacle to the traffic was actually caused by the tunnel in spite 
of the easy grade. It is interesting to note that an attempt was made to 
get over the difficulty by providing specially designed oil-burning Mallet 
engines as helpers to draw the trains with their engines through the tunnel. 
A passenger-train could not occupy the tunnel at the same time as a freight- 
train moving in an opposite direction. The corrosive action of the fumes 
and the abrasion caused by the excessive use of sand on the rails reduced 
the life of the rail to three or three and a half years, and large mainten¬ 
ance gangs were necessary, as there were long periods during which work 
in the tunnel was impossible. Electrification has doubled the capacity of 
the tunnel for traffic on account of the introduction of the block system, 
the tunnel being divided into three blocks, whilst the expenses have been 
considerably reduced. 
Other tunnels which proved an obstacle in the same way are the 
St. Clair Tunnel, the Baltimore and Ohio, the Detriot Biver tunnels ; and 
they have been electrified for the length of the tunnel and some short 
extensions and yards outside. 
Conclusion. 
Enough has been said to reveal the evolutional process of main-line 
electrification as it proceeds in other parts of the world, and it may be 
concluded that it will proceed on the same lines in the Dominion of New 
Zealand. 
The process would appear to be as follows : Here and there a tunnel, 
then a division with steep grades, after that a division with lesser grades, 
are converted to electric working, whilst steam service is maintained over 
the remainder of the system. All the examples quoted, however, have one 
feature in common : extraordinary methods have been employed to carry 
on the service with steam locomotives ; new and larger locomotives are 
designed for work on the grades, one locomotive taking the place of two 
previously employed. In case of the tunnel, special oil-fuel locomotives 
are employed, or the fires are drawn before entering the tunnel and fresh 
fires built up of special non-smoking coal; ventilating-systems have been 
tried, all to no purpose ; and finally electrification is adopted with marked 
advantage. 
It would appear at first sight as if there were an extraordinary reluctance 
on the part of railway engineers to adopt electric traction and they were 
unduly conservative in this matter. The real explanation, however, of this 
procedure will be found in the fact that when the necessity first arose there 
was no electric power available of which the railway engineers could avail 
themselves, and they were faced with the necessity of seeking out water¬ 
power sources or building fuel-power stations in positions where cheap 
coal was unprocurable, which is a formidable task and one involving a big 
