292 The N.Z. Journal of Science and Technology. [Jan. 
slightly cheaper with a wider gauge. The only items in which savings 
occur with narrower gauge are sleepers and earth-cuttings. Rock-cuttings 
are not affected, as their width is governed by the width of the vehicles ; 
but earth-cuttings must be formed with sloping sides which are far enough 
apart at the bottom to allow drains to be formed on each side outside the 
ballast. A narrower gauge, therefore, only saves a few cubic yards of earth 
in certain cuttings and a few inches in length of the sleepers. The 
factors that do chiefly influence the cost of the permanent-way are, first, 
axle-load, which determines the rail-weight and the size of sleepers; 
secondly, loading-gauge, which defines the clearance of structures, the size 
of tunnels, and the distance apart of adjacent tracks ; and, thirdly, the 
character of the road with respect to grades and curves. These three 
factors are all independent of the track-gauge. 
The next question to consider is speed ; and here again gauge has no 
practical influence. As the speed increases the gauge should theoretically 
diminish, until with very high speeds the monorail type of construction 
is reached. The stability of any moving vehicle increases with the speed, 
as is well seen in the bicycle ; and there is a slight reduction in curve 
friction as the gauge is reduced, while the overturning effect on curves is 
resisted by the super-elevation, or cant, of the outside rails, the angle of 
which is independent of the gauge. High speed is, indeed, only a question 
of the diameter of the driving-wheels of the engine ; and this is a matter 
that is governed by curve-radius on the one hand and by loading-gauge, 
or tunnel-height, on the other, while track-gauge has no absolute power 
over it. Certainly the height of the centre of the boiler above the rails 
can be kept lower on a wider gauge when very large driving-wheels are 
used, but a high boiler-centre has lost all terror for the modern designer, 
and for all practical purposes the highest economic speeds can be obtained 
with equal safety, ease, and comfort on any gauge. In point of fact, 
higher speeds are daily recorded in the 4 ft. 8J in. gauge in England than 
are reached on the 5 ft. 6 in. gauge in Ireland, India, or Victoria, and very 
smart running is done on the 3 ft. 6 in. gauge in Java and the Sudan. The 
old Great Western gauge of 7 ft. was the scene of some very fast running 
in its day, but the 4 ft. 8J in. was equally notable at that time, and in 
New Zealand as elsewhere the speeds are now limited by the rails and 
ballasting and not by the locomotive or the gauge. Wherever the standard 
of track construction and maintenance permits it, speeds of sixty miles per 
hour can now be easily attained by modern engines on the New Zealand 
gauge, and, if economic conditions called for or allowed it, locomotives could 
easily be designed to greatly exceed this speed. 
The next question is that of design of rolling-stock and locomotives 
on varying gauges. The width and height of carriages and wagons is not 
dependent on the distance apart of the rails on which they run, but is 
solely governed by. the size of tunnels, the clearance of structures, and the 
distance apart of adjacent tracks (see diagram). The New Zealand Main 
Trunk car-body, for instance, is the same width and height as the usual 
English one, while on the 3 ft. 6 in. gauge in South Africa we find carriages 
and wagons wider, higher, and heavier than any used on the 5 ft. 6 in. gauges 
or on any 4 ft. 8J in. lines in England or Europe. At slower speeds—say, 
under fifty miles per hour—vehicles have a tendency to roll and ride roughly, 
but this is more dependent on the type of draw-gear used than on any other 
feature of the design, and is quite unaffected by the track-gauge. It might 
be thought that side-rolling would be less with the wider gauge, but this 
