1922.] Jenkinson.—Development of the Locomotive. 293 
again is a fallacy. The swaying of car-bodies is caused by uneven track, 
and is aggravated by slack couplings and the absence of side buffers, while 
it is finally resisted by the-side bearing shown in the figure. These side 
bearings are usually kept close together (well inside the wheels on a 
4 ft. 8J in. or 3 ft. 6 in. gauge) to minimize the derailing - moment on 
curves, but their position is not dependent on the gauge, and is in fact 
practically the same on any gauge. Thus the angle of roll of the car-body 
is also independent of the gauge. The cost and weight of cars and wagons 
decreases slightly with the gauge, because of the shorter axles and narrower 
AMERICAN LOADING GAUGE 
-»---, 
Diagram comparing New Zealand and American loading-gauges, and 
showing the bearings. 
bogie-framing, but this is virtually unimportant, and where the gauge is 
narrower than 3 ft. there is great difficulty in finding room laterally between 
the wheels for spring- and brake-gear, air- and gas-reservoirs, and all the 
apparatus of modern bogie stock. The conclusion is unavoidable that 
there is no advantage in a wider gauge than 3 ft. 6 in., and a decided 
disadvantage in a narrower gauge than 3 ft. from the point of view of 
rolling-stock. 
When the locomotive is considered, the limitation of gauges narrower 
than 3 ft. is increased. The size of engines is limited by the allowable 
pressure between the wheel and the rail, and this is in the neighbourhood 
of 10 or 11 tons (i.e., an axle-load of 20 to 22 tons) with modern steel tires 
