1878.] Continuous Railway Breaks. it 
had experience of its working was generally favourable ; but 
it appears in the evidence that it is in no sense automatic, 
and it is entirely under the control of the guard, and not of 
the engine-driver. One necessity of its successful working 
is that the pipes should always be full of water, and in the 
event of a leak occurring in any part of the train its effi- 
ciency might be seriously interfered with, but when in 
proper working order it is no doubt a very powerful break. 
3. The Vacuum Break. — Smith’s vacuum break, which 
formed one of those experimented with by the Royal Com- 
mission, may be thus described -On the side of the 
smoke-box of the locomotive there were two steam ejedtors 
for exhausting air, operating conjointly, but adting inde- 
pendently in case one should part. Under each carriage 
and van throughout the train there was an india-rubber 
cylinder, of 15 inches diameter and 16 inches extreme 
stroke, stiffened with internal metal rings, and capable of 
collapsing and extending lengthwise. Under the tender 
there were two such cylinders. These cylinders were in 
communication with the ejedtors on the engine by means of 
a double line of pipes, connected at the tail of the train 
and forming a complete circuit through it, with hose 
couplings between the carriages. On steam being admitted 
to the ejedtors by the driver, the air is exhausted from the 
collapsing cylinders, and the movable end of each being 
connedted with the ordinary break gear of each carriage, 
the breaks are at once applied. By opening an air-valve 
the cylinders refill, and the breaks are released. In addition 
to the above there was in the front and rear guards’ van 
another arrangement for applying the breaks in case of 
emergency. This consisted of an air-exhauster in each van, 
nearly over one of the axles. On this axle a grooved 
fridtion-wheel was bolted and keyed, and in line with this 
another grooved fridtion-wheel of the same dimensions was 
suspended from the carriage in such a way that it could be 
thrown into gear with the first wheel or kept clear at 
pleasure. By means of a belt which passed up through the 
floor of the van, the second wheel, when set in motion, drove 
the wheel of a rotary pump-exhauster which was fixed in 
the van. The exhauster was made to run either way. 
Near the pump in the van there was a lever held up by a 
notch in a standard, and when the pump was required to 
work the lever was pushed out of the notch by a cam lever. 
By this operation the second fridtion-wheel under the car- 
riage was thrown into gear with the axle-wheel, and, if the 
train was in motion, the pump was set to work and the air 
