he author would in conclusion
draw attention to what may possibly be one course of locomotive
development in the future. Time is money, and it may be in the coming
years that a demand will arise for faster means of transit than that which
we possess at present. How can we meet it? With our railways laid out with
the curves and gradients existing, and with our national gauge, and our
present type of locomotive, no great advance in speed is very probable;
the mean speed of express trains is about fifty miles an hour, and to take
an average train of 200 tons weight at this speed over a level line
requires between 650 and 700 effective horse-power, within the compass of
the best engines of the present day. But if instead of fifty miles an hour
seventy is required, an entirely different state of things obtains. Taking
a train of 100 tons, with engine and tender weighing 75 tons, or 175 tons
gross, the first question to determine will be the train resistance, and
with reference to this we much want careful experiments on the subject,
like those which Sir Daniel Gooch made in 1848, on the Bristol and Exeter
Railway, which are even now the standard authority; the general use of oil
axle-boxes and long bogie coaches, irrespective of other improvements,
would render this course desirable. With regard to the former, they appear
to run with less friction, but are heavier to start, oil boxes in some
experiments made on the South-Western Railway giving a resistance of 2.5
lb. per ton, while grease boxes ranged from 6 lb. to 9 lb. per ton. Again,
the long and heavy bogie Pullman and other coaches have the reputation
among drivers, rightly or wrongly, of being hard to pull. The resistance
of an express train on the Great Western Railway at seventy-five miles an
hour was 42 lb. per ton, and taking 40 lb. per ton for seventy miles an
hour would give a total resistance on the level of 7,000 lb.,
corresponding to 1,400 horse-power--about double the average duty of an
express engine of the present day. The weight on the driving wheels
required would be 183/4 tons, allowing one-sixth for adhesion, about the
same as that on the driving axle of the Bristol and Exeter old bogie
engines. Allowing 21/2 lb. of coal per horse-power per hour would give a
total combustion of 3,500 lb. per hour and to burn this even at the
maximum economic rate of 85 lb. per square foot of grate per hour would
require a grate area of 41 square feet, and about 2,800 squar