,
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 square feet of
heating surface. Unless a most exceptional construction combined with
small wheels is adopted, it appears almost impossible to get this amount
on the ordinary gauge. It is true the Wootten locomotives on the
Philadelphia and Reading Railway have fire-boxes with a grate area of as
much as 76 square feet, but these boxes extend clean over the wheels, and
the heating surface in the tubes is only 982 square feet; but although
these engines run at a speed of forty-two miles an hour, they are hardly
the type to be adopted for such a service as is being considered. On the
broad gauge, however, such an engine could easily be designed on the lines
now recognized as being essential for express engines without introducing
any exceptional construction, and there appears but little doubt that were
Brunei's magnificent gauge the national one, competition would have
introduced a higher rate of speed between London and our great towns than
that which obtains at present.
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