miles the speed was 64 miles an hour. In ordinary working
these engines convey trains of sixteen to twenty-six coaches from
King's-Cross with ease, and often twenty-eight are taken and time kept.
Considering that the Great Northern main line rises almost continuously to
Potter's Bar, 13 miles, with gradients varying from 1 in 105 to 1 in 200,
this is a very high duty, while, with regard to speed, they have run with
sixteen coaches for 15 miles at the rate of 75 miles an hour. Their
consumption of coal with trains averaging sixteen ten ton carriages is 27
lb. per mile, or 8 lb. per mile less than the standard coupled engine of
the North-Western with similar loads. Mr. Stirling's view, that the larger
the wheel the better the adhesion, seems borne out of these facts; thus to
take twenty-eight coaches, or a gross load of 345 tons, up 1 in 200 at a
speed of 35 miles an hour, would require an adhesive force of 8,970 lb.,
or 600 lb. per ton--more than a quarter the weight on the driving wheels.
These engines are magnificent samples of the most powerful express engines
of the present day.

The London, Brighton, and South Coast Railway Company has in the last few
years had its locomotive stock almost entirely replaced, and instead of
seventy-two different varieties of engines out of a total of 233, which
was the state of locomotive stock in 1871. a small number of
well-considered types, suited to the different class of work required, are
now in use. Mr. Stroudley considers--contrary to the opinion once almost
universally held--that engines with a high center of gravity are the
safest to traverse curves at high speed, as the centrifugal force throws
the greatest weight on the outer wheels, and prevents their mounting; also
that the greatest weight should be on the leading wheels, and that there
is no objection to these wheels being of a much larger diameter than that
usually adopted; in fact, by coupling the leading and driving wheels where
the main weight is placed a lighter load is thrown on the trailing wheels,
thus enabling them to traverse curves at a high speed with safety, while
it permits of a larger fire-box being used; and these principles have been
carried out in the newest class of engines, especially designed for
working the heavy fast passenger traffic of the line.

The modern express engines are of two types. The first is a single engine
with 6 ft. 6 in. driving wheels, and leading and trailing wheels 4 ft. 6
in.