engines. They are single engines of 7 ft. gauge
with inside cylinders 18 in. diameter, and 24 in. stroke; the
driving-wheels are 8 ft. in diameter, and there are two pairs of leading
wheels, and one of trailing, all of 4 ft. 6 in. diameter. The total wheel
base is 18 ft. 6 in.; the boiler is 4 ft. 6 in. diameter, and 11 ft. 3 in.
long. The grate area is 21 square feet, and the heating surface is, in the
fire-box, 153 square feet; tubes, 1,800 square feet; total, 1,953 square
feet. The weight in full working order is, on the four leading wheels, 15
ton 18 cwt.; driving wheels, 16 tons; trailing wheels, 9 tons 10 cwt.;
total, 41 tons 8 cwt. The tender, which is low-sided and very graceful in
appearance, weighs 15 tons 10 cwt., and will hold 2,700 gallons of water.

The boiler pressure is 140 lb. on the square inch, and the tractive power
per pound of steam pressure in the cylinders is 81 lb. These engines take
the fast trains to the West of England; the Flying Dutchman averages 170
tons gross load, and runs at a mean time-table speed of 53 miles per hour,
which allowing for starting, stopping, and slowing down to 25 miles per
hour through Didcot gives a speed of nearly 60 miles an hour.

[Illustration: FIG. 1.--GREAT WESTERN RAILWAY.]

The average consumption of coal per mile, of thirteen of these engines,
with the express trains between London and Bristol, during the half-year
averaged 24.67 lb. per mile, the lowest being 23.22 lb., and the highest
26.17 lb., the average load being about eight coaches, or 243 tons. We
have already seen that in 1849 the Great Western express ran at a higher
rate than at present, being an exception to the general rule; and the
fastest journey on record was performed at this time by one of these
engines, when on May 14, 1848, the Great Britain took this Bristol
express, consisting of four coaches and a van, to Didcot, fifty-three
miles, in forty-seven minutes, or at the average speed of sixty-eight
miles an hour. The maximum running speed was seventy-five miles an hour,
and the indicated horse-power 1,000. A class of engines corresponding to
this type in their general dimensions, but with 7 ft. coupled wheels, was
introduced on the line, but it was not found successful. Through the
courtesy of Mr. Dean, I am enabled to give a table showing the running
speeds and loads of the principal express trains, broad and narrow gauge,
to the West and North of England, run on the Great Western Railway.