friction is less, the working parts are simplified, it takes less oil,
and is well under the driver's eye. It also allows larger cylinders to be
got in between the frames of inside cylinder engines, as, the slide valves
may be placed on the top or bottom of the cylinders. This latter advantage
is a great one, as, with the ordinary link motion, large cylinders are
exceedingly difficult to design so as to get the requisite clear exhaust.
The action of the gear is as follows: A rod, a, is fixed by a pin at b, on
which it is free to turn, and is attached to a rod, c, at d, the other end
of which link is fastened to the connecting rod at e. At the point, f, in
this rod another lever, g, is connected to it, the upper end of which is
coupled to the valve rod, h, at i, and just below this point a second
connection is made to a block at j, sliding in a short curved piece, k.
The inclination of the block, k, governs the travel of the valve. The
total weight of the engine in working order is: On the leading wheels, 10
tons 8 cwt.; front drivers, 14 tons 4 cwt.; rear drivers, 13 tons 10 cwt.;
total, 37.75 tons. The tender weighs 25 tons in full working order. The
boiler pressure is 150 lb., and the usual point of cut-off in the high
pressure cylinders, when running at speed, is half-stroke, while the
pressure of steam admitted to the large cylinder is never to exceed 75 lb.
per square inch. The average consumption of coal between London and Crewe
is 26.6 lb. per train mile, or about 8 lb. per mile less than the standard
coupled engine. In an experiment made in October, 1883, one of these
engines took the Scotch express from Euston to Carlisle at an average
speed, between stations, of 44 miles an hour, the engine, tender, and
train weighing 230 tons, with a consumption of 29½ lb. of coal per mile,
and an evaporation of 8.5 lb. of water per pound of fuel.

Mr. Webb's object, in designing this engine was to secure in the first
place a greater economy of fuel, and secondly, to do away with coupling
rods, while at the same time obtaining greater adhesion, with the freedom