interest. The locomotive of the Great Northern has a leading
four-wheeled bogie, which considerably increases the steadiness of the
engine, and counterbalances the disturbing effect of outside
cylinders. Acting on the same principles which have animated M.
Estrade, that is to say, with the aim of reducing the retarding
effects of rolling friction, the constructor of the locomotive of the
Great Northern has considerably increased the diameter of the wheels
of the bogie. In this engine all the bearing are inside, while the
cylinders are outside and horizontal. The tender has six wheels, also
of large dimensions. It is capable of containing three tons and a half
of coal and about 3,000 gallons of water. This type of engine is now
in current and daily use in England.

M. Nansouty next considers the broad gauge Great Western engines with
8 ft. driving wheels. The diameters of their wheels approach those of
M. Estrade, and exceed considerably in size any lately proposed. M.
Nansouty dwells especially upon the boiler power of the Great Western
railway, because one of the objections made to M. Estrade's locomotive
by the learned societies has been the difficulty of supplying boiler
power enough for high speeds contemplated; and he deals at
considerable length with a large number of English engines of maximum
power, the dimensions and performance of which are too well known to
our readers to need reproduction here.

Aware that a prominent weak point in M. Estrade's design is that, no
matter what size we make cylinders and wheels, we have ultimately to
depend on the boiler for power, M. Nansouty argues that M. Estrade
having provided more surface than is to be found in any other engine,
must be successful. But the total heating surface in the engine, which
we illustrate, is but 1,400 square feet, while that of the Great