ines attain a speed of 80
miles an hour.

Leaving the question of boiler power, M. Nansouty goes on to consider
the question of adhesion. About this he says:

Is the locomotive proposed by M. Estrade under abnormal conditions as
to weight and adhesion? This appears to have been doubted, especially
taking into consideration its height and elegant appearance. We shall
again reply here by figures, while remarking that the adhesion of
locomotives increases with the speed, according to laws still unknown
or imperfectly understood, and that consequently for extreme speeds,
ignorance of the value of the coefficiency of adhesion f in the
formula

d 2 I
fP = 0.65 p ------- - R
D

renders it impossible to pronounce upon it before the trials earnestly
and justly demanded by the author of this new system. In present
practice f = 1/7 is admitted. M. Nansouty gives in a table a
_resume_ of the experience on this subject, and goes on:

"The English engineers, as will be seen, make a single axle support
more than 17 tons. In France the maximum weight admitted is 14 tons,
and the constructor of the Estrade locomotive has kept a little below
this figure. The question of total weight appears to be secondary in a
great measure, for, taking the models with uncoupled wheels, the
English engines for great speed have on an average, for a smaller
total weight, an adhesion equal to that of the French locomotives. The
P.L.M. type of engine, which has eight wheels, four of which are
coupled, throws only 28.6 tons upon the latter, being 58 per cent. of
the total weight. On the other hand, that of the English Great Eastern
throws 68 per cent. of the total weight on the driving wheels.
Numerous other examples could be cited. We cannot, we repeat, give an
opinion rashly as to the calculation of adhesion for the high speed
Estrade locomotive before complete trials have taken place which will
enable us to judge of the particular coefficients for this entirely
new case."

M. Nansouty then goes on to consider the question of curves, and says:

"It has been asked, not without reason, notably by the Institution of
Civil Engineers of Paris, whether peculiar difficulties will not be
met with by M. Estrade's locomotive--with its three axles and large
coupled wheels--in getting round curves. We have seen in the preceding
tables that the driving wheels of the English locomotives with
independent wheels are as