miles of level at a mean rate of 9.7 miles per hour. On both levels
there were 141/2 chain curves of good length, and the speed, from 9 to 12
miles an hour, at which the train entered the respective levels, was not
quite regularly maintained throughout the half hour expended in running
over them. But if even 7 lbs. per tun of the total weight be taken as
the resistance at these speeds, the tractive force will be 11,004 lbs.,
which is more than one fourth the adhesion weight of 40,050 lbs. On
the next day, the same engine drew 30 wagons weighing 4661/2 tuns, or,
including engine and tender, 514 tuns nearly, up a gradient of 1 in
1171/2, three miles long, at a mean speed of 101/4 miles an hour. The
resistance due to gravity was 9,814 lbs., and supposing the other
resistance to traction to amount to no more than 7 lbs. per tun, the
total resistance would be 13,412 lbs., corresponding to a mean effective
cylinder pressure of 117 lbs. per square inch, and to a co-efficient of
adhesion of almost exactly one third.

"It is needless to repeat instances of much the same kind, as occurring
during the experiment referred to. The author is bound to say that they
were, no doubt, influenced by the favorable circumstances of weather,
and something is to be allowed also for the great length of train drawn,
very long trains having a less tractive resistance per tun on a level
than short ones, and something, possibly more than is commonly supposed,
may have been due to the use of oil-tight axle boxes, the saponaceous
compound known as 'railway grease' being nowhere in use on railways in
the States. It could not possibly be used, except in a congealed form,
in the severe American winters; and Messrs. Guebhard and Dieudonne's
experiments (_vide_ "De la resistance des trains et de la puissance des
machines." 8vo. Paris, 1868, p. 36) made in 1867, on the Eastern Railway
of France, showed a very considerable diminution in the resistance of
oil-boxed rolling stock as compared with that fitted with grease boxes.