its diameter, and that the difficulty of
making a suitable and perfect casting increases with the diameter.
Cast iron, therefore, would receive no attention if it were not for
its far greater cheapness as compared to wrought iron or steel. This
fact makes its use either wholly or in part very desirable for freight
service, and even causes some roads in this country, notably the one
with which I am connected, to find it profitable to develop and
perfect the cast iron wheel for use in all but special cases.

Steel, on the other hand, notwithstanding its great cost, is coming
more and more into favor, and has the great recommendations of
strength and safety. It is also of such a nature that wheels tired
with it run much further before being unfit for further service than
those made of cast iron, and consequently renewals are less frequent.
The inference would seem to be that a combination of steel and cast
iron would effect the desirable safeness with the greatest cheapness;
but up to the present this state of affairs has not yet been realized
to the proper extent, because of the labor and cost necessary to
accomplish this combination and the weakness involved in the manner of
joining the two kinds of material together.

Taking up the consideration of the diameter of the wheel now, and
allowing that on the score of economy cast iron must be used for
wheels in freight service, we are led to reflect that here heavy loads
are carried, and there is a growing tendency to increase them by
letting the floor of the car down to a level with the draft timbers.
All this makes it desirable to have the wheels strong and small to
avoid bent axles and broken flanges, to enable us to build a strong
truck, to reduce the dead weight of cars to a minimum, and have wrecks
quickly cleared away. The time has not yet come when we have to
consider seriously hot journals arising from high speed on freight
trains, and a reasonable degree only of easy riding is required. The
effect on the track is, however, a matter of moment. Judging from the
above, I should say that no wheel larger than one 33 in. in diameter
should be used under freight cars. Since experience in passenger
service shows that larger cast iron wheels do not make greater mileage
and cost more per 1,000 miles run, and that cast iron wheels smaller
than 33 in., while sometimes costing less per 1,000 miles run, are
more troublesome in the end, it is apparent that 33 in. is the best
d