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
diameter for the wheels we have to use in freight service.

When we take up passenger service we come to a much more difficult and
interesting part of the subject, for here we must consider it in all