Item 10 represents
very old practice, certainly prior to 1882, and is "second-hand." The
load consisted of empty coal cars, and the line was very tortuous, so
that it is quite probable that the resistance assumed in the calculation
is far below the actual. Items 15 and 17 are both high. To account for
this, it is to be noted that this road has been recently completed,
regardless of cost in the matter of both track and rolling stock, and
doubtless represents the highest development of railroad practice. Its
rolling stock is all new, and is probably in better condition to offer
low resistance than it will ever be again, and there were no "foreign"
cars in the trains considered. The train resistance, therefore, may be
naturally assumed to be much less than that of roads hauling all classes
of cars, many of which are barely good enough to pass inspection. As the
grades are light in both cases, this feature of train resistance is
larger than in items including heavier grades. Attention should be
called to the fact that a line connecting the two points representing
these items on Fig. 1 would make only a small angle with the sketched
curve, and would be practically parallel to a similar line connecting
the points represented by Items 13 and 16. There is, therefore, an
agreement of ratios, which is all that needs consideration in this
discussion.
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