on the drivers--was subject to no small modification in practice.

In order to obtain a working basis, for use in relation to this feature,
he undertook the collection of data from the practical operation of
various roads. Subsequent engagements in an entirely different direction
caused this to be laid aside until the present time. The results are
given in Table 1, from which it will be seen that the percentage of
driver weight utilized in draft is a function of the length as well as
the rate of grade encountered in the practical operation of railways.

In this table, performance will be found expressed as the percentage of
the weight on the drivers which is utilized in draft. This is calculated
on a basis of 6 lb. per ton of train resistance, for dates prior to
1880, this being the amount given by the late A. M. Wellington, M. Am.
Soc. C.. E.,[A] and 4.7 lb. per ton for those of 1908-10, as obtained by
A. C. Dennis, M. Am. Soc. C. E.,[B] assuming this difference to
represent the advance in practice from 1880 to the present time. Most of
the data have been obtained from the "Catalogue of the Baldwin
Locomotive Works" for 1881, to which have been added some later figures
from "Record No. 65" of the same establishment, and also some obtained
by the writer directly from the roads concerned. Being taken thus at
random, the results may be accepted as fairly representative of American
practice.

Attention should be directed to the fact that the performance of the
10-34 E, Consolidation locomotive on the Lehigh Valley Railroad in 1871
is practically equal to that of the latest Mallet compounds on the Great
Northern Railway. In other words, in the ratio between the ability to
produce steam and the weight on the drivers there has been no change in
the last forty years. This would indicate that the figures are not