The use of the percentage of weight on drivers which is utilized in
traction as a measure of the efficiency of the locomotive, while,
probably, not applicable to individual machines, is sound for the
purposes of comparison of results to be obtained on various portions of
a line as far as affected by conditions of grade and alignment. It has
the advantage of disregarding questions of temperature, condition of
track, character of fuel, etc., which, being the same on all portions of
the line, naturally balance and do not affect the comparison. It is, of
course, simply a method of expressing the final efficiency of the
various parts of the locomotive, and, since it depends entirely on
actual results already accomplished, leaves no room for difference of
opinion or theoretical error.

The writer has always considered an "under-cylindered" locomotive as a
defective machine. All weight is a distinct debit, in the shape of wear
and tear of track and running gear, resistance due to gravity on grades,
interest on cost, etc. When this weight fails to earn a credit in the
way of tractive efficiency, it should not be present.

The statement relative to the performance of locomotives on "Hill _C_"
is interesting, especially in that it appears to have been immaterial
whether they made a dead start after stopping at the station or
approached the foot of the hill at 16 to 18 miles per hour. The momentum
would appear to be an insignificant factor.

It is gratifying to note that Mr. Trautwine has been able to brace up
the weak member of Table 1 so completely with his detailed data; also
that his other results strengthen the conclusions reached in the
paper.