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.
FOOTNOTES:
[ [A] "The Economic Theory of Railway Location," 1887 edition, p. 502.
[ [B] Transactions, Am. Soc. C. E., Vol. L, p. 1.
[ [C] "Nearly 200 tons exclusive of eng. & ten." (Vol. III, p. 176-1/10.)
[ [D] American Railway Engineering and Maintenance of Way Association, Bulletin 84, February, 1907, p. 99.