lway Economics," which is studying such matters, but
so far as the writer knows it has not given this question any
consideration.

The writer hopes that the author will follow up this subject, and that
other members will join, as a full discussion will no doubt bring some
results on a question which seems to be highly important.

JOHN C. TRAUTWINE, JR., ASSOC. AM. SOC. C. E. (by letter).--In his
collection of data, Mr. Randolph includes two ancient cases taken from
the earliest editions (1872-1883) of Trautwine's "Civil Engineer's
Pocket-Book," referring to performances on the Mahanoy and Broad
Mountain Railroad (now the Frackville Branch of the Reading) and on the
Pennsylvania Railroad, respectively.

In the private notes of John C. Trautwine, Sr., these two cases are
recorded as follows:

"On the Mahanoy & Broad Mtn. R. R., _tank_ Engines of 35 tons, _all
on 8 drivers_, draw 40 _empty_ coal cars weighing 100 tons, _up_ a
continuous grade of 175 ft. per mile for 3-1/2 miles; & around
curves of 450, 500, 600 ft. &c. rad., at 8 miles an hour. (1864)
This is equal to 77-14/100 tons for a 27-ton engine." (Vol. III, p.
176.)

"On the Penn Central 95 ft. grades for 9-3/4 miles, a 29-ton engine
all on 8 drivers takes 125 tons of freight and 112 tons of engine,
tender, & cars, in all 237 tons,[C] and a passenger engine takes up
3 cars at 24 miles an hour (large 8 wheels). When more than 3, an
auxiliary engine."

It will be seen that Mr. Randolph is well within bounds in ascribing to
the Mahanoy and Broad Mountain case (his No. 10) a date "certainly prior
to 1882," the date being given, in the notes, as 1864; while another
entry just below it, for the Pennsylvania Railroad case, is dated 1860.

It also seems, as stated by Mr. Randolph, quite probable that the
frictional resistance (6 lb. per 2,000 lb.) assumed by him in the
calculation is far below the actual for this Case 10. The small, empty,
four-wheel cars weighed only 4,400 lb. each. Furthermore, the "tons," in
the Trautwine reports of these experiments, were tons of 2,240 lb. On
the other hand, the maximum curvature was 12 deg. 45' (not 14 deg., as given by
the author), and the engine was a tank locomotive, whereas the author
has credited it with a 25-ton tender.

After making all corrections, it will be found that, in order to bring
the point, for this Case 10, up to the author's curve, instead of his 6
l