here is a field at least for
long-leaf pine for such construction. Washington fir was found admirable
in every respect, and was moderate in cost at that time.

The bands were bent in the field, and, after heating in an oven for
about 3 min., were dipped in bunches of five into a kettle of melted
mineral rubber at a temperature of about 400 deg. Fahr., and then hung up
for the coating to harden. This took place rapidly, as the work was done
in winter. If the band were wound spirally, the coating would have to be
done in the shop, but field coating is preferable, as it avoids injury
to the coating during transportation.

An advantage of wood pipe for conveying water is its low coefficient of
friction. The results obtained by the author (_n_ = 0.00866 to 0.0092)
appear to be very low as compared with determinations made for
wood-stave pipe. Kutter's coefficient for the latter varies from 0.0096
in the case of the 30-in. pipe at Denver,[B] to from 0.012 to 0.015 as
determined by Messrs. Marx, Wing, and Hoskins for the 72-in. pipe of the
Pioneer Power Plant of Ogden.[C] Probably 0.011 would be a fairly safe
figure to use in designing new work.

[Illustration: FIG. 3. DETAILS OF OLD WOOD PIPE.]

J.L. CAMPBELL, M. AM. SOC. C.E. (by letter).--Referring to Mr. Smith's
question about the velocity measurements by bran, the first appearance
of the bran and the colors was taken because the intervals of time given
thereby were in close accord among themselves and with the weir
measurements. The time from the first trace of bran or color until final
disappearance varied between 15 and 20 min. Bran in abundance or
pronounced color showed in 2 min. after the first appearance, while the
disappearance or fading was noticeable after a period of from 7 to 10
min. It required 2-1/2 min. to get the bran or colors into the intake at
the head of the line and leave the water clear.

[Footnote B: _Transactions_, Am. Soc. C.E., Vol. XXXVI, p. 26.]

[Footnote C: _Journal_, New England Water Works Assoc., Vol. XXII, p.
279.]

Mr. Allen refers to the bored wood pipe laid many years ago in Eastern
cities. The writer's experience indicates that a bored pipe will not
deliver as much water as a planed stave pipe, on account of the greater
interior roughness of the former.

Referring to the profile, the 8-1/2-in. pipe between Corona and Duran
had a theoretical capacity of 744,000 gal. per day. A recent test showed
it to be delivering wate