which is of a temperature of 360
Fahr. The canal for the first twenty miles collects but little snow
even during heavy storms ; in the lower twenty miles, the water having
become more chilled, snow collects rapidly at times, and the ditch has
upon a few occasions been blockaded.
Other
ditches in the same locality, of nearly equal capacity, but lying on
the cold north hillsides and drawing water from creeks and rivers, have
great difficulty in running water in cold, stormy winters, owing to the
formation of ice, snow slides, and snow blockades.
The
head of the Milton ditch being on the north side of a cold canon, the
temperature at times falls as low as — 21° Fahr. Notwithstanding this
excessive cold, the ditch is kept open the greater part of the winter
when there is a sufficient supply of water, and with a flow of 80 cubic
feet per second probably but little difficulty would be experienced in
keeping up a constant supply.
Experience in the Black Hills.—In
the winter of 1879-80, on the line of the Wyoming and Dakota Water
Company's open flume, at the head of the Speartish River in the Black
Hills, Dakota, with the mercury ranging from 5° t° 350
(Fahr.) below zero, no difficulty was experienced in running the water
a distance of about six miles (the portion then finished) during the
entire season, the temperature of the water varying from 42° to 350 Fahr.
On
one occasion the thermometer reached 43° below zero, as indicated by
the spirit thermometers, the mercurial thermometers bursting at —42°
Fahr. The temperature of the water at this time fell to 350
Fahr. The extreme cold lasted but a few hours, still no ice formed in
the flume. The water (a continuous flow of 350 cubic feet per minute)
in the flume was drawn directly from the Spearfish River (supplied at
the upper end by springs), which was at this season frozen over. The
water did not freeze because the flume was well protected and set in
close to the bank, thus allowing no circulation of air under the sills,
the outer ends being covered with
