280 NOTES.—ORIGINAL AND SELECTED.
quantities of salt required for domestic use before the employ-
ment of it in manufactures, and may serve to show that in
England the making of salt from sea-water must have been a
great industry prior to the discovery of rock-salt.—Ed.
Water Power from the Thames.—"Mr. T. B. Stoney,
M. Inst. C. E. I. (Raphoe, co. Donegal), in an interesting letter on
the question of power for the metropolis, draws attention again
to the water power in the estuary of the Thames, which could
probably, he states, be made available in large quantities for
industrial purposes by simple and inexpensive works. He
instances those reaches of the river in which there is a mean
tidal rise of 161/2 feet. In the Essex marshes bordering the
Thames, he remarks that there are extensive tracts of land at a
level of several feet below high water mark. In these marsh
basins reservoirs could be constructed, which would be filled by
the tide every twelve hours to a depth of (say) five feet at mean
high water. When the tide falls, he proceeds, the outflow from
these reservoirs into the sea could be used to drive pumps, which
would raise water out of the reservoirs to a height of 6 feet above
mean high water to feed turbines. These turbines, fixed at low
water, would be driven under an average head of 161/2 feet. When
the tide rises within 4 feet of high water, the discharge of the
turbines into the sea would be stopped and diverted into the now
empty reservoirs. By this arrangement, our correspondent
concludes, the turbines would produce energy for commercial
use for 24 hours continuously."—The Times, Feb. 14, 1906,
Engineering Supplement.
[End of Volume XIV.]