540 to 0.700, air
being 1.000. Its weight may be called one-thirty-second of a pound to
the cubic foot and atmospheric air about three-fourths of a pound.
R. B. C., of Pa., says: "Here is a proposition in geometry which I would
like to see demonstrated theoretically by one of your correspondents.
The side of a regular heptagon is equal to half the side of an
equilateral triangle inscribed in the same circle. The mechanical
construction is very simple and will be found useful. I discovered it
some years ago and am not aware of its ever having been in print."
F. H., of Mich., asks "if sal-soda will scale a boiler?" H. N. Winans,
11 Wall street, N. Y. replies that in some waters it is partially
effective but at the expense of the boiler, with a certainty of foaming
and corrosion. The most reliable and positively uninjurious remedy for
incrustations is his anti-incrustation powder--in successful use for 12
years past.
T., of R. I., speaks of the famous mechanical horse shown at the Paris
Exposition which is said to have accomplished with its rider a little
over an English mile in fifty seconds, and asks what is the motive
power.
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