Evening star. [volume] (Washington, D.C.) 1854-1972, 1931-11-17

This Is a special department devoted
to the handling of inquiries. You have
at your disposal an extensive organ
ization In Washington to serve you In
any capacity that relates to intorma-
ton. Write your question, your name,
and your address clearly, and enclose
cents in coin or stamps for reply.
Send to The Evening Star Information
Bureau. Frederic J. Haskin, Director,
Washington, D. C.
Q. What is meant by persistence Of
vision in motion picture parlance?-
w. K
A. This means that the eye retains
single visual impression for about one
sixteenth of a second. Motion picture
projection is therefore a series Of pic
lures thrown upon the screen at inter-
walls OF approximately one-SiXteenth OF
q second. Because the interval between
these pictures synchronizes approx
mately with the duration of vision, the
projected motion picture gives the
illusion OF actual movement instead OF
appearing to the eye as q series OF I'M
connected pictures.
@. Does the freezing of canned food
make 1t unfit to eat?-C. T.
A. 1t does not. The texture of GER
tain types of food is affected, but the
titles Of the food taken on the Byrd
Antarctic expedition were in cans, were
frozen solid for months, but were in
edible condition.
@. What caused the drought of 1890?
&C. r.
A. DR.. Humphreys of the Weather
Bureau says that in 1880 such large
amount of cold air rushed over Europe
causing unusually great rainfall there,
the abnormal flow of polar air in that
direction withdrew much of the pres
sure that causes currents to move down
the usual American paths. Much Of 1t
was dissipated in Canada, causing q
wet season there. The United States
was therefore blanketed with warm air.
In many sections it was heavy with
moisture, but the necessary cold air
currents required to produce rain did
not arrive from the north.
@. Why do some issues of paper cur
rency have stars before the serial num-
bers?-M. G.
A. Paper currency is printed and
finished in sheets of IL subjects. The
in series. It occasionally happens after
serial number Is imprinted that the
bill Is discarded because Of some i'm
perfection. Bills discarded are replaced
| with a perfect bill which has been pre-
pared for such an emergency and bears
a number not in the regular series, but
which Is distinguished by a star pre-
ceding the number.
@. What kinds Of wood are used by
the wood carvers of Germany and
Switzerland?-W. G. NJ
A. The Forest Service says that they
generally use mountain pine, walnut
and Eastwood.
d. B.
A. They are not immune to poison.
Their comparative immunity lies in the
fact that they have very thick skins
underlain by a thick layer of fat For
this reason poison often fails to pene-
trate to the blood stream of a hog at
tackled by a poisonous snake or in some
other way subjected to poison.
Q. How does a Maxim silencer work?
&C. B.
A. The National Rife Association
says that 1t works on the same prin-
ciple as an auto mufler The tube is
screwed on the muzzle of the gun. This
tube consists of series Of baffies that
causes the gases to issue slowly instead
Of with q sudden rush. It is this rush
of powder gas from the muzzle of the
gun which creates a vacuum, causing
the report when discharged.