Chicago eagle. [volume] (Chicago, Ill.) 1889-19??, 1893-07-29
POPULAR SCIENCE NOTES.

A PORTABLE ELECTRIC FAN-The
electric fan has come to be such an in
dispersable element of comfort. if not Of
existence during the summer months.
that new and improved forms are con
stantly making their appearance. One
of these adds the very decided recon-
mendation of economy to that of eff
cheney Its first cost, with battery com
plete, is small, and the cost of operating
it afterward is put at two and three
quarter cents an hour 1t is claimed that
the battery will last ten weeks without
renewal at one hours work daily, or ten
days at a steady operation of seven and a
half hours per diem 1t is designed to be-
suitable for the parlor or dining table,
being both ornamental and noiseless It
will not drop grease on the tlblecIoth or
carpets, for its bearings are self-oiling
and carry on their own fabrication with
out loss of the lubricant The whole
outfit packs up in small box, and can
be carried without Inconvenience.
ELECTRIC CAR HEATING. Said lee
turer in Chicago recently: The electric
railway opened up the field for electric
heating. Reports from ROADS operating
in Northern Michigan and in other por-
tions of the United States and Canada,
where the winters are unusually cold,
show that from 1900 to 1900 watts is
sufficient current to keep the average
sixteen-foot car warm in all kinds of
weather. 1t will be seen thai, inasmuch
as the heaters require no attention what
ever, and are practically a fixture of the
car, the cost of maintaining and operat-
ing on the average electric road will be
simply the cost of current. Coal stoves
take from twenty to forty cents per day
to operate, If the least account is taken
of time used to keep them in heat
ing condition. The coal stove also
takes up room for one or more passen.
gers while it remains in the car which,
on Il road doing good business, is a
very important item. Coal stoves, too,
on cold days, when being heated unus-
ually warm, become so hot that it is
often impossible to stand Immediately in
front of the stove without burning the
clothing of the person standing near
The electric heaters, being placed under
the seats out of the way aud furnishing a
lower temperature, cannot be objected to
on this score, and BEING entirely out of
the way of passengers and taking up NO
space in the car which can be utilized to
bring in dividend, often saves in day
more than the entire cost of the current
furnished them for the days run. There
are many times in the spring and fall
when the mornings and evenings are
cool and the middle of the day warm,
when heated car for few hours each
day would add greatly to the comfort of
passengers. With coal stoves this is
often impossible, unless the car can be
taken out of service long enough to have
fire rebuilt in the stove.
CURVATURE OF THE EARTH's SURFACE.
GENERALLY speaking, we say that the
curvature of the earth amounts to about
seven inches to the statute mile; it is ex-
actly 6. 80 inches or Z. 962 inches for
geographical mile. The effect of the
known curvature of our globe may be
illustrated in the following manner;
Take down your globe, place book,
pane of glass or even II ruler against it,
either of the two objects first named be-
ing best adapted to such an experiment.
You will observe instantly that the book
pane or ruler only touches the miniature
representation of the earth at one point
the globes surface falling away in all
directions from the point of contact
Now, suppose the oceans surface was
calm and frozen anda sheet of glass many
miles square laid upon it. At one mile
from the place of contact the glass would
stand out nearly eight inches (this meas
urement upon the ocean. the mile is a nau-
teal one)--in fact, will lack but 80 1000
of an inch of being eight inches from the
pane; at three miles it will be six feet
and at nine miles tiftyfour feet, and so
on aceorl ling to the regular ratio. In
order to get the whole matter in nut.
shell remember that the number of feet
of depression is equal 10 two-thirds of
the square OF the number Of miles for
any observable distance There is. how
ever, an error resulting from refraction
which must be cancelled. The commonly
used formula for correction is MS follows:
square the number of miles aud take
four seventies of it for the correction in
feet. Thus, IL an object is visible nj
distance of five miles we may know that
is height is at least lit feet. Or,
IL the height Of visible obiecI Is known
say 100 feet take one .fourth Of that
number, or IS. multiply by seven aud take
the square root OF tho product aud you
will have the dismuo 81 the object,
which i Ia this ease "a fraction over a.
miles. A mau swimming in The ocean
NAV see tuWer 40 miles away. even
though BE- onH bo sul leot high, hui
unw elevate chat man To- fDol above tht
surface Hl the wafaF aHl he enud
phlaf $500 4 uHrf mF lui lrr
hsh etrn though be bo sa mlIu
ahat