St. Landry democrat. (Opelousas, La.) 1878-1894, 1893-09-02
POPULAR SCIENCE NOTES,

electric fan has come to be such an inl
dspcE sable 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-.
mcndation of economy to that of eff
cheney Its first cost, with battery coma
plctc, is small, and the cost of operating
it aftcrward is put at two and three1
quarter cents an hour. 1t is claimed that
the battery will last ten weeks without
renewal at one hours work daily, CT ten
days at a steady operation of scycQ and q
halt hours per diem. 1t is designed to be
suitable for the parior Or dining table,
being both ornamental and noiseless. 1t
Will not drop grease on the tlhlecloth or
carpets, for its bearings are sclf-oiling
and carry on their own fabrication with.
out loss of the lubricant. The whole
outfit packs up in small box, and cant
be carried without Inconvenience.
ELECTRIC CAR HEATING. Said a 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<
tons of the United States and Canada,
where the winters are unusually colds
show that from 1, 200 to 1, 500 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 fixture of the
car, the cost of maintaining and operate
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 a road doing a good business, is a
very important item. Coal stoves, too,
on cold days, when being heated unus-
ually warm, become 50 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 and furnishing q
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 a heated car for few hours each
day would add greatly to the comfort of
passengers With coal slaves 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 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. 50 inches or 1869 inches for O
geographical mile. The effect of the
known curvature of our globe may be
illustrated in the following mannerl
Take down your globe, place book,
pane of glass or even a ruler against it,
either of the two objects first named be-
ing hes. 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 III all
directions from the point of contact.
New, suppose the oceans surface was
calm and frozen aud sheet Of glass many
miles square laid upon it. At one mile
from the place of contact the glass would
stand out nearly eight inch+s this meas
urement upon the ocean the mile IS maui
tical one)-in fact, will lack but $4,000
of an inch of being eight inches from the
pane; at three miles it will be six feet
and at nine miles tifty-four feet, and so
on accor ling to the regular ratio. In
order to get the whole matter IN nut
she'll rcmember>lhat the number of feet
of depression is equal 10 two-t thirds OF
the square of the number OF miles for
anv observable distance. There is, how
ever. an error resulting from refraction
which must be cancelled The commonly
used formula for correction is as follows:
square the number of miles and take
four sevenths of it for the correction in
feet. Thus, if an object is visible at
distance of five miles we may know that
its height is at least 14b feet. Or,
if the height of visible OBJ ject is known
: say 100 feet--takc one-tourth OF that
number, or %, multiply by seven and take
the square root of the product and you
will have the distance of the object,
which is in this case Il fraction over IL
miles. A man swimming in the ocean
NAV see a tower 10 miles away, even
though it only be 2O) feet high, but
now elevate that man l0) feet above this
surface of the water and he could
plainly see a tower only 1O) feet
high, even though it be 26 miles