Daily inter mountain. [volume] (Butte, Mont.) 1881-1901, 1900-08-18
PUZZLING

Many persons do not understand why
we do not feel, in some way, the rota-
ton of the earth on it's axis. The speed
of rotation is about 1000 miles an hour,
which is simply enormous compared
with anything that we have eve ex-
perienced. If we ride in an open a at
a speed of SO miles ar hour, the air al
most blows us off; what would h eff
feet be if the car moved at a speed Of
1000 miles an hour?
I There is another thing connected with
the earth's rotation that puzzles many
people; we IA been asked about it
time and again. Let us p that a
man ascends in a balloon to a height of,
say, 5000 feet on a day when the air is
still. Now, if he remains there. station
cry in. the air, for two hours, and then
comes down, would he reach the ground
at the point from which he
During these two hours the earth has
turned 1000 miles, and as he has been
for that time 5000 feet above it's sur
face, why has not the place from which
The assembled moved away toward the
east, and left him behind?
The first question that arises, Is this:
docs the air fully take on the earth's
motion of rotation, or, because of its
soft and yielding nature. does 1t tend to
fall behind the earth, as the water on a
grindstone goes slower than the stone,
and so has a motion backward? OBJ
servation shows that the first is the
case; the air has taken up the motion of
the earth. and moves with it quite as
evenly and as perfectly as do the oceans
or the solid crust.
And this will continue as long as the
learth's motion is uniform, n the air is
at rest relative to it. If the earth should
begin to turn slower or faster. there
would be a motion in the air until it
lsettled down to the new motion of the
Iearth. Such changes do not take place;
-. z 49, IL - - xr,tth v<rNyp, rlNyy
mess. Thus the rotation of the earth
does not cause motion in air at rest. It
is only when the air moves that the
earth's rotation affects 1t.
| This is the case in whatever way the
air moves. whether vertically or hori-
zontally. What is true of air in motion
is true of all other motions. and may be
applied to anything. Fol instance, if a
stone be dropped down the shaft of a
deep mine. or from the top OF a high
tower. will it fall exactly under the spot
from which it was dropped. or at one
side? 1t would fall a little to the east.
This has been proved by mechanics and
tested by experiment. For anything
moving upward, the result is the reverse,
except that it is affected by the friction
of the air. In any case the effect in ver-
teal motion is slight, and in problems of
the weather it may be neglected.
The important case is that of a body
moving horizontally. that is. along the
earth's surface or parallel to it. The eff
feet is Their so considerable as to be seen
in many kinds of motion. 1t is a guild
ing principle, which directs in some de-
gree the motions of water on the ee
and really controls the great motions of
the atmosphere as to the direction thew
must take. The effect may be stated
in a simple rule. which is of great inter-
est and Importance: In the case of any
BODY in horizontal motion. the rotation
of the earth causes a divergence toward
the right in the northern and toward the
left in the southern hemisphere.
The deviation may be detected in the
case of any rapidly moving body. when
the motion will admit of precise obser-
walton. Cannon balls deviate appre-
ciably to the right, and railway trains
show a strong tendency. when they leave
the track. to do so on the right-hand
side. Streams are more likely to eat out
the right bank han the left. In the
great rivers of Siberia. flowing for hun
dreds of miles through open plains in
high l%atitudes, the r~ight-hand banks are
usually steep. and are SO continuously
eaten away by the water. that, in man.
cases. village sites must be moved back
The effect of the earth'S rotation is
shown still more distinctly in the grea'
ocean currents. Each ocean in eacl
hemisphere is practically one grea
whirl in very slow motion. So far as TIL
combining shores permit. the divergence
of the currents making these whirls i
in accordance with the rule lust lai
down as to the effect of the earth's rota
ton. A similar, though still slowe
whirl, exists in each of the great lakes.