The daily morning journal and courier. [volume] (New Haven, Conn.) 1894-1907, 1897-11-16

Populaires, Paris. 'The direction fol-
lowed by the clouds In their passage
across the sky constitutes, with the
hight of the barometer and the temper
allure of the air. the three principal ele-
ments by whose aid we foretell the
weather by purely local observations.
The clouds do not move haphazard;
they obey the general atmospheric
| movements, and their motion is regula-
ted by the law of Buys-Ballot; that is,
they so move that atmospheric pressure
is always less on the right than on the
left OF the cloudy current. This Is
consequence of the earth's rotation and
of the solar action in displacing the air
from the equator toward the poles.
| When the clouds come from the south
they indicate that minimum of pres
| sure exists in the west; when they
move from the north, that proves that
| there is center of low pressure to-
ward the east, and SO on. The observa-
| ton of the clouds thus enables us to
| know, first, the approach of centers Of
disturbance second, the relative posi-
ton that we occupy in the region where
| these centers may cause atmospheric
perturbations.
by combining these data with the
indications Of the barometer and tax
ing account of the season of the year,
we may, after judicious experimental
| ton, be able to foretell the morroW's
weather with great probability Of ex-
actness.
1T is, then, matter of great interest
to determine the movement Of clouds
exactly. The determination is effected
easily and quickly when one is accus-
toned to it. But for persons who are
not used to the process it is troublesome
and almost always somewhat inexact,
because Of certain illusions that one
must know how to avoid.
1.-THE first condition to fulfil Is to
know the orientation Of the place Of OBJ
servation. That presents no difficulty
for localities where we live or with
which we are familiar; for others it is
necessary to use a small compass, TAX
ing care to remember that the geo
graphical north does not coincide exact
ly with the magnetic north.
ITO know exactly the direction of mo-
ton of the clouds, 1t is indispensable
that the observers head should remain
immovable; it is a good thing to fur
nish it with something to lean against.
We must also have a fixed point of
view situated in the direction Of the
visual ray, that is, directed toward the
cloud to be observed; the corner of a
house, the branches Of a tree, the sash
of window can serve for this purpose.
1.-THE observatories commonly en-
ploy for current observation Of the
clouds a special apparatus known as
the 'nephoscope;' 1t is a mirror of black
glass on which have been traced with a
diamond concentric circles and also di-
ameters forty-five degrees apart. The
mirror can be turned in it's own plane
about it's center by the aid of a proper
mounting. A verticle strip divided into
millimeters is fixed on the edge 1t
moves with the mirror and can be
raised and lowered. The observer looks
at the instrument so as to see the i'm
age of cloud reflected at its center, and
at the same time, by combining the
motions of the mirror and the vertical
strip, the end Of the latter is brought
into such a position that it also is pro-
jected on the center on the image of
I the cloud. If the cloud moves, its re-
Election will leave the center and the
radius that it follows will indicate the
direction Of motion.
"The hight of the end of the vertical
strip above the mirror and the number
of seconds taken by the image to move
from the center to one of the concentric
circles, enable us to determine the an
gular velocity of the observed cloud
To obtain the actual velocity, that is
the distance moved over in given
time-we must know the hight Of the
cloud above the mirror. In using the
, nephoscope, a fixed position for the OBJ
server is obtained by the necessity of
looking at the end of the strip in such a
way that 1t is always in line with the
enter of the mirror
!, 1.-THE price of the instrument is quite
high; so we advise meteorologic sta
} tons and individuals who do not wish
to obtain it, but who desire to deter
mine with precision the directions OF
clouds, to use the following arrange
ment, which is both good and cheap:
"On four posts three to four yards
high fixed in the ground so as to form
square whose diagonals are respec-
lively north and south and east and
west, are fastened the four angles of
wooden frame on which wires are
SCTeLCHeu parallel 10 Inc uldSohoio
The posts serve as resting places fol
:. the observers head, and he can thus
} very easily determine the direction fol
} lowed by the clouds by watching then
and the wires at the same time.
"As much as possible he should OBJ
serve the regions of the sky that are
not too far from the zenith, and choose
for observation clouds that are very
| ia
tant, in fine, to prove that the whole