Hopkinsville Kentuckian. [volume] (Hopkinsville, Ky.) 1889-1918, 1913-05-03
HEIGHT OF CLOUDS
instruments for Measuring Ele-
walton and Movement.
Workings Of the Besson Nephoseope.
an Ingenious Device for Extract
Ing Secrets From the skies
Motion Of Vapor Masses.

How many people that one meets
IN the course OF the day have evel
observed carefully the motion Of the
clouds that are 80 uncomfortable
prevalent this summer? Or. II asked
about the matter would not most Of
them say that the clouds move In the
same directions as the wind at the
surface of the earth? Perhaps one
more observant than the rest would
recollect that thunder clouds have q
way of coming up against the wind,
and he might even add that he had
observed a high cloud moving in a
direction different from one lower
down. Again, would not most people
say that the mares tall" or, as the
meteorologist would call them, the
cirrus clouds, never move at all. or, at
least, only very slowly, and that low
clouds move more quickly than the
cirrusi
interchangeable word which has
lost its original meaning to such an
extent that II now denotes simply
'the science OF the atmosphere" and
includes, therefore, the study OF eli
mate and weather, including clouds
and their 'motions-has extended Its
operations within recent years very
notable by considering more definitely
the conditions prevailing In all the
layers of the atmosphere and not
merely in the surface-layer. 1t is
true that clouds have been observed
and their motions studied scientifical-
ly for a long time. but since instru-
have taught us so much about the
temperature conditions in the air up
to heights Of sixteen miles and more,
a renewed interest has been taken in
the forms and motions of clouds, for
the motion of a cloud usually (but
not always) indicates also that of the
air In which II is floating.
One of the best instruments for OBJ
serving the motion of a cloud is the
Besson nephoscope. The instrument
consists simply of an inverted harrow
or comb fixed horizontally at the end
Of a vertical rod which is mounted
in bearings carried by an upright
post, so that the rod can be rotated. |
Near the bottom of the bar is a
crosspiece, to the ends of which two |
strings pass to the hands of the OBJ |
server, while underneath is a circle |
graduated with the points Of the COM
pass. The method of observation is
to select the cloud to be observed, |
stand on the side of the post opposite |
the cloud, and with the strings rotate |
the upright rod and therefore the !
comb until the cloud appears to pass
along the points of the comb. It will |
be necessary to approach or recede |
from the pole until this appears to
take place. Then, standing still, note
the time the cloud takes to move
from one point to the next. Finally,
note the orientation of the comb by
means Of the graduated circle at the
bottom of the rod, This gives at
once the direction of motion of the
clouds while the apparent velocity os
the cloud along the comb is a meas
lring of the rate at which the cloud
IS moving, expressed in terms of the
height of the cloud. For example, II
two clouds at heights of 5000 feet
and 5000 feet appear to be moving at
the same rate along the comb, then
he latter is actually moving twice as
fast as the former.
The height of a cloud is not so
easily determined. Usually two OBJ
servers, each provided with a theo-
dolite, are required, but sometimes
one theodolite can be made to suffice.
This instrument has its telescope re-
moved and two parallel plates OF
glass arranged in place of the tele-
scope. Then two images of the cloud
-one formed by reflection in the
glass, tho other by reflection in a
small sheet of water lying on the
ground below. are made to coincide
by rotating the plates of glass. The
position of the plates so determined
Is read or on the graduated circle
shown near the observers hand. The
height can then be computed mathe-
AS a result of these observations. il
S found that, in general, If one stands
with ones back to the wind. low
clouds move in about the same d.
'ection as the surface air. while the
higher clouds travel nearly in the
iame direction, but have a motion
rom left to right which becomes
more pronounced as the height in
'reases. High clouds usually travel
much more quickly than low ones.