Spirit of the age. [volume] (Woodstock, Vt.) 1845-1913, 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 ever
observed carefully the motion OF the
clouds that are so uncomfortably
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 a
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 TAIL or. as the
neteorologist 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
Meteorology-the word which has
lost it's original meaning to such an
extent that 1t now denotes simply
the science OF the atmosphere" and
includes. therefore. the study OF elf
mate and weather. including clouds
and their motions-has extended tts
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. II IL
true that clouds have been observed
and their motions studied scientifical-
ly. for long time. but since instru-
ments carried by kites and balloons
have taught US so much about the
temperature conditions In the air up
to heights OF sixteen miles and more.
renewed interest has been taken In
the forms and motions Of clouds. for
the motion of 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 cloud is the
Besson nephoscope. The instrument
consists simply of an inverted harrow
or comb fixed horizontally at the end
Of q vertical rod which IN mounted
In bearings carried by an upright
post. SO that the rod can be rotated.
Near the bottom of the bar 10 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 -
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 tho
comb until the cloud appears to pass
along the points of the comb II will
be necessary to approach OF recede
from the pole until this appears 10
take place. Then standing stiil. 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 o;
the cloud along the comb Is a meas
is moving. expressed In terms Of the
height of the cloud. For example. r.
two clouds at heights Of 5000 feet
and 5000 feet appear to be moving at
the same rate along the comb. then
the latter is actually moving twice as
fast as the former.
The height of a cloud 10 not SO
easily determined Usually two OBJ
servers. each provided with theo-
dolite, are required but sometimes
one theodolite can be made to suffice.
This instrument has It's 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. the other by reflection in
small sheet OF water lying on the
ground below, are made to coincide
by rotating. the plates OF glass TIL
position OF the plates so determin
is read of on the graduated circ'p
shown near the observers hand Tn,
height can then be computed math
AS a result of these observations
is found that. in general. tf one star-i
with ones back to the wind 10,
clouds move in about the same y
rection as the surface air. white -
higher clouds travel nearly in m
same direction. but have a motion.
from left to right which becomes
more pronounced as the height il
creases. High clouds usually tray.
much more quickly than low on
although apparently they do not
The highest clouds rarely exceed a .
height OF six miles