A knowledge of the heights and movements of the clouds is of much
interest to science, and of especial importance in the prediction of
weather. The subject has therefore received much attention during
recent years from meteorologists, chiefly in this country and in
Sweden. In the last published report of the Meteorological Council for
1885-86 will be found an account of the steps taken by that body to
obtain cloud photographs; and in the _Meteorologische Zeitschrift_ for
March last, M.M. Ekholm and Hagstrom have published an interesting
summary of the results of observations made at Upsala during the
summers of 1884-85. They determined the parallax of the clouds by
angular measurements made from two stations at the extremities of a
base of convenient length and having telephonic connection. The
instruments used were altazimuths, constructed under the direction of
Prof. Mohn, specially for measuring the parallax of the aurora
borealis. A full description of these instruments and of the
calculations will be found in the _Acta Reg Soc. Sc. Ups._, 1884. The
results now in question are based upon nearly 1,500 measurements of
_heights_; the _motions_ will form the subject of a future paper. It
was found that clouds are formed at all levels, but that they occur
most frequently at certain elevations or stages. The following are,
approximately, the mean heights, in feet, of the principal forms:
Stratus, 2,000; nimbus, 5,000; cumulus (base) 4,500, (summit) 6,000;
cumulo-stratus (base), 4,600; "false-cirrus" (a form which often
accompanies the cumulo-stratus), 12,800; cirro cumulus, 21,000;
cirrus, 29,000 (the highest being 41,000). The maximum of cloud
frequency was found to be at levels of 2,300 and 5,500 feet.
Generally speaking, all the forms of cloud have a tendency to rise
during the course of the day; the change, excepting for the cumulus
form, amounting to nearly 6,500 feet. In the morning, when the cirrus
clouds are at their lowest level, the frequency of their lowest
forms--the cirro-cumulus--is greatest; and in the evening, when the
height of the cirrus is greatest, the frequency of its highest
forms--the cirro-stratus--is also greatest. With regard to the
connection between the character of the weather and the height of the
clouds, the heights of the bases of the cumulus are nearly constant in
all conditions. The summits, however, are lowest in the vicinity of a
barometric maximum. They increase in the region of a depression, and
attain their greatest height in thunderstorms, the thickness of the
cumulo stratus stretching sometimes for several miles. The highest
forms of clouds appear to float at their lowest levels in the region
of a depression. The forms of clouds are identical in all parts of the
world, as has been shown in papers lately read by the Hon. R.
Abercromby before the English and Scottish Meteorological
Societies.--_Nature_.
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