References
1. “International Atlas of Clouds” (Atlas International des Nuages). Hildebrandsson, Riggenbach, and Teisserenc de Bort. Paris. 1896.
This is the atlas referred to in the text. The letter-press is short, and is repeated in English, French, and German.
2. “Annals of the Astronomical Observatory of Harvard College.” Vol. XXX. Observations made at the Blue Hill Meteorological Observatory. Part III. Measurement of Cloud Heights and Velocities. By H. H. Clayton and S. P. Fergusson. Part IV. Discussion of the Cloud Observations. By H. H. Clayton.
This last gives a very concise account of all the different proposals which have been made for the systematic naming of clouds.
3. “Études International des Nuages.” 1896-1897. Observations et Mesures de la Suède. I., II. Publication de l’Observatoire Météorologique de l’Université Roy. d’Upsala. H. H. Hildebrandsson.
An account of the Upsala observations referred to in the text.
4. Quarterly Journal of the Royal Meteorological Society.
Helm Wind. Marriott. 1886 and 1889.
The Thickness of Shower Clouds. Clayden. 1886.
Methods of Cloud Measurement. Ekholm. 1888.
Cirrus Formation. Clayton. 1890.
Nomenclature of Clouds. Hildebrandsson. 1887.
„ „ Abercromby. 1887.
„ „ Wilson-Barker. 1890.
„ „ Gaster. 1893.
„ „ Scott. 1895.
A New Instrument for Cloud Measurement. Ekholm. 1893.
Calculation of Photographic Cloud Measurements. Olsson. 1894.
The Motion of Clouds. Shaw. 1895.
5. Reports of the British Association. Reports of the Committee on Meteorological Photography. Clayden. 1891 to 1900.
The reports for 1896 and 1900 refer mainly to the measurements described in the text.
6. “Cloudland.” Clement Ley.
The work in which Mr. Ley set forth his proposed scheme.
7. “A Popular Treatise on the Winds.” Ferrel.
Not a “popular” work in the usual sense, but contains lucid descriptions of the mechanics of the atmosphere.
8. There are many excellent text-books on meteorology, all of which deal more or less with the movements of the atmosphere and the formation of clouds.
Footnotes
1 See reference No. 2 on p. 181.
2 The telescope with which these observations have been made is a 6·8-inch refractor equatorially mounted.
3 Ferricyanide of potassium and hyposulphite of soda.
4 From the declination of the sun corrected for variation and from the known latitude, the meridian zenith distance is calculated.
From the Greenwich time, the longitude, and the equation of time, the hour angle is obtained.
Now, if H be the hour angle, D the reduced declination, and M the meridian zenith distance, the sun’s altitude may be calculated by the formula—
log versin H + L cos lat. + L cos D-20 = log n,
where n is a natural number, and
n + vers M = covers alt.
Again, to find the azimuth—
vers sup. (lat. + alt.)-vers polar dist. = m,
where m is another natural number, and
log m + L sec. lat. + L sec. alt.-20 = log vers azim.,
reckoned from the south.
Hence the position of the sun is ascertained for both negatives.
By actual measurements on the plates and reference to a previously constructed scale the position of the cloud as seen from each camera is next determined, and the angle subtended by the base line at a point X vertically beneath the cloud is calculated. If A and B are the stations, and a and b the angles from them respectively, the distance AX is given thus—
log AX = L sin b-L sin AXB + log AB,
and the height h of the cloud above X is given by—
log h = log AX + L tan alt.-10.