SUPPLEMENTARY REPORT ON METEOROLOGY. 137 
first. The angle of obliquity in which any light will reappear 
must depend upon the size of the opake particles; con- 
sequently, such coloured rings as this cause produces will vary 
with the size of the interposed globules of water or vapour, and 
will generally be larger as these are smaller. This was the 
principle of Dr. Young’s Eriometer for measuring the diameter 
of fibres and powders*. Thus Dr. Young has shown7, that a 
Corona, 8° in diameter, corresponds to the existence of drops 
(or spherules of any kind) 335; in diameter. 
296. As might be expected, this dimension varies with the 
season. It appears, from the careful observations and compu- 
tations of Prof. Kamtzt{, that the diameter of the spherules is 
least in May, being then ‘00054 French inch; and greatest in 
January, when it is *00107 inch. This is one of the most 
certain data relative to the constitution of clouds. There seems 
no doubt that these are the “ Vesicles”’ observed by Saus- 
sure§. 
297. The successive orders of colours recur at angular di- 
stances, nearly, or exactly, in arithmetical progression from the 
centre||. 
298. Glories.—The well-known phenomenon of coloured 
rings surrounding the shadow of an observer thrown upon a 
cloud, has an evident analogy with the preceding one; and up 
to a certain point, the same explanation may apply. But there 
are peculiar difficulties connected with this appearance, which 
seem to be yet imperfectly resolved. 
299. Bouguer observed in South America his shadow thrown 
on a cloud, and surrounded by coloured rings of 5° 20', 11°, and 
17°, and a white ring of 67° in diameter]. Scoresby observed 
at sea a similar phenomenon on a thin stratum of fog. The 
rings had radii of 12° or 2°, 4° 45!, 6° 30!, and a whitish circle 
extending from 36° 50! to 42°. A larger and still fainter circle 
was once observed**. Professor Kamtz has seen on the Rigi 
similar circles of radius 37° 27' on one occasion, and 42° 10! on 
another, which he considers as true rainbows, very faintly 
tinged with red outside, and with blue within. At the same 
* Described in his Introduction to Medical Literature. 
¢ Art. Chromatics, Encyc. Britt., Sect. xi. 
+ Lehrbuch der Meteorologie, iii. 102. § See above, Art. (218) and note. 
|| Young. Compare Herschel on Light, Art. 701. Fraunhofer, quoted by 
Kamtz, iii. 96. Babinet, Comptes Rendus, iv. 643. 
| Mémoires del’ Académie des Sciences, 1744, 4to edit., p. 264. Each man 
saw only his own shadow; but the reason assigned is not very clear. ‘“ Chacun 
de nous vit son ombre projetée dessus (i. e. on the cloud), et ne voyait que la 
sienne, parceque le nuage n’offroit pas une surface unie.” 
** Kamiz, ili. 108. 
