Yune 25, 1885] 
colours of some Alpine Coleoptera are brighter than those of the 
warmer plains, and that the species of small islands often show a 
tendency to melanism, are at present simply inexplicable, but, 
as far as I can see, do not tell for or against either theory. It 
would certainly be a strong case against the "present view if any 
animal could be named which became white in winter and was 
not an inhabitant of a country subject to cold winters. As far 
as my knowledge extends no such species exists. The light 
colour of desert mammals is most probably due to predatory 
advantage—the melanism of desert insects mentioned by Sig. 
Camerano is, I must confess, a new fact to me, and not at all 
in accordance with my own limited experience. The strongest 
objection raised by Sig. Camerano is, perhaps, contained in the 
statement that in the birds of the Antarctic region black is much 
more prevalent than in those of the Arctic regions. It is un- 
fortunate, however, that the writer adduces in illustration such 
countries as Australia and New Zealand, which certainly can- 
not be considered within the Antarctic region. 
In conclusion I should like to emphasize that the theory of 
climatic protection is not, as Mr. Wallace appears to believe, 
opposed to the theory of adaptation. If my first letter gave 
rise to this impression, I will take the present opportunity of 
pointing out that the animal kingdom abounds with cases of 
what our German colleagues happily call “functional change i 
(Functionswechset)—that is, the conversion of a character (or 
function) originally acquired for one purpose to a totally new 
use. It is thus not at all improbable that a mode of coloration 
originally acquired as a climatic protection, may afterwards be 
found to be of adaptive value, so that climatic and natural selec- 
tion would in such cases work together. 1 fully concede that 
many of the Arctic and Alpine species now derive such advant- 
ages from their white covering ; the question is whether this 
colouring was originally acquired solely for this purpose, or 
whether climatic adaptation may not have had an equal or even 
a greater influence in its production. R. MELDOLA 
Clifford and Professor Tait 
May a “(so-called) Metaphysician”—who has modestly 
waited to see if some one for whom Prof. Tait could have more 
respect would anticipate him—venture to remark upon a passage 
in the review of Clifford’s ‘‘ Exact Sciences” that appeared in 
Nature of June Ir? 
Prof. Tait first calls ‘‘ awkward” and ‘‘ unnecessarily 
puzzling ’ Clifford’s statement that ‘if we can fill a box with 
cubes whose height, length and breadth are all equal to one 
another, the shape of the box will be itself a cube’; and then, 
declaring with greater emphasis that it ‘‘at first sight seems to 
be nonsense,” he adds :—‘‘ Read it, however, thus: ‘ If we can 
fill with cubes a box whose height, &c. . . . the shape of the 
box itself will be a cube,’ and the absurdity, suggested by the 
collocation, disappears.” 
Now Clifford’s statement is not sufficiently guarded, being, as 
it stands, not true of the cube only ; but it surely conveys a real 
meaning, in a “collocation” of words as plain as possible. It 
is something (whether much or little) to be told that a cube can 
be made up of a number of equal cubes ; especially in view 
of the context (p. 16). But does Prof. Tait, with /zs sentence, 
tell us anything at all, except that a cube is—a cube; or say even 
that plainly ? R. 
June 22 
Unusual Atmospheric Phenomenon 
THE accompanying drawing—a copy of a sketch taken at the 
time—represents an unustial atmospheric phenomenon witnessed 
by several friends and myself during a recent visit to Ireland. It 
occurred on the 6th inst., a bright warm day, with a light 
breeze blowing from the east. The sky was free from clouds, 
excepting a few cirrus and cirro-stratus collections on the 
northern horizon. Engaged at the time in fishing from a boat 
on one of the Irish loughs, I was conscious of a change in the 
character of the light reflected from the water and distant 
objects and looking towards the sun (/), noticed that it was 
surrounded by an exceedingly brilliant halo (@ 4) of about 48° 
diameter, the contained space (g) being filled with vapour of 
a dull leaden blue colour, which, by obscuring some of the solar 
rays, apparently produced the peculiar light effects that first 
attracted my attention. The time was 1.30 in the afternoon. 
Calling the attention of my friend, Dr. Simpson, to the pheno- 
NALTOKRE 
17 
Oo 
menon, I recorded the accompanying details. The primary 
liula (2 4) consisted of a brilliant, well-defined band of about 8 
width, composed of the spectral colours in the usual sequence, 
the red ring being nearest the sun. The whole band was most 
vivid, but the northern half the brightest. At about two o'clock I 
noticed a bulging (2) of the leaden-coloured vapour of the primary 
halo (a2) to the extent of 6° or 7°, and in its south-eastern 
quadrant, and this protrusion, at first only faintly fringed with 
colour, soon was bounded by a spectral bow (e) at least as vivid 
as the brightest portion of the primary halo. The adjacent 
portion of @ 4, whether by comparison with e or whether 
because partially obscured by the protrusion of the vapour 
around which e was formed, I cannot be sure, seemed much 
paler than the rest of @é. Simultaneously with the formation of 
this secondary bow a large white ring, represented in the 
drawing by cd, slowly formed around a centre to the north of 
the sun, and rapidly assumed a well-defined contour. Its 
diameter was 72°. Had it been complete it would in its 
southern portion have passed through the sun, but after 
cutting the primary halo (@é) at the points (m and %), 
which it rendered more faint, it gradually disappeared before 
reaching the sun. This latter ring (cd) began to disappear 
about a quarter of an hour after 1 first noticed it, its no th- 
western portion fading first. I noticed no mock-suns at the 
points of contact of either of the excentric rings, and was, un- 
fortunately, unprovided with my small pocket polariscope, and 
therefore unable to ascertain how much of the phenomenon was 
due to double refraction. The portion (e) may have been thus 
produced, but it certainly appeared, as drawn, to be a portion 
of a ring of smaller radius than (a6). The Rev. T. G. Beau- 
mont, who also observed this spectacle, states that he saw the 
primary halo (@4) gradually start from a much smaller ring 
around the sun. The accompanying drawing, though rough, is 
as accurate as compatible with the absence of measuring instru- 
ments. ALEX. HODGKINSON 
26, King Street, Manchester, June 16 
Sky-Glows 
Your correspondent of Clairvaux-sur-Aube says (NATURE, 
vol. xxxii. p. 147) the sky-glows are again visible in France. I 
