294 
NATURE 
[ Fan. 25, 1883 
appeared to be black, and the motion either corkscrew like or 
snake-like, with v rtical undulations. Three of the observers 
have since made sketches from memory, quite independently of 
the impression left on their minds, and on comparing these 
sketches, which slightly varied, they have agreed to sanction the 
accompanying outline as representing as nearly as possible the 
object which they saw. The party consisted of W. Barfoot, 
J.P. of Leicester, F. J. Marlow, solicitor, of Manchester, Mrs. 
Marlow, and several others. They discard the theories of birds 
or porpoises as not accounting for this particular phenomenon. 
F. T. Morr 
Birstal Hill, Leicester, January 16 
A Novel Experiment in Complementary Colours 
THE old maxim of an adjacent gray in crder to give visibility 
to a complementary colour seems to hold its ground. Mr. 
Charles T. Whitmell puts it very clearly when he alludes to 
“the advantage of a reduction of brightness to a level com- 
parable with that of the existing colour.”’ 
Mr. Whitmell will find, I think, that this brightne-s may be 
sill further reduced below the level of the existing colour. This 
may be shown by one or two remarkable experiments with light 
admitted through a small needle hole the one-fiftieth of an inch 
in diameter, made through the bottom of a half ounce pill-box 
painted inside with Jampblack. On placing a sheet of white 
paper on the table at night in a room hghted with ordinary gas, 
and looking through the small hole with one eye, Joth eyes being 
open, he will see on the paper a disc of asbeautiful cobalt 4/ze colour, 
evidently the complementary of the yellow light of the gas. On 
examining the sky in the same way in the morning, there will be 
seen, especially if the weather is dull and hazy, as it has been of 
Jate, a disc of a primrose yellow colour, the complementary of 
the blue sky, which, although invisible, is stil] making its im- 
pression on the sensitive retina. 
five and six o’clock, when the weather is murky, the disc has a 
well-marked zk colour, the atmosphere being evidently tinged 
with dark green. Thee several results I have witnessed from 
day to day for the last fortnight, and they have been verified by | 
others to whom I have shown them. But when the sky is very 
blue and clear, there is seen, for obvious reasons, a blue disc 
only. 
In the above experiments there is the curious anomaly of 
having one eye impressed with the exciling colour, the other 
with its complementary. JOHN GORHAM 
Bordyke Lodge, Tunbridge, January 20 
The Projection of the Nasal Bones in Man and the Ape 
In my letter in the Jast number of NATURE (p. 266) the walls 
of the human nose were carelessly ascribed to the elevation of 
the 7e-maxillary bones. This is not the case. It is only in the 
ape and lower animals that the ascending processes of tke pre- 
maxillary assist in forming the external nose-case, or muzzle, 
above the nostrils. The frame-work of the rose in the lower 
types of the negro seems, therefore, in this respect, to differ 
more from the nose-case of the ape, than it does owing to any 
great development of the nasal bones, 
I take this opportunity to mention that the wocdcut of the | 
embryo, which I referred to, appeared firt in Quaiu’s 
““Anatomy.” Also, the quotation about the nasal bones of the 
orang, I have since found trom my notes, to have been derived 
from Prof. Mivart’s ‘‘ Man and the Ape.”’ 
January 22 J. PARK HARRISON 
HOVERING OF BIRDS 
(ails problem, to account for the phenomenon of the 
motionless hovering of hawks and other birds in 
mid-air, was the subject of correspondence in NATURE, 
vol. vill. pp. 86, 324, 362; vol. ix. p. 5; vol. x. pp. 147, 
262: vol. xi. p. 364. The only plausible explanation 
advanced (by Joseph Le Conte, vol. ix. p. 5, and pre- 
viously by the present writer, vol. viii. p. 362) was that 
the birds take advantage of slant upward currents of 
wind sufficiently strong to neutralise the force of gravity. 
But the arguments brought forward in support of this 
explanation were perhaps not quite conclusive, for lack 
of a sufficient series of observations. 
Later on in the day, between 
During the past six years I have noted such instances 
as I have chanced to witness in the course of a wandering 
occupation, and now offer the results as a further contri- 
bution towards the solution of the question. 
I may state at once that in every case where I have 
seen a bird hovering, the following three conditions have 
obtained :— 
(1) There was a fresh wind blowing. 
(2) The bird was facing the wind. 
(3) Beneath the bird there was a steep slope of ground 
facing the wind. 
The particular localities in which I have observed the 
phenomenon are the following :— 
(1) 1877, September 17.—Driving from Aberayron to 
Llanrhystyd (Cardiganshire). Wind W.N.W., moderate. 
Cliffs facing N.W. Gulls under cliff top, below road. in 
poise. Hawk under hill top, above road, in perfect 
oise. 
i (2) 1877, October 13.—Approaching Llantrisant town 
(Glamorganshire) from Llantrisant Junction. Wind S.W., 
moderate. Hawk over S.W. slope, barely poising, partly 
fluttering, tail plainly brushed up. 
(3) 1877, October 14.—Llantrisant (Glamorganshire). 
Wind S.S.W. Rooks upborne, above S.S.W. slopes of 
hill with entrenched fort (Caerau). 
(4) 1877, October 20.—Cliff facing S. between Longland 
and Caswell Bays, Gower (Glamorganshire). Gull and 
crows upborne. Wind moderate, S.S.W. 
(5) 1877, October 21.—Cefn Bryn, Gower (Glamorgan- 
shire), facing S.S.W,, climbing from Reynoldston. Rooks 
upborne. Wind strong, S. by W. 
(6) 1879, October 17.—On road from Llantrisant to 
Pontypridd (Glamorganshire). Wind W. Rooks up- 
| borne over slopes facing W. 
(7). October 28.—Killay, near Swansea (Glamorgin- 
shire). Hawk poised above hill-side facing N.E., to the 
west of Killay railway station. Wind N.E. I wasalmost 
under the bird, and could see the conduct of wings and 
tail suiting the ripples of wind. p 
(8) 1879, November 5.—Near Merthyr Tydfil (Glamor- 
ganshire). Hawk poised over N. slope of hill above (to 
| S. of) tunnel on Merthyr-Abernant Railway. Wind N. 
(9) 1880, March 13.—Near Penally (Pembrokeshire). 
Sea-gulls, rooks, and jackdaws upborne and floating with 
wings outstretched all along cliff line facing S., between 
Penally and Lydstep. Wind S., full on cliff from the 
sea. Gulls up to 200 feet above cliff edge. At greater 
| height and inland, they were flapping. Different be- 
haviour of rooks over inland northern slope. 
Further on, over caves at north end of Lydstep Sands, 
hawk poised for 1 min. and 1} min. at a time, just over 
cliff line, in teeth of wind off sea. ‘ 
(10) 1880, March 17.—Near Cardiff (Glamorganshire). 
Hawk poised about Io or 12 feet above railway embank- 
ment facing E.N.E. (20 or 25 feet high) of Llandaff and 
| Penarth line, near Ely Station. Wind E. 
(11) 1880, March 27.—Gulls uplifted over E. scarp of 
Beachy Head Down (Sussex). Wind E.N.E. 
(Same day)—Over N.E. slope of Lighthouse Down. 
| Bevy of eight gulls, all in perfect poise, immediately over 
edge of cliff. 
(1z) 1880, August 8.—Wells next-the-sea (Norfolk). 
Wind N.W. Hawks poising over W. slope of sea-wall, 
and over N.W. slope of sand-hills (projecting from the 
main line of dunes that runs east and west), and trying 
unsuccessfully over railway embankment which runs 
N.W. and S.E. 
In several of the instances here recorded I was near 
enough to see that the bird was delicately adapting the 
| slope and spread of its wings to the momentarily varying 
inclination and force of the wind. Among the sand- 
| hillocks near Wells, on the Norfolk coast, I succeeded in 
approaching, under cover of ridges and long grass, with- 
| in about ten yards of a hovering hawk, and saw the 
