266 
NATURE 
[ Fan. 18, 1883 
on pp. 961-963. These works are all in German, and the 
only English mathematician whose works are cited is Dr. 
Salmon, in Teutonic dress. 
LETTERS TO THE EDITOR 
[The Editor dss not hold himself responsible for opinions expressed 
by his corre:pondents. Neither can hz undertake to return, 
or to correspond with the writers of, rejected manuscripts. 
No notice is taken of anonymous communications. 
[The Editor urgently requests correspondents to keep their letters 
as short as possthle. The pressure on his space is so great 
that it is impossible otherwise to ensure the appearance even 
of communications containing interesting and novel facts.] 
Pollution of the Atmosphere 
IN answer to Mr. Joseph John Murpby’s letter in NATURE, 
vol. xxvii. p. 241, stating that the radiation of marsh gas (from 
the incomplete combustion of coal) would be insignificant com- 
pared t» that of vapour, I would like to say that their behaviour 
in the atmosphere is different ; the moisture in the air is there, 
so to speak, on sufferance as long as the pressure and temperature 
allow it ; that is, it is held in suspension by what might be called 
the capillary attraction of the air of a certain pressure and tem- 
perature. If you reduce the temperature you reduce the capacity 
of air for vapour, first by its reducing the capillary attraction, 
and secondly, by redu:ing one of the conditions that makes OH, 
avapour. If you reduce the pressure, you enlarge the spaces 
between the molecules and reduce the capillary attraction, if I 
may apply this term toa gas. This is borne out by the balloon 
ascents of Mr. Glaisher, At 4 miles high the temperature was 
8°, the dew-point was — 15°, or a difference of 23°; at § miles it 
was 28°, and at 30,009 feet he stites that there is no doubt that 
the dew-point is a difference cf 50° ; that is, the higher, the less 
vapour. But this will not be the case with marsh gas, as it is a 
permanent gas, and being of less densi'y than even vapour, or 
about half the density of air, there is no reason why it should 
not be found in larger quintities at greater altitudes ; and I think 
that its effect there would be that in the temperate zones and at 
the poles it would radiate its temperature of say from —§ at 
30,000 to — 30, and produce cold and rain, snow and floods as 
the storms on the Alps and the floods on the Continent, and in 
the Tropics to make the nights colder. In fact, it will have a 
tendency to do the reverse of vapour ; vapour retains our heat 
and shields us from the cold of space. This radiator and ab- 
sorber will tend to radiate the cold to us or to the vapour in the 
lower atmosphere, and produce rain and wind. 
9, Bootham Terrace, York, January 13 4H. A. PHILLIPS 
A “Natural” Experiment in Complementary Colours 
SiNCE I wrote to NATURE last October (vol. xxvi. p. 573) on 
the above subject, I have been both surprised and gratified to 
read no less than six communications on the same matter (vol. 
xxvi. p. 597, vol. xxvii. pp. 8, 78, 150, 174, 241). Only to-day 
I have received a letter from a German friend drawing my atten- 
tion to Goethe's observation at Schaffhau-en, he evidently being 
unaware of Mr. W. R. Browne’s interesting letter (vol. xxvi. 
p- 597). My friend goes on to point out that ‘‘Gischt” is cer- 
tainly foam, for in the context Goethe describes how he saw a 
rainbow in the ‘‘ Dunst,” or mist, thus enabling us to contrast 
the two words, 
The special point of my com nunication was the excellent 
illustration, afforded us naturally, of tue advantage of toning 
down the brightness of the white surface, upon which the com- 
plementary tint is to be cooXed, until that brightness is suitable 
to that of the exciting colour. In the experience related by me 
I was unable to see complementary tints in the foam, upon 
which full sunlight was falling; the glare of light was too 
strong. 
Mr. C. R. Cross (vol. xxvii. p. 150) speaks of seeing them 
even in strong sunlight on the crests of waves; may not these 
crests have been in slight shadow, if the waves were just curling 
over? The example he gives of cloud shadows appearing purple 
on the ocean illustrates excellently my own observations. The 
letter from Mr. E. J. Bles (vol. xxvii. p. 241) gives a quotation 
from Sir C. Lyell, but without further detail I do not feel that 
much weight can be given to his observation from my special 
point of view. But Ido not at all wish to say that comple- 
mentary tints are not visible on a white surface in full sunshine ; 
but theory and my own observations are certainly in favour of 
the advantage (and this isall I claimed) of a reduction of bright- 
ness to a level comparable with that of the exciting colour. 
Cuas. T, WHITMELL 
8, Maryland Street, Liverpool, January 15 
The Comet 
In my letter relating to the September comet, published in 
vol. xxvil. p. 108, I was guilty of carelessness in copying from 
my notes the difference of micrometer readings instead of their 
value in arc. The value of one revolution of the screw is 
15”"31075, and consequently the distances given in my letter 
should be as follows :— 
6°57 
16°90 > November 3 
$°34 
7°36 
16°51 » November 6 
IO'lS 
Hou Ww a at 
SRO BAR 
W. T. SAMPSON 
U.S. Naval Observatory, Washington, D.C., January 2 
The Transit of Venus 
WILL you be kind enough to make the following correction in 
your published report of the times of contact of phases of the 
transit of Venus. The third contact should be 2h. 39m. 57s. in 
place of 2h. 38m. 57s. These were both inadvertencies. From 
a comparison of Mr, Finlay’s place at the Cape of Good Hope 
on September 8, I find that these elliptic elements satisfy the 
place within 7 seconds of arc in Right Ascension and 1°5 seconds 
of arc in Declination. EDGAR FRISBY 
U.S. Naval Observatory, Washington, D.C., January 3 
Early Coltsfoot 
LAsT year I recordel (NATURE, vol. xxv. p. 241) Coltsfoot in 
blossom on January 6, on the sides of the railway near here, 
probably an unprecedentedly early date. The mild weather 
lately prevailing induced me to suspect the former early blossom 
ing might find a parallel ¢#/s year. I saw the plant in flower 
this morning, near the same spot; one flower-stalk was fully 
four inches high, so it should have been observed some days 
previously had sunshine prevailed. Last year the winter was 
practically over (so far as hard frost was concerned) at the 
beginning of January. Will this be paralleled by the winter of 
1882-83 ? R. McLACHLAN 
Lewisham, January 12 
Baird’s Hare 
SOME of your readers may be interested in reading the fol- 
lowing extract in which me ition is made of a fact similar to that 
found in NATUuRE vol. xxvii. p. 241, about Aairt’s Hare. The 
extract is from the Life of St. Francis Xavier, by H. J. Cole- 
ridge, S.J. In a letter written from Amboyna in May, 1546, 
Francis says :— 
. . . ‘*In the island of Amboyna I have seen what no one 
would bel'eve . . . a e-goat giving suck to his young kids with 
his own milk ; be had one breast which gave every day as 
much milk as would fill a bain. I saw it with my own eyes, 
for 1 would not believe it without seeing it. A respectable 
Portugese has the goat, and is taking it away, meaning to carry 
it to Portugal.” T. MARTYR 
49, High Street, Clapham, S.W., January 15 
The Projection of the Nasal Bones in Man and the Ape 
Tue form and projection of the osseous frame-work of the 
human nose being considered by anthropologists of considerable 
value in a racial point of view, a close comparison his recently 
been made of the profiles of the external nose of man and the 
nose-case of the anthropoid apes. It has resulted in the convic- 
tion (1) that the ab-ence of projection in the nasal bones of the 
chimpanzee, the gorilla, and the orang constitutes a distinction of 
more importance than has generally been assigned to it, and not 
the less so seems the fact (2) that a slight nasal elevation is 
——- 
