oS 
Aug. 17, 1871] 
NATURE 
395 

Daylight Auroras 
I HAVE frequently seen the appearances described by Mr. 
Winstanley in your issue of August 3, and I think I must have 
seen the one he mentions. I have on two occasions watched 
similar phenomena caused by the moon. These phenomena re- 
quire the cloud or clouds, from which they are formed, to be of 
about the same azimuth as that of the sun (or moon), and vary 
with the form and motion of the cloud, being, I think, simply a 
deflection of the sun’s rays from the more salient points of the 
cloud. The streamers I saw on June 27 (sce Nature of July 
g) were of an entirely different nature, rising near the south 
horizon somewhat to the east of the meridian, and flashing 
towards the moon, which had recently passed the meridian, while 
the sun was near setting in the N.W. 
Ihave had nearly thirty years’ experience in observing, and 
have no doubt that what I described were true streamers of an | 
aurora australis. 
Joun Lucas 
Radcliffe Observatory, Oxford, Aug. 17 
The Late Thunderstorm 
THE thunderstorm which has just broken up the spell of hot 
weather for the past week presented some peculiar features as 
seen from this:place. Commanding rather a wide horizon, I 
noticed about 8.30 last evening two distinct centres of disturb- 
ance, one S.W., the other N.E. It is impossible to estimate 
the distance by sound, as the thunder was inaudible. The electric 
spark, however, was visible enough, and I noticed that with one 
exception it went invariably from S. to W. in the one case, and | 
from N. to E. in the other, and always horizontally from cloud 
to cloud. When I came out again at 10.15 I found the two 
centres had moved, so that one was slightly S. of E., and the 
other N. of W., but still directly opposite each other, 
too, that they had gone in the direction in which the electric 
spark had passed. 
This seemed to me interesting, and I thought your readers 
micht find it so too, 
Upton-on-Severn, Aug. 14. W. M. Rosperts 
Sir William Thomson and the Origin of Life 
T AM sure that Sir William Thomson will feel gratified rather 
than annoyed to be informed that he has been anticipated in his 
remarkable hypothesis regarding the origin of life on our globe. 
In a very curious book called ‘‘ A Visit to my Discontented 
Cousin,” published some months ago, there is a portion of one 
chapter headed ‘* The Aerolite.” The ‘*‘ Discontented Cousin ” 
having seen and heard a discussion on a meteoric stone, went 
home and ‘‘dreamt a dream,” in which he saw the surface of 
the mass undergo various changes, and organic dots appear, 
one of which began to wriggle, rose to its microscopic legs, and 
confronted ‘‘the dreamer with a bold and self-confident mien.” 
This microscopic man, after having enjoyed ‘‘a glass of some- 
thing stiff and a pipe,” told the story of his own planet, begin- 
ning with the not very complimentary remark, ‘‘ We know all 
about you, o!d boy, and the British Asscciation ; and we don’t 
think much about you, either.” 
For the story itself I must refer to pp. 186-192 of the book. 
Torquay, Aug. 8 G, E. D. 
Meteorology at Natal 
IN your issue of November 1o last I was glad to see that you 
were alive to even humble efforts to assist science in so distant a 
place as Natal by your remark on the new Meteorological 
Observatory for the Durban Station. 
As it may be interesting also to know what has been done, I 
append a list of the instruments ordered by the Natal Govern- 
ment. They are to supplement a few already on board. Unfor- 
tunately for the furtherance of this object, the state of affairs at 
present will not admit of any large expenditure of public money 
in this direction, but I have been enabled to get the sum of 10/, 
in 1870 and 25/. in 1871 for the purchase of instruments. The 
Government, at the same time, pay the observer 12/, per annum 
for the trouble of registering the results regularly. 
At present the military authorities have an observatory at Fort 
Napier, in Pietermaritzburg, at a height of 2,200 feet above and 
forty-five miles from the sea, A station on the coast was required 
to complete the observations, and the Government liberally came 
It seems, | are 
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forward with the means. Hitherto a system of registration has 
been followed in which the instruments were suspended in 
wooden boxes agains: the sides of dwelling-houses. Though 
such a system, perhaps, 1s advisable as giving the temperature 
| ordinarily felt by residents, it nevertheless is more or less uncer- 
tain for the purposes of comparison, from the fact of some of the 
dwellings being built of wood and others of stone, and again 
some roofed with slates and others with galvanised iron. 
The present system is that pursued by the military authorities. 
The thermometers are placed under a Glaisher’s stand in the 
open air. Whether the military authorities are right or wrong 
| matters little so long as one universal system is pursued, so that 
exact comparison can be made between each station, The 
results will always be sent to the Meteorological Society of Eng- 
land, and published in the Colonial Blue Book for each year. 
VINCENT ERSKINE 
Pietermaritzburg, Natal, May 16 : 
P.S.—I expect the Observatory to be in thoroughly good order 
from the 1st of January, 1872. 

On the Colours of the Sea 
THE following is submitted on the above subject, referred to 
in NaTuRE of July 13, as showing that the colour of the sea is 
not altogether dependent on the purity and depth of the water. 
At Zante, and southward as far as I have seen, it is of a deep 
| blue at midday, but in the evening it is that described by Homer 
as ** wine-like.” I have observed this particularly when passing 
Navarino and Cape Mataplan. At night, looking down upon it 
from the steamer, it is quite black, lighted up, where the waves 
are broken, with white phosphorescent light. 
I had once the gratification of seeing the whole of the solar 
spectrum spread out upon the sea, at Zante, on December 26, 
The weather was very unsettled at the time. During an 
interval, when the rain had ceased, a little before 10 A.M., the 
light of the sun descended from behind a cloud, and was reflected 
| up to the height on which I was standing. Purple was the most 
remote colour ; red the nearest ; the space between was occupied 
| by the other colours, of which green, yellow, and blue were the 
most marked, JouN J. Lake 
Origin of Cyclones 
In NATURE of 23rd of June, 1871, there is an account of a 
paper, by Mr. Meldrum, on the origin of storms in the Bay of 
Bengal, showing reason to believe that the cyclones of the Bay of 
Bengal and the Southern Indian Ocean originate in the meeting 
of the trade-winds of the northern and southern hemispheres at 
some distance north or south of the equator. Ido not know of 
any equally complete evidence on the subject for the cyclones of 
other parts of the world, but there is very strong reason for 
thinking that they always so originate. The line along which 
the two trade-winds meet each other approximately coincides with 
the equator : whenit actually or nearly coincides with the equator, 
no cyclones are formed, because the rotation of a cyclone depends 
on that of the earth, and the earth at the equator has no rotation 
round an axis drawn vertical to the horizon. Over the greater 
part of the Pacific, cyclones do not appear to be formed: the 
reason of this probably is, that in consequence of the tempera- 
ture of the sea changing but little with the seasons, the two trade- 
| winds over the Pacific meet each other nearly on the equator all 
the year round ; though I donot know how far this is confirmed 
by observations on the winds of that ocean. But we know that 
in the Indian Ocean the trade-winds cross the equator and are 
deflected into monsoons, so that in the summer of the northern 
hemisphere they meet to the north of the equator, and in the 
summer of the southern hemisphere they meet to the south, 
(This statement as to seasons will have to be qualified 
presently. ) 
We may consequently expect to find that the farther the sun 
is from the equator, the farther from the equator will be the 
meeting of the trade-winds, and consequently also the cyclones. 
This is the fact. In Dove’s ‘‘ Law of Storms,” translated by 
Mr. Scott, at page 193, there is a chart of the tracks 
of the cyclones of the Chinese Sea, which shows that they 
occur in all months from June to November, and that the 
later in the season the nearer to the equator is usually their track. 
In the Chinese Sea, where they are called typhoons, they are 
most numerous in the summer months ; in the Bay of Bengal 
they are most numerous after the equinoxes. This will appear 
