182 
NATURE 
[Fuly 3, 1873 
of the air above surrounding districts of the coal measures, or 
statistics of the fertility and periods of fructification of crops 
under similar differences of conditions. Of course the great 
ditficulty affecting the last point is the difference in the chemicai 
constitution of the soils produced by the decomposition of trap 
and stratified rocks. THOMAS STEVENSON 
Edinburgh, June 21 
Winters and Summers 
A FRIEND writes to me :—‘‘ From my observations of climate 
here (Belfast) I should say that I never saw a severe winter fol- 
lowed by a really fine summer. The severest winters I remember 
were those of 1854-5, and 1859-60. The summer of 1855 was 
very wet, and that of 1860 deplorable. The finest summers I 
remember were those of 1842, 1857, and 1868; in every case 
the preceding winter was very mild.” 
I would add to this, that the severe winters of 1865 and 1870 
were not followed by remarkably fine summers. The harvest 
weather of 1866 was unusually bad. 
Can any of your readers throw light on this subject from care- 
fully kept registers ? JosErH JOHN Murry 
Old Forge, Dunmurry, June 6 
Cyclones 
Mr. Maury’s theory of Cyclones, as stated in NATURE of 
the rgth, is, in my opinion, true and valuable. I hope you will 
permit me to call the attention of your readers to my letter in 
Nature, Vol. iv. p. 305, where it will appear that I had inde- 
pendently arrived at the conclusion stated by him, “that the 
origin of cyclones is found in the tendency of the south-east 
trade-winds to invade the north-east trades by sweeping over the 
equator into our hemispheres’ Only the words ‘‘south-east ” 
and ‘north-east ” must exchange places, and ‘‘the opposite 
hemisphere,” must be read, instead of ‘* our hemisphere,”’ if we 
are to apply the theory to the cyclones of the Southern Indian 
Ocean and of the Southern Pacific. On this latter subject, see 
Mr. Woaitmee’s letter in \NaATURE, vol. vi. p. 121. 
I wish, however, to call your attention to what I think an 
error in the diagram of the winds, which Mr. Maury reprints 
from Prof. Ferrel. It represents the winds at the surface of the 
earth in the Polar regions as blowing in nearly the same direction 
as the trade winds, This appears mechanically impossible, and 
T cannot think that Prof. Coffin’s data are extensive enough as 
regards the Polar regions. As the late Capt. Maury remarks, 
the west winds of the higher and middle latitudes constitute 
‘an everlasting cyclone on a great scale ;” that is to say, a vast 
vortex whereof the poleis the centre. But it appears impossible 
that the direction of the motion of a vortex should be reversed at 
its centre. JoserH JOHN MurPHY 
Old Forge, Dunmurry, June 24 
A Mirage in the Fens 
As the phenomenon called Mirage is not very common in this 
country, though more frequent in the Fens, perhaps, than else- 
where, [ presume that a description of one which was seen on 
Thursday, May 29, last, will be interesting to the readers of 
NaTURE. 
Driving from Wisbech towards Thorney on the morning 
named, I stopped at Guyhirne, and my friend, Mr. S. B. J. 
Skertchley, of H. M. Geological Survey, who accompanied me, 
mounted the parapet of the bridge of the March and Spalding 
Railway, to view the Fens from that elevation, and then called 
my atteation to what appeared a beautiful lake spread out a few 
miles distant. The illusory waters were of a bluish grey cvlour, 
and being apparently raised from the level, presented the per- 
spective of a Mere of considerable breadth. But this was not a 
dull expanse ; there were variously formed indentations—islands 
dotted here and there, pollard willows inverted, and the reflec- 
tion of tall poplars and elms on the glassy surface. The use of 
my field-glass only brought these features more distinctly to the 
eye. As we stood on the bridge, we were looking from W. by 
S. to W. Whittlesea Church was eight miles distant, and 
Thorney Abbey seven miles. The mirage was stretched ont 
from Eastern Fen over Prior's Fen to the west of Thorney, #7, 
three or four miles. It was 11 o'clock. There was a fresh 
breeze from N.E, ; the sky was not half obscured by cloud ; the 
barometer stood high, being four degrees difference between the 
dry and wet bulb thermometers at 9 A.M. All these conditions 
were favourable to evaporation ; there had been more than half 
an inch of rain the Monday previous. Mr. S. had witnessed a 
similar phenomenon from another point of view (see NATURE, 
vol. ii. p. 337) in 1870, when he saw it both E. and W. of his 
position, but on Thursday last there was not even a mist in any 
other part of the horizon. On both occasions the wind was N.E. 
It may be interesting to know whether these phenomena appear 
with a mild and moist S.W. or W. bre€ze. 
Wisbech, June 5 Sami, H. MILLER 
The Westerly Progress of Cities 
REFERRING to Mr. W. F. Barrett’s letter I would remark 
that there is a similar phrase, viz the westerly or north-westerly 
progress of nations, which is intimately connected with “the 
westerly progress of cities,” and the former helps to explain the 
latter. As a rule the more westerly of two peoples inhabiting a 
country is there by compulsion, having been driven thither by 
the invader who, as a rule, makes the attack from the east. 
The remnants of the ancient Celtic race, inhabiting portions of 
the western shores and highlands of Spain, France, and the 
British Isles, are an evidence of this. We see the same process 
going on now in America: the aborigines being driven before 
the invader, to the west. There are insignificant exceptions, 
both in ancient and modern times, but they only prove the 
tule. : 
So much then for the westerly among the peoples of a land: 
they are in the west by violent compulsion. Among the inhabi- 
tants of a city the westerly are there also by compulsion—not a 
compulsion by violence, but by uncomfortable pressure; in 
which case it is the powerful or wealthy who retire before the 
weaker or poorer. 
The very fact of the westerly progress of nations establishes 
the further fact that what becomes afterwards more or less the 
eastern part of the city is the older and that where the first 
habitations were erected. An exception would be such a case 
as a city built on a western coast without any adjacent country 
to the west. Here the wealthy in retiring before their less for-— 
tunate fellow-citizens must necessarily go more or less to the 
east. B. G. JENKINS 
London, June 9 
To the instances of ‘‘ westing ” adduced by Mr. W. F. Barrett 
as occurring in the large towns of the Old World it is desirable 
to add that a similar tendency prevails in the large towns of the 
New, excepting, of course, the cases in which physical barriers ~ 
impede or prevent it. ctu 
It should be observed, also, "that this westward current of 
progress in cities appears to be but the special manifestation of 
a principle much more general—the direction of great emigra- 
tions and of the advance of civilisation, apparently in pre-historic 
and certainly throughout historical times, having been uniformly 
towards the west. Gus 
How does the Cuckoo deposit her Eggs? 
A FEW days ago while examining a reed bed in the fens of 
Lincolnshire, near Wainfleet, [ found a Reed Warbler’s nest, in 
which was deposited a Cuckoo’s egg. From the shape of the 
nest, which was very narrow and deep, and from the posttion of 
the nest, which was built on slender reeds, on the outer edge of 
the bed, it was utterly impossible that the egg could have been 
laid, as, in the first place, the nest was far too small for so large 
a bird as the cuckoo tositin ; and in the second, the weight of the 
bird would have inevitably swamped the nest. Does not this fact 
go far, at any rate, to confirm the theory held by many ornitho- 
logists to be the correct one, that the female cuckoo drops her 
eggs into nests by means of her bill, as it is well known she is 
provided by Nature with an enlargement in the throat, in which 
the egg could be carried in safety during her flight in search of a 
suitable place in which to deposit it. I give here a quotation 
from Bewick on the subject -— 
‘* Naturalists are not agreed as to whether the female cuckoo 
lays her egg at once in the nest of another bird, or whether she 
lays it first on the ground, and then, seizing it with her bill, con- 
veys it in her throat (supposed to be enlarged for this purpose) 
to the nest which is to be its depository.” 
I should be glad if any of your correspondents will inform me 
if the male bird has a like enlargement in the throat, or is it only 
to be found in the hen? 8 +.) T. Aupas 
Regent's Terrace, Hull 
