306 

suchas bleaching. While in agricultural districts much might be 
done towards making the field labourer a more intelligent being 
than he is usually supposed to be, by giving lessons in agricultural 
chemistry, the art of draining, the laws of evaporation and con- 
densation, the value of woodland, the construction of various 
implements used, &c. But in every locality lessons should be 
given in physiology, health, and ventilation, while natural 
history would everywhere form a not less pleasing than instruc- 
tive alternative subject. The walls of every school, upper, middle, 
or elementary, should be covered with diagrams, and at the foot 
of these should be descriptive and explanatory notes. 
As regards the teachers themselves, it may be left an open 
question as to whether they should be required to go through 
the ordeal of an examination in the subjects they take up, or 
whether it may be taken for granted that the mental discipline 
undergone for two years in the training college is sufficient to 
enable them to perfect themselves for the task. Those among 
them who have been at work for ten or fifteen years might 
probably feel indisposed to prepare again for examination ; and 
we are ready to admit that if a man can bring up his pupils to 
the required standard, he may well be excused from any other 
test. At any rate it is to be hoped that the subject of scientific 
instruction in our elementary schools will receive that attention 
from Government which is due to it, and that having been once 
again taken up, it will never be allowed to fall into desuetude. 
HENRY ULLYETT, 
Hon. Sec. Folkestone Nat. Hist. Soc. 
National School, Folkestone 
The Prevalence of West Winds 
In Nature of 29th September, 1870, there is an abstract of 
a paper read at the British Association by Mr. Laughton, 
maintaining that the preponderance of west over east winds over 
the entire globe is such as to point to a cosmical force of some 
kind, moving the atmosphere round the earth from west to 
east ; and concluding ‘‘that the motive force for which we are 
seeking, is really the disturbing force of the attraction of the 
heavenly bodies.” 
The course here suggested, if it were operative at all, would 
act in the opposite direction to that required. The only 
possible effect of the attraction of the heavenly bodies on the 
atmosphere is an atmospheric tide, and the motion of a tide 
is necessarily from east to west, with the apparent diurnal 
motion of the heavens. But it is only when resisted that a 
tidal wave can give origin to currents, and it is scarcely probable 
that any tidal current can be formed in the atmosphere of 
sufficient force to blow a feather. I maintain the truth of the 
ordinary theory, that all winds originate in a disturbance of 
atmospheric equilibrium by unequal solar heating in different 
parts of the earth, but are changed in direction by the earth’s 
rotation. This theory is quite consistent with the fact on which 
Mr. Laughton insists, that west winds preponderate over east 
winds. It is true that the mechanical effect of any wind whatever 
must be balanced by an equal mechanical effect in the opposite 
direction. Mr. Laughton appears to see that this would neces- 
sarily be the case if the ordinary theory of the winds is true, but 
he does not see how the compensation is effected. Were the 
winds all from the west, they would in an infinitesimal degree 
accelerate the earth’s rotation; were they all from the east, 
they would in an infinitesimal degree retard it: and if either of 
these effects were proved to take place, the inference would be 
certain that the winds are set in motion by some other agency 
than unequal heating in different places; because, in virtue of 
the universally true principle of the “conservation of rotation,” 
no such motive power could have any effect on the earth’s 
rotation whatever. 
The unbalanced effect of any wind on the earth’s rotation 
will be due to the product of three factors, namely, the area 
covered by the wind, the east or west component of its force, 
and the radius of the parallel of latitude at the place. Mr. 
Laughton has probably overlooked the last-mentioned factor. It 
gives /everage. An east wind near the equator has more effect 
in retarding the rotation of the earth than a west wind of equal 
extent and force at a higher latitude has in accelerating it, just as 
a weight at the end of the long arm of a lever outweighs an equal 
weight at the end of the short arm, It is for this reason that the 
west winds, which are mostly in the higher latitudes, are of 
greater force, and probably cover a greater area than the east 
winds, which, under the name of the trade-winds, predominate 
near the equator. _ JosepH JOHN MURPHY 
Old Forge, Dunmurry, Co, Antrim, Jan, 25 
NATURE 




| Feb. 16, 1871 

Can Weather be Influenced by Artificial Means? 
SoME remarks on this subject made by the Rey. R. B. Belcher 
before the Geological Section of the British Association (reported 
in the Atheneum of October 29), reopen a question of popular 
meteorology, which has not, perhaps, been sufficiently attended 
to, from an exact and scientific point of view. Such evidence 
on the subject, as is at present available to the public, is too 
general to have much claim to correctness of detail on points 
which require particular and Zoca/ information; and I offer the 
following abstract of it principally in the hope that it may lead 
to further inquiry and observation. 
The idea that large fires do, insome way, bring on rain, is very 
old ; but it was, I believe, for the first time stated as a fact and 
explained on scientific grounds by the late Professor Espy. His 
theory is, that the heating of the air causes a rapidly ascending 
current, and that the moisture which air near the surface always 
contains, is thus carried into the upper regions of the atmosphere 
to be condensed and to fall as rain. In support of this view, he 
has given several instances in which rain did immediately follow 
the kindling ofa fire, when no clouds had previously been visible, 
but ina problem of this nature, negative examples have more 
weight than positive ; and it is necessary to admit that, though 
in some very remarkable instances rain has followed a large fire, 
in other instances, quite as remarkable, there is no notice of rain, 
It is, of course, difficult to speak with absolute certainty ; it may 
almost always be said that a few drops have fallen, sufficient to 
bear out the truth of Espy’s theory, but it seems to me that to 
establish it in its entirety, something more than this is necessary, 
and that an extraordinary fire ought to produce a very decided 
shower, if not a heavy downpour. Last summer, in July, 
a large fire raged for several days on the moorland and 
through the pine copses a few miles to the east of Wimborne- 
Minster. The weather was hot and dry. I was myself 
on a walking tour in that part of the country, and passed 
close by this fire, near the village of Longham, where it 
had been burning with great fury for a week. ‘The farmers were 
all complaining of the long and excessive drought, and I can 
give my personal testimony to the fact that there was absolutely 
no rain, Similarly in the very dry summer of ’68, the papers 
were for some weeks filled with accounts of fires raging fiercely 
in various parts of Wales and Scotland ; but there was no word 
of any break in the drought. It is only by referring to excep- 
tional and recent examples of this kind that we can feel any 
degree of certainty ; wet weather and heavy rain are so common 
in this country, that under circumstances not very remarkable, 
they would scarcely be noticed ; and these instances I have just 
mentioned show the necessity for caution before attributing to fire 
and cénsequent rain the relationship of cause and effect ; and, as 
bearing directly on Espy’s theory, I may add that there are no 
observations which would show that the rainfall in our large 
towns is greater than in the adjacent country ; yet the thousands 
of fires in London, for example, must heat the air sufficiently to 
cause some ascensional tendency. 
The evidence regarding the effect of violent explosions is in 
very much the same state of imperfection. Theoretically, we 
can admit that a violent shock may throw large masses of the 
lower air to a considerable height, so as to cause condensation of 
its vapour ; and there are many instances which seem to support 
the conclusion that it does do so. The clearest on record are 
periaps those mentioned by Dr, Darwin, in his Journal of Re- 
searches, where he describes how on several occasions a shower 
of rain fell, in the middle of the dry season, in Chili and other 
parts of South America, after an earthquake. After the earth- 
quake in Peru, in the latter part of the year 1868, I went care- 
fully through the published accounts, but found no mention of 
any similar showers. In our own climate, in which rain is not 
uncommon at any time of the year, the circumstances require to 
be examined into more critically, and the evidence afforded by 
them can never be quite so satisfactory. _Whitaker’s Almanack 
for last year, in the list of Remarkable Occurrences, &c., 
for 1869, mentions several serious explosions of powder mills, 
collieries, &c., but not one of them is followed by any notice of 
remarkable weather, storm, or rain; still, as one of these is the 
conflagration at Bordeaux on September 28th, which, as Mr. 
Belcher has pointed out, was followed by very heavy gales, 
both in the Bay of Biscay and in the English Channel, it is 
likely enough that heavy weather following some of the other 
accidents may have been omitted, or have been insufficient to 
call for special mention in such a general list. 
The effect of great battles, again, has always been a favourite 
