4 
NATURE 
~~ te ee ee ne 
| Nov. 2, 1882 
the friction between air and water is as great as he 
supposes, it ought to produce a sensible effect, and since 
winds blow as often and as long down-stream as up- 
stream, the water-surface should as often be accelerated 
as retarded, and the vertical velocity parabola should as 
often have its axis above the water-surface as below it. 
Boileau does indeed suggest that the absorption of air 
by the water and the evaporation of the water cause a 
loss of energy near the surface, but here again the cause 
seems as inadequate as air-friction. The experiment of 
Francis, quoted on p. 107, is admitted by Major Cunning- 
ham, to prove that ‘‘there is a continual transfer of water 
from the bed towards the surface, even in water in ap- 
parently tranquil motion,” and his own float-observations 
(p. 269) show that “‘near the edge of a stream there is a 
persistent flow of the water at and near the surface from 
the edge towards the centre.” Now the flow from the 
bottom and sides towards the top and centre brings 
water, stilled by impinging on roughnesses of the bed, to 
replace the quick moving surface-water. It is not true 
that the water so rising must acquire the velocity of the 
layers through which it passes, for it may rise in eddying 
masses, which are but little affected by the friction on 
their surface, or the motion of the water may be in hori- 
zontal spiral paths, which allow the bottom water to reach 
the surface without passing through the quicker moving 
central parts of the stream. At all events the transfer of 
the bottom water to the surface is a known phenomenon, 
and it is adequate as an explanation of the diminution of 
surface velocity. 
In Chapter XVI. is given a somewhat elaborate theory 
of the motion of a rod-float, which leads to the result 
that the rod-velocity is slightly less than the true mean 
velocity of the water past the immersed portion of the 
rod. Quite apart from the question of the general un- 
steadiness of the motion of the water, it may be pointed 
out that the relative velocity ~—w of the streams im- 
pinging on the rod must for the most part fall below the 
limit for which the pressure due to impact or friction can 
be assumed to vary as the square of the velocity. Hence 
the calculation that the rod-length should be o0’94 of the 
depth of the water to give a true mean velocity, seems an 
extremely doubtful one. 
In criticising thus two or three points of theory, it must 
be pointed out that these matters do in fact lie somewhat 
outside the main objects of the experiments, and an error 
on these points detracts nothing from the practical value 
of Major Cunningham’s work. W.C. U. 
LETTERS TO THE EDITOR 
[The Editor does not hold himself responsible for opinions expressed 
by his correspondents, Neither can he 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 possible. The pressure on his space ts so great 
that it ts impossible otherwise to ensure the appearance even 
of communications containing interesting and novel facts.) 
“Weather Forecasts ” 
WILL you permit me to call attention to the apparently com- 
plete failure of the Forecasts of Weather given in the daily 
papers with respect to the storm of Tuesday, October 24? The 
matter seems to me to be one of much practical moment. Here 
is an extract from the *‘ Weather” article in the Zzmes, which I 
presume agrees with that given in each of the daily papers :— 
4 
Forecasts of Weather for Tuesday, October 24 (issued at 8.30 p.m. 
on the previous day). 
o. SCOTLAND, N.—South-westerly breezes, fresh or moderate ; 
showery. 
SCOTLAND, E.—South-westerly breezes, moderate; some 
showers, with bright intervals. 
. ENGLAND, N.E.—Same as No. 1. 
. ENGLAND, E.—Same as No. 5. 
. MIDLAND CounTies.—Same as No. 1. 
. ENGLAND, S. (London and Channel).— Westerly and south- 
westerly breezes, light to fresh ; fine and cold at first, some 
local showers later, 
. SCOTLAND, W.-—Same as No, 0, 
. ENGLAND, N.W. (and N. Wales).—Same as No. o. 
. ENGLAND, S.W. (and S. Wales).—South-westerly winds, 
fresh to strong ; showery. 
9. IRELAND, N.—Wind returning to south-west, and freshen- 
ing ; weather showery. 
Io. IRELAND, S.—Same as No. 9. 
Warnings.—None issued. 
UpbWN 
cow CV 
By order, 
Rosert H. Scort, Secretary. 
Notice particularly the concluding words : ‘‘ Warnings ; none 
issued ;” and then remember what took place. It is curious to 
compare in this respect the 7zmes of October 24 with that of 
October 25. In the latter issue we read as follows :— 
“*Vesterday morning a violent gale of wind, accompanied by 
a heavy downpour of rain, visited London. The previous 
night was beautiful, but at three o’clock yesterday morning the 
sky became overcast, and from half-past four o’clock up to ten 
o'clock there was an incessant downpour of rain. At half-past 
nine o’clock the upper part of 19, Windmill Street, King Street, 
New Cut, was stripped off, and the occupiers of the upper floors 
had a narrow escape. At ten o'clock a sign-board was carried 
away from the frontage of a house in Jewry Street, Aldersgate 
Street, Although the street was crowded, no one was reported 
hurt. At Five Fields, Dulwich, the grass was strewn with 
broken arms from the trees, and a large elm at Norwood was | 
blown down. A portion of a large shed situated near the. 
Surrey Gardens Estate was unroofed. The trees in the various | 
metropolitan parks have suffered severely from the gale. The 
River Thames at ten o’clock resembled a small sea, and much | 
damage was done to the shipping below London Bridge.” 
And much more to the same purpose. 
T feel desirous of knowing, both on general and scientific 
grounds, and also for obvious practical reasons, whether any 
explanation can be given of this absolute breakdown of weather | 
science. It would seem to be possible that a storm can visit our | 
coasts, and do immense destruction both by sea and land, and 
yet not give the faintest notice to our weather prophets of the 
impending danger ; and it really almost makes one smile to per- 
ceive that on the day of the storm no warnings were issued,’and _ 
that on the day after ‘‘the South Cone was hoisted this morning 
in Nos. 2, 3, 5, 7, and 8.” 
If no mistake has been made in the observations, and a mis-) 
take seems scarcely possible, we seem to be driven to the con-) 
clusion that a storm of the first magnitude can come upon us 
unawares ; and if this be so, the conclusion is discouraging and) 
very strange as regards science, and it is very serious as) 
affecting the value of forecasts of the weather to fishermen and 
others. 
I write this letter with the hope that some light may be 
thrown upon the subject to which it refers. H. CARLISLE | 
Rose Castle, Carlisle, October 26 
The Comet | 
I BEG that you will allow me space for a few lines of comment 
upon the letters and drawings of the comet in your last issue, 
my own included. While thanking the engraver for the gene- 
rally accurate reproduction of my sketch, it is clear that wood4 
engraving scarcely admits of a perfect rendering of stumped! 
shading. A few words of correction will serve all the purpos 
of preserving for possible future use the evidence which I wished 
to put on record. The chief defect is in the zso/ation given tq 
the ‘‘ wisp,” described by another correspondent as a ‘‘ horn.” 
It seemed rather to be an inclined elongation of the brightest 
part. The inclination too is exaggerated: its prolongation 
should have passed within the star on the northern! border, but 
» The tail lies nearly along a parallel of declination. 
