~ 
” 
DECEMBER II, 1913] 
NATURE 425 
result of these it appears in the period July to October, 
which is usually taken as the flood period, the dis- 
charge of 1913 is between 50 and 60 per cent: below 
the average. In early times the effect of such a 
flood would have been disastrous, but the recent rais- 
ing of the Aswan Dam, the reservoir being filled to 
its full capacity for the first time this year, and the 
construction or strengthening of the four barrages 
on the Nile, have removed the possibility of extensive 
loss and enabled the deficiency, due to the late arrival 
of the flood, to be tided over. 
There is no need to point out the importance to 
Egypt of a knowledge of the causes of the Nile flood, 
and of the value of a prediction which could be given 
with fair accuracy a month beforehand. The flood 
of this year having been so exceptional, there is every 
possibility that useful clues may be obtained to its 
detailed causes, and to further this object I should be 
glad to have copies of any meteorological observations 
made in Central and South Africa, and the South 
Atlantic in this and previous years. 
H. E. Hurst. 
Meteorological Office, Survey Department, 
Giza (Mudiria), Egypt. 
Pianoforte Touch. 
I po not think that Prof. Bryan will find any diffi- 
culty in sounding a single note of the same loudness 
a sufficient number of times for the test suggested, 
if he eliminates, as I did, those which are perceptibly 
louder or softer than the average; and the task for 
the listener is a very different one from sipping blind- 
fold coffee and tea, where the two different tastes 
persist for a long time, and soon become hopelessly 
superposed. Certainly the problem as to whether a 
difference is caused by the nature of the blow given 
to the strings cannot be solved by playing a succession 
of notes, instead of a single one, for such a succession 
at once introduces a number of other factors. 
The instrument which I used was an Erard grand 
of the latest type. Such an instrument, owing to the 
fact that the hammer strikes the string twice for each 
blow on the keys, is specifically favourable for produc- 
ing differences which might be impossible in other 
cases. SPENCER PICKERING. 
Mr. PickeErinG tells us that in his latest Erard piano 
“the hammer strikes the string twice for each blow 
on the keys.” If this is really the case the statement 
will go a long way towards clearing up the theoretical 
difficulties which have arisen in the attempt to explain 
the possible production of variations of tone quality by 
differences of touch. It is very difficult to obtain 
any definite information regarding the action of piano- 
forte hammers. Both Helmholtz’s and Kaufmann’s 
theories are inadequate, and an investigation recently 
started with one of my pupils seems to show that the 
action is much more compiex than is usually supposed. 
But inquiries in other directions have merely elicited 
the dogmatic statement that the whole object of the 
check action is to prevent the hammer striking the 
string twice. In my Collard horizontal piano of 1892 
the arrangement ot the check action is distinctly 
favourable to a muitiple impact, for when the action is 
removed and the hammer projected into the air it 
certainly rebounds considerably. Granting such an 
action to take place. we are no longer thrown back 
on the vibrating-shaft theory as the only possible ex- 
planation. The extent to which such effects are or 
are not noticed must necessarily be a matter of per- 
sonal opinion, although I hope shortly to repeat the 
experiment described by Mr. Pickering when I can 
obtain a music-roll cut with the necessary repetitions. 
G. H. Bryan. 
NO. 2302, VOL. 92] 
Alfred Russel Wallace Memorials. 
May we appeal through these columns to men of 
science, both here and abroad, to contribute to a 
fund which we are raising for the purpose of placing 
a suitable memorial to the late Dr. Alfred Russel 
Wallace in Westminster Abbey? We should like also 
to be able to offer to the Royal Society a posthumous 
portrait of the late distinguished naturalist, and Mr. 
J. Seymour Lucas, R.A., has consented to execute this 
work. It is further contemplated that a statue or 
bust should be offered to the trustees of the British 
Museum (Natural History) if the necessary fund is 
subscribed. In view of the great services to the cause 
of science rendered by Darwin’s contemporary and 
colleague, the duty of handing down to posterity a 
memorial worthy of the man and his work obviously 
devolves upon those of the present generation who 
have in so many diverse ways benefited both by his 
teaching and by his example. The whole sum asked 
for to enable us to carry out all the objects which we 
have in view is comparatively modest, viz. 110ol., and 
we hope that this amount will be reached. The pre- 
liminary list of subscribers is sufficiently weighty to 
convince us that in undertaking the organisation of 
this movement we have not only the sympathy of the 
scientific world, but also the approbation of leaders 
of thought and of culture in other spheres of activity. 
Thirty fellows of the Royal Society, including the 
present and past presidents, have already given their 
adherence, and among those representative of other 
interests will be found the names of Mr. Arthur Bal- 
four, Lord Haldane, Dr. Warren, the president of 
Magdalen, and the Dean of Westminster. We have 
only to add that permission to place the memorial, 
which it is proposed should be in the form of a 
medallion with a suitable inscription, in Westminster 
Abbey, has been cordially given by the Dean and 
Chapter. 
We shall be willing to receive and acknowledge 
subscriptions, but it will be most convenient if these 
are sent directly to the manager, Union of London 
and Smith’s Bank, Holborn Circus, E.C., in the form 
of cheques made payable to the ‘‘ Alfred Russel Wal- 
lace Memorial Fund.” 
RapHaEL MELDOLA, 
6 Brunswick Square, W.C. 
Epwarp B. Poutton, 
Wykeham House, Oxford. 
James Marcuant, 
(Secretary), 42 Great Russell Street, W.C. 
Tue family of the late Dr. Alfred Russel Wallace 
having invited me to arrange and edit a volume of 
letters and reminiscences, they would be thankful if 
those of your readers who have letters of reminiscences 
would kindly send them to me for this purpose. The 
letters would be safely and promptly returned. 
Will provincial American, Colonial, and foreign 
newspapers kindly republish this letter? 
James Marcuant. 
Lochnagar, Edenbridge, Kent. 
Distance of the Visible Horizon. 
Asout forty years ago I learnt a formula which I 
have used ever since. It was 7x=4y?; x=height of 
| observer in feet, y=distance of horizon in miles. I 
do not now know where I found this formula, but it 
will be seen, if a few examples are worked out, that 
it agrees very closely with that given in your issue 
of November 20. At tooo ft., for instance, the dis- 
tances are 42 and 41-9 miles respectively. 
R. Lancton Corr. 
Sutton, Surrey, November 30. 
