'January 23, 1915. i 
LAND AND WATEE5 
explosive eS.(x>t of a mine is intensely local, and if only it can 
be kept twenty or thirty feet from the side of tho ship, its 
destructive energy becomes practically innocuous. 
Admirals and other naval experts often object to net- 
defence on the ground that it is cumbersome and diflBcuIt to 
handle, that it is, under modern conditions, largely ineffective, 
and that it tends to interfere vrith the speed and manoeuvring 
qualities of the ship — but in reply it may be said that these 
nets and their supports can easily be designed so as to become 
completely effective for the purpose proposed, and that it is 
better to lose a few knots' speed, notably ■^"ithin the narrow con- 
fines of the North Sea, than to lose the vessel itself; and there 
can, I fear, be little doubt but that we shall continue to be 
, horrified by news of fresh naval disasters, and the still more 
irreparable loss of gallant lives until our naval authorities 
take into more serious consideration this most pressing prob- 
lem of Net-Defence. — Yours faithfully, 
Arnold F. Hills, M.I.N. A. 
Hammerfieldj Penshurst, Kent. 
RUSSIA AND AVIATION. 
To the Editor of Land and Watee. 
SiE, — Having lately come over from Russia on important 
business which has kept me very occupied, I was fortunate 
enough in a spare moment to read Mr. L. Blin Desbleds' 
article on " The Airship in Naval Warfare," published in 
your esteemed journal of January 9th, 1915. 
With all due respect to Mr. Desbleds, with whom I am 
somewhat acquainted tlurough correspondence, I cannot agree 
with his views on the subject treated by him in the before- 
mentioned article. 
Haying had intimate experience of dirigibles or airships 
. for many years I may state that the capability of the airship 
to remain stationary over any given point is extremely pro- 
blematical. In practice I have never seen it done in average 
weather or even under the ideal conditions of the White 
Nights of Northern Russia, better conditions than which it is 
impossible to find, except perhaps on the paper of the mathe- 
matician. 
When attempting to keep an airship stationary over any 
given point, instead of doing so the airship, even when on its 
best behaviour, drifts slightly about in every direction, with- 
out any definite wish of its own as it were, the toy of every 
phenomenon of the element in which it floats, and not even 
superior miinagement of the vessel will fully counteract this 
behaviour, which those having deep practical experience of 
airships know to be sufi&ciently aggravating and disconcerting 
when endeavouring to do wiUi accuracy anything requiring 
this quality of remaining stationary, which the airship is gene- 
rally supposed to possess, such work can be better carried 
out when the airship has a certain amount of engine-driven, 
accurately-gauged headway I 
Under the general term of aeroplane, it is apparent from 
Mr. Desbleds' article that he compares the small type of aero- 
plane generally known with the modern airship, quite ignoring 
the existence of the large 400-h.p. to 900-h.p. aeroplanes, an 
equally modern development, which Russia, keeping its own 
counsel, has brought to a high pitch of perfection during the 
past two or three years, and with which I have had also much 
to do. 
The comparison made by Mr. Desbleds is unfair, as these 
large aeroplanes are as superior for general utility to their 
small sisters as the modern airships are to the early smaller 
airships. 
These large aeroplanes can be made so to hover as it were 
over any given point, as to attain very similar conditions to 
those obtained on an airship having a very slight amount of 
headway as aforesaid, for periods of time amply sufficient for 
their operators, with the modern perfection of instruments, to 
fulfil -n-ith accuracy anything which previously it has been sup- 
posed could better be accomplished on airships,^ when trying 
to make them remain stationary over a given point. 
These large aeroplanes are fitted with four engines, and 
have a speed of seventy miles per hour, and can be made to 
fly non-stop, whenever so required, for twelve hours, and they 
can be as easily navigated at night for such periods as in the 
daytime. They have ample crew accommodation, and carry 
an installation of wireless telegraph with a range of not less 
than 200 miles, searchlights, machine guns, bomb-dropping 
apparatus, and photographic laboratory. 
Such aeroplanes have proved their complete superiority 
to airships, and their use during this war has brought great 
benefit to Russia, and the sooner Great Britain has such 
machines the better. — I am, Sir, yours truly, 
C. J. H. Mackenzie-Kennedt. 
Member of Technical Committee, 
Imperial All-Russia Aero Club. 
.33, St. Swithin'fl Lane, London, E.C. 
PROTECTION AGAINST SUBMARINES. 
To the Editor of Land and Water. 
Deak Sir, — I enclose a memo, re submarines. I have 
already sent the substance of it to the Admiralty, but it was 
mixed up with other proposals, and not so clearly put as 
it now is. They do not consider the idea practicable. I 
have asked them whether I may communicate my ideas to 
the Press, as some others have done, and they agree. 
I should be extremely glad if you would (in Land and 
Water) give, briefly, your ideas on the proposal. I know 
you take great interest in such matters. Various similar 
ideas were commented on in The Times in. November. 
1. Main Idea.— The idea is to arrange so that a submarine, 
in fairly shallow or confined waters, shall notify ita pre- 
sence and its whereabouts. It is proposed to lay down wires 
which the submarine will touch and break or displace. 
Since the vertical height from keel to top of periscope is 
considerable, a system of horizontal wires would be most 
ef&cient. 
2. Wires. — To be ledd horizontally one above another, 
and at such intervals — say 25 feet — that a submarine must 
strike one or other. To be suspended at suitable intervals 
by cords or wires from floats. To be anchored at the ends 
and at other points if necessary. See sketch Fig. 1. Length 
of a wire not to be so great as to seriously retard the sub- 
marine, otherwise the latter would become aware of the fact 
that it was entangled and might go astern and shake off the 
wire. 
Aitchor 
0= WoodenTlocxt^ 
3. Indicator Floats. — A submarine striking a wire would 
double it up and carry it along. Connected with each 
end float there would be an indicator float (A, fig. 1 and 2), 
which would remain on the surface and move along in wake 
of submarine and show a flag. A watching destroyer could 
follow. At night the float could carry a light or be coated 
with luminous paint. 
4. Remaik-s. — Wires could be laid acrosa mouths of har- 
bours, etc., or around selected areas of sea (e.g., areas near 
Belgium when ships shell the coast), or even right acro-ss 
the Straits of Dover. The south part of the North Sea i} 
only about 120 feet deep. The wires would be in lengths, 
eaoE overlapping the next. They would be more simple 
than a system of nets such as has been proposed. In some 
cases it might be suitable to attach the ends of the wires 
strongly to the shore. The breaking of the wire might in- 
terrupt an electric current, and so signal the presence of the 
submarine. Of course ships crossing the wire would have to 
stop engines and slow. 
^ E. S. Bellasis, M.I.C.E. 
30, Lansdown Crescent, Cheltenham, 
