LAND AND .WATER. 
April 17, 1915. 
indirect, as a Ser'i:'. the latter must, for tlie maximum 
efficiency, be used as au Arm. Considered as such, an air 
fleet must, therefore, be subordinated to the commander of 
the force with which it is operating, whether it be a land or 
a sea force. An aerial squadron may be a cavalry arm, or an 
artillery arm, or a naval arm. In days to come both navies 
and armies will, no doubt, be provided with air squadrons, 
specially equipped and manned, for these three, and very 
likely for other purposes. A study, therefore — even such an 
incomplete one as is being made in theso Notes on 
the I'jfluence of Air Power — shows that, in order 
to derive the fullest advantage of the indirect influence 
of air power, it is necessary to subordinate the work 
of air fleets to that of the various arms they may be employed 
to assist. But, in the present war, on account of the fact 
that the aerial arm is being seriously employed for the first 
time, it has not been found possible to give the amount of 
co-ordination and subordination which is neces.sary for maxi- 
mum effieisncy. The present campaign has witnessed an im- 
provised utilisation of the new arm, and in that improvisa- 
tion Great Britain has shown adaptability to such an extent 
that fhe has acquired, over her opponents, an ascendancy of 
the greatest value. 
Such direct influence of air power, however, as would re- 
sult from aerial attacks, aerial bombardments, and other 
offensive operations can only be obtained by the organisation 
of aerial forces as a Service, with the same liberty for inde- 
pendent action as is enjoyed to-day by navies. 
The primal difference that exists between naval and aerial 
power ia the following : A navy exercises its maximum direct, 
IS well as its maximum indirect, influence by being an 
independent Service, whereas an aerial force exercises ita 
greatest indirect influence by being considered as a supple- 
mentary arm, and would exercise its maximum direct 
influence were it, like the Army and the Navy, an inde- 
pendent Service. 
Previous to this war the lack of knowledge and experi- 
ence with regard to the military capability of aircraft led to 
a very crude system of dividing service aeronautics into (i.) 
military and (ii.) naval aeronautics. Now, experience in the 
employment of aircraft in actual warfare demands the more 
scientific and truer division of: (i.) Service, (ii.) Arm. This 
latter would itself be subdivided into (a) the military aerial 
arm and (b) the naval aerial arm. The present organisation 
of aerial forces docs not permit the fullest advantage being 
taken of the direct as well as of the indirect influence of air 
power, because an aerial force is, at present, a hybrid which 
has to perform both the duties of an arm and those of a 
Service. In consequence there arises an aerial dilemma of 
great interest, to which attention has already been drawn in 
the previous article on the Influence of Air Power. This 
dilemma is the following: Shall a commander look upon Lis 
air fleet as a service and employ it to exert direct influence, 
in which case he would havo to forgo the advantages 
resulting from the co-ordination of his aircraft with the 
other arms, or shall he employ his aerial force as an arm to 
exert the indirect influence of air power, in which case ho 
would have to renounce the possible effect of the direct in- 
fluence of air power ? No solution has yet been offered to this 
aerial dilemma now facing commanders, who have had, there- 
fore, to content themselves with a compromise, the result of 
this compromise being that the only effort to use the direct 
influence of air power has been the carrying out of a number 
of timid raids. But to this dilemma, as far aa it concerns 
Great Britain, the writer hopes to be able to offer a solution 
in his next article. 
CORRESPONDENCE. 
ANTI SUIJMARINB TACTICS. 
To the Editor of L.4nd and Wateb. 
Sib, — My letter, which you published a few weeks ago, 
has resulted in an interesting discussion on the subject of anti- 
submarine tactics. Your two correspondents have described 
the types of submarine chasers which they recommend, and, 
from their technical knowledge, as naval architects, their 
views on the various points at issue are evidently 
valuable. There is, however, one important point which 
I raised in my letter, which neither "J. R." nor 
"J. D. C." has referred to — viz., the desirability 
of attacking the submarine by the method of ramminc. 
Both your correspondents, apparently, rely for their 
offensive entirely on the gun and the torpedo. Either 
of these weapons would doubtless be effective against a sub- 
marine on the surface, but I fail to see how they could be 
used with advantage against a submerged submarine, the 
periscope only being visible above the surface of the water. I 
presume that the only objection to endowing a submarine 
chaser with ramming power is that she would havo to be more 
strongly constructed, and that consequently she would have 
less speed for a given length of water-line — in other words, 
she must be a longer and larger boat for a given rata of 
speed . 
All these points, however, must clearly bo left in tho 
hands of the Admiralty, who, of course, will consult com- 
manders of our own submarines and commanders of those 
destroyers who have had opportunities of attacking the 
enemy's submarines. What we want is that the Admiralty 
should build as quickly as possible, and if they are uncertain 
as to the best type of boat, that they should build a few boats 
of different types. For Instance, they might build a few 
boats designed to ram, with a speed of 20 to 24 knots, and a 
few others of lighter construction with a speed of 28 to 
30 knots. — Yours faithfully, 
DUNLEATH. 
GUN EMPLACEMENTS. 
To the Editor of Lakd and Wateb. 
Sir, — I have read somewhere that there inay be a diffi- 
culty in providing emplacements for guns aa our troops 
advance, owing to the time it takes for ordinary concrete to 
Bet or become solid. 
A quick-setting cement is probably known to the 
authorities, but in case it is not, I would Inform you that rach 
a cement exist* in a mixture of magnasito and magneaium 
chloride. 
I have never used this cement to make a concrete, bul 
pave used it as a quick-setting mortar. I may say thafe 
within twelve hours this mortar becomes as hard aa- ordinary 
Portland cement mortar does in three or four days. 
I do not ask for any acknowledgment of this in your 
columns, but in case any further information is desired on 
this subject I am willing to give it. — Yours faithfully, 
Francis Drake. 
Mining and Metallurgical Club, London Wall BuUdings, 
London Wall, London, E.C. 
WAR LECTURES. 
Many additional inquiries with regard to tha Land and Watks 
lectiira scliera* havo been received by Queen Alexandra's Field Fore* 
Fund aa a, result of our recent article. Arrangements are being mada 
for lectures well into May, and theT« is still ample time to fix up datea 
before the season is over for indoor meetings. 
Both as a means of patriotic propaganda and as practical aid to th« 
fund that supplies, on properly organised lines, tho comforts so urgently 
needed by our soldiers in France, the scheme has proved a gratifying 
success. 
Clergymen, members of political bodies, and public men generally 
are earnestly invit«l to v/rite for particulars and texts of the lectures t.<» 
tlie hon. secretary, Queen Alexandra's Field Force Fund, 24a, Hill 
Street, Eaiijhtsbridge, London, S.W. 
SMALL FIRMS. 
We have received a letter from a firm of aeronautical engineer! 
who would like to get in touch with some of the small firms whose plant 
at the present time is idle. If the princip-ils of these firms will kindly 
communicate with the Editor of Land and Wateb he will put them 
in communication with the correspondent. Envelopes should ba marked 
" Small Firma." 
MR. HILAIRE BELLOGS WAR LECTURES. 
Preston Town Hall Wednesday 28 April, 3 4 8. 
Blackpool Winter Gardens Thursday 29 April, 3.30 & 3. 
Liyerpool Philliarmonic Hall... Fridiiy 30 April, 8.30. 
LiverpooL Philharmonic Hall.. Saturday 1 May, 3. 
London Queen's Hall Wednesday 5 May, 8.30. 
MR. FRED T. JANE ON THE NAVAL WAR. 
ShefCeld Victoria Hall Friday 16 April, 8. 
Harrogate Korsaal Saturday 17 April, 5.3a 
Blackpool Winter Gardens Monday 19 April, 8. 
LiverpooL Philharmonic Hall.. Tuesday 20 April, 8. 
SonthporL...,„...Cambr:dg« Hall Wednesday 21 April, 8. 
Buzton „„.... Opera House Thuisdav 22 April, J," 
Manchester..^.,.. Free Trade Hall Friday..'.... 23 April, 8. 
Bcarborough Opera House Saturday 24 April, 3.. 
MR. C31AWFURD PRICE ON "SERBIA." 
Southport. „.,.>.. Cambridge HalL..... Friday 16 April, 8. 
aorqnay....„ Pavilion „..,^ Wedn68day..„..21 AprU, 3. 
Woymonth Barden Rooms...^^ Thursday „ 22 April. B. 
Boarnemonth.... Winter Garden*..^ Friday.... 23 AprU, Iki, 
14» 
