464 
ADJUNCTS OF DEFENCE. 
a ship running a straight course across the front of the installation 
should be hit with certainty, provided that no smoke intervened to 
perplex the observer. 
(4.) The cost of an installation is necessarily great, equalling that 
of a completely equipped battery of four or five 6-inch B.L. guns. 
The cost of maintenance will prove high and the personnel must be 
specialist and expensive. 
Even when due reservations have been made, the torpedo must 
evidently be regarded as an extremely formidable weapon within the 
limits of its action. The question of its application is of a different 
kind. It is clearly unnecessary as a provision against unarmoured 
ships, with which the gun can effectually deal even at greater than 
Brennan ranges. It provides no defence against torpedo-boats—the 
principal danger to shipping in ports situated near an enemy’s base. 
Its range is less than that at which a ship’s fire is effective—far less, for 
example, than the range at which good practice was made by the 
Inflexible and Temeraire at Alexandria. For the defence of a sea front, 
it is quite unsuited. In many positions it would not range up to the 
water which an armoured ship would attempt to navigate. 
These considerations appear to limit the justifiable employment of 
the Brennan torpedo to the defence of deep channels not exceeding 
about 1500 yards in breadth. 
But a further limitation arises. Whither does the channel lead and 
what is the nature of the inner waters ? If the channel open rapidly 
into broad and deep water which it is necessary to deny, if, in fact, it 
is a passage which can be rushed, 1 a Brennan installation is a suitable 
protection. In such a channel as that of the Thames, it would be 
obviously superfluous. To superimpose the Brennan upon an effective 
existing mine defence would clearly be unjustifiable. If a mine-field 
is real, that is to say intended for physical as well as moral effect, it 
will suffice; if not, it is a useless expense. 
The Brennan torpedo, therefore, enters into competition with observa¬ 
tion mines, over which in some cases it possesses undoubted advantages. 
In a deep channel with a strong current, for example, the mine is 
impossible. When the conditions are equally favourable to both 
weapons, the decision must turn upon relative economy which appear 
to be worth more careful consideration than has at present been forth¬ 
coming. At the same time, for the defence of a narrow deep channel 
opening into broad waters, and at a sufficient distance from a dockyard 
to render effective bombardment impossible, 2 3 the torpedo would pro¬ 
bably be a more formidable defence than the gun. If, in such a case, 
the installation is rendered self-defensible, and supplemented by a few 
quick-firing guns as a protection against boat attack, there seems to 
1 Such cases are few in the British Empire. The Heads at Sydney and the Syemun Pass at 
Hong Kong may possibly be included in the category. The idea of a heavy ship “rushing” 
into such a harbour as Malta is obviously preposterous. 
3 By effective bombardment is meant fire capable of causing serious injury to national resources 
required for war. Such bombardments can under no circumstance be so undertaken unless certain 
immunity from naval intervention exists. 
Even in the peculiar case of Foochow, the effect of bombardment proved to be strictly limited. 
