OUR SUBMARINE DEFENCES. 
371 
starboard side, caused great injury to the ship ; thwart plates, 
casks, and fittings suffered severely, and much leaking was caused. 
No. 7, May 20. — The charge was placed vertically beneath 
the starboard side, and the explosion broke the vessel’s back, 
leaving her a complete wreck, as indeed was to be expected. 
The general result of these experiments is rather in favour 
of the ships than of the mines. It is true that the back of an 
armour-clad ship might be broken rather more easily than that 
of the comparatively light Oberon ; but making all possible allow- 
ance, it appears that submarine mines, to effectually close a 
channel, would have to be so close to each other that an explo- 
sion might extend from mine to mine, and the first casualty 
would open an indefinitely wide gap in the line of defence. In 
short, the system we proposed to adopt fails, and must be given 
up. This may be considered a discouraging result to follow on 
so costly an investigation. It at all events proves the necessity 
for such experiments, and it is well that they were carried out 
before the country was involved in more expensive operations. 
We have now, it may be hoped, time to look for a substitute to 
a line of large ground mines. We have already mentioned the 
alternative, namely, a system of small floating charges, which 
should be fired by contact in close proximity to the ship’s side. 
This change, however, is one involving new difficulties. Tides 
and currents cause increased complication with this system. 
Doubtless it may be argued that the action of the small 
charges, like that of the large ones, depends on the completion 
of a circuit that may be broken at the will of an operator on 
shore, so that the channel may be in an instant opened to 
friendly vessels ; nevertheless, the firing will probably have to 
be effected by gfear which is self-acting on the contact of a 
vessel ; and firing at the will of an operator will hardly be 
attempted. Hence it will be more than ever important to 
guard lines of submarine mines by powerful batteries, for the 
process of fishing up charges becomes more easy when the vessel 
is safe from an operator on shore, and when it is known a 
charge can only be exploded by actual contact. Moreover, the 
use of fenders or guards to explode the charges at a distance 
from the ship’s side becomes more feasible. 
The next experiments made on submarine defence may be 
expected to take a new form ; 30 to 50 lbs. of cotton is likely 
to be the maximum charge. The desideratum will be probably 
a network of such charges floating sufficiently near the surface 
to catch any vessel at high tide, and yet in place and concealed 
from view at low tide, with simple galvanic connexions, and not 
liable to entanglement from currents. This is a problem that 
may well give Mr. Abel and our officers enough to occupy them 
for many months to come. 
B B 2 
