186 
POPULAK SCIENCE KEVIEW. 
good example of the mechanical method of ignition. They 
contained a chemical fuze, which has also been used in fixed 
torpedoes. It consisted of a thin glass globule filled with sulphu- 
ric acid, and so arranged that, when the torpedo struck a ship’s 
side, a bolt would break the glass and let free the acid. This 
would fall on a mixture of chlorate of potassium and powdered 
loaf-sugar, and by chemical action set it on fire^ thus igniting 
the charge. As we have said before, all contrivances of this 
kind are terribly dangerous, as any carelessness on the part of 
those placing them in position will fire the fuze. By some 
improvements made by Captain Harding Stewart in the methods 
of constructing and mooring them, they have been rendered 
somewhat safer ; but where electrical torpedoes are available 
they are infinitely to be preferred. 
Of locomotive torpedoes, the one which has perhaps excited 
most public attention is Lupin and Whitehead’s “ Fish Tor- 
pedo,” which was adopted by our government in 1870. No 
detailed description of its mechanism has yet been published ; 
indeed, its structure is kept as secret as possible. Its case is 
roughly fish-shaped (whence its name), being a cylinder nar- 
rowing to both ends, and having a point at one extremity and 
a small screw-propeller at the other. It is discharged from a 
tube fittted in the bow of a man-of-war below the water-line, 
and is driven by the propeller, the motive power being (it is 
conjectured) compressed air. It explodes mechanically on 
hitting its mark. In a trial at Chatham in 1870 it was very 
successfully employed in sinking an old man-of-war, but it is 
believed that with a strong current, or at a considerable range, it 
could not be aimed with any great accuracy ; and how easily a 
ship could be defended from it was shown in another experi- 
ment, in which it was caught in a net hung at some distance 
from a vessel’s side, and exploded without doing any damage. 
Another torpedo, which was invented about the same time, and 
which has met with general approval, is Harvey’s Towing 
Torpedo. It is a metal case, containing a heavy charge to be 
ignited by a sulphuric acid fuze, which is fired by a bolt being 
pressed against it by a projecting metal arm. This is towed 
out at an angle from the side of the attacking ship, which runs 
past her antagonist so as to bring the torpedo in contact with 
her bottom, when the projecting arm is forced down by the 
collision, and the charge is fired. A ship, manoeuvring to 
avoid these torpedoes, has been struck three times out of four 
attacks. Of course, on the one hand the torpedoes were not 
charged, and on the other the ship attacked did not use her 
guns, but offered only a passive resistance. It yet remains to 
be seen how these contrivances will work in actual warfare. 
In the American war many ships were destroyed by being 
