116 Description of the different Methods 
the Mediterranean, and rivers where the assistance of 
the tide cannot be employed, the tube of tin plate which 
contains the train rises only 3 decimetres above the rock, 
but is terminated by a leather pipe covered on the outside 
with some water-proof substance, and in the inside with 
an incombustible varnish, and secured from the pressure 
of the water by a spiral winding made of wire. Its ex- 
tremity must be carefully closed, and a buoy attached to 
it carries it to the surface of the water when the air-boat 
is afloat. 
4th, I shall say nothing further of these methods, 
which suppose, as may be seen, the assistance of the 
air-boat. I only wished to point them out, because they 
may be useful in many cases, and may, besides, give rise 
to new ideas, and serve to modify the three particular 
methods which are the object of this memoir. 
I. Method of blowing up Docks at the Depth of 15 or 18 
Centimetres under Water . 
5th, This method consists in the following operations : 
First, bore the hole at the bottom of the water by the 
help of borers, and instruments of proper length. 
Then place in the hole a tube of tin plate closed at the 
lower extremity. The exterior diameter of this tube is 
of such a size that, when introduced into the bore, it may 
fill it ; and its length must be such as that it shall rise 
some centimetres above the surface of the water. 
Then send down to the bottom of this tube the car f 
tridge filled with powder ; introduce the priming rod, and 
ram round it clay or plaster according to the usual pro- 
cess, and only to the height corresponding to the summit 
of the hole. 
In the last place, draw the priming rod and introduce 
the train, and set fire to it with all the necessary precau- 
tions, that the workmen may be sheltered from danger at 
the time of explosion. 
