114F Description of the different Methods 
No. 15. 
Description of the different Methods of blowing up Mocks 
tinder Water. By A. Baillet, Inspector of Mines.* 
1st, The operation of blowing np rocks, which the 
French call tirage des mines , is not in general attended 
with much difficulty, when the hole of the mine is pierced 
in dry compact ground without any fissure or cavity. 
When the ground is cavernous or hollow, or when wa- 
ter oozes through its pores, it becomes more troublesome, 
and requires particular care. When it is necessary to 
blow up rocks at the bottom of the water, the difficulties 
are increased. In that case the usual processes must be 
abandoned, and others must be resorted to. 
Sd, The method of blowing up rocks in the latter 
case is little known, and not much practised : it may, 
however, be of great utility in many cases, not only in 
the working of mines, but in the execution of public 
w r orks of importance. These motives have induced me 
to give a description of the three principal methods of 
blowing up mines under water. 
The first is that used in the mines in the northern part 
of the republic : it is proper to be resorted to when the 
depth of the w ater which covers the ground intended to 
be blow n up is not above 15 or 18 decimetres. 
The second has a great resemblance to the process 
usual in mines when the ground suffers the water to ooze 
through it. It is simpler and less expensive than the 
preceding, and appears to me to be very proper for cases 
w hen there are only a few decimetres of water above the 
ground. 
The third is suited to great depths of water, such as 
Tilloch, vol 13, p. 268. From the Journal des Mines, No. 56 , 
