i&0 Description of the different Methods 
On the plane face of these wedges is a groove made 
with a file which reaches to the powder : this groove is 
continued throughout the whole length of the tube of tin 
plate by means of a wooden rod d 9 hollow on the side 
turned towards the iron rod, to which it is made fast with 
strong packthread. 
Before this rod is attached to the iron one, a match, 
which proceeds from the upper extremity and communi- 
cates with the interior of the cartridge, is placed in the 
groove. 
e is a train applied to the end of the match. 
B C are two rafts which enable the workmen to bore 
the rock and blow it up. 
I) is a weight which prevents the iron from being re* 
pelled too far when the explosion takes place. 
EFGHI are different pieces necessary for charg- 
ing. E is the cartridge furnished with its wedge, seen 
sideways ; F the wedge seen in front ; G the wooden 
rule and its groove ; H the upper wedge and its iron 
rod ; I the tube of tin plate ; K section of the wooden 
rule and its groove. 
When the rock has been bored according to the usual 
method by employing a borer pretty strong and of such 
a length as the depth of the water may require, intro- 
duce into it the tube into which the charge has been put ; 
then apply the train e, and having placed the weight D 
above the rod, set fire to it. The explosion will imme- 
diately take place : the wedge h would be expelled but 
for the wedge c, which cannot give way ; and the two 
wedges being thus united, confine the charge, the effect 
of which will never fail, as has been proved by expe- 
rience. 
Four feet of the tube and the lower wedge are in ge- 
neral lost ; but the upper wedge may be employed for 
new charges, because it is never damaged. 
