ROUGH CONVERSION. 



249 



on again after a cap has been inserted. The charge is 

 fired on the removal of the pin by means of a long cord, 

 the needle being driven down on to the cap by a strong 

 spiral spring placed above the ledge (m). The advantage 

 of this apparatus consists in the fact that it is not necessary 

 to fill it with powder, but a cap only is required, and the 

 firing of the charge follows immediately on the release of 

 the needle, which can be done from a distance with perfect 

 safety, whilst no tamping is required for the blast, the strong 

 apparatus screwed into the bore-hole serving instead; the 



a 



Kiir. l.V>. I'rieh's detonator. 



T. 1 .1;. Section of same. 



results are excellent, the largest stumps being split into two 

 or more pieces. 



Whenever only a fuse is used, after less than half the 

 powder has been poured into the bore-hole, the fuse, made of 

 tarred yarn surrounding a thin column of powder is inserted, 

 and then the rest of the powder. Then the remainder of the 

 bore-hole is filled with earth or clay as a tamping, and firmly 

 rammed-down. 



The portion of the fuse 4 6 inches long, which protrudes 

 beyond the hole, is lighted with a match and in 1 2 minutes 

 the explosion follows. 



