SCIENTIFIC NEWS. 



At Pesey it sue- This method has likewise been tried at the mines of Pesey\, 

 rateblocks^but^ 11 a se P arate block it was completely successful; but it 

 not in the solid was not so in the solid rock. Eight or ten holes 3 cent. 

 (11*8 lines) in diameter, and 3 or 4 dec. (12 or 15 inches) 

 deep, were bored at the same time in the vein itself. Some 

 were charged in the old method, others in the new, putting 

 into each the quantity of powder judged to be sufficient by 

 the workman himself and varying from 6 to 9 decigrammes 

 (2 to 3 oz). All the holes stemmed in the old way blew up 

 the rock ; those covered with sand did not even split it. — 

 Some of the latter were charged in the same way with a 

 double or triple quantity of powder, so that it occupied 

 half or two thirds of the hole, the remainder being fdled 

 with sand; and the explosion again took place without any 

 effect on the rock. The same holes, which had resisted this 

 double trial, being charged again in the old way with the 

 usual quantity of powder, produced a complete fracture. 

 Perhaps the ef- From these trials we should be led to conclude, that the 

 feet of this me- new process, though very good for blasting rocks, will not 

 always succeed, when applied to the solid rock of a moun- 

 tain, which generally presents itself bare but in part; and 

 still less in the interior parts of mines, where the points of 

 contact are more numerous. There seems to be a limit of 

 resistance, beyond which we cannot go by the new method, 

 as we may by the old. 

 An improve- Professor Pictet has proposed another improvement. It 

 ment by Mr. j s we j| ] cnownj that, in military operations, by making the 

 capacity of the chamber of the mine equal to four times 

 the bulk of the powder employed, a less concentrated ex- 

 plosion is produced, but more destructive at a distance, than 

 if the wadding were in contact with the powder itself. — 

 . Muskets too, and cannons are daily burst by leaving a space 

 between the powder and the wadding. Now in working 

 mines, this lateral explosion is exactly what is wanted as 

 Leaving a va- strong as possible; it is probable therefore, that it might be 

 cuity over the obtained with less powder, by leaving an empty space be- 



powder 



Great saving by tween the wadding and the powder. This method is said 

 this in the to have saved several thousand crowns annually, by diminish- 

 ing the consumption of powder to that amount, in the mines 

 of the Hart/,. 



Mr. 



