Intelligence and Miscellaneous Articles, 237 



depth, then charged with 1 \ litre of nitroglycerine, corresponding 

 to about 5 feet of the hole ; after placing the patent plug and the 

 fuse, the mine was filled with sand and then fired. The mass to be 

 removed was not thrown out, but simply cracked ; for on the one 

 hand the volume was too great, and on the other the hole was 

 not deep enough, and, lastly, the quantity of nitroglycerine was 

 insufficient. Yet the effect was enormous. A crater of an elliptic 

 section was formed around the mine, filled by little fragments. 

 After having cleared them away, it was found that the rock was 

 strongly cracked, and, so to say, powdered even below the bottom of 

 the hole ; a crack 50 feet in length on the surface divided the rock 

 in the direction of the major axis of the crater ; another 20 feet in 

 length in that of the minor axis. 



The total effect can only be judged of when all the mass has been 

 cleared away little by little by small mines. 



Second experiment. — The mine was sunk at an angle of 50 degrees 

 in a dolomite rock exposed on three sides ; it was 34 millims. in 

 diameter and 7 feet in depth ; at 5 feet a fault 6 inches thick was 

 traversed. The aperture of the hole was 15 feet above the upper 

 level of the quarry ; the distance to the sides was 10 feet, to the top 

 of the rock 10 feet also. 



The charge consisted of | of a litre of nitroglycerine, correspond- 

 ing to about 2 feet of hole. After inserting the plug and filling the 

 hole with sand, the match was lit. The sound was dead, and the 

 effect complete and immense. If powder had been used, the gases 

 would doubtless have been lost in the fissures, and only a very feeble 

 efFe.ct would have been obtained even with a maximum charge. 



The explosion produced its effect on all sides ; at more than 10 

 feet distance the rock was fissured and split ; a quarter of the mass 

 was thrown out, and all the rest so smashed that, by means of crow- 

 bars and three small mines, a total volume of 100 cubic metres 

 were removed. 



The cost of this second trial was 94*10 francs. 

 For this cost 100 cubic metres of rubble stone were obtained, for 

 which labourers are paid at the rate of 1 franc 30 cent, per cubic 

 metre ; so that besides their day's wages, at the rate of 2 francs 50 

 per diem, they would still have earned 35 francs 90 cent, if they had 

 had to pay for the nitroglycerine. If the same amount had been 

 blasted by powder, at least twenty ordinary mines of 20 to 36 inches 

 in depth must have been used, and the cost would have been in this 

 case 125 francs. 



Third experiment. — The third trial was made with a block of cast 

 iron 40 inches long, 20 inches broad, and 1 1 inches thick, weighing 

 1000 kilogrammes ; a hole 8 inches deep by -|ths of an inch in dia- 

 meter was bored in the middle of one of its two largest faces ; at a 

 depth of 6 inches the borer had traversed a bar of iron which was 

 placed in the iron at the time of casting : hence the hole was not 

 water-tight. After having lost about 2 cubic inches of nitroglycerine 

 in these fissures, the hole was lined with clay to make it tight, and 



