HYDRAULIC MINING. 



431 



devised machines called " stamps," to pass the powder through 

 mercury, which amalgamated with the gold, and gave it up 

 again on being heated to a certain temperature. 



Now a different mode of mining is brought into operation, 

 the pickaxe, spade, and stamps, with all their expensive machi- 

 nery, being abandoned, and water made to do the duty of all 

 three, some ingenious individual having noticed the effect which 

 water has on the hardest rock. 



Such, for example, is the case with those wonderful Yic- 

 toria Falls of Africa, where the rushing water has cut its 

 sinuous channel through so many hundreds of yards of rock. 

 Such, also, is the case with the more celebrated, but not so 

 wonderful, Falls of Niagara, which have been gradually work- 

 ing their way backwards, having worn away the rocks over 

 which they fall, and which are shown to be many miles away 

 from the spot where the river first discharged itself over the 

 cliff. 



In fact, it is well known that the Falls are receding at a 

 definite rate annually, and that the rate has been calculated 



HYDRAULIC MIXING. 



WATER-FALL. 



with scientific accuracy. The cliffs of our own coasts say of 

 Margate or Ramsgate crumble away with equally calculable 

 speed. 



In the hydraulic mining system large tanks are erected, at 

 least two hundred feet above the level of the mine. From 

 these tanks proceed pipes, terminated by hose, just like those 

 of our ordinary fire-engines. The miners, instead of using 

 pickaxe or crowbar, simply direct the streams of water against 

 the solid rock. Their effect is tremendous. They tear it 

 to powder, and carry it down the wooden troughs called 



