1870.] Mining. 555 



82-07; hydrogen, 5 * 30 ; oxygen, 3 * 35 ; nitrogen, 2 * 72 ; sulphur, 

 1 • 64 ; ash, 4 • 90 * loss, • 02. The samples taken from the level 

 drives, showing a specific gravity of 1*231, are scarcely less satis- 

 factory. On first firing up, the coal is said to give out smoke rather 

 freely, but this soon passes off, and its deposits of soot are not more 

 than would accrue from good English coal. The following remarks 

 of Mr. Madden, chief engineer of Her Majesty's ship ■ Ocean,' are 

 very conclusive as to its merits : — " Keeping steam with ease at 

 50 lbs. pressure. Full speed for five hours with a continuous steam 

 exhaust blast from four cylinders, being a very severe test of evapo- 

 rative qualities for bituminous coal, which involves large quantities 

 of smoke each firing for a short time, but if used in ordinary boilers, 

 without blast and slow combustion this would be considerably 

 reduced. I consider the two samples as tested above to be equal in 

 general steaming properties to English North Country ; and com- 

 pared with Welsh, repeatedly tested under same circumstances, as 

 shown to be best Welsh 5 cwt. = 7 cwt. Takasima." 



We have recently visited the Hayle Foundry Wharf at Nine 

 Elms to see the operation of some pneumatic stamps. The import- 

 ance of introducing the utmost economy into the ore-dressing 

 arrangements of the tin mines of Cornwall renders this invention of 

 the highest importance. The following is a brief description of the 

 machine : — 



In the pneumatic stamp the motion is conveyed from the crank 

 to cap and guide cross-head, on piston-rod, by an ordinary connect- 

 ing-rod. Attached to its lower end is the piston-rod, and piston 

 packed with double reverse cup-leather packings* the piston is 

 4rJ inches diameter, and operates freely in the upper part of a gun- 

 metal cylinder Si feet in length ; attached to the bottom of this 

 cylinder, by a socket in the usual manner, is the round stamp-head 

 of chilled cast-iron, 9 inches diameter. The upper end of the 

 cylinder is bored, to receive the piston, to a depth of 14 inches ; 

 the piston-rod plays air-tight through the cylinder cover, which is 

 screwed metal to metal on the cylinder. The working barrel of 

 cylinder is pierced with two sets of small holes, for the ingress and 

 egress of air, discharging the air behind the piston after it has been 

 once used as an elastic cushion. Suppose the head to be set in 

 motion with the crank in a horizontal position, the piston being in 

 the middle, vertically, of the working barrel of cylinder, and mid- 

 way between the two sets of air-holes referred to. As the crank 

 and attached piston rise, the air is compressed between the piston 

 and cylinder cover, and the cylinder, with stamp-head attached, is 

 forced upwards. When in rapid motion, the elasticity of the com- 

 pressed air between the piston and cover flings the cylinder, with 

 head, some inches above the range due to the motion of the crank ; 

 on the descent of the piston below the bottom set of holes in the 

 VOL. vii. 2 p 



