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(4) BORING, SINKING, AND WINDING MACHINERY. 
The Sub-Wealden boring, which has up to the present 
time reached a depth of 635 yards, was instituted to decide 
at what depth Palaeozoic rocks lie, between the EngKsh 
Channel and the Thames. When the boring was started it 
was thought they might be reached at a depth of 500 yards. 
The result shows that this was an under-estimate. 
The Sub-Wealden boring, as also No. 6 in the above 
table, were executed by means of the Diamond Rock Boring 
Machine, the ingenious invention of Major Beaumont, R.E., 
M.P. In this process, a steel tube, which is faced at the 
lower end with a number of rough uncrystallised carbonites 
or diamonds, is fixed on the bottom of the boring- rod. This 
tool is then made to revolve with its face in constant con- 
tact with the rock, like the drill or cutter used in boring 
iron or other metals. A jet of water is forced down the 
centre of the hollow boring-rods, which keeps the face of 
the cutter cool, and which at the same time carries up the 
debris to the surface. 
The rate at which this machine usually accomplishes its 
work, under ordinary conditions, is about 8 feet per day. 
Some excellent borings have been executed by the 
invention of Messrs. Mathers and Platts, but as yet the 
greatest depth they have reached is about 466 yards, which 
was done at the rate of 4 feet per day, the diameter of the 
bore-hole being 18 inches throughout the entire depth. 
This arrangement differs from the others, herein described, 
in the mode of Avorkino^ the machine at the surface, and in 
the character of the tool used, the latter consisting of a long 
heavily weighted iron rod, made by an ingenious appliance 
to revolve the tool. The tool is suspended by a flat steel 
wire rope. 
Having briefly presented to you a general account of the 
greatest achievements in deep mining and boring with which 
