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with a cutting edge at the bottom, was sunk down to about 
28 yards, and tubbing put in and secured to a depth of 34 
yards, the water being kept out entirely by the pressure of 
air, amounting to 45 pounds per square inch above the 
atmospheric pressure ; the men working in this pressure for 
shifts of two hours each in duration. 
An inner tube, 6 feet in diameter, connected by a bell- 
mouthed piece to the outer tube, contained the compressed 
air, and the locks through which the men and materials 
passed. The sea surrounded the pit, and the pressure of air 
required to keep out the water rose and fell with the tides. 
This shaft was completed down to the solid ground without 
pumping a drop of water, and was then continued down to 
a depth of 290 yards. This successful process is one that 
the special conditions of sinking in the bed of the river Dee 
rendered necessary, and consequently is not so generally 
applicable in this district, unless at some future time it was 
considered desirable to sink in the bed of the Humber at, 
or in the neighbourhood of, Goole or Selby. 
The surface arrangements of a mine, with regard to 
pumping and winding engines, show a great improvement 
on those in use at the beginning of the present century. 
The best types of the winding engine indicate a wonderful 
improvement in speed and economy of power, as compared 
with the low-pressure beam engines that characterised early 
mining operations ; and greater safety is now secured by 
means of the hooks or catches for disengaging the cages in 
case of over winding, and where the rope breaks in passing 
up and down the mine. A similar improvement is observed 
in the spiral drum and round steel ropes, as also in the 
iron head gearing now frequently used. 
