TWELVE MILES INTO THE EARTH.

Digger (Invercargill RSA), Issue 3, 1 April 1920, Page 3

TWELVE MILES INTO THE EARTH.

SIR CHARLES PARSON'S SCHEME. Sir Charles Parsons, lecturing at tbe Royal Institution, referred to liis proposal for sinking a bore hole 12 miles deep into Ihe earth. He said that tne cost of boring the hole would not be so very great. The deepest single-stage shaft on the Rand is the Hercules, 4500ft deep vertically and rectangular in section. The deepest shaft in the world is the Morro Velho in Brazil; its bottom is 6400ft vertically below the surface, and it has been sunk, and is worked, in stages, two of which are about 1200ft vertical. The deepest shaft designed on the Rancl is one of the City Deep Company's 7000ft vertically, ( of circular section, 20ft in diameter, and to be worked in two stages of 3500ft each. In countries where the atmosphere is dry the sides of the shaft are cooled by sprinkling " them with water, the evaporation of which cooled the rock. This effect might be augmented by artificially drying and cooling the air before passing it down the mine. With still greater depths of shaft further raethods of cooling would probably be necessary. Tbe heat might be carried upwards by means of brine circulated in a closed ring of steel pipes with a rising and descending column, or a simpler method would be to arrange for a rain of liquid air down the shaft. When sinking the deeper portions of the shaft, probably skields would be required to protect tlie miners from the splintering of the rock, since the intense compressive stress splits off scales from the surface, v>metimes with considerable violence. When Sir Charles Parsons first brought forward his suggestion in 1904, the estimate of the time required to sink a shaft twelve miles deep was eighty years; but with improved machinery and methods the records liave been so mucli lowered that he now tbinks an estimate of thirty years reasonable. At tbe Crown Mines, 310ft of a circular shaft 20ft in diameter, were sunk in a monih.