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Of late years, however, machines have been devised for boring or breaking the rock. Some form a hole by the continuous motion of a rotating drill, others by means of intermittent blows. One of these rock-boring machines, manufactured by Messrs. Turner, of Ipswich, performs its work by a combination of both these operations.
Hoe's printing-press, moved by steam, seizes on the blank paper, severs it from the roll in sheets of the right size, prints it on both sides, and folds it in a convenient shape, all with miraculous rapidity. Inventions in rock-boring and rock-drilling have made it possible to tunnel mountains.
There are certain rock-boring animals, such as the Pholas, which help to decay the rocks. Each mollusc cuts a series of augur-holes from two to four inches deep, and so assists in destroying the bulwarks of England. Atmospheric action, the disintegration of soft rocks by frost and by the attack of the sea below, all tend in the same direction.
Accordingly it happened that, when afternoon was drawing towards a close, he sat under the veranda of a rickety wooden saloon, hurling drowsy encouragement at the freighter who was loading rock-boring tools into a big wagon.
The mining speculators he called upon received him coldly, and although he had a warmer welcome from the manufacturers of giant-powder and rock-boring machines, they demanded prompt payment for their goods. When Thirlwell stated that this was impossible they told him to come again.
He adds that on the giant specimen just referred to be wrote his name with his finger as it lay on the deck in a tub at night, and in a few seconds he had the gratification of seeing his name come out in "letters of fire." Among mollusks, the best known instance of phosphorescence is in the rock-boring Pholas, the luminosity of which after death is mentioned by Pliny.
The Aqueous Works and Diamond Rock-boring Company, Limited, of London, show at the Inventions Exhibition, London, a light portable rock-boring machine for prospecting for minerals, water, etc. It is capable of sinking holes from 2 in. to 5 in. in diameter, and to a depth of 400 ft.
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