Engineering Wonders of the World
Volume III

... ■ 338 SOME OF THE TOOLS USED IN WELL SINKING. A and B, rod tiller for rotating boring tools; C, a T-chisel for piercing rock; D, a clay chisø . rope The bore if a ENGINEERING WONDERS OF THE WORLD. made in lengths of ten feet, and are turned by means of long “ tillers,” or handles, clamped upon the square part. As the auger fills with clay it must be withdrawn—a tedious process, involving the unscrewing of the rods one by one. When rock is met with, the auger is re- placed by a chisel of flat or of T shape, and the operation of chiselling is carried on by wrapping the winding rope round the winch barrel a couple of turns. The loose end is hauled by hand, causing the rope to grip the rotating barrel, and the rods and chisel are lifted a few inches. Then the rope end is released suddenly, and the chisel falls on the rock and outs it. The rods are rotated slightly between every two strokes, so that the chisel may not fall twice in the same place. The side of the chisel trims the hole truly circular. (Sometimes a circular chisel is used, to cut cylindrical cores of rock. In American prac- tice the tools are made very much heavier and the derricks are much more lofty than is usual in England, and the rods are lifted and dropped by means of an oscillating beam worked by an engine, as described in a previous article dealing with petroleum wells (vol. ii., p. 321 foil.). Sometimes in place of rods, which take so long to draw up, a rope is used, and a heavy string of tools is attached to it. The can be wound up rapidly by the winch, string of tools must be long, so as to a straight and truly vertical hole ; for hole goes very crooked, progress will be slower and the tendency may be, and sometimes is, to increase the crookedness and stop progress. A great invention was the method of boring with diamonds. In this system the boring rods are of iron pipe, and the boring bit is a short cylinder, about f" to ... , i p j- j The Diamond thick, having a tew diamonds ... mi Drill. set round its lower end. The best stones for the purpose are Brazilian car- bonadoes, or black diamonds. The holes in which they are set are drilled into the edges and end of the crown, and cut by chisel to fit the stones, which are made fast by burring over the soft iron of the crown. Boring is effected by rotating the crown rapidly upon the rock, a copious stream of water pumped down the hollow rods washing up to the sur- face the débris through the annular space between rods and rock. Diamond crowns bore their way several feet per day into rocks so hard that the ordinary chisel cannot ad- vance six inches in the same time. Diamonds were first used by a man named Leschot, who was able to buy them for about twelve shillings per carat. But after the in- troduction of the diamond drill the previ- ously almost worthless black diamonds rose steadily in Calyx price until, ten years ago, they reached the high figure of £7 per carat, and diamond drilling became too costly Out