Engineering Wonders of the World
Volume III

ARTESIAN WELLS, AND HOW THEY ARE BORED. 337 there is no real permanence of supply in a well dug barely below this zone. What is needed is evidently some method of making wells which shall reach far enough below the lowest drought water- level, and shall be safe from any of the dangers of pol- lution enumerated above. The wells of Artois, which were bored into the earth by means of chisels and augers, have furnished the solution, though it is only by modern methods and Lining materials that Artesian Wells tlie full safety of the artesian method has been secured. The SINKING A WELL IN A RIVER BED. {Photo, by courtesy of Messrs. Duke and Ockenden.) earlier borod wells wore lined in a very inferior manner. Simple tubes of riveted sheet-iron were employed to prevent the earth from being pushed inwards. These crude pipes were in- serted in the bore-hole and driven down with wooden mallets. Fresh lengths were riveted to the top of the pipe and forced down until no further progress could be made. Then a similar pipe of less diameter was inserted within the outer pipe, and this in turn was sunk into the boring as this proceeded below the lower end of the lining tube; and similarly other pipes of successively decreasing diameter, until finally the work was stopped by the finding of water, or the hole became too small to continue. Practice and local knowledge determine the initial diameter which should enable water to be reached. A modern lining tube is never less than thick, increasing to TV, or even s for larger sizes. The pipes are of lap-welded wrought-iron or steel, and are turned off squarely at each end to an exact length, usually of ten feet. A screw thread is cut on each end, after it has been ‘ cressed ” in, or (1,408) ’ . reduced in diameter, by | inch. Then upon the ends are screwed thin sockets of steel. As a result of the “ cressing,” the outer diameter of the sockets is only slightly larger than the body of the pipes. When tightly screwed up, the pipe ends butt closely to- gether exactly at the middle of the socket. Pipes thus jointed will bear driving down into the earth by a heavy ram or monkey. The lower end of the bottom pipe is shod with a cutting edge of steel, and the top length of pipe is protected, during the operation of driving, by a heavy cap. When a well is commenced, it is very usual to begin by digging a pit several feet deep. This is covered in with a stout platform, and through a hole in this the boring tools are worked. Boring Tools. Should the first stratum be clay, as it usu- ally is in London, the tool employed resembles a huge carpenter’s “ nose bit,” a sort of open- sided quill of sheet metal about 30" or 40" in length. On the upper end is screwed the first of a succession of rods from 1" to 2* square with threaded ends. These rods ar© vor.. ttt