BORED AND PUNCHED WELLS 95 



but its use is often objectionable because of the ease with which 

 it becomes clogged. 



The larger bored wells are often equipped with wooden casings 

 (Figs. 35 and 40) which are driven down by wooden maul. This 

 type of curb has many disadvantages (see table, p. 70), and tile or 

 cement casings are to be preferred whenever they are obtainable. 

 All joints lying above water level should be tightly cemented. 



Sinking Punched Wells. This type of well is most common 

 in regions of coherent soils such as the clays of Louisiana, Arkan- 

 sas, etc. The apparatus is described by A. C. Veatch as a cylin- 

 der of steel or iron from one to two feet in length, split along one 

 side. The lower portion is slightly expanded, sharpened and tem- 

 pered into a cutting edge. In use it is attached to a rope or 

 wooden poles, and is lifted and dropped in the hole by means of 

 a rope given a few turns around a windlass or drum. By this 

 process the material is forced up into the bit, slightly springs it, 

 and is so held. Water is sometimes added when drilling in dry 

 materials to aid the bit in "picking up." Sand layers are passed 

 by throwing clay into the well and mixing it with the sand until 

 the drill bites. 



The diameters of punched wells are usually only a few inches, 

 and their casing and pumping equipment is commonly similar to 

 that of the small bored wells. Wood casing is occasionally used 

 in the larger holes, which are sometimes as much as 6 inches in 

 diameter. 



Depths of Bored and Punched Wells. --The boring (auger) 

 process is best adapted to shallow wells, from 20 to 30 feet in 

 depth, but is commonly used to depths of 50 feet. It is carried 

 to greater depths with difficulty and is seldom used where the 

 water is more than a hundred feet from the surface. 



In the smaller bored holes, the diameter of the boring is com- 

 monly insufficient to admit of the insertion of a pump cylinder, 

 hence the depth to the supply must not exceed that from which 

 water can be conveniently lifted by suction, or about 25 feet. 



The limitations of the smaller punched wells are similar to 



