GEOLOGY. 299 



wards horizontally, so as to give some support to the load when packed 

 above the auger. The upper portion of the central blade terminates 

 in a strong tube, with a screw. The auger thus made is screwed to a 

 metal tube eighteen or twenty feet long, and this again is screwed to 

 the lowest or first rod. The earth cut bv the side bitts in shavings, 



/ O ' 



ascend their inclination, and is gradually packed around the stem. In 

 a tenacious soil, such a load soon becomes an air and water-tight pis- 

 ton in the well, which cannot be extracted from a great depth without 

 great risk of breaking tools and machinery. In Mr. Welton's auger, 

 this difficulty is admirably obviated. The stem, or metal tube, above 

 the auger, has three or four suitable orifices near the top. As the 

 load is raised the water above enters into these, passes down through 

 the stem and upper portion of the auger, and issues through two 

 apertures beneath the side bitts, into the cavity under the load. By 

 a dexterous manipulation of this instrument, in a suitable soil, ten 

 feet may be bored, and the entire load brought up at a single inser- 

 tion of the auger. Where rocks are encountered, the chisel must be 

 used. This is made in the usual form, and is rendered weighty by 

 the use of one or two iron rods to which it is screwed. A slip-link 

 two feet long, unites this tool to the wooden rods, which are so sus- 

 pended that when the chisel is on the bottom the slip-link has five or 

 six inches play. The upper rod is raised say two feet and a half, by 

 which the slip-link is tightened and the chisel is raised two feet. The 

 whole is let fall ; the chisel strikes the rock, the rods continue their 

 descent for six inches more, and thus escape the shock of the concus- 

 sion, which would otherwise quickly shatter their joints. The detri- 

 tus of rocks chipped by the chisel, or the mud or sand that collects in 

 the bottom of the well is extracted by a copper tube or bucket, 20 feet 

 long, of nearly the same diameter as the well, and having a valved 

 bottom. This is likewise the most efficient tool for penetrating loose 

 sands, provided the tubing of the well is made to keep pace with it. 



The Charleston Basin is formed by a depression in the cretaceous 

 strata, as they descend the Atlantic slope, and pass under the waters 

 of the Atlantic. Its narrow diameter or minor axis, from near George- 

 town to Beaufort, is a little over 100 miles along the coast, northeast 

 and southwest, while the semi-major axis, from Charleston to Lex- 

 ington, is about 120 miles. To the northeast the cretaceous strata 

 crop out ; to the southwest, the lower eocene beds, immediately over 

 the cretaceous strata, are seen on the surface, while to the northwest, 

 the sands and tertiary clays lie on the granite. It was originally 

 hoped that the lowest tertiary stratum under Charleston, would be a 

 water-bearing sand, the continuation of that which on the northwest 

 edge, immediately over lies the granite, and is traversed by the chief 

 river of the state. This hope has not been realized. The lowest 

 tertiary stratum proved to be under Charleston an argillaceous marl, 

 in which little or no water was found. We are now boring to reach 

 those cretaceous sands, which are exposed on the northeast edge of 

 the basin, and which, in Alabama, yield a plentiful supply of water 

 to several hundred wells. So far several streams of water have 



