482 AGRICULTURAL ENGINEERING 



should be made water-tight for some distance below the sur- 

 face; (2) the well should have a good, tight platform or cover; 

 and (3) the surface of the ground should be raised about the 

 well so that all surface drainage will be away from the well. 



Surface wells are the cheapest of all wells. The cost per 

 foot, with curb, varies from 50 c for a 12-inch hole, to 

 over $2 for a well four feet across and walled with loose 

 stone. A good platform cemented over will cost about $10. 

 It might be mentioned here that concrete makes an ideal 

 pump platform and will last indefinitely. One slab can be 

 made loose to furnish access to the well. 



Deep wells are usually either driven or drilled. A driven 

 well is made by attaching a sand point to a casing, usually 1 J4 

 inches in diameter, and simply driving it into the ground 

 until the point reaches a water-bearing stratum of gravel or 

 sand. The sand point is made of perforated brass over an 

 iron frame, through which the water will readily pass into the 

 casing. The pump cylinder is made a part of the casing, and 

 valves are set at proper places by expanding rubber rings to fit 

 the casing. Driven wells never extend through a rock stratum. 



Drilled wells are made by operating a drill inside a casing 

 which sinks as the drill provides the way. The mud and chips 

 of stone are removed by pumping a stream of water through 

 the drill and out through the casing. If the casing is of small 

 diameter, about two inches, with the cylinder a part of it, it 

 is called a tubular well. The usual diameters for drilled 

 wells are 6 and 8 inches. These diameters permit the pump 

 cylinder and piping to be entirely independent of the well 

 casing. The usual cost of tubular wells, with casing, is SI 

 to $1.50 per foot. Drilled wells range in cost up to $6 per 

 foot for an 8-inch well drilled in granite rock. 



Deep wells are rightly considered a better source of water 

 supply than shallow wells, yet they aro by no means entirely 



