28 



CLAYS AND CLAY INDUSTRY 



an auger furnish a more satisfactory and rapid means of deter- 

 mining the thickness of the clay deposit away from the outcrop. 

 An auger for this purpose (Fig. 21) can be made easily and 

 cheaply by welding a one and one-half inch, or two-inch car- 

 penter's auger to a piece of three-fourths inch gas pipe. The 

 latter is cut into' short sections and by means of a T joint, a 



S7 



Fig. 21. 



Auger used for boring clay. 



handle can be screwed to the upper length. When the bore hole 

 is started only one section is used, but additional ones are added 

 as the hole increases in depth. In very wet, sandy clays augers 

 are of little value as the bore hole washes in and fills up as soon 

 as the auger is withdrawn. The only way to prevent this is to 

 drive a pipe down in the bore hole, keeping the auger slightly in 

 advance of the lower end of the pipe. It is of the highest im- 

 portance that a sufficient number of borings should be made to 

 determine the extent and thickness of the clay deposit. 



