METHODS OF WORKING CLAY DEPOSITS. 29 



From comparison of the data obtained from the bore holes and 

 outcrops, any vertical or horizontal variations in the deposit can 

 usually be traced. Limonite concretions or crusts, if present in 

 any abundance, are almost sure to' be discovered, and even the dry- 

 ness of the beds can be ascertained. Variations in the thickness 

 of the bed and amount of stripping are also determinable. If 

 small samples are desired for laboratory testing these can be 

 taken from the outcrops and bore holes, but if large samples are 

 wanted from the intermediate points it is best to* sink test pits 

 where the borings were made. 



Many of the clay miners in Middlesex county make use of the 

 auger to guide them in their digging operations, this being often 

 necessary on account of the rapid variations that may occur in 

 any one deposit. The auger used in this case consists generally 

 of one thin stem, often of square cross section and eight or 

 ten feet long. A small handle, fastened by means of two clamps, 

 slides up and down the stem and can be clamped at any point. As 

 the auger is pushed deeper into the clay, the handle is undamped 

 and fastened higher up the stem. 



ADAPTABILITY OF CLAY FOR WORKING. 



Having determined the thickness, extent and character of the 

 clay, there still remain several important points which have to 

 be considered. 



One of these is the amount of stripping. Unless the clay is of 

 high grade it will not pay to remove much overburden unless the 

 latter can be used. It is sometimes utilized for filling where the 

 factory is to be erected next to the bank, or for admixture with 

 the clay, especially if the latter is too plastic or fat. In such 

 event, however, the overburden should be free from pebbles, or 

 if not it should be screened. Frequent neglect of this often in- 

 jures the bricks. If the overburden is clean sand, there is in some 

 localities a market for it for foundry use, building or other pur- 

 poses. 



Drainage facilities must be looked out for, since dryness is 

 essential for successful and economic working of the clay bed, 



