SOURCE OF FLINT PEBBLES 135 



valley at greater heights than 100 feet have not afforded 

 implements of human workmanship. 



The flint pebbles in the gravel are evidently not in 

 their original home ; they have been rolled down by a 

 river, and if we would trace them to their source we 

 must follow them up stream. If we ascend the Thames 

 or its tributaries to the high ground which bounds a part 

 of its basin as, for instance, the Chiltern Hills, or the 



FIG. 35. Section in a Chalk Quarry, a. Soil 

 cumbered with flints. 6. A. thin bed of 

 flint. c. Chalk. /. Beds of nodular 

 flints, j. Joints, g. Joint filled with flint. 



North Downs we shall view with surprise the vast 

 quantity of flint, no longer in the form of pebbles, which 

 lies scattered over a wide expanse of soil. Let us now 

 enter one of the numerous quarries which are dotted 

 about every here and there in the chalk hills, and we shall 

 encounter the object of our search. The chalk (Fig. 35) 

 itself lies in beds of great thickness, which are defined 

 by more or less horizontal lines, generally sloping or 

 dipping towards the south-east in the Chilterns, but to 



