RAMBLES OF A GEOLOGIST. 305 



found them exceedingly well marked, the polish as decided 

 as the soft red stone could receive, and the lines of scratching 

 running in their general bearing due east and west, at nearly 

 right angles with the course of the stream. Wherever the 

 rock had been laid bare during the last few months, there 

 were the markings ; wherever it had been laid bare for a few 

 twelvemonths, they were gone. I next marked a circum- 

 stance which has now for several years been attracting my 

 attention, and which I have found an invariable characteris- 

 tic of the true boulder-clay. Not only do the rocks on which 

 the deposit rests bear the scratched and polished surfaces, but 

 in every instance the fragments of stone which it incloses 

 bear the scratchings also, if from their character capable of 

 receiving and retaining such markings, and neither of too 

 coarse a grain nor of too hard a quality. If of limestone, or 

 of a coherent shale, or of a close, finely-grained sandstone, or 

 of a yielding trap, they are scratched and polished, inva- 

 riably on one, most commonly on both their sides ; and it is 

 a noticeable circumstance, that the lines of the scratchings 

 occur, in at least nine cases out of every ten, in the lines of 

 their longer axes. When decidedly oblong or spindle-shaped, 

 the scratchings run lengthwise, preserving in most cases, on 

 the under and upper sides, when both surfaces are scratched, 

 a parallelism singularly exact ; whereas, when of a broader 

 form, so that the length and breadth nearly approximate, 

 though the lines generally find out the longer axis, and run 

 in that direction, they are less exact in their parallelism, 

 and are occasionally traversed by cross furrows. Of such 

 certain occurrence is this longitudinal lining on the softer 

 and finer-grained pebbles of the boulder-clay, that I have 

 come to regard it as that special characteristic of the deposit 

 on which I can most surely rely for purposes of identification. 

 I am never quite certain of the boulder-clay when I do not 

 detect it, nor doubtful of the true character of the deposit 



