EXCURSION XV. 187 



compared the two beds in Cloinid burn, an observer would 

 be very apt to confound this shell-bed with the boulder-clay. 

 88. We pass now to Slaodridh Water, about a mile west 

 of Lag. Less than half-a-mile above the bridge, a large 

 tributary from the north-west joins the Slaodridh. This 

 is the Crook-crever burn, on whose east bank in several 

 places the shell-bed occurs. A very little way up the burn 

 there begins a highly picturesque gorge, with steep banks of 

 wild wood, cut by the stream through beds of variegated 

 sandstone, alternately hard and soft, crumbling shale falling 

 fast away, and the hard sandstone projecting in ledges. 

 A good way up, this gorge expands into a wide open 

 space, and high clay banks form the eastern side, but im- 

 mense slips greatly confuse the order of the beds. After a 

 repeated and careful survey, and having eliminated the 

 various sources of error, we made out the succession of the 

 beds as follows : Sandstone rock is the base of the whole 

 section; over this a bed of the true boulder-clay, thirty 

 or forty feet deep, reaching about half-way up the bank, 

 the clay being of the usual hard compact, almost unworkable 

 structure, and with some very fine examples of striated 

 stones, blocks, as well as others of lesser bulk. Its upper 

 part becomes, through a space of nearly a foot, a hard, 

 dark-coloured gravelly sand, extremely compact and ob- 

 durate under the pick-axe. On the top of this, and strongly 

 contrasted with it, rests the shell-bed, of almost exactly 

 the same composition as that already described in the other 

 two sections; a dark compact clay, with small stones rarely 

 striated veiy different from the boulder-clay in the com- 

 parative facility with which it is worked. In addition to 

 the shells already named, most of which were found, there 

 was a perfect Leda, the valves united, and fragments of 

 Balanus. Above this bed are the upper drifts very similar 

 to those already noticed, and here, as in the former case, 

 very strongly contrasted, if carefully examined, with the 

 boulder-clay; yet, there can be very little doubt that they 



