168 Proceedings of the Royal Physical Society. 



boulder-clay on which it still rested; the striae became 



Fig. 3. 

 Greenstone Boulder, Rothesay Terrace, Edinburgh. Length, 6 feet. 



lighter and fewer at about half-way down the sides, and died 

 out at about a foot and a quarter from the bottom. The ice 

 had moulded itself to the stone (Fig. 4). Along its middle 



Fig. 4. 

 Sketch-plan, Rothesay Terrace Boulder. 



line it was glaciated in the true direction, but as the striae 

 passed round its curving flanks, they diverged (as the arrows 

 on the map diverge around Arthur's Seat), rounding the bulges 

 and bending into the hollows — especially into one deep, bay- 

 like curve on the side. The ice had behaved like water, which 

 partly rides over the top and partly washes round the sides ; 

 and it was now as if the movements of the current had been 

 rendered diagrammatic by means of incised lines. This 

 boulder, like most others, had made something of an inclined 

 slide of itself, by canting at 7 degrees towards the ice. At 

 the averted end, the striae and polishing ceased at once, and 



