C. E. De Ranee — Glaciation of N. W. of England. 413 



have been formed beneath loio-water mark, either by the grounding 

 of icebergs, or by the seaward prolongation of glaciers, which, on 

 retreating, left a vacant space, afterwards filled up by Boulder-clay, 

 with or without subsidence of the sea-bottom. Mr. Mackintosh 

 states^ that "one of the fundamental principles of geology" is, "that 

 the sea preserves the most delicate marks on rocks in areas of 

 deposition" and accuses me of overlooking it, in affirming that the 

 Grange roche moutonnee has not been touched by the sea since its 

 formation.^ It appears to me, if we assume these rocks to have 

 been rounded under the sea, and the associated mounds to be of 

 marine origin, that as they are now above the sea (and, in fact, above 

 Derwentwater), their movement betwixt land and water must have 

 been in an upioard direction, and that Mr. Mackintosh must, there- 

 fore, prove another fundamental principle (?) in geology, "that the 

 sea preserves delicate marks on rocks in areas of elevation.'" If the 

 striee were made under the sea, as they are now above it, they 

 necessarily, in process of elevation, must have been exposed to the 

 action of the waves on the tidal or littoral zone, and when so exposed 

 must have suffered denudation. 



Mr. Godwin- Austen, F.E.S., has shown,^ " that the tidal zone * 

 is capable of division into two belts, an upper, composed of clean 

 shingle, and a lower, seldom broken up, and covered with sand 

 and mud, with various species of plants and animals growing on the 

 isolated stones. He has also shown that the greatest movements of 

 pebbles on a beach take place on the upper zone, especially at its 

 upper edge. I have generally found the lower sub-belt to commence 

 a Utile below neap-tide high-water mark, ending at the lowest water 

 margin, the upper sub-belt terminating at the highest limit of 

 breaker action. It is along this edge, or upper margin, that the sea 

 exerts its denuding agency : for in the lower portion it merely causes 

 a movement of pebbles, in the direction of the " flow-tide," but in 

 the seaward sub-belt, stones of only two or three pounds weight will 

 remain, when the coast slopes at a low angle, for weeks and even 

 months, in the same position : delicate Confervce, and numerous, but 

 slightly prehensile marine organisms, remain unscathed, and the 

 fine striee of glaciated stones and boulders retain the sharpness 

 of their sculpturing. It follows, (1) that should a rock- surface 

 be glaciated above the sea-level, and be afterwards submerged 

 beneath the waves, it will necessarily suffer denudation on passing 

 the upper edge of the tidal or marginal zone ; (2) should a surface 

 of rock be glaciated in the lower belt of the tidal zone, say by 

 land-ice, and then submerged, and never again elevated to a 

 higher level, than it had when first glaciated, it will retain its 

 striations and smooth surface; and (3), similarly, rock-surfaces 



1 Geol. Mag., Yol. VIII., p. 305. 



2 Idem, " On the Two Glaciations, etc." 



3 Quart. Journ. Geol. Soc, and "On the Valley of the English Channel," vol. vi., 

 1850, p. 69. 



* The "littoral zone" of Forbes and Audouin, and the "marginal zone" of 

 Godwin-Austen. 



