20 PESCRIPTION OF THE STRATA. 



The thickness of the alluvial beds, as might be expected, is 

 greatly diversified. The most lofty of the alluvial cliffs on the coast 

 are from 120 to 150 feet high, or perhaps somewhat more. The cliffs 

 near Upgang, and those opposite Griraston and Aldborough in Hol- 

 demess, are among the highest. The alluvium at Aldborough, how- 

 ever, must be vastly thicker than at Upgang ; for at the latter place 

 the rock is found near the base of the cliff, and may be seen at low 

 water stretching into the sea ; whereas at the former, the rock being 

 at an unknown depth, there is probably as great a thickness of allu- 

 vium below the level of the sea, as we find above it. 



Though the alluvial beds are in general pretty level, especially 

 where they fill up the vacancies or breaks in the regular strata; yet 

 we often see them assuming, in some degree, the shape of the strata 

 which they cover, and having the same inclination or dip. Hence, 

 as the chalk of Flamborough, where it sinks beneath the horizon, 

 dips towards the Humber, the alluvial covering of Holdemess, though 

 broken in many places by the openings of the rivers and meres, pre- 

 serves a general slope in the same direction ; and at its extremity, 

 the Spurn, becomes a low point, only a few feet raised above the 

 level of the ocean.* 



To enumerate the different kinds of rock occurring in the allu- 

 vium, in rounded nodules or angular fragments, and the different 

 kinds of pebbles of which the gravel is composed, would be to go 

 through nearly the whole nomenclature of the rocks known to exist. 

 It is easy to meet with fragments of granite, gneiss, porphyry, mica- 

 slate, with almost every variety of the primary and transition rocks. 

 Blocks of beautiful porphyry, with large flesh-coloured crystals of 

 felspar, occur in considerable quantity on the Stainton Dale shore, 



* Hence we may observe, that those antiquaries who consider the Spurn as Ptolemy's 

 Ocellum promontorium, and derive that name from the British word Uchel — high, must at 

 least be mistaken in their etymology. 



