304 Dr. FiTTON on the Strata below the Chalk. 



height on the north-east of Bedfordshire: Kensworth Hill, south of Dunstable, 

 being- 904 feet above the sea at low water ; the hills east of that town 850 feet; 

 Lilleyhoe, 664; Barkway, Windmill-hill, 513; the station near Royston, 

 484 feet; Balsham, on the east of Cambridge, 380; Newmarket station, 

 267; Brandon in Suffolk, 190 feet. The summits of the lower chalk suc- 

 cessively decline in the same direction ; Orwell station being 250 feet, Chapel- 

 Bush, near Haslingfield, 220 ; Swaff ham-Prior (near Reach), 140. And the 

 lower green-sand also falls rapidly : the hills near the outcrop at Bow Brick- 

 hill being 683 feet high ; that of Haddenham on the north of Cambridge, 

 133 feet; and the general surface of the lower green-sand, which tops the 

 hills near that place, ranging from a'bout 60 to 120 feet; at Ely 75 feet. 

 The level of the Cam, upon the gault, at Cambridge, is only 24^ feet above 

 the sea at low water on Lynn Deeps ; that of the Kimmeridge clay at Ely 

 Bridge, 14 feet ; and of the Cam, at Upware, probably not more than 12 feet. 

 So that if the sea were not dammed out by artificial means, a great part of 

 the marshy tract on the confines of this county, Huntingdonshire, and Nor- 

 folk, would be inundated at high water, as appears to have been the case at 

 no very distant period. The hydrography and drainage of this low tract, 

 which are intimately connected with geological principles, have been the 

 subject of some valuable publications, but do not fall within the immediate 

 scope of these pages. 



(157.) Another general circumstance which characterizes the north-west of 

 Cambridgeshire, is the great extent and varied composition of the transported 

 masses with which the strata are in many instances thickly invested. This 

 superficial deposit includes worn masses of greenstone, with fragments of 

 many of the lower members of the English series, — and rounded pebbles of 

 chalk, in such abundance as to form a very large proportion of the entire 

 mass. With these stony substances are fragments of the fossils of most of 

 the strata, Belemnites, large Gryphites, the Ostrea (or Gryphite) of the Ox- 

 ford clay, and portions of the skeletons of Elephants, Rhinoceros, Hippo- 

 potamus, Deer of several species, gigantic Oxen, and of the Horse. 



The mass thus composed forms many of the hills on the borders of Cam- 

 bridgeshire and Essex, and occupies a great part of the platform which runs 

 along the confines of the former county and Huntingdonshire; a brown 

 Variety of it obscures the junction of the gault and lower green-sand on the 

 west of Cambridge, forming an upland which extends from Bourne by Toft 

 and Hardwick to Dry Drayton, where it declines into the plain*. 



* Mr. Hailstone mentions particularly, that the deposits just described are perfectly distinct 

 from that which occurs above the Gault in Cambridgeshire. The former are very well known 



