Dr. FiTTON on the Strata below the Chalk. 293 



The series of strata in Sections 21 and 21', differs from that of the preceding- 

 sections, principally in the absence of all the beds between the lower green- 

 sand and the Kimmeridge clay, which are found in immediate contact, at the 

 village of Little Brickhill, on the brow of the descent to Fenny Stratford : 

 — this junction, which was to have been expected hereabouts, from the evident 

 thinning out of the Purbeck and Portland formations in the north-east of 

 Buckinghamshire, is continued thence, through Bedfordshire, into Cambridge- 

 shire, and even to the coast of Norfolk. 



The great accumulation of gravel and transported matter, rising in several 

 places into hills and extensively concealing the strata, is another circumstance 

 which distinguishes the vicinity of Leighton Buzzard from the country towards 

 the south-west, and renders the examination of the strata difficult or impracti- 

 cable. A similar coating of gravel is found not only throughout Bedfordshire, 

 and a great part of the counties on the north-east of it, but far to the east of 

 (he chalk escarpment itself*. The fossils, and stony substances, which com- 

 pose this deposit, have been derived from many different formations, some of 

 them very remote, and are deserving of attentive examination. My collec- 

 tion includes only a few specimens from one of the ravines which descend from 

 Little Brickhill, and from the Platform between Stewkley and Soulbury, 

 about 510 feet above the sea, where the multifarious gravel includes frag- 

 ments of granite, and a large proportion of chalk. This deposit does not 

 there form an escarpment, like the sands at Brickhill, but declines gradually 

 towards the north, in a series of lower inequalities : on the ^south and east, it 

 occupies a great part of the surface towards Leighton, Wing, and Cub- 

 lington. 



On the line of the Section, No. 21, the ridge of the chalk attains nearly 

 the greatest height which it anywhere exhibits, — Kensworth Hill, south of the 

 road near Dunstable being 904 feet above the sea; but the general elevation 

 and that of the principal summits both rapidly diminish towards the north- 

 east. Near Tring, the difference in height of the upper and lower chalk 

 escarpments is strongly marked ; and the retreat of the former is still more 

 conspicuous near Dunstable; but the boundary of the lower chalk is less 

 distinct. 



The Upper chalk forms the elevated range from the Five Knolls, and Kensworth Hill, 904 feet, 

 by the heights above Zouche's Farm, 850 feet, towards Luton, and thence to Whitehill Farm, on 



* At Muswell Hill, on the north of Highgate in Middlesex, an accumulation above the Lon- 

 don clay, includes worn fragments of granite, porphyry, micaceous sandstone, mountain-lime- 

 stone, coal, lias, and chalk, with many of the characteristic fossils of those formations : the chalk 

 especially being so abundant, as to give the whole a chalky character. — Mr. Spencer, in Proceed- 

 ings of the Geol. Society, 1835 — 6; vol. ii. p. 181. 



