Geology of England and Wales. 147 
pecially about Cowes, Bembridge, and Binstead, and it is quar- 
ried as a building stone between Calbourne and Thorley. To 
this stratum succeeds the upper marine formation, and then we 
arrive at a series of beds of siliceous, calcareous, and argillaceous 
marls, abundant in fresh-water shells, but wholly deficient in 
marine relics; these beds constitute the LowER fresh water form- 
ation, and may be seen extending round the north side of Headen 
Hill, into Totland Bay. 
We now descend to the strata which lie immediately below 
the London clay. | They consist of irregular alternations of sand, 
clay, and pebble beds, forming a series of contemporaneous de- 
positions intermediate between the chalk and clay, and usually 
described under the very inappropriate term plastic clay formation. 
The sands are of various colours and qualities, so are the clays, 
some of which are used for pottery, some for tobacco-pipes, and 
some for bricks: they contain imperfect coal, pyrites, gypsum, 
and abundant organicremains in some places, while in others there 
arenone. The highest northern point at which this formation is 
seen is near Hadleigh, in Essex, whence it borders the clay to 
about five miles south-west of Braintree. Halstead and Cog- 
geshall, and the intermediate tract, are upon the plastic clay; 
it also extends from Ware to near Edmonton, over Enfield 
Chase, and passing close to St. Albans, skirts the London clay 
to Uxbridge, on the north of which it takes a westerly direction 
towards Beaconsfield, and thence runs nearly south to the Thames. 
*¢ It is seen again at Reading in Berkshire, and extends thence, though 
not in astraight line, to a few miles beyond Hungerford, which may be 
said to be its extreme point on the west, except a few outlying masses 
south of a line from the latter place to Marlborough in Wiltshire. Turning 
south from a little on the west of Hungerford, to the foot of the chalk hills, 
it passes east by Kingsclere, Basingstoke, and Odiham in Hants, and Guild- 
ford in Surrey ; thence rather in a north-easterly direction a little to the 
south of Croydon, it continues to skirt the foot of the chalk hills by Farn- 
borough and Chatham in Kent, and thence by Milton and Ospringe, to the 
fout of Boughton Hill, where it divides ; passing on the one hand in a north- 
easterly direction, it skirts the London clay to Whitstable on the coast ; 
and on the other nearly east to Canterbury, (which stands on the beds of 
this formation,) to the coast of the Reculver, whence again it passes to the 
south-west, except where marshy lands intervene, by Sandwich, which is 
built upon it, a little to the south of Deal.”—p.p. 39, 40. 
We now arrive at Book II. in which our authors describe 
what they call the swpermedial order of rocks, comprising the 
several formations which intervene in descending from those 
which have been described in the former book, to the coal 
measures. These formations, though admitting of several sub- 
divisions, may generally be referred to the following classes, 
enumerated in the order of their succession descending from the 
plastic clay. 1. Chalk. 2. Ferruginous sand. 3. Oolite, in- 
cluding lias. 4. New red sandstone and magnesian limestone. 
Vou. XIV. L 
