144 Analysis of Scientific Books. 
The boundary of the first of these basins may be stated generally as a 
line running from the inner edge of the chalk, south of Flamborough-head, 
in Yorkshire, nearly south, till it crosses the Wash, then south-west to the 
upper part of the valley of the river Kennet, near Hungerford, in Wilt- 
shire, and thence tending south-east to the north of the Thames, and the 
north-west angle of the Isle of Thanet ; in all these directions the bounding 
line is formed by the chalk hills; on the east side the boundary is the 
coast of the German ocean. 
The boundaries of the Isle of Wight basin may be generally assigned by 
the following four points: On the north, a few miles south of Winchester ; 
on the south, a little north of Carisbrook, in the Isle of Wight; on the 
east, Brighton; andon the west, Dorchester. It is every where circum- 
scribed by chalk-hills, excepting where broken into by the Channel between 
the Isle of Wight and the main-land.—P. 7. ~ 
Among the substances found in these basins, none are more 
remarkable than the strata of bluish or black clay, which, from 
its forming the general substratum of London and its vicinity, is 
usually called London elay ; it occasionally includes calcareous 
and siliceous sand or sandstone; and in other countries the 
corresponding stratum is nearly entirely a calcareous freestone ; 
such is the calcaire grossier, of which Paris is chiefly built. 
This clay is with us remarkable for its horizontal layers of 
septaria, which are flattened masses of argillaceous limestone, 
traversed by veins of carbonate of lime, or sulphate of baryta. 
These nodules, when calcined and ground, form that very useful 
material for stucco and building under water, commonly known 
under the name of Parker’s Cement. The London clay also 
affords specimens of blue pulverulent phosphate of iron, pyrites, 
amber, fossil resin, and selenite; the hardness of the water 
found in this stratum is chiefly referable to its containing the 
last-mentioned substance in solution. The blue clay is also 
abundant in organic remains of crocodiles, turtles, vertebral 
and crustaceous fish, and testaceous mollusc in great number 
and beauty, but differing, though often very slightly, from recent 
genera; yet evtinct genera, so common in the older formations, 
are rare in this; we believe, however, that cornua ammonis and 
belemnites have been found. Zoophytes are likewise of very 
rare occurrence. Among vegetable remains we here find pieces 
of wood in various states, and others perforated by teredines 
like these which infest the West Indian seas. In the Isle of 
Sheppey there have been found in these clay strata no less than 
700 varieties of fruit and ligneous seed-vessels, very few of 
which agree with any known varieties at present in existence ; 
some seem to be species of cocoa-nuts, and various spices. 
The greater part of the soil of Middlesex, Essex, and Suffolk, 
and considerable portions of Berkshire, Surrey, and Kent, con- 
sist of London clay ; and in the Isle of Wight basin, it forms 
the whole coast from Worthing, in Sussex, to Christchurch, in 
Hampshire, and extends from the latter place, inland by Ring- 
wood, Rumsay, Fareham, and passing a mile or two south of 
