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Book II. Chap. II. Beds belzteen the

( e ) Elevation. This formation never rises into hills of anyheight. In the Weald, where alone it possesses sufficientthickness and extent to give any character to the general formof the surface, that surface is an uniform broad vale.

(f) Thickness. We possess no data for estimating itsthickness, beyond those which may be deduced from the con-sideration of its superficial extent. On this ground we maysafely assign to it in the Weald of Kent more than 300 feet.In the Isle of Wight it Appears not to exceed 100.

(g) Inclination. We have no particular observations tomake concerning the inclination of its strata, which appears tobe always parallel to the superstrata of green sand and chalk.

(A) Agrictillural character. This formation presents tothe agriculturist a soil of pale, cold, and retentive clay, natu-rally covered with woods, and requiring a large capital, com-bined w ith superior skill, attention, and activity, to convert itto any other purpose.

(>\ Phenomena of springs, Sfc. The aluminous chalybeatespring, analysed by Dr. Marcet, in the Isle of Wight, appearsto have its origin in this formation.

Section V. »

IRON SAND*

In arriving at this, the lowest of the formations which inter-vene between the chalk and oolites, we become released fromthe difficulties w hich still partially obscure the history of someof those strata of w hich we have lately treated. We are ableto trace and identify the present series throughout the island.

This formation may be best studied in the neighbourhood ofHastings. In different counties it has received the name ofCarstone and Quern stone. It is not possible to assign thesynonyme employed in the geological works of Mr. Smith,since from an erroneous identification of the strata in differentdistricts, he has attached different names, and attributed dif-ferent geological positions, to this formation. It foims themicaceous brick earth of the midland counties in his descrip-tion ; but in the Weald, he ascribes this to the Folkstone clay,and confounds this sand with that which underlies the coralrag.

(«) Chemical and external characters. This formation iscomposed of a series of strata, in which sand and sandstone

* Chiefly by the Rev. W. D. Conybearc. 1