21 6 Review of " Outlines of the 



generally nearly horizontal ; but not always, as the follow 

 ing extract will show. 



" But crossing to the Isle of Wight, the chalk re-emerges 

 from the superstrata near its eastern point, and rises with 

 its usual magnificence into Culver Cliffs. Here, indeed, 

 appearances of more than usual interest occur ; for here we 

 first enter upon that remarkable district in which these 

 beds so generally characterised by their horizontal position, 

 assume that vertical arrangement which has been hastily 

 assumed as peculiar to older and more chemical deposi- 

 tions, and as resulting in such from the circumstances of 

 their original formation j but which, as we shall hereafter 

 have occasion to show, are limited to no single geological era, 

 and in the great majority of instances, if not in all, have 

 been demonstrably produced by the mechanical force of 

 subsequent convulsions." — p. 106. 



The chalk formation has not been discovered beyond the 

 boundaries of Europe : but since we have reason to con- 

 clude that the Plastic Clay formation exists extensively in 

 the United States, and the chalk in England lies immedi- 

 ately beneath this ; we ought by no means to despair of 

 finding it in this country. Indeed, appearances are so fa- 

 vourable in some places, (e. g. Martha's Vineyard,) that we 

 should suppose it would justify an exploration by boring. 

 The thickness of the Plastic Clay in England, is not com- 

 monly above 100 feet ; althok/gh in one instance it is 1,100. 



Beds behoeenihe Chalk and Oolitic Series. — "Viewed on the 

 large scale, the interval between the chalk and Oolites may 

 be described as occupied by a series consisting principally 

 of beds of siliceous sand, which probably have an aggregate 

 thickness in the greater part of their course of not less than 

 1,000 feet and form that extensive sand tract which is uni- 

 versally to be traced beneath the escarpment and inferior 

 terminations of the chalky ranges." — p. 11. 

 . The subdivisions of this series are 1. Chalk Marie ; 2. 

 Green Sand; 3. Weald Clay ; 4. Iron Sand. 



The chalk marie consists of cretaceous, argillaceous, and 

 sandy matter, often sufficiently consolidated for architectu- 

 ral purposes, and sometimes forming a fine grained i;ray 

 sandstone of loose texture. Its minerals are iron pyrites, 

 septaria, calc. spar, selenite, and sulphate of lime ; and its 

 fossils (all of marine origin) are vertebral animals, fish, 

 wood, zoophites, and testaceous moUuscse. 



