422 Geological Society. 



and again resumed on the same parallel along the great elevated 

 plain of the chalk. 



Mr. Martin traces the most northerly and greatest of these anti- 

 clinal lines from the vale of Peasmarsh, between Guildford and 

 Godalming, along the entire base of the North Downs, eastwards 

 to the sea at Folkstone, and westwards to Farnham, Alton, and 

 Popham Beacon, where it terminates in the high flat dome or table- 

 land of chalk. The most southerly anticlinal line extends from Green- 

 hurst, near Steyning, eastward to Lewes, and along the base of the 

 escarpment of the South Downs to East Bourne and Beachey Head ; 

 and westwards by Midhurst and Petersfield to the Downs of East 

 Hampshire, through which it emerges in valleys of elevation at East 

 and West Meon, and in the valley between St. Giles's and St. Cathe- 

 rine's Hill at Winchester. The central anticlinal line of the Wealden 

 he traces westward from Hazlemere to Liphook, Selbourne, and Can- 

 dover near Arlesford, and Beacon Hill near Amesbury. 



The anticlinal elevation of the valleys of Wardour, Warminster, 

 and Pewsey, after advancing some miles eastward into the chalk, 

 tenninate in the high table-lands of Salisbury Plain and the North 

 Hampshire Downs, which form a great flat dome of elevation be- 

 tween the counties of Sussex, East Somerset, and North Wiltshire. 



Mr. Martin considers many of the higher crests and ridges that run 

 in an eastern and western direction above this elevated plain, to be 

 due to saddle-shaped elevations on one or other of the great lines of 

 fracture that attended the upward movement of the chalk. In the 

 details of his paper he confirms and extends the observations of 

 Mr. Mantell and Dr. Fitton, upon the very interesting district which 

 forms the subject of their common investigations*. 



* Id his Geological Memoir on a part of Western Sussex, Mr. Martin 

 put forth in 1828 some judicious remarks, showing, on the theory of de- 

 rangement and denudation, that the Weald of Kent and Sussex, as well as 

 the London and Hampshire Basins, had a common origin in a system of 

 elevatory movements posterior to the formation of the tertiary strata. He 

 considers that the strata which compose these basins, and were originally 

 horizontal, suffered great disruption in the act of forming basins, either 

 by the elevation of the sides or subsidence of the central portions of each 

 basin ; that in this operation deep and extensive fissures were formed in 

 certain parts of the strata thus disturbed, analogous to those we see in 

 the elevation and cracking of the flour which covers the fermenting nucleus 

 of dough in a baker's trough ; that the great undulations of the strata are 

 not due to original deposition, but result from subterraneous movements, 

 attended by enormous pressure. Mr. Martin also makes some judicious 

 observations on the too-prevalent habit of using the term chalk basin in a 

 manner that seems to imply local depressions peculiar to the site of each 

 so-called basin, forgetting that the chalk itself (although it forms a very 

 convenient and obvious geological horizon) is only an intermediate layer 

 in a succession of basin-shaped strata ; and contends that as the forma- 

 tions superincumbent upon and subjacent to it have a conformable dis- 

 ])osition, it is just as correct to call them London clay, or greensand, or gait 

 basins, as chalk basins. Again he observes, respecting the deposits of the 

 basin of Paris, that their occurrence elsewhere in horizontal and appa- 

 rently undisturbed positions, indicates the strata above the chalk to be of - 



