48] 
Mr. Mantell and Dr. Fitton, upon the very interesting district which 
forms the subject of their common investigations *. 
POSITIVE GEOLOGY.—EXTENSIVE RECOGNITION OF SILURIAN AND 
DEVONIAN SYSTEMS ON THE CONTINENT. 
We may congratulate ourselves on the advance that has been 
made during the past year, by the extension of our knowledge as 
to the existence of the Silurian, Devonian and Carboniferous 
systems over large districts of the continent of Europe. In my last 
address I endeavoured to explain the reason why the old red 
sandstone formation, which occupies so very extensive a place in 
England, had been scarcely anywhere recognized on the Continent ; 
namely, because we had till lately failed even in our own country to 
refer to this system those extensive slaty forms of it, which, both 
here and upon the Continent, had been referred to the grauwacke 
of the Wernerian series, and had applied the name of old red sand- 
stone only to a part of this formation, which had hitherto been con- 
sidered as the type of the whole, namely, to the red marly, sandy, 
and conglomerate strata of Herefordshire and the adjacent counties, 
* In 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 supermcumbent upon and subjacent to it have a conformable dis- 
position, it is just as correct to call them London clay, or greensand, or galt 
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 
a date anterior to their present curvilinear disposition in the form of basins, 
He further shows, that the act of denudation was not confined to the di- 
strict of the Weald along the lines of movement in which the greatest 
elevations took place, but equally laid bare the highest summits of the 
chalk hills and elevated plains, and swept away much of the contents of 
the basins; and endeavours to establish the connexion of these elevations 
and subsidences with diluvial action, by showing that. an adequate cause 
for this action maybe found in the elevatory movements produced by 
forces acting upwards from the interior of the globe, 
