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REVIEWS. 
to more or less distinctly marked dysgeogenous situations, and others to more or less 
distinctly marked eugeogenous situations : but a greater number can adapt them¬ 
selves, more or less decidedly, to stations of either class. 
“ In proportion as we advance from an austral to a boreal, and from a conti¬ 
nental to an insular climate, the proportion in number which the restricted (i\ e. 
dysgeogenous and eugeogenous) bear to the ubiquitous species, lessens, principally 
through reason of many of the eugeogenous species being able, under more humid 
conditions of climate, to adapt themselves also to dysgeogenous situations.’’ 
Having thus defined his soils, according to their mechanical properties, 
it is easy to divide the surface of Great Britain, or, indeed, of Europe, into 
six lithological zones, which are familiar to geologists, as—1st, the Grani¬ 
toid and Metamorphic; 2nd, the Slaty, or Silurian and Devonian; 3rd, 
the Carboniferous; 4th, the new Red Sandstone; 5th, the Oolites and 
Cretaceous ; 6th, the Clay soils of the London and Hampshire basins. 
An attempt to arrange the flora of Great Britain according to these 
geological groups alone must be faulty, for the following reasons:— 
1st. The Granitoid zone is confined principally to the northern part of 
Scotland, where altitude and latitude have more to do with the question 
than our author admits. 
2nd. None of the six zones are lithologically the same throughout their 
extent. What relation, for instance, exists between the tenacious clays 
of Oxford and Kimmeridge and the crystalline limestones of the Isle of 
Purbeck, which are included in the same category ? 
We should like to hear from the author why the red sandstone of Here¬ 
fordshire is so fertile ; and whether it would continue so if the limestone 
layers, significantly called cornstones, were absent from its barren sandstones; 
or whether the County Carlow could grow its heavy crops of wheat and 
onions, if the calcareous gravels and corn clays, which cover the surface of 
that fertile county, were stripped off, and the bare granite rock exposed. 
According to modern ideas respecting mineral manures, the chemical 
composition of the soil has at least as much influence on plants as its 
porosity ; and we believe that a tabular view of analyses of soils, compared 
with the plants that grow upon them, and the composition of their ash, 
would do more to throw light upon the question discussed by Mr. Baker than 
any artificial classification of a geognostic character, which tacitly assumes 
the erroneous theory, that rocks of the same age have a similar chemical 
and lithological character. 
