162 Reriews—Prof. Prestwich’s Geology, Vol. II. 
ing a much larger proportion of carbon than any existing forest 
vegetation.” With regard to the excess of carbonic acid gas, Mr. 
Carruthers has expressed an adverse opinion, and experiments made 
on living plants have shown that they are liable to be poisoned, like 
animals, by an excess of the gas.! 
On the question of the duration of Coal, Prof. Prestwich adheres 
to the opinion expressed by the Royal Commission of 1871, that 
allowing for the rapidly increasing rate of consumption, the supply 
may last for about 400 years. It is interesting to learn that a coal- 
pit at Ashton Moss in the Manchester Coal-field has recently been 
sunk to the great depth of 2850 feet, and another pit in Belgium to 
o411 feet. 
In dealing with the Permian and Triassic rocks the author refers 
to the great earth-movements that took place before and between 
these periods, but it is not perhaps sufficiently pointed out that in 
this country the greatest physical break is at the base of the Permian. 
With regard to the Trias, the central division known on the Continent 
as the Muschelkalk ‘is wanting, unless it be represented by the 
‘ Water-stones.’”’ Here some allusion might have been made to the 
sequence of Red Rocks in Devonshire, and to Mr. Ussher’s sub- 
divisions of Upper, Middle, and Lower Trias. 
The author devotes some space to the subjects of rock-salt and 
gypsum, and illustrates his remarks with an account of a boring in 
Haute-Sadne. The origin of the colour of the red rocks and the 
causes of the rarity of fossils are also discussed. 
The Rheetic Beds are grouped with the Trias, but the White Lias 
is divorced from them and placed with the “Infra-Lias.”’ This is 
not a happy arrangement, especially too when the White Lias and 
Sutton Stone are associated and their fossils intermingled. The 
latter deposit was grouped by Charles Moore in the Zone of 
Ammonites angulatus, and although this is a debateable subject, yet 
in the tabular arrangement given by Prof. Prestwich (p. 175) we 
have the ‘‘ White Lias and Sutton Stone Beds” with A. angulatus, 
Lima gigantea, ete., placed below the zone of Ammonites planorbis. 
The White Lias is distinguished from the Lower Lias by the absence 
of Cephalopoda, while it contains Cardium Rheticum, Pecten Valoni- 
ensis, Lima precursor, and species of Pleurophorus, Aainus, etc., that 
link it with the Avicula-contorta shales. Moreover, at the localities 
mentioned, where the surface of the Rhetic beds is said to be eroded, 
it is above the White Lias that this “slight break” locally occurs. 
A tabular list of the Lias zones is given (pp. 182, 185), including 
those of A. opalinus and A. Jurensis, the Midtord Sands being taken 
in with the Lias, although regarded as passage-beds between that 
formation and the Inferior Oolite. In this table A. capricornus 
should come below A. margaritatus. We are glad to see that Prof. 
Prestwich prefers the old generic name of Ammonites to the many 
subgeneric names introduced by some paleontologists. <A full 
general account of the organic remains of the Lias is given. 
The various divisions of the Oolites are treated mainly from a 
1 See Grou. Mac. 1869, p. 300, 1871, p. 497. 
