150 Analysis of Scientific Books. 
been mistaken for crocodiles. The other organic relics in these 
strata are described at length by our authors; and here we can- 
not help smiling at human vanity, when we see such names 
as the following associated with an antediluvian ammonite! 
We have among the list of testaceous molluscze the Ammonites 
Walcott, Brookii, Bucklandi, Greenoughii, Henleyi, Loscombi, 
Birchii, Bechet and Conybearez: all this is very bad taste. 
In the fourth chapter of this second book, our authors give a 
perspicuous description of the strata which intervene between 
the lias and the deposits of coal; these are referable to two 
formations very intimately connected together, viz., 1. a series 
of marly and sandy beds, intermixed with conglomerates derived 
from older rocks, containing gypsum and rocksalt; and, se- 
condly, a calcareous formation, often brecciated and containing 
magnesia, lying below or in the lower portion of the above series. 
The former deposits are commonly called red marl, or new red 
sandstone ; the latter, magnesian limestone. 
Red marl is a very extensive deposit, stretching from the 
northern bank of the Tees in Durham, to the southern coast of 
Devonshire; its texture is various, and it is especially remarkable 
for containing beds of gypsum and of rocksalé, and for the 
absence of organic remains. 
In respect to the magnesian limestone, our authors remark, 
that much confusion has arisen from neglecting to distinguish 
between that associated with the red marl, and the older rock 
of similar composition associated with the mountain limestone, 
and from which it is distinguished by its organic remains and 
geographical position; the latter is also marked by the fre- 
quent occurrence of extensive beds of calcareous conglome- 
rate. It differs from common limestone in having a sandy 
structure, glimmering lustre, and yellow buff or fawn colour ; it 
often occurs in concretional masses, dispersed through an 
arenaceous form of similar materials; it is sometimes composed 
of small rhombic crystals; occasionally oolitic, and often cellu- 
lar ; that of Sunderland is flexible; at Ferrybridge it is fetid ; 
and the lime which it affords, when calcined, is injurious as a 
manure, unless it be very sparingly employed. Organic remains 
are rare in this formation. 
The third and last book of the present volume embraces the 
carboniferous strata, here called the medial order of rocks. The 
first chapter includes a general view of these formations; the 
second describes the coal district north of Trent; the third 
the central coal district; and the fourth the western coal. dis- 
trict. In the fifth and sixth chapters, we have an account of the 
trap rocks occurrigg in the several coal districts above specified. 
The series of rock formations included in the medial or car- 
boniferous order, admit of the following subdivision: 1. Coal. 
