1868.] Siluria. 199 
oldest rocks in the Lake-district of Cumberland by Professor Hark- 
ness, and the reference of the Devonian, or Old Red, rocks of the 
south-west of Ireland to the upper member of that formation. 
In some respects the author of ‘ Siluria’ holds aloof from pro- 
posed alterations in the interpretation of the relations of Paleozoic 
rocks of Britam. He does not accept Mr. Jukes’s views on the 
Devonian rocks—a course in which he is supported by most of his 
contemporaries ; nor does he yield to Mr. Salter’s attempt to sepa- 
rate the Lingula flags from the Silurian System. We also perceive, 
with some surprise, that he does not completely agree with Dr. 
Holl’s interpretation of the structure of the Malvern Hills, on the 
ground that the crystalline rocks have a strike parallel with that of 
the flanking Silurian rocks, Dr. Holl’s statement being, that the 
former strike obliquely across the range. ‘This, however, is a 
question of fact which will be easily decided by future observers. 
In the last chapter of his work Sir Roderick Murchison gives a 
general view of ancient life from its earliest traces, and attempts to 
sketch the progress of creation from the commencement of geo- 
logical time. He describes, first, a long period, characterized only 
by Invertebrata, and ending with the first appearance of Fishes in 
the uppermost Silurian deposits; this period of Fishes was followed 
by the appearance of Reptiles, and afterwards of Mammals, in sub- 
sequent formations. 
Progression has long been a favourite hobby with our author, 
and if by it he simply means that Invertebrates appeared before 
Fishes, Fishes before Reptiles, and so on, who will quarrel with him. 
It is, then, simply a statement of a broad fact, and means very little. 
We suspect, however, that Sir Roderick has not sufficiently con- 
sidered the fact that Fishes, Amphibia, Reptiles, Birds, and Mammals 
are merely classes of animals, whereas the great group of Inverte- 
brata comprises about a dozen such subdivisions. No naturalist is 
yet in a position to show even the probability of all the classes of 
animals having appeared in the order of their organization, begin- 
ning with the most simple and ending with the most complex. 
And if the theory of progression is really the explanation of the 
order of creation, it should hold good for each and every of the 
orders, families, &c., into which classes are subdivided by naturalists. 
The author then describes the former changes of the earth’s 
surface, and illustrates their magnitude by striking examples of 
fractures, dislocations, and reversals of strata, coming to the conclusion 
that such great movements are inexplicable by reference to modern 
causes, so far at least as regards their intensity. At the same time 
he admits that “the former physical agencies were of the same 
nature as those which now prevail.” Although we cannot bring 
ourselves to agree with Sir Roderick’s views on this subject, we 
freely acknowledge the desirability of so eminent a member of the 
