Bibliographical Notices. 135 



dififerent degrees of development, to each of which a distinct name 

 has been given. 



Without proceeding with further details on the many interesting 

 points treated of, we may cordially recommend this work to the 

 student of palaeozoic geology, not only as illustrating a chapter of 

 its history, but from the fact that the Trilobites play an important 

 part in the Silurian fauna. The naturalist also, interested in the 

 study of the Articulata, will here observe the frequent anomalies that 

 are found in the arrangement of the elements of the bodies of these 

 ancient crustaceans, compared to the regularity of the law recog- 

 nized among the modern forms, — presenting an important suggestive 

 subject, and which must not be forgotten in the great question re- 

 garding the successive development of this group of animals. We 

 may therefore hope that the zoological interest, which has long ex- 

 isted respecting the Trilobites, will be still further excited by the 

 great variety of new facts observed in the Bohemian species. 



Popular Physical Geologxj. By J. B. Jukes, F.R.S. 12mo. 

 Reeve and Co., London, 1853. 



This volumeforms part of a series of useful works on Natural Science, 

 and is intended to convey, in a popvdar manner, the general principles 

 of physical geology. The author, who is well acquainted with prac- 

 tical field geology, does not pretend to have given much original 

 matter, in the sense of new facts, the object being to describe the 

 common facts and principles of geology, in a clear and concise manner, 

 without entering too much into the detail of the obsenations by 

 which those facts have been discovered, or on which those principles 

 have been established. In this respect he has somewhat succeeded, 

 treating the subject with a freshness and spirit, and showing that 

 "geology is not a mere dull and barren disquisition on the nature 

 and composition of rocks and stones, but has become incidentally, as 

 it were, the opening to a full, rich, and varied history of the earth, 

 embodying the labours of the naturalist, the chemist, and the physi- 

 cist, — of all who study the living beings that people it, the consti- 

 tution of the matter that composes it, or the laws of force that act 

 upon it — into one great harmonious whole." The first part of the 

 work contains the elementary facts and principles, and is followed 

 by a general sketch of the series of stratified rocks. The subject of 

 the formation of sand, gravel, clay, &c., is clearly and concisely 

 treated, and it is well observed, that he who thoroughly understands 

 the origin and nature of common sand, has made no despicable com- 

 mencement in the study of the science. We could have forgiven 

 the author, had he ventured a little more into the domain of 

 palaeontology, when treating of the stratified rocks, for it has become 

 so essential a part of geology, that some acquaintance with it is 

 necessary, just as a knowledge of chemistry and mineralogy are 

 equally useful to the student of the crystalline and volcanic rocks. 

 The accompanying plates are artistic, and illustrative of some prin- 

 cipal features in physical geology. 



