410 Bibliographical Notices. 



which interesting illustrations of certain portions are given in the 

 volume before us. 



. In no science more than geology is correct observation necessary ; for 

 it has been well remarked by Humboldt, to behold is not to obsen-e, 

 that is, to compare and combine ; and the author states that the pre- 

 sent work was undertaken in the hope that the experience of many 

 years might assist and abridge the labours of those entering upon the 

 study of this science, especially in the field, so as to afford a general 

 view of the chief points, such as existing observations would lead us 

 to infer were established ; sho\ving how the correctness of such ob- 

 servations may be tested, and sketching the directions in which they 

 may be extended. To effect this, the work is divided into a series of 

 sections, of which the greater portion are devoted to the consideration 

 of the effects of igneous and aqueoiis agencies in present and past 

 time ; thus, amongst the former may be classed — volcanos and their 

 products, and salses or mud volcanos — temperature of the earth — 

 igneous products of earlier date than those of modern volcanos — 

 earthquakes — rise and subsidence of land — bending, contortion and 

 fracture of bedded rocks, &c. Resulting from aqueous agency may 

 be noticed — removal of the parts of rocks by water — action of the sea 

 on coasts — distribution and deposit of sediment in tidal and tideless 

 seas — chemical deposits in seas — transportal of mineral matter by 

 ice — preservation of remains of existing life in mineral matter : 

 under this head the valuable researches of Prof. E. Forbes on the 

 distribution and modification of marine life and their bearing on geo- 

 logical inquiry are concisely treated ; as is also the subject of coral 

 reefs and islands, the theory of formation of the different classes, and 

 the varied effects of their submergence and elevation in reference to 

 the changing anangements of the surface distribution of land and 

 water. 



The subject of ossiferous deposits is also fully treated by the au- 

 thor ; and as the extinction of the great mammalia in connection with 

 the glacial period, and the occurrence of their remains in deposits 

 both anterior and posterior to the " drift" is at present engaging the 

 attention of geologists, the following remarks are quoted : — " It is 

 only as regards the probable connection with the inferred interval of 

 increased cold at a particular time in the northern hemisphere that 

 ossiferous deposits are here noticed. Under the hypothesis of this 

 increase of cold being accompanied by the submergence of a large 

 portion of Europe, such submergence being gradual and followed by 

 a rise of the same area, and with very considerable modifications of its 

 surface, there are apparently conditions for much movement amid the 

 f terrestrial animals of this portion of the northern hemisphere. They 

 :. would be sometimes isolated and destroyed, as by continued depres- 

 sion the sea passed over their feeding-grounds ; at others they would 

 'retreat to regions where they could, for a time, establish themselves 

 ' and increase, some species being better able to preserve themselves 

 jithan others. Upon a rise of the sea bottom, and the consequent for- 

 - /niation of new lands, migrations would be effected, according to the 

 relative levels of these lands, as regards the sea, and as passages for 



