Natural History of the United States. 201 



furnish a simple and comprehensive explanation of several of the 

 most difficult problems of chemical and dynamical geology. 



To sum up in a few words the views here advanced, We con- 

 ceive that the earth's solid crust of anhydrous and primitive igneous 

 rock is everywhere deeply concealed beneath its own ruins, which 

 form a great mass of sedimentary strata permeated by water 

 As heat from beneath invades these sediments, it produces in them 

 that change which constitutes normal metamorphism. These 

 rocks at a sufficient depth are necessarily in a state of igneo-aqueous 

 fusion, and then in the event of fracture of the overlying strata, 

 may rise among them, taking the form of eruptive rocks. Where 

 the nature of the sediments is such as to generate great amounts 

 of elastic fluids by their fusion, earthquakes and volcanic eruptions 

 may result, and these, other things being equal, will be most 

 likely to occur under the more recent formations. 



ABT. XXII. — Agassiz 1 Contributions to the Natural History of 

 the United States. (Vols. 1 & 2. Boston.) 



Anything from so great an authority as Professor Agassiz 

 commands the attention of naturalists ; and especially an elabo- 

 rate work like the present, giving matured views on leading sub- 

 jects in Zoology. For this reason we propose to devote some 

 pages to a sketch of the contents of these volumes. The work, 

 it is true, has had a circulation unexampled in the case of such a 

 book, and we are glad to see several Canadian names on the 

 subscription list ; but many of our young Naturalists may not 

 have had access to it, and it is too elaborate and scientific to 

 reach the mass of readers. 



The first volume is in great part occupied with investigations of 

 general principles ; and chiefly with those concerned in classifi- 

 cation, considered in its widest sense as the attempt of the 

 human mind to explore the plans of construction adopted in 

 nature and to represent them systematically. 



The first topic under this head is the unity of plan in nature, 

 and its origin from an all pervading Intelligence. Unity, 

 design, and creative power, as evidenced in nature, are no new 

 ideas. From the time of the Hebrew lawgiver downward, they 

 have been articles of faith with all true philosophers, and in more 

 modern times have been popularly expounded in a multitude of 

 works, from Paley down to Hugh Miller and McCosh. It might 

 indeed, in this period of the world's history, seem superfluous to 



