376 Reviews — Prof. Prestwich on the Past and Future. 



enters on the consideration of the various cosmical hypotheses as to 

 the origin of our earth, and probably of the other planets, in the 

 condensation of nebular matter. In this he brings forward the yet 

 unpublished and perhaps uncompleted views of Mr. Norman Lockyer, 

 communicated by the latter to Mr. Prestwich, suggesting, from the 

 analogy of the apparent solar constitution, that our globe in its 

 nebular condition had its materials arranged in zones of different 

 densities, the densest of course being innermost — a notion which 

 Mr. Lockyer and Mr. Prestwich both think to be supported by the 

 existing order of the materials constituting the earth, the metalloids 

 forming the outer zones, succeeded by the denser substances, such as 

 the metals, in the interior ; granite and other acidic rocks being con- 

 sidered the chief substance of the earliest outer crust, underlaid by 

 the more basic rocks, basalts, magnesites and ferruginous rocks in 

 the first instance, and further towards the centre by the metallic 

 bases. This is a bold speculation, which we will not further remark 

 upon, but leave it as a nut to be cracked by other cosmical geologists. 



Mr. Prestwich then proceeds from these highly speculative views 

 to the more direct questions of geology proper, namely, Stratigraphy 

 and Palgeontology. He gives several ingenious diagram-illustrations 

 of the proportionate occurrence of different species of organisms 

 in the successive known strata. These must, however, be seen and 

 carefully studied, as it would be impossible to explain them fully, 

 unless we could introduce illustrations of them here. 



Mr. Prestwich then comes to what he calls the more especial 

 ground of the geologist (p. 30), namely, "the various chemical and 

 physical questions connected with inorganic matter," in other words, 

 "the great mechanical phenomena exhibited on the surface of the 

 globe," — the first question being whether these phenomena are most 

 expressive of "energy" or of " time;" in other words, the old dispute 

 between the Cataclysmic and Uniformitarian theories. 



Upon this point Mr. Prestwich ranges himself rather with the 

 former than the latter. Admitting the enormous and scarcely con- 

 ceivable periods of time with which geology has to deal, Mr. 

 Prestwich deduces from this not that the minor phenomena which 

 come within the range of our limited experience may, by their mul- 

 tiplication in the course of these countless ages, be made to account 

 for all the larger past changes of which we have evidence, but, on 

 the contrary, that in the vast extent of previous time there is ample 

 room for the possible occurrence of paroxysmal events infinitely 

 exceeding in energy any with which our petty experience lias made 

 us acquainted ; and here he suggests the rather ingenious argument 

 that, as the recognition of a glacial period has led to the admission of 

 an early greater intensity of cold, so the evidence of a greater in- 

 tensity of heat should by analogy be equally admissible (p. 36, note). 

 From this Mr. Prestwich naturally proceeds to consider the hypo- 

 thesis of central heat, and of the presumed contraction of the earth 

 on cooling, " accompanied by a shrinking (? crumpling) of the crust, 

 to which the trough of oceans, the elevation of continents; the pro- 

 trusion of mountain chains, and the faulting of strata, are to be 



