Eevieivs and Notices of Books. 



143 



themselves which we cannot account for, and which, in the mean- 

 time, we must be content to leave unexplained. 



In referring to theories of the earth, the author remarks : — 

 " The philosophy of our science is thus neither to ignore nor re- 

 ject hypotheses, but merely to receive them as tentative processes 

 and provisional aids towards the attainment of veritable theory. 

 .... Granting the value of hypotheses in occasionally directing 

 the way to a solution of our problems, it cannot be denied that 

 indulgence in speculation has been the great bane of geology. 

 .... The earlier progress of geological inquiry was encumbered 

 by its absurdities, which would have been simply ridiculous but 

 for the discredit they attached to the science, and the obstacles 

 they threw in the way of its acceptance. There is nothing so 

 easy as generalisation, where the facts are few ; nothing more 

 difficult than adherence to a course of induction where the field 

 of observation is wide, and the facts numerous and complicated. 

 On this ground the many 'theories of the earth' that prevailed 

 towards the end of last century and the beginning of the present, 

 are in some degree excusable ; but now that geology has taken her 

 proper place among the natural sciences, all such attempts should 

 meet with the most steadfast discountenance and reprobation." 



The subjects of the Direction of Drifts, Chemical Formation, 

 Metamorphism, Mineral Veins, &c., are discussed. The author 

 points out that in regard to them there are many difficult pro- 

 blems in geology still to be solved. The question of Time as a 

 factor in geology is considered ; and it is shown that while we 

 admit a prodigious amount of geological time, we have no means 

 of approximating to its duration. Calculations founded on the 

 deposit made by rivers of the present day are very fallacious. 

 All that can be done at present is to arrange the stratified forma- 

 tions into systems, groups, and series, each section representing a 

 relative but inadequate amount of time, but occupying its own 

 proper chronological position, A proper nomenclature and classi- 

 fication of formations is an important object, and in this point of 

 view palaeontology has done great service. At the same time, 

 there can be no doubt that much remains to be done in these de- 

 partments. Geologists have often drawn very rash conclusions 

 from fossil specimens, both as regards their nature and the indi- 

 cations which they afforded of soil and climate, A deficient 

 knowledge of the zoology and botany of the present epoch is one 

 great cause of geological error. The following remarks of Mr 

 Page deserve attention : — 



While we must admit the vast benefits conferred on our 

 science by palaeontology, let us take care that we are not mis- 

 led by the dicta of its earlier cultivators into beliefs which are at 

 variance with the known principles of biology and physical geo- 



