t> Sir Charles LyeU and Modern Geology. [Jan., 



countries, and that in the event of Tertiary deposits being discovered 

 in any region they could be referred, by means of the percentage of 

 recent forms amongst their fossils, to their place in the Tertiary 

 series. For many years this test has been applied with useful, even 

 if but temporary, results ; but it must also be admitted that in 

 several cases the application has not been successful. We have 

 Eocene and Miocene deposits in India, for instance ; but the deter- 

 mination of the former depends almost entirely upon the fact of 

 their containing a large number of species of Nummulites, and not 

 upon any percentage calculation ; while the reference of the latter 

 to the Miocene division is wholly based on its Mammalian fauna. 

 In Australia a very varied series of Tertiary deposits has been 

 known for many years ; but even the percentage test has not yet 

 enabled Australian geologists to come to any agreement as to their 

 Eocene, Miocene, or Pliocene date. One amateur geologist, indeed, 

 appears to have been for years in a state of perpetual oscillation 

 between the three. 



In a series of papers Mr. Charlesworth stated thirty years ago* 

 some of the objections which he then saw to the use of the per- 

 centage test; but although he alluded to other sources of error, 

 he more especially dwelt on the disagreement existing between 

 naturalists as to the amount of divergence necessary to constitute 

 a "species. To render this nugatory, he suggested an attempt to 

 classify Tertiary strata by means of " the totality of the characters 

 which each series exhibits," on the principle that there is a 

 "uniform approximation to existing species, shown by the fossils 

 of different deposits, corresponding to their respective antiquity."! 

 But it is to be regretted that he did not himself construct the 

 " table of degrees " which he proposed, nor illustrate his suggestion 

 by making the attempt to classify Tertiary strata by means of it. 

 The principle is no doubt correct, and has been used with signal 

 success in the classification of plants into Natural Orders; it is 

 also the one commonly used in classifying the older rocks, and 

 ought not to be difficult of application to the Tertiary. The 

 misfortune is that while many men possess a "destructive" faculty 

 in an eminent degree, there are so few who, like Sir Charles Lyell, 

 are gifted with a " constructive " genius. The former class of men 

 do not benefit science, although they show that a scheme which 

 works well is nevertheless faulty ; but the latter are entitled to our 

 gratitude for a system which, faulty though it may be, is infinitely 

 better than none.J 



* « Mag. Nat. Hist.,' vol. ix., p. 537. ' Phil. Mag.,' 3rd ser., vol. vii., p. 81 ; 

 vol. viii., p. 529 ; vol. x., p. 1. 



f ' Phil. Mag.,' 3rd ser., vol. x., p. 8. 



j " A maxim which it may be useful to recollect is this, — that hypotheses may 

 often be of service to science, when they involve a certain portion of incompleteness, 

 and even of error." — Weeweli's Philosophy of the Inductive Sciences, vol. ii., p. 225. 



