130 



THE GEOLOGIST. 



24. Why the extinct fauna of a country bears a close analogy to 

 the living fauna. 



25. Why the proportion of species increases from the oldest forma- 

 tions to the newest. 



2G. Why species were more widely distributed formerly than now; 

 for as more species were developed, the more local they must 

 have become. 



I know of no answers to these arguments ; they are simply facts 

 acknowledged by everybody, except perhaps those for which I have 

 given my authority. 



Taking everything then into consideration, I think that the evidence 

 is greatly in favour of variation being at present unlimited.* 



The second argument against Mr. Darwin's theory is that natural 

 selection, although allowed to be a "vera causa" of variation, is not 

 powerful enough to produce the great differences that exist among or- 

 ganic forms ; or, in other words, that the cause is not equal to the effect. 



The cause may be compared to the power of a machine that has to 

 be increased or diminished according as the time in which it is re- 

 quired to produce a given effect is shortened or lengthened. I believe 

 that no one but a geologist has any conception of the enormous length 

 of time comprehended in the term " geological period ;" and, although 

 all or nearly all of my readers will be geologists, yet I think that it 

 will perhaps be as well to try to get some very rough idea of it, 

 especially as " time" has been brought forward in answer to other 

 arguments. 



Mr. Darwin has shown that for long periods of geological time 

 volcanic action has been pretty regular and persistent beneath Chili, 

 and that the average elevation of the coast is about three feet in a 

 century ;f but in the " Pampean mud," in which the remains of 

 Megatherium, Mylodon, &c, are found, is sometimes twelve thousand 

 feet above the level of the sea ; this would make its age four hundred 

 thousand years, yet it is only of Pleistocene age, and was formed 

 I >erhaps since man inhabited the globe. How old then is the Pliocene ? 

 I low old the Eocene ? How old the chalk ? Ten million years is the 

 Least that can represent it ; and yet it is not more than a twenty-fifth 

 part of the thickness of the sedimentary strata of Great Britain. 



I u such an enormous time, then, how small may have been the cause 

 of the gradual change of the lowest form of life into the highest ? — 

 in noli Uss ! I inn a struggle for life or death. 



* By at present unlimited, I mean that there is no limit between the lowest 

 and i be highesl known forms of life, but beyond the highest there may be a limi^ 

 to which wo arc approaching. 



t Proceedings of the Geological Society, vol. ii., p. 416, and Darwin's "Geology 

 of South America." London: 1846. 



(To be Continued.) 



