426 ALFRED C. LANE 



the Straits of Mackinac some time, and perhaps a very long time. 

 Therefore the postglacial epoch begins later at Mackinac than at 

 Cincinnati. Yet I do not think that it necessarily should have a 

 different name, any m.ore than April i8 has a different name for 

 Europe and America. Of course, there are difficulties, just as there 

 are difficulties in saying what is the birthday of a child born near 

 midnight, or near the date-line in the Pacific. But they are inherent 

 in the facts, and are not lessened by introducing new terms, which 

 indeed may lead one to overlook the realities of the case. All these 

 difficulties as to exact time, however, real as (for instance, to friends 

 of the Psychical Research Society, discussing apparitions of the dying) 

 they are at times, form but a fraction of the total application of the 

 usual terms, "day," "year," and "hour," which are ordinarily intel- 

 ligible and unambiguous. Is it not so with the geologic terms, and 

 may we not ordinarily be justified in speaking of our Eastern and 

 Western Niagaran by the same name as belonging to the same geolo- 

 gic year and coeval, even though we know one lithologic unit may 

 have begun to form somewhat sooner than the other ? 



Difficulties have arisen from the fact that the lithological evidences 

 of contemporaneity do not always agree with that furnished by fos- 

 sils, and the early assumption (really a relic of the old cataclysmic 

 theory, according to which God made one set of created beings, 

 then wiped off his slate and began over again) was that fossils were 

 the best and surest index of contemporaneity, in comparison with 

 which all other factors or means of determination were of no weight. 



No competent paleontologist now holds this extreme view, and 

 many of them, like Williams, have shown clearly that fossils are not 

 absolutely inerrant evidence of contemporaneity. Yet the influence 

 of the old views, and the idea that the lines of a division of geological 

 time must be lines separating different faunas, has so clung on that 

 the tendency has naturally been, where the faunas proved mislead- 

 ing, to give up the idea of time entirely, and refer merely to 

 homotaxis. 



This will be a mistake. The idea of time is present in our geologi- 

 cal divisions and their narnes, and though our divisions be imperfect 

 expressions of our ideal, for that reason to throw away the ideal 

 would be to make the same mistake as Hobbes, to whom a straight 



