GLACIAL PERIOD. 



349 



the Countess of Tiffenbach, widow of Prince 

 Frederick of Nassau, from whom he obtained a 

 judicial separation in 1872, also disclaiming the 

 paternity of her child. His earliest essay in 

 literature was a novel containing a plea for ille- 

 gitimate children. He published during his 

 long journalistic career several pamphlets and 

 collections of articles, and also a number of 

 plays, only one of which, " Le Supplice d'une 

 Femme," in the authorship of which Dumas the 

 younger was joined with him, ever came upon 

 the stage. Girardin wrote in a striking and 

 popular style, and was full of ingenious and 

 original ideas of the kind which are effective 

 in journalism. He inaugurated a new epoch 

 in journalism, and the influence which he ex- 

 erted upon the character and aims of the news- 

 paper, though not altogether salutary, extended 

 far beyond the boundaries of France. " One 

 idea a day " was the motto which he enunci- 

 ated in one of his papers. He used to launch 

 forth original propositions, often of a startling 

 character, but which never conflicted with the 

 drift of popular sentiment. Some of his schemes 

 were carried oilt by dint of the public opinion 

 he created in their favor. He was thus the 

 author of the reduction in the postage. In the 

 tribune he was not effective, being no orator. 

 His last public act was a spirited defense of the 

 cause of General de Cissey in the Chamber. 



GLACIAL PERIOD. The cause of the ex- 

 treme cold which once prevailed in latitudes of 

 the northern hemisphere now embraced in the 

 temperate zone has been a frequent subject of 

 scientific speculation. That a great change in 

 climate has taken place was made evident by 

 the discovery of the marks of glaciers, scratches 

 in the rocks, ridges of detritus pushed up in 

 front of the moving masses of ice, and debris 

 deposited by them upon melting, which show 

 that a great part of Europe and America was 

 once within the region of perpetual ice ; and 

 also by the numerous fossils of animals which 

 have been found associated with the earliest 

 remains of man, some of still existing and some 

 of extinct species suited to an Arctic habitat. 

 The problem was complicated by the discovery 

 in the same geological strata with animals 

 which were adapted to an extremely cold cli- 

 mate, such as the reindeer and the musk-ox, of 

 others whose habits were suited to all kinds of 

 climate from the frigid to the tropical. In the 

 same geological period with the above species 

 lived, not only man, but the mammoth and the 

 woolly rhinoceros, the grizzly bear and the 

 Irish elk, the cave-lion and the hyena, and even 

 the hippopotamus, which could only have flour- 

 ished in a warm climate. 



The occurrence of Arctic plants in the mount- 

 ainous regions of lower latitudes, and of fossil 

 plants of warmer climes in the tertiary depos- 

 its of the polar regions, presents a striking 

 confirmation of this theory of extreme oscilla- 

 tions of climate. Fossil remains of the tertiary 

 forests of deciduous trees have been collected 

 by travelers in Arctic America, Siberia, Spitz- 



bergen, and other lands. They included not 

 only the genera now common to both conti- 

 nents of the northern hemisphere the planes, 

 beeches, maples, ashes, etc. but also genera 

 which are now of rare occurrence or narrow 

 distribution, such as sequoia, liquidambar, 

 magnolia, tulip-trees, gingkos, and the like. 

 In the Antarctic hemisphere as well as in the 

 Arctic, the distribution of plants bears evidence 

 of the influence of glacial causes. The flora of 

 the islands of the Antarctic Ocean reappear in 

 the mountains of Chili. The plants of the 

 south temperate zone are found growing on 

 the mountains of the tropics, those of the Cape 

 in the African lake-region, Australian genera 

 on Kini-Balu in Borneo, New Zealand types 

 in the highlands of New Caledonia, etc. Fos- 

 sil tree-trunks found in Kerguelen's Island 

 prove that the climate there was once warmer 

 than at present. 



The astronomical cycles of variation in the 

 obliquity of the ecliptic and in the eccentricity 

 of the earth's orbit taken together are com- 

 monly assigned now as the cause of the glacia- 

 tion of Europe as far down as Switzerland, 

 and of North America to New Jersey, and also 

 of the enormous changes in climate of which 

 the glaciation seems to have been one of the 

 stages. Recent calculations of these astronom- 

 ical periods by Croll and Stone are of interest 

 as bearing upon the duration of the Pliocene 

 and Quaternary periods, and upon the ques- 

 tion of the antiquity of man. The cycle of 

 the obliquity of the ecliptic is 21,000 years. 

 During one half of each such period the 

 northern hemisphere is colder than the south- 

 ern, and during the other half the latter is 

 the coldest. The northern hemisphere re- 

 ceives the greater share of heat at present, and 

 in consequence an accumulation of ice is tak- 

 ing place at the south pole. The climatic 

 changes due to the oscillations of the obliquity 

 of the earth's orbit are, however, very slight 

 in the present form of the orbit. But the 

 form of the ellipse is subject to periodical va- 

 riations, the eccentricity changing from '016, 

 as at present, to '57. When the earth's path 

 is nearly circular, as it now is, the differences 

 in temperature between the hemispheres due 

 to the oscillations of the ecliptic are almost 

 nothing. When the eccentricity of the orbit 

 was considerable, the effect of these oscilla- 

 tions in producing variations in climate which 

 complete their cycle in periods of 21,000 years, 

 must have been very much increased. The 

 changes in the eccentricity of the earth's orbit 

 have been calculated for the last million years. 

 During the period commencing 300,000 and 

 ending 100,000 years ago, the eccentricity 

 ranged between '26 and '57. During that pe- 

 riod wide variations of climate must have 

 taken place, ranging, when the eccentricity 

 was greatest, between a sub-tropical and an 

 Arctic climate in the successive periods of 

 10,500 years in the latitudes of Paris or Bos- 

 ton. During a considerable part of this period 



