On the Ancient Plant- World. 265 



the polar forms did not travel far from the glaciers themselves, and 

 that the valleys enjoyed a more humid and temperate climate, and 

 evidences the observations of Haast as to the descent of glaciers in a 

 humid climate in New Zealand. 



The mean annual heat of Lyons is now 11° Centigrade; in 

 Quaternary times it was 14° to 15°; in Pliocene times it was 17° to 

 18° ; the flora of the Canaries flourishing on the banks of the Saone. 



The author lays great stress on the discoveries of Nordenskjold, 

 in Southern Spitzbergen, of plants of Carboniferous, Jurassic, Cre- 

 taceous, and Tertiary times, and states the labours of Professor Heer 

 show the position of the earth's axis was the same in Tertiary times 

 as at present. To Greenland he assigns a mean temperature of 9 "7° 

 Cent, in Miocene times, rising to 22° in Switzerland, the northern 

 limit of Palms traversing the Ehine provinces and Belgium about 

 the 50th parallel, while at the present time (excepting the Chamcerops 

 liumilis at Nice) their limit is the 30th to the 35th parallel. 



The Eocene era was marked by the multiplication and extension of 

 Palms, Pandanas, Bananas, and other tropical plants in England 

 and Germany, indicating a mean temperature of 25° Cent. 



The Cretaceous flora of Bohemia (Cenomanian) is characterized by 

 the first appearance of Dicotyledonous plants, including the genus 

 Credneria, Magnolias, and Laurels ; at Toulon, seven degrees further 

 south, these are rare, and Conifers are the dominant forms, especially 

 a fine Araucaria, and the author concludes that Dicotyledonous plants 

 travelled from north to south, and that climate in this period first be- 

 came differentiated. In Jurassic times the same vegetation spread 

 from India, Siberia, and Spitzbergen to Europe. 



The author considers in early times the earth was covered with 

 thick fogs, the atmosphere being charged with a diffused light. 

 With Buffon, he believes that life originated at the Poles, and 

 travelled equatorially, and he comments on the fact that the chief 

 Coal deposits occur at the polar sides of the equatorial zone, and 

 that the still older Eozoon of the United States and Bohemia are 

 similarly limited in area, and he regards the 50th parallel as the 

 equator of the origin of life. An equal distribution of heat, probably 

 not exceeding 25° or 30° Cent., prevailed throughout the world in 

 the early periods, the contrasts of clay and night, summer and winter, 

 being but slightly marked ; that light, though diffused, was certainly 

 present, is proved by the existence of the reticulated eye of the 

 Trilobite. 



He considers the former tropical heat of the earth to be in no way 

 connected with its central heat, nor does he ascribe the gradual 

 secular cooling of the crust to have influenced the cessation of warm 

 conditions on the surface — no signs of gradual decrease being 

 apparent, as would have been the case, and especially no signs of 

 intense heat, in the indication given by the earliest vegetation ; 

 and agrees with M. Burmeister that the earth's crust had so far 

 solidified as to be a considerable thickness before life appeared on 

 its surface, and points out the low conducting power of the rocks 

 forming this crust. 



