SAP ORTjVS WORLD OF PLANTS. 449 



indicating a very cold climate are found associated with those of a 

 diametrically opposite character. Besides the mammoth, we encoun- 

 ter the ancient elephant, approaching that of India ; the hippopotamus 

 of African rivers peopled the waters of the Seine ; while the hyena of 

 the Cape frequented the meridian of France. The study of the forest 

 flora, of which we find numerous remains in the contempoi-aneous tufa, 

 leads to the same results ; the vine, the laurel, the ivy, are found in 

 abundance, not only in our southern regions, but also at Moret, near 

 Paris. "We find there also the much tenderer laurel of the Canaries. 

 The northern trees of the same epoch were pines, lindens, maples, and 

 oaks. 



All these facts prove that the quaternary animals and plants char- 

 acteristic of a cold climate existed only in the neighborhood of gla- 

 ciers ; and that, close by, in the valleys, lived creatures whose presence 

 indicated a climate softer and more humid than ours. The mean an- 

 nual heat necessary to their existence would be, at least, 14° or 15° 

 centigrade. But, if we place ourselves now in the full Pliocene 

 period, say near Lyons, we encounter the same vegetables, with others 

 of a more southern character. At this epoch, in fact, the laurel-rose 

 flourished on the banks of the Saone in company with the laurel, the 

 avocatier of the Canaries, the bamboo, the magnolia, and the evergreen 

 oak. The well-known climatic needs of these species warrant us in 

 assigning to the country a mean annual temperature of 17° or 18° 

 centigrade, and, as the actual mean temperature of Lyons is only 

 11°, we can judge of the difference of temperature which separates 

 our epoch from that of the Pliocene. Moreover, as Saporta remarks, 

 the figures which express the climate of Lyons during the Pliocene 

 epoch are not only higher than those which apply to the neighborhood 

 of Marseilles in Quaternary time, but, in place of corresponding to 

 the 43° of latitude, these higher figures coincide with the 46°, They 

 mai'k a progression of heat corresponding with latitude, the effect 

 of which is to raise the temperature of northern regions in proportion 

 as we bury ourselves in the past. 



These curious phenomena appear still more evident and more gen- 

 eral, if we transport ourselves in thought to the Miocene epoch. The 

 entire unbroken documents abound in the boreal hemisphei-e, and we 

 can there exactly determine the climates of all latitudes from 40° to 

 80°. Admirably preserved fossil plants, brought from the polar re- 

 gions by different travelers, show that glaciers have not always deso- 

 lated the pole. One of the principal deposits of these vegetables was 

 found on the western side of Greenland at Atanekerdluk in 70° of 

 latitude in the adjacent island of Noursoak. On the steep sides of a 

 ravine one thousand feet deep, there exist entire beds of petrified 

 leaves and other debris imbedded in a very ferruginous rock. The 

 vast accumulation of leaves is truly surprising — trunks yet in place ; 

 flowers, fruit, insects accompanying them. M. Heer, who has studied 



VOL. XTI. — 29 



