2 76 Jleer — Miocene Flora of the Polar Regions. 



summer, and this glacier every year sends out into the ocean thousands 

 of icebergs, which lower the temperature of the southern latitudes ; 

 but at one period this very country was covered with a luxuriant 

 jjrimieval forest, composed of a great variety of trees, such as we 

 now find onl}' in the warmer parts of the temperate zone ! In fact 

 we find Taxodics and plane-trees in Spitzbergen in 78 degrees N. Lat., 

 nay even a lime-tree and a poplar in 79 degrees N. Lat., consequently 

 only 11 degrees distant from the pole. The lime-trees, the Taxodice, 

 and the plane-trees may here have reached their most northern 

 limits ; but this was certainly not the case with the firs, and the two 

 kinds of poplar, which were living in Spitzbergen ; for we know 

 that at the present day firs and poplars go 15 degrees further north 

 than plane-trees. There is no ground for doubting that it would be 

 the same in the Miocene ages ; and if so, these trees will have 

 reached the pole, provided land then existed there. The Miocene 

 limits of trees were therefore very different from those of the present 

 day. This was made very evident by a glance at a large map of the 

 Arctic zone, exhibited by Professor Heer, on which he had laid down 

 the limits of trees ; he pointed out that this boundary coincides with 

 the July isothermal of 10 degrees centigrade (50 Fahr.) : this falls 

 under the normal parallel of 67 degrees N. Lat., so that at present 

 the normal limit of trees is but a short distance within the polar 

 circle, while in the Miocene age it reached to the very pole. This 

 indicates a great change in the climate, and this was proved more 

 definitively by the lecturer from the evidence given by the fossil 

 flora of Spitzbergen and Greenland. From the character of the 

 specimens brought from Spitzbergen, he concluded that it must, in 

 79 degrees N. Lat., have had at that time a mean annual temperature 

 of 5 degrees cent. (41 Fahr.). He had formerly estimated that in 

 those ages Switzerland must have had a mean temperature of 21 

 degrees cent. (69.8 Fahr.), so that the difference between the two is 

 16 degrees cent. (28.8 Fahr.), or a decrease in going northward of 

 0.5 cent. (0.9 Fahr.) per degree. According to this calculation we 

 should have in Spitzbergen, in 78 degrees N. Lat., an annual 

 temperature of 5.5 cent. (41.9 Fahr.), and in Greenland, at 70 de- 

 grees N. Lat. an annual temperature of 9.5 cent. (49.1 Fahr.) ; but 

 in Iceland, and on the Mackenzie, in Q5 degrees N. Lat., the 

 temperature of 11.5 cent, (about 53 Fahr.), which enables us to 

 explain all the phenomena in the vegetable world just described.^ 

 At present the difference of temperature between Switzerland (in 

 47 degrees N. Lat., and calculated at the level of the sea) and 

 Spitzbergen (in 78 N. Lat.) is 20.6 cent. (37.08 Fahr.), which 

 gives a difference per degree of 0,66 cent. (1.188 Fahr). In the 

 Miocene times, therefore, the warmth was more equally distributed, 

 and the diminution of heat in advancing to the north was much 

 more gradual, so that consequently the isothermal of zero (cent., 32 

 Fahr.) fell under the pole, while at the present day it comes down to 

 58 degrees N. Lat. 



Lastly, the lecturer controverted the opinion that these plants had 

 ^ This is fully sliown in tiie •' Fossilen Flora der Polarlander," by Prof. Heer, p. 72. 



