250 DISCUSSION OF THE DESICCATION QUESTION. 



The great interest attaching to Ileer's results has caused them to be so 

 extensively quoted and commented on, that it is only necessary, at the 

 present time, to recall the essential fact, which is this: that the climate of 

 North Greenland, in the Miocene epoch, was much warmer than it now 

 is, and that this diflerence of temperature must amount to at least thirty 

 degrees (Fahrenheit). This conclusion is based on a careful review of the 

 climatic conditions indicated by the vegetable growth of the Miocene period 

 in Greenland, as compared with what the same or closely related species 

 prove to be a congenial temperature for their development at the present 

 day. As an illustration of the method by which the results given above 

 were attained, the following quotation may be made from the article on the 

 Miocene Flora of North Greenland, in the British Association report lor 

 1866:* "He [Ileer] then selects Sequoia Langsdoi'ffii, the most abundant of 

 the trees at Atanekerdluk, and proceeds to investigate the conclusions as to 

 climate deducible from the fact of its existence in Greenland. Sequoia sem- 

 pervirens, Lamb. (Red-wood) is its present representative, and resembles it 

 so closely that we may consider S. senqyervircns to be the direct descendant of 

 S. Langsdorffii. This tree is cultivated in most of the botanical gardens of 

 Europe, and its extreme northern limit may be placed at lat. 53° N. For its 

 existence it requires a summer temperature of 60° F. Its fruit requires 

 a temperature of 65° for ripening. The winter temperature must not full 

 below 31°, and that of the whole year must be at least 50°. Accordingly we 

 may consider the isothermal of 50° as its northern limit. This we may then 

 take as the northern temperature of the Sequoia Langsdorffii, and 50° F. as the 

 absolute minimum of temperature under which the vegetation of Atanekerd- 

 luk could have existed there. The present [mean] annual temperature of 

 the locality is about 20° F. Dove gives the normal temperature of the lati- 

 tude (70° N.) at 16° F. Thus Greenland has too high a temperature ; but if 

 we come farther to the eastward, we meet with a temperature of 33° F. at 

 Altenfiord. Even this extreme variation from the normal conditions of cli- 

 mate is 17° F. lower than that which we are obliged to assume as having 

 prevailed during the Miocene epoch. The author [Heer] states that the 

 results obtained confirm his conclusions as to the climate of Central Euiope 

 at the same epoch."! 



* Repiintetl iu tlie "Arctic Manual," p. 368. (A resume of Heer's discoveries, made by R. H. Scott.) 

 t Compare Heer, Recherclies sur le Climat et la Vegetation du Pays Tertiaire, p. 193, aud (iu German) Unter- 

 suuhungeu iiber das Klima, uud die Vegetationsvurlialtuijse des Tertiarlaudes, p. 127. 



