358 THE POPULAR SCIENCE MONTHLY. 



early geological times, if the same causes then existed. Whether they 

 have been specially searched for, I do not know ; but their absence, if 

 established, would strengthen the conviction that the conditions of 

 arctic climate which produced such a peculiar mode of growth did not 

 exist in the time many thousand years earlier when libocedrus, 

 magnolia, and zamia were denizens of high latitudes. 



There are other facts whose tendency is in the same direction. 



It is admitted by all that the climate in the earlier geological times 

 and down to the end of the Miocene was warm through the whole 

 year. If, therefore, the earth's axis was then inclined 23^- as now, the 

 plants of Spitzbergen and other high latitudes must have spent during 

 every year of their existence more than four consecutive months with- 

 out a ray of sunshine, and surrounded by an atmosphere moist and 

 warm. 



Their condition resembled that of plants in a warm, dark, and moist 

 cellar. Modern vegetation so placed soon bleaches and dies. Un- 

 doubtedly it was possible for a specially adapted flora to exist under 

 such circumstances. And a special flora is what we should expect. 

 But the flora of Spitzbergen was not special ; it was cosmopolitan in all 

 the earlier periods, and in the Miocene some of the identical species 

 flourished there with " amazing luxuriance," whose descendants, with 

 specific character unchanged, are now found in the Southern States of 

 our own country. It seems to me that this is presumptive evidence, if 

 not demonstration, that as late as the Miocene the long arctic nights 

 were unknown. 



Moreover, this very luxuriance of foliage, which so surprised Lyell 

 and other geologists, tends to the same conclusion. It is a matter of 

 common observation that plants exposed to the full force of the sun's 

 rays have smaller leaves than others of the same species which are 

 somewhat protected. It would seem as though Nature compensated 

 for the inferior intensity of the solar action by giving more surface 

 to be acted upon. Now, since the intensity of the sun's rays varies as 

 the cosine of the latitude, it is evident, in case the sun underwent no 

 change in declination, that, while the length of the day in Spitzbergen 

 and Florida would be the same, the intensity of the light in the latter 

 would be almost double. Hence, if the earth's axis really was nearly 

 or quite perpendicular, with the same conditions as to moisture and 

 warmth, we ought to look for greater breadth and length of leaves in 

 Spitzbergen than in regions much farther south, and we find them. 



I know of but one fact in the geological record which seems to 

 point to the existence of changing seasons. Fossil exogenous trees of 

 very early times have been found with well-developed growth-rings, 

 and, as these are usually attributed to seasonal changes, it has been said 

 that they prove the existence of seasons ; and, as these are due to the 

 obliquity of the earth's axis, any inference to the contrary from other 

 facts must be wrong. But growth-rings do not of necessity indicate 



