Date of the Glacial and the Upper Miocene Period. 379 



or immediately after those periods, or perhaps both before and 

 after the cold period. This follows as a necessary consequence 

 from the cosmical theory of climate. For it is physically impos- 

 sible that we can have a cold and Arctic condition of climate on 

 the one hemisphere, resulting from a great increase of excentricity, 

 without at the same time having a warm, equable, if not an 

 almost tropical, condition of climate prevailing on the other 

 hemisphere. Whether a high state of excentricity will produce 

 in our northern hemisphere a cold and glacial condition of cli- 

 mate or a warm and equable condition, depends solely upon the 

 position of the winter solstice in relation to the perihelion at the 

 time. But if the excentricity continues at a high value during 

 a long course of ages, then, owing to the precession of the equi- 

 noxes and motion of the perihelion, the conditions of climate on 

 the two hemispheres will be reversed every ten or twelve thou- 

 sand years. Consequently when we find, as we do in the Upper- 

 Miocene period and Middle-Eocene period, evidence of a cold 

 condition of climate, we may reasonably expect to find also evi- 

 dence of a much warmer and more equable condition than now 

 prevails. And this is actually what we do find. "The Upper- 

 Miocene flora and fauna of the whole of Central Europe/'' says Sir 

 Charles Lyell, " afford unmistakeable evidence of a climate ap- 

 proaching that now only experienced in subtropical regions." 

 " In the present state of the globe the island of Madeira pre- 

 sents the nearest approach to such a flora. The proportion of 

 arborescent as compared to the herbaceous plants is very great ; 

 and among the former the predominance of evergreens implies 

 an absence of severe winter cold " *. And in regard to the con- 

 glomerates of the Superga, near Turin, in which the erratic 

 blocks are found, " the fauna and flora both of the overlying 

 and underlying rock," says Sir Charles, " have the same subtro- 

 pical character as that of Miocene date in Switzerland and Cen- 

 tral Europe generally." "Hence," he continues, "the hypo- 

 thesis of the transport of such huge blocks by ice-action has 

 naturally been resorted to most unwillingly; but in the present 

 state of our knowledge it is the only one which appears 

 tenable." 



Here is a case which, if found to be general, ought to settle 

 the whole question of geological climate. Here is a bed of con- 

 glomerate indicating a cold and arctic condition of things when it 

 was formed, with icebergs floating around the place now occupied 

 by the city of Turin, overlain and underlain conformably by- 

 strata indicating a subtropical condition of climate. But this 

 is not all. This warm condition of things was not confined to 

 Central Europe, but extended probably over the entire northern 

 * e Principles/ vol. i. p. 200 (10th edition). 



