PLEISTOCENE 



235 



is told by the boreal and Arctic species of molluscs 

 which occur more or less abundantly in the shelly 

 clays of north, Germany, Scandinavia, and the 

 British Islands, and by the presence of northern 

 forms in the Pleistocene marine beds of the Medi- 

 terranean area. The character of the land animals 

 is quite in keeping with this evidence. Living 

 in the low grounds of central and southern Europe 

 at this time were reindeer, glutton, musk-sheep, 

 Arctic fox, Alpine hare, marmot, snowy vole, 

 mammoth, woolly rhinoceros, &c. The remains 

 of these northern and Arctic plants and animals 

 are met with both in glaciated countries and in the 

 caves and fluviatile deposits that occur in regions 

 that never were covered with glacier-ice. The 

 relics and remains of man himself also accompany 

 the same flora and fauna. In strong contrast with 

 such an assemblage of plants and animals is that 

 of which we find abundant traces in interglacial 

 beds and cave- and river-deposits. In northern 

 France grew willows, hazels, ash, dwarf elder, 

 sycamore, spindle-trees, perfumed cherry-tree, box, 

 clematis, common ivy, jndas-tree, Canary laurel, 

 &c. The presence of that laurel, which flowers in 

 winter, proves that the winters must have been 

 very clement, and the other plants are indicative 

 of a genial humid climate. The summers were 

 not so hot and dry as they now are in France, and 

 the winters were not so cold ; and similar condi- 

 tions obtained in Germany and the Mediterranean 

 TH'/ii in although the floras of those different zones 

 were distinguished from each other by the presence 

 of certain forms and the absence of others. The 

 land and fresh-water shells associated with this 

 flora are equally indicative of genial conditions, 

 and similar evidence is supplied by the mammalia. 

 Thus, we find a strange commingling of southern 

 and temperate forms which is quite in keeping 

 with the similar association in one and the same 

 place of various plants which no longer live to- 

 gether in Europe. Amongst the animals were 

 hippopotamus, African elephant, hyaena, serval, 

 lion, leopard, various extinct species of elephant 

 and rhinoceros, an extinct dwarf hippopotamus and 

 machairodus. Contemporaneous with these were 

 urn-, bison, horse, stag, roe, saiga, beaver, hare, 

 rabbit, otter, weasel, wild-cat, fox, wild-boar, 

 brown bear, grizzly bear, cave-bear, Irish deer, &c. 

 The relics and remains of Paleolithic man likewise 

 accompany this flora and fauna. 



It is obvious, therefore, that the Pleistocene 

 period was distinguished by great climatic oscilla- 

 tion*. At one time the whole of northern and 

 north-western Europe, down to the 50th parallel 

 N. lat., was covered with avast?ier de glace, while 

 from the Alps and all the considerable mountain- 

 ranges of middle and southern Europe great glaciers 

 descended to the low grounds. From ice-sheet and 

 glaciers mighty rivers flowed all the year round, 

 but in summer they rose in flood and inundated 

 wide tracts, which in time l>ecame overspread with 

 sand and loam. It was under such conditions that 

 a boreal and Arctic vegetation clothed the low 

 grounds of middle Europe. Considerable tracts 

 of that region, during the last cold stage of the 

 glacial period, appear to have resembled steppes, 

 and to have been inhabited by jerboas (jumping 

 hare), spermophiles, &c. The same lands, which 

 in some places were clothed with pine-forests, were 

 roamed over by great herds of reindeer, mammoths, 

 &c. the bones of which sometimes occur together 

 in such large numbers as to lead to the belief 

 that the animals may have perished in snow- 

 storms or 'blizzards.' It was then, too, that the 

 reindeer and its associates flourished in the low 

 grounds of southern France, where they were hunted 

 by I'ahi-olithic man. With the advent of inter- 

 glacial times such ungenial conditions of climate 



passed gradually away the ice-sheet vanishing 

 from the low grounds of north-western Europe, 

 while the mountain-glaciers of central and southern 

 regions dwindled to insignificance. Great migra- 

 tions of plants and animals accompanied these 

 changing conditions, the Arctic-alpine flora and 

 northern and alpine fauna retreating northwards 

 and retiring to mountain elevations. At the 

 climax of interglacial times an extremely mild 

 and genial climate, recalling that of the Pliocene, 

 prevailed in Europe. The Canary laurel, the fig- 

 tree, the judas-tree, and many others flourished 

 then as far north as Paris, in which region frost 

 in winter was rarely or never experienced. Ele- 

 phants, hippopotamuses, rhinoceroses, &c., and 

 vast herds of bovine and cervine animals then 

 wandered over all temperate Europe the British 

 area included. How often such changes of climate 

 were repeated has not yet been ascertained, but 

 interglacial beds occur on at least two horizons as 

 in France and the alpine lands of central Europe. 

 Hence there would appear to have been at least 

 three glacial epochs separated by two intervening 

 epochs of genial climatic conditions. In northern 

 Europe only one well-marked interglacial epoch 

 is generally admitted by geologists. But the 

 evidence is not conclusive. It is obvious, indeed, 

 that the preservation of interglacial accumulations 

 must have been exceptional within regions which 

 have been severely glaciated. With the return of 

 ice-sheet and glaciers, fluviatile and other deposits 

 which had been laid down during interglacial times 

 would be ploughed up and commingled with other 

 morainic material. It is only here and there, 

 therefore, that patches of such deposits have 

 escaped destruction. The relics of interglacial 

 times are most abundantly met with in countries 

 which were beyond the reach of the ice. The 

 closing stage of the Pleistocene was a glacial one ; 

 so that in the valleys of central and western Europe 

 the ossiferous river -gravels of the last interglacial 

 period are more or less buried under the fluvio- 

 glacial gravels and loams of the latest glacial 

 epoch. The latest Pleistocene deposits in the 

 British area are marine clays containing Arctic 

 and boreal shells. These deposits go up to 100 

 feet or so in Scotland. 



Considerable geographical changes supervened 

 during Pleistocene times. The proofs are seen in 

 certain raised beaches in the maritime districts of 

 north-western Europe, in the marine clays with 

 their Arctic and l>oreal shells, and the marine 

 sands, &c. of glacial and interglacial age, which 

 are well developed in the British area. Again, the 

 distribution of the mammalian fauna of the Pleisto- 

 cene points in like manner to considerable changes 

 in the relative level of land and sea. Thus it would 

 appear that in interglacial times Europe was con- 

 nected, across the Mediterranean, by one or more 

 land passages with north Africa; while at the same 

 time the British area was continental. Indeed, 

 certain evidence leads to the belief that the Euro- 

 pean lands stretched out into the Atlantic as far 

 as what is now the line of 100 fathoms. Towards 

 the close of the last interglacial epoch, how- 

 ever, a considerable submergence of the British 

 area supervened for undisturbed interglacial shell- 

 beds have been met with up to heights of 

 several hundred feet. It is noteworthy also that 

 the low grounds of north Germany were likewise 

 submerged just before the invasion of that 

 region by the last great mer de glace. The cause 

 of such changes of level has been much canvassed 

 by geologists. From the fact that evidence of 

 submergence so frequently accompanies proofs of 

 severe glaciation, it has been inferred that the 

 sulwidence may have been due to the presence of 

 the ice. It has been suggested, for example, that 



