BIBLIOGRAPHY
Reid, C. “Submerged forests.” Cambridge University Press, 1913.
Lewis, F. J. “The history of the Scottish peat-mosses and their relation to the Glacial period.” Edinburgh, Scot. Geogr. Mag., 22, 1906, p. 241.
CHAPTER XVI
THE “CLASSICAL” RAINFALL MAXIMUM, 1800 B.C. TO A.D. 500
About 1800 B.C., or the beginning of the Bronze Age in Britain, the subsiding land finally attained approximately its present level. At the same time the climate of western Europe deteriorated, becoming much more humid and rainy, and there set in a period of intense peat-formation in Ireland, Scotland and northern England, Scandinavia and North Germany, known as the Peat-Bog Period or Upper Turbarian. The peat-beds choked and killed the forests which had developed on the older peat-bogs, and grew up above the stools and fallen trunks, so that we have two layers of peat separated by an old forest. The forest level contains neolithic articles, the peat contains gold collars, bronze swords and pins, and other objects of the Bronze Age. This growth also went on even over high ground, which had not previously been covered by peat, for Professor Henry informs us that on Copped Mountain, near Enniskillen, and at other places in Ireland, Bronze Age cairns and tumuli are found resting on rock and covered by several feet of bog. Peat-beds on the Frisian dunes between two layers of blown sand are dated about 100 B.C., and some bogs in northern France were formed during the Roman period. There is also some much-disputed contemporary Latin evidence that at the time of the Roman occupation the climate of Britain was damp and boggy, while Gibbon (“Decline and Fall of the Roman Empire”), referring to the climate of central Europe at the beginning of the Christian era, points to some evidence that the climate was colder. This is, that the Rhine and the Danube were frequently frozen over, so that the natives crossed them with cavalry and wagons without difficulty, although at the present time this never happens. It is possible that this severe climate is referred to in the Germanic legend of the “Twilight of the Gods,” when frost and snow ruled the world for generations. The Norse sagas point to a similar cold period in Scandinavia. This lapse of climate occurred in the Early Iron Age, about 650 to 400 B.C., when there was a rapid deterioration from the high Scandinavian civilization of the Bronze Age. This deterioration of culture was probably the direct result of the increased severity of the climate.
This Pluvial period has been made the subject of special studies by Ellsworth Huntington in several important books and papers; he finds evidence of a distinctly Pluvial period in three regions—the Mediterranean, central and south-western Asia, and an area including the southern United States and northern Mexico. In the first of these, the Mediterranean, Huntington considers that the Græco-Roman civilizations grew up in a period of increased rainfall which lasted from about 500 B.C. to A.D. 200. These states were able to develop in comparative peace because during this time there were no great invasions of nomadic peoples from eastern Europe or central Asia, a fact which points to good rainfall in these comparatively dry regions, so that their inhabitants had no need to emigrate in quest of a living. In the Mediterranean itself the heavier rainfall allowed a solid agricultural basis which produced a sturdy race of peasants who made good soldiers. Owing to the greater cyclonic control of climate and consequent changeable weather, these inhabitants were more vigorous in mind and body, for Huntington’s researches have demonstrated that long spells of monotonous weather, either fine or rainy, are unfavourable for human energy. Finally the heavier rainfall maintained a perennial flow in the rivers, giving plentiful supplies of good drinking water. These conditions broke down earlier in Greece than in Italy, as the latter naturally has a heavier rainfall. Huntington considers that the decline of Greece was largely due to malarial poisoning, the decreasing rainfall causing the river-flow to break down in summer, leaving isolated pools forming a breeding ground for mosquitoes.
After A.D. 200 the climate of Italy also deteriorated. The decrease of rainfall, combined with gradual exhaustion of the soil, made wheat-growing more and more difficult for the small agriculturalist, and the farms came into the hands of large landowners, who worked them by slave labour, and in place of wheat either grew vines or olives or raised flocks and herds. The agricultural population gravitated to Rome and a few other large cities, and had to be fed by imported wheat. The decline was probably aided by the introduction of malaria, as in Greece.
In north Africa and Palestine the question is more debatable. C. Negro, who has investigated the supposed desiccation of Cyrenaica, concludes that there has been no change of climate since Roman times, but a careful study of his evidence suggests that his conclusions are open to criticism. All that he has proved is that there has been no marked progressive decrease of rainfall since about A.D. 200; he has ignored the possibility of great fluctuations before and since that date. In north Africa it seems difficult to believe that the great cities of antiquity could have existed under present climatic conditions, but when we turn to Palmyra in the Syrian desert we have practically incontrovertible proof in the great aqueducts, built to carry from the hill-springs to the city large volumes of water which these springs no longer deliver, so that even where they are intact the aqueducts now carry only the merest trickle.
In Persia we find numerous ruins, which point to a much greater population two thousand or more years ago. This population lived by agriculture, and the remains of their irrigation works are now found in regions where running water never comes. Even the scanty population of to-day can hardly live on the present rainfall of the country, and it is unbelievable that the much greater population indicated by these ruined cities could have existed without a very much greater supply of water. The same condition is indicated by the ruined cities of the great deserts of central Asia. These cities were inhabited by agriculturalists, and the remains of tilled fields, terraces and irrigation works abound in places where the supply of brackish water would now be barely sufficient for drinking purposes for such a large population. Huntington has also made a careful study of the water-level of the Caspian Sea in classical times, and finds that there was a great period of high water extending from unknown antiquity to about A.D. 400.