Many of the great historic movements of peoples were doubtless due to the gradual change of geographical or climatic conditions; and the slow desiccation of Central Asia has been plausibly suggested as the real cause of the peopling of modern Europe and of the medieval wars of the Old World, the theatres of which were critical points on the great natural lines of communication between east and west.
The nature of the soil appears, however, to be of secondary importance, provided that it is able to hold moisture and that climatic conditions of high and even temperature with considerable rainfall and absence of wind are satisfied.
For instance, a Fungus epidemic is impossible unless the climatic conditions are such as to favor the dispersal and germination of the spores; and when plants are killed off owi~ig to the supersaturation of the soil with water, it is by no means obvious whether the excess of water and dissolved materials, or the exclusion of oxygen from the root-hairs, or the lowering of the temperature, or the accumulation of foul products of decomposition should be put into the foreground.
The difficulty of sharply delimiting edaphic and climatic factors is seen in the case of temperature.
The evidence which has thus been briefly summarized, points unmistakably to the conclusion that existing vegetation originated in the northern hemisphere and under climatic conditions corresponding to what would now be termed sub-tropical.
In regions where climatic conditions are favourable, cotton grows more or less successfully on almost all kinds of soil; it can be grown on light sandy soils, loams, heavy clays and sandy " bottom " lands with varying success.
Queensland, New South Wales and South Australia possess suitable climatic conditions, and in the first-named state the cotton has been grown on a commercial scale in past years, the crop in 1897 being about 450 bales.
To 44.4 The climatic conditions of the western districts of the state are entirely different from those of the other two regions.
Diogenes made this conception of a vital and intelligent air the ground of a teleological view of climatic and atmospheric phenomena.
The development of man is explained in connexion with that of the earth, and in relation to climatic variations, &c.
Hence, in any cosmopolitan treatment of vegetation, it is necessary to consider the groups of plant communities from the standpoint of the climatic or geographical district in which they occur; and this indeed is consistently done by Schimper.
Finally, within any district of constant or fairly constant climatic conditions, it is possible to distinguish plant communities which are related chiefly to edaphic or soil conditions; and the vegetation units of these definite edaphic areas are the plant formations of some writers, and, in part, the edaphic formations of Schimper.
In external habit these exhibit adaptations to every kind of climatic or physical condition:
Of this line it is customary to distinguish several zones, lying, generally, parallel to it, and, differentiated chiefly by climatic differences.
==Fauna== The three climatic regions of Alberta have naturally a varying fauna.
It is thinly wooded, except in the north, where the climatic conditions approach those of the Amazon valley.
These arrangements have doubtless some reference to climatic phenomena, continuity of growth being arrested by cold and promoted by warmth.
For example, rae Arenarion in one climatic or geographical region might be in~~ med an a-Arenarion and one in a different region a a-Arena- ~j1j ri, and so on (Moss, bc. cit.).
Such groups are interesting in that they are vegetation units whose physiognomy is, in a broad sense, related more to climatic than to edaphic conditions.
This evidence of a gradual process of upheaval still in action may throw some light on the physical (especially the climatic) changes which must have passed over that part of Asia since Balkh was the " mother of cities," the great trade centre of Asia, and the plains of Balkh were green with cultivation.
- As already stated, the " Mediterranean region " forms a distinct climatic unit, chiefly due to the form and position of the Mediterranean Sea.
The prevailing winds, mild and humid, are west winds from the Atlantic; continental climatic influence makes itself felt in the east wind, which is frequent in winter and in the east of France, while the mistral, a violent wind from the north-west, is characteristic of the Mediterranean region.
In reality, however, it experiences fewer climatic variations than the other great continents, owing to its distance (28°) from the Antarctic circle and (11°) from the equator.
Practically the whole of the territory between the 145° meridian and the Great Dividing Range, as well as extensive tracts in the south and west, are a natural sheep pasture with climatic conditions and indigenous vegetation pre - eminently adapted for the growth of wool of the highest quality.
The climatic conditions in the British Islands are such that it is not possible to maintain, in unfavourable weather, a higher standard than that named, which is the insulation obtained when all the insulators are in perfect condition and only the normal leakage, due to moisture, is present.
Equally disastrous are those climatic or seasonal changes which involve temperatures in themselves not excessive but in wrong sequence; how many more useful plants could be grown in the open in the United Kingdom if the deceptively mild springs were not so often followed by frosts in May and June!
Physical FactorsThese are frequently classified as edaphic or soil factors and climatic factors; but there is no sharp line of demarcation between them.
Climatic factors include all those relating to atmospheric temperature, rainfall, atmospheric humidity, and light and shade.
The types of vegetation (tropical forests, sclerophyllous forest, temperate forests, tundra, &c.) thus briefly outlined are groups of Schimpers climatic formations.
On the other hand, adaptations, especially those evoked by climatic or edaphic conditions, may only, be shown by the seedling if grown under the appropriate external conditions; here what is hereditary is not the actual adaptation, but the capacity for responding in a particular way to a certain set of external conditions.
They endeavoured to define aspects of vegetation in which the forms exhibited an obvious adaptation to their climatic surroundings.
As Clement Reid remarked: World-wide floras, such as seem to characterize some of the older periods, have ceased to be, and plants are distributed more markedly according to geographical provinces and in climatic zones.
The indirect geographical elements, which, as a rule, act with and intensify the direct, are mainly climatic; the prevailing winds, rainfall, mean and extreme temperatures of every locality depending on the arrangement of land and sea and of land forms. Climate thus guided affects the weathering of rocks, and so determines the kind and arrangement of soil.
The maximum gradient possible depends on climatic conditions, a dry climate being the most favourable.
Eaton discovered on the desolate shores of Kerguelen's 'Island apterous and semi-apterous Diptera (Tipulidae and jEph_ydridae) of a degraded type adapted to the climatic peculiarities of the locality.
The foregoing brief review of the principal territorial divisions according to which the forms of life are distributed in Asia, indicates how close is the dependence of this distribution on climatic conditions, and this will be made more apparent by a somewhat fuller account of the main features of the flora and fauna.
The principal varieties of Egyptian cotton are: Mitafifi, the bestknown and most extensively grown, hardy and but little affected by climatic variation.
Various climatic factors may cause temporary checks, but the growing and maturing period is sufficiently long to allow the plants to overcome these disturbances.
- Climatic conditions in Egypt differ radically from those in the United States, the rainfall being so small as to be quite insufficient for the needs of the plant, very little rain indeed falling in the Nile Delta during the whole growing season of the crop: yet Egypt is in order the third cottonproducing country of the world, elaborate irrigation works supplying the crop with the requisite water.
The improvements desired in cotton vary to some degree in different countries, according to the present character of the plants, climatic conditions, the chief pests, special market requirements, and other circumstances.
In spite of somewhat adverse climatic conditions, live stock is reared with a fair amount of success.
The winter rains of the Karst region show that it belongs to the sub-tropical climatic zone.
It has generally been forgotten that the utter want of march discipline in the French, and not the climatic conditions, was responsible for the appalling disasters which ensued.
His travels had convinced him that a full and comprehensive knowledge of classical antiquity could only be acquired by a thorough acquaintance with Greek and Roman monuments and works of art, and a detailed examination of the topographical and climatic conditions of the chief localities of the ancient world.
The Sao Francisco, which belongs to the inland plateau region, is the largest river of the eastern coast of Brazil and exists by virtue of climatic conditions wholly different from those of the coast where it enters the Atlantic. The tributaries of the lower half of this great river, which belong to the Atlantic coast region, are small and often dry, but the upper river where the rainfall is heavier and more regular receives several large affluents.
At Santos the rainfall is exceptionally heavy and the mean temperature high, but below that point the climatic conditions are considerably modified, the range in temperature being greater, the mean annual temperature lower, and the rainfall more evenly distributed throughout the year.
The climatic conditions of the Brazilian plateau are widely different from those of the coast in many respects.
The rainfall throughout this region is abundant, except in northern Minas Geraes, where the climatic conditions are influenced to some extent by the arid eastern plateau.
West and north of the Drakensberg the general level of the low veld is not much below that of the lowest altitudes of the middle veld, though the climatic 1 By the Boers the western and less elevated part of the plateau is known as the middle veld.
The flora of Venezuela covers a wide range because of the vertical climatic zones.
The climatic conditions are not so favourable as in Argentina, but these are counterbalanced to some extent by the great river system of the Orinoco, whose large navigable tributaries cross the plains from end to end, and whose smaller streams from the surrounding highlands provide superior opportunities for water storage and irrigation.
As an instance of the influence of climatic conditions combined with high cultivation the cane lands of the Sandwich Islands may be cited.
But the lowness of stature extends to the lower animals - cattle, horses, donkeys, &c. - and this may indicate that climatic causes have some part in the matter also, though Sergi denies this.
Passing from the coast to the tableland, a distinct climatic region is entered.