Valencia where there is a slightly better chance of dry than of wet weather is May, which the foregoing table, shows to be also the driest month in London. The figures for Cobham, however, are very interesting as compared with those for London. In the first place, the predominance of January, as the wettest month, does not hold for the longer period at Cobham, where the highest probability is for November and the lowest for August, instead of May. These figures FIG. 39. JAN. FEB. MAR. APR. MAY JUNE JULY AUG. SEP. OCT. NOV. DEC. 9 •2 СОВ'НАМ $826-1865. •1 Monthly Rain Probability for 0.01 in. for Valencia and London, for are, however, only for a hundredth of an inch of rain, an amount which is practically insignificant. The last column shows for Cobham the probability of the fall of a tenth of an inch of rain, that is, of what might ordinarily be called a wet day. This shows a very decided maximum in the autumn months and a minimum in February and March, months which are shown to be nearly as damp as any, as far as the absolute occurrence of any rain is recorded. These facts show us 8 זי 6 2 •2 •1 that in the winter small rain and mist contribute largely to make up the total fall, while in the autumn the rain comes down in heavy showers. FIG. 40. J. F. M A. M. J. J. A. S. O. N. D. J. Dr. Köppen' gives the preceding diagram (fig. 40) of the rain probability over Europe, which shows very clearly 1 'Ueber Regen wahrscheinlichkeit in einigen Theilen Europas,' Zeitschrift der ö. met. Gesellschaft, vol. iii. 1868, p. 497. where we should not go if we want fine weather in our autumn holidays. On the Mediterranean coast the curve is at its lowest in summer. In Hungary the lowest point is in October and the highest in May. In Transylvania the same features are more strongly marked, but the wettest month is June. The conditions for the Channel coast and the Baltic are generally similar to those shown in the table on p. 334 for the British Isles, while the predominance of summer rains in the Urals is very decided. N CHAPTER XVII. CLIMATE. UNDER the term Climate we understand the combined effect of all the phenomena whose distribution over the globe we have recently been considering, and which determine the suitability of various districts for the support of their respective fauna and flora. Beyond all doubt the most important factor in these determinations is the temperature. We all know that vegetation attains its greatest luxuriance in the damp heat of the tropical regions, while it can hardly be said to exist in the extreme cold of the polar lands. The law of decrement of heat with ascent above the sea-level has already been explained, and, accordingly, it will be understood, as Herschel says, that in ascending a mountain from the sea-level to the limit of perpetual snow, we pass through the same series of climates, so far as temperature is concerned, which we should do by travelling from the same station to the polar regions of the globe; and in a country where very great differences of level exist we find every variety of climate arranged in zones according to the altitude, and characterised by the vegetable productions appropriate to their habitual temperatures.' 1 The old division of the earth by Parmenides into 2 Physical Geography, Section 249. the five zones of geography has been found to be quite inadequate as a representation of the climatology of the globe. Merely to take the phenomenon which we have most recently been treating, the distribution of rainfall, we have seen that the subtropical conditions of fall extend far up into the temperate zone. We are, however, hardly prepared to agree with Professor Supan, who, in Petermann's 'Mittheilungen' for 1879, proposed a formal abandonment of the old zones in favour of a system more in accordance with climatic facts. Speaking very generally, we may say that the dis tribution of the plants most important to mankind, such as the cereals, depends on the summer temperature, for the temperature prevailing in winter, when the seed is not in the ground at all, exercises only an indirect effect by its influence on the condition of the soil. The district of Manitoba yields magnificent crops of wheat, despite its winter temperature, which often falls far below zero of the Fahrenheit scale. The distribution of animals is more dependent on the winter temperature, and, as animals can bear a greater range of temperature than plants, their distribution is more extensive. The contrast between different localities as to the extent of variation of temperature which they experience in the yearly period is a factor of great importance in the determination of climate, and one to which, as yet, comparatively little attention has been directed. The first to draw Range Maps of the globe was the late A. Keith Johnston, jun., who, in the Proceedings of the Royal Society of Edinburgh' for 1869, published such maps, but on a very small scale, and on the polar projection. The maps were reproduced in his 'Physical |