If there is one feature in the material relations of a country which may be considered as characteristic-as of itself sufficient to define the qualities of the inhabitants, and the position they are fitted to occupy in the, world's history - it is climate. 'It includes,' says Humboldt, 'all those modifications of the atmosphere by which our organs are affected-such as temperature, humidity, variations of barometric pressure, its tranquillity or subjection to foreign winds, its purity or admixture with gaseous exhalations, and its ordinary transparency - that clearness of sky so important through its influence, not only on the radiation of heat from the soil, the development of organic tissue and the ripening of fruits, but also on the outflow of moral sentiments in the different races.' I do not propose, however, to deal with the constitution of the climate of Great Britain under this general view. To do so, indeed, would require somewhat more space than can in this volume be conveniently allotted to a single subject. I wish chiefly to consider the subject of temperature (mean annual and extreme winter or summer temperature); though I shall have a few words to say respecting that feature of our climate which most foreigners consider to be its chief defect-the want of transparency or clearness in our skies as compared with those of some other European countries.

The mean annual temperature of a country is less important to the welfare of the inhabitants than the extreme range of temperature exhibited in the course of the year. Of two countries which have the same mean annual temperature, one may have a climate most admirably adapted to the welfare of its inhabitants, while the other may have a climate offering such fierce and violent extremes of heat and cold that its inhabitants resemble the unfortunates described by Dante, doomed

' - a soffrir tormenti e caldi e geli.'

However, I shall deal first with this feature-mean annual temperature - as affording a starting-point from which to proceed to other considerations.

If the surface of the earth were perfectly uniform, or symmetrically distributed into districts of land and water arranged in zones along latitude-parallels, and if the strata of the soil were throughout of like density, radiating power, and elevation, the lines of equal mean temperature would be parallels of latitude. This hypothetical condition of things is, we know, very far from representing the true condition of the earth's surface. Land and water are distributed in a manner which hardly presents the semblance of law; elevations and depressions, not merely of areas of limited extent, but of whole countries, are exhibited in each hemisphere; and endless diversities of soil, contour, and distribution, disturb that mathematical uniformity and exactness, which could alone produce the co-ordination of climates under latitude-parallels.

It is to Humboldt that we owe the valuable proposition that maps of the world should exhibit parallels of heat, as well as latitude-parallels; and no atlas is now considered complete without maps in which isotherms, or lines of equal mean annual temperature, isochimenals or lines of equal winter heat, and iso-therals or lines of equal heat in summer, are exhibited.

These lines are usually presented in maps on Mercator's projection, an arrangement which has some advantages, but is not, on the whole, very well suited to exhibit the true conformation of the isothermal lines-the study of which, it has been well remarked, constitutes the basis of all climatology.

In Figs. 1 and 2, the northern hemisphere of the earth is presented on a projection (the equal surface) which has been discussed in my 'Essays on Astronomy.' The smallness of the scale would not readilypermit of the introduction of the system of isothermal lines usually presented, therefore I have only introduced the isotherm which passes through London. In both figures this isotherm is represented by a dotted closed curve passing across the south of England, thence across the Atlantic in a south-westerly direction, and across the continent of America nearly on the latitude of New York. After it has entered the Pacific Ocean, the isotherm passes somewhat northwards, but trends southwards again as it nears the Asiatic continent, reaching its greatest southerly range in the sea of Japan, traversing Asia nearly on the latitude of the Aral Sea, and thence passing somewhat northwards through the Crimea, Vienna, and Brussels to London. Along its whole extent the isotherm nowhere has a higher latitude than where it crosses the British Isles; in other words, the mean annual temperature of Great Britain is higher than that of any country lying between the same latitude-parallels. The advantage of this arrangement is second only in importance to that which England will be seen to possess when we come to consider the extreme range of temperature during the year. In fact, England is thus brought to the centre of the true temperate zone of the northern hemisphere; and the consideration of Figs. 1 and 2 will show that the isotherm of London approaches as near to the tropic of Cancer in one part of its course, as to the Arctic circle in another.

Fig. 1.

The Climate Of Great Britain 3

Northern hemisphere on an equal-surface projection, showing curves of mean annual and midwinter temperature through London.

Before leaving this part of the subject, let me note a circumstance, not immediately connected with the climate of Great Britain, but geographically interesting. In examining the polar presentation of the London isotherm, we see that in two parts of its course it exhibits a tendency to travel northwards, and becomes, in fact, convex towards the pole. If we laid down isotherms of greater mean temperature-that is, nearer the equator-we should find this peculiarity gradually diminishing. But if we laid down isotherms of lower mean temperature, we should find the convexities gradually becoming sharper and more defined, approaching each other more and more nearly, until finally they would meet, and the isothermal curve be divided into two irregular ovals. Proceeding to trace out curves of still lower temperature, we should find the two ovals closing in towards two poles of cold. These are indicated in Figs. 1 and 2 by two black spots, one north of the American, the other north of the Asiatic continent. It is to be noted, however, that at the American pole the mean annual temperature is not quite so low as at the Asiatic pole, the former temperature being 3 1/2°, the latter 1° Fahrenheit.