that can be handled. Observe with how little clothing they work, for at these depths the temperature is high. Our final scene in a tin mine is comparatively near to the surface. [Sidenote: 6. Map showing Coalfields of United Kingdom.] [Sidenote: 7. Map showing distribution of Population about the Coalfields.] But, although some tin is still got, tin mines are now relatively unimportant in the life of the country. There has developed in Britain in the last century and a-half a vast system of industries based, not merely on the use of human muscles, but on power derived from the burning of coal. Here is a map showing, in black, the coalfields of Britain. They lie chiefly in South Wales, in the Midlands, in the North of England, and in Central Scotland. Those of Ireland produce but little. Compare this map with the next, which shows, in red, all the districts of denser population. It is obvious that of all the larger areas coloured red, only the London district is devoid of coal, and coal can easily be brought to London by sea. These facts tell us at once that in their modern growth the activities of the British population are based chiefly upon coal. Three-quarters of all the people in Britain live within the areas coloured pink, which measure not more than about one-twentieth of the British Isles. In the main, therefore, Britain is a country of town and factory populations, and in lesser degree only of agricultural and fishing people. A hundred years ago the population of the whole British Islands was not more than 16 millions, and it was mainly agricultural. To-day it numbers 43 millions, and is mainly industrial. [Sidenote: 8. A seam at Glasgow dissected to show the origin of Coal.] Coal is won from the depths of the earth, where it is laid in great sheets, which are known as coal seams, and these are underlaid and overlaid by the solid rock. Immediately under each coal seam there is usually a layer of clay, and if you examine that clay you will often find in it, here and there, threads of coal penetrating downward from the seam above. These are obviously the blackened roots of trees. Sometimes, in the coal itself, you will find complete stumps of trees preserved. For, in fact, the coal seams are nothing more than the buried, rotten forests of vastly ancient times. You know that in our great tropical forests when the wood rots it turns brown, and even black. Wherever wood grows old in the use of men it darkens. So we see that though the climate of Britain is cold, and though vegetation does not grow with the same colossal power as when driven by tropical rain and heat, yet buried deep in the rocks of Britain there is compensation in the shape of ancient timber called coal. The sunshine and rain of far-off times are thus the chief bases of British prosperity, just as the sunshine and rain of to-day are the chief bases of our prosperity in the tropics.