Vapour is always present in the air; sometimes a large amount, as much as the atmosphere is able at that particular temperature to hold; sometimes a less amount, not so much as the air could contain. In the latter case “drying” goes on briskly; in the former case it languishes, and wet clothes, wet pavements, remain long damp. Warm air can hide away a much more abundant supply of vapour than cold air; so the hotter and drier the air, the quicker is the evaporation or drying-up of water-surfaces. This is remarkably seen in the Red Sea. An amount of water passes away from that sea in a single year, sufficient to bring down its level some fifteen or twenty feet,--which it would do, but for a powerful current always flowing in from the Indian Ocean. When sea-water thus passes off in vapour, it leaves the salt behind. Were this amount of evaporation to go on steadily in the Red Sea, without any fresh supplies of water being received, about two thousand years would suffice to dry up the whole Sea, nothing but a great mass of salt remaining in its bed. If the Red Sea alone loses in one year a slice of water, fifteen or twenty feet thick, imagine what the enormous quantity must be which is raised, year by year, from the surfaces of all tropical oceans, and in a less degree from the seas in colder regions. The weight of the whole could only be told in hundreds of millions of millions of tons. And this vast mass is drawn up, gently and mildly, particle by particle; to be wafted by breezes to regions where water is urgently required, and there to be poured down as rain upon the thirsty ground. Thus the great exchange is carried on, with steady sequence, between Land and Ocean, Ocean and Land. When showers come to gladden the hearts of our farmers, and to provide food for the people, they might sometimes give a thought to the Ocean--to the manner in which, with Sun and Air as helpers, he sends aloft millions of tons of water, for the use of those on land. For “unto the place from whence the rivers come, thither they return again.” There are parts of the world where rains, like winds, come at regular and almost unfailing dates. In disappointing years, when they fail, an Empire may be disorganised in consequence. But in our British Isles no such regularity has sway; and a pleasing uncertainty prevails about Weather in general. This gives scope for something to talk about, and something to grumble at. What the average Briton would do without these perpetual possibilities is a serious question. No doubt our Weather _is_ a very uncertain quantity to be reckoned with. Yet it may be that we are unfair to our friend the Ocean, who does so much for us in the weather-line--ever at work as he is, night and day, sending upward supplies of water, bringing to our shore stores of tropical heat, softening the westerly breezes which excel.