The west coast of Great Britain illustrates the same thing on a smaller scale. There the warm waters of the Gulf Stream, travelling in a northeasterly direction straight away from the Gulf of Mexico, strike the west coast of Ireland, England, and Scotland; and as most people are aware, the mild climate of Great Britain is chiefly due to this fact. If you contrast for a moment the east and west coasts of Britain, you will see that the latter is much more rocky and mountainous than the east coast. Mountains run down nearly all our western coasts. Now, it is this elevated and rocky side of Britain which catches most of the rain. Very instructive it is to compare the annual rainfall in different parts of Britain. On Dartmoor about 86 inches of rain fall every year, while in London only about 24 inches fall annually; but then London has no range of mountains near, and is far away from the west coast. Again, while people in Ambleside have to put up with 78 inches of rain, in Norfolk they are content with the modest allowance of 24 inches or so. At a place called Quoich on the west coast of Scotland, about 117 inches fall every year. These differences are chiefly due to the different contour of the land down the west side of Britain, which is mountainous, while the east side is flat, and also to the fact that while easterly winds, which have come over the continent, are dry, our prevailing winds are from the west and southwest, and are consequently heavily laden with vapour from the Atlantic Ocean. These winds follow the direction of the Gulf Stream, driving it along before them; and in so doing they take up large quantities of vapour from its surface. When these warm winds touch our western coasts, they receive a chill, and consequently are no longer able to contain all the vapour which they bring with them, and so down comes the rain. II. _Mountains are elevated reservoirs of water in one form or another, and thus not only feed the streams and rivers, but give them force and direction as well._ It is very important that the mountains should not allow the waters they collect to run away too fast. Try to think for a moment what would happen if instead of being, as it were, locked up in the form of snowfields and glaciers, the water were all in the liquid form. It would soon run away, and for months together the great river-valleys would be dry and desolate. When the rain came, there would be tremendous floods; dire destruction would be wrought in the valleys; and very soon the great rivers would dwindle down to nothing. Vegetation too would suffer seriously for want of water during the summer months; and the valleys generally would cease to be the fertile sources of life which they are at present. The earth would become for the most part like a stagnant marsh.