Scotland, though small in area, shows great inequality in the distribution of its rainfall, due to the diversity of its surface and to the fact that most of its rain is brought by westerly winds. Districts near the west coast, especially if mountainous, have a much greater rainfall than those towards the east, which are also on the whole less elevated. Thus considerable portions of the West Highlands have an annual rainfall of over 80 inches, Ben Nevis recording over 150. Many parts of the eastern Lowlands, on the other hand, have only 30 inches or less; and Cromarty, which is the driest station in Scotland, has only 23 inches. Compared with the mainland of Scotland, then, it does not seem that the climate of our islands gives us much cause for grumbling, for our annual rainfall varies from 37·7 inches at Sandwick to 30·7 at Start Point in Sanday. Our wettest months are October, November, and December, during which we receive from one-third to one-half of our yearly rainfall; our driest months are April, May, and June, which together give us only one-eighth of the total. One fact about rain is sometimes overlooked: in cool climates rain brings heat. This may not be noticeable at the time, but its general effect can be observed. Just as it requires heat to turn water into vapour, and as evaporation always produces cold, so the change back again from vapour into water sets free some of this heat, raising the temperature of the air, of the rain itself, and of the land on which it falls. Much of the warming effect of our westerly winds is due not to the direct warmth of the Gulf Stream, as used to be supposed, but simply to the fact that these winds are rain-carrying winds. They thus bring to us the benefit of that solar heat which far away to the south-west caused the vapour to rise from the surface of the ocean.