All elevated situations are more exposed to the prevailing winds of a country than plains; but, as the highest winds of any particular locality generally blow from one direction only, situations that are equal in point of elevation may be quite different in point of exposure. In the neighbourhood of London, where the most disagreeable winds are from the northeast, a house placed on that side of a hill will be more exposed to cold winds than on any other side. The exposure, also, is very much affected, in irregular hilly situations, by the influence of other hills, in directing currents of wind out of their natural course; so that while the north-east side of an isolated hill may be the most exposed side, the south or the north side of a hill,' situated among other hills, may be equally exposed as, or more so than, the north-east side. Though a situation exposed to the prevailing winds of the district can seldom be considered the most desirable for a dwelling-house, and never for a garden, unless it be one where none but the hardiest plants are to be grown, yet there are exceptions, .arising from local circumstances: for example, in the immediate neighbourhood of smoky towns, such as Manchester or Birmingham, any situation on the side of the town most exposed to the prevailing winds will be the best, as being the most free from smoke.