1242. Changing the condition of lands, as to solar influence, is but a limited means of improvement; but is capable of being turned to some account in gardening. It is effected by altering the position of their surface, so that the surface may be more or less at a right angle to the plane of the sun's rays, according as heat or cold is to be increased or diminished. The influence of the sun's rays upon any plane is demonstrated to be as their number and perpendicularity to that plane, the effects of the atmosphere being excepted. Hence one advantage of ridging lands, provided the ridges run north and south; for on such surfaces the rays of the morning sun will take effect sooner on the east side, and those of the afternoon will remain longer in operation on the west side; whilst at mid-day his elevation will compensate, in some degree, for the obliquity of his rays to both sides of the ridge. In culture, on a small scale, ridges or sloping beds for winter crops may be made south-east and north-west, with their slope to the south, at an angle of forty degrees, and as steep on the north side as the mass can be got to stand; and on the south slope of such ridge, oï¾µteris paribus, it is evident much earlier crops may be produced than on level ground. The north side, however, will be lost during this early cropping; but as early crops are soon gathered, the whole can be laid level in time for a main crop. Hence all the advantage of grounds sloping to the south, southeast, or south-west, in point of precocity, and of those sloping to the north for lateness and diminished evaporation. Another advantage of such surfaces is, that they dry sooner after rains, whether by the operation of natural or artificial drainage; or, in the case of sloping to the south, by evaporation.