It is a well known fact, that summer-fallowing always dissipates a portion of the vegetable matter in the soil, although it may, at the same time, tend to fertility, especially in adhesive soils, and where the climate is not very arid and warm, overbalancing the loss from dissipation by the advantage resulting from aëration and absorption of gases and heat, and the sun’s rays; by the mechanical disposition and comminution from being thoroughly dried and then moistened; and, probably, by the formation of salts, {324} stimulative to vegetation; or, as it has been thought, by the resting for a season. In the case of any tannin or inert vegetable matter existing in the soil, the heat and drying will tend to reduce these to a condition suitable for vegetable food. In the West Indies, when a summer fallowing is resorted to in order to get clear of the weeds, the fertility of the ground is considerably lessened, from the evaporation or burning out of the putrescent or carbonaceous matter. Were the fallowing continued for several successive seasons, there is no doubt that the whole matter, which, combined with earth, forms mould, would be dissipated. About a century ago, it was the practice, in our neighbourhood (an alluvial clay district), to build up the soil of the fallow division, furrow deep, into thin dikes, or walls, about 5 feet high. This was done in early summer. After being dried and aërated by the summer’s drought, the dikes were levelled down in the autumn and sown with wheat. This system was considered so fertilizing as to counterbalance the labour and the loss of a crop.