The opportunity of an experiment on a comparatively large scale, and under conditions of comparative isolation, can occur but rarely in such a science as Meteorology. Hence Mr. Milne Home's proposal for the plantation of Malta seemed to offer an exceptional opportunity for progress. Many of the conditions are favourable to the simplicity of the result; and it seemed natural that, if a searching and systematic series of observations were to be immediately set afoot, and continued during the course of the plantation and the growth of the wood, some light would be thrown on the still doubtful question of the climatic influence of forests. Mr. Milne Home expects, as I gather, a threefold result:--1st, an increased and better regulated supply of available water; 2nd, an increased rainfall; and, 3rd, a more equable climate, with more temperate summer heat and winter cold.[46] As to the first of these expectations, I suppose there can be no doubt that it is justified by facts; but it may not be unnecessary to guard against any confusion of the first with the second. Not only does the presence of growing timber increase and regulate the supply of running and spring water independently of any change in the amount of rainfall, but as Boussingault found at Marmato,[47] denudation of forest is sufficient to decrease that supply, even when the rainfall has increased instead of diminished in amount. The second and third effects stand apart, therefore, from any question as to the utility of Mr. Milne Home's important proposal; they are both, perhaps, worthy of discussion at the present time, but I wish to confine myself in the present paper to the examination of the third alone.