The Moon's Climate

In iliustratiou of the important olimatio effects of an atmospbere, I need do little moro than cite the case of thp moon. Onrsatellite i praotically at tlit samedistancefrorn the sun astbeeartb, and in its case also interna] heat has 110 present effect on the temperature of its superficial portions. It would therefors siem that, so far as sun heat isconeerued, the moon must be in much tbeéamu condition as the earth. Bot if we theuco dednced the infereuoe that the temperature conditions prevailing on our satellite bear auy resemblaneo to the temperature conditions prevailing on the earth we should ruake a great mistake, Obseryations of the moon 's heat show that its surface is exposed to a tremendons range of temperature, extending te hundreds of degrees. It bas been demonstrated that the temperature of tbe moon under the full glare of the sub rises toa point iu excessof that of boiling water, whiJe it is equally certain that wheu the suubeams are withdrawn the temperature of the moon sinks to a poiut far below that with whioh auy arcticexplorer has made us acquainted. Here. then, is aglobo fed just as we are, wito sunbeams, and yet undergoing tremendoua vioispitndea of climate, surpassing auy changos endured by the earth. The climatic difference between these two neighboring globes is certainly conuected with the fact that the moon has very little atmos-phere, even if it be not completely destitute thereof. Our atmosphere acts as a climatic regulator. It reduces the degree in which the intense fervor of the suu affects the earth, and it mitigates the rigor of the cold to which the earth wonld.be exposed when the sunbeams are withdrawn. Such an ameliorating agent is absent from the moon, and henee arise those violent extremes of its climatic condition. We thus see what potent factors the existence and the extent of au atmosphere beeoine in determining the nature of the climate tbat a planet is to have. We do not know eiiough regarding the atmospheres oí Mars, Venus and Mercury tobo able to draw any certain cönclusions with regard to their climates. But this we may at least affirm, that it seems quite possible for the different influentes we have named to go a long way toward neutralizing the contrasts that tbe climates of these globes would otherwise present in oonsequeuce of thn different supplies of sunbeams that they receive at their actual solar distances. So far as mere climate is concerned, it seems quite possible that appropriato atmospheres and land distributions might be adjusted on the earth and Mars, Mercury and Venus in snch a manner that certain organic types might be common to all the four