Page:The Moon Maid.pdf/52

RV 38 (Rh) ing from widely different sources, the chief of which was due to the considerable radium content of the internal lunar soil, and principally of the rock forming the loftier mountain ranges, the radium being so combined as to diffuse a gentle perpetual light which pervaded the entire interior of the Moon. The secondary source was sunlight, which penetrated to the interior of the Moon through the hundreds of thousands of huge craters penetrating the lunar crust. It was this sunlight which carried heat to the inner world, maintaining a constant temperature of about eighty degrees Fahrenheit.

Centrifugal force, in combination with the gravity of the Moon's crust, confined the internal lunar atmosphere to a blanket which we estimated at about fifty miles in thickness over the inner surface of this buried world. This atmosphere rarefies rapidly as one ascends the higher peaks, with the result that these are constantly covered with perpetual snow and ice, sending great glaciers down mighty gorges toward the central seas. It is this condition which has probably prevented the atmosphere, confined as it is within an almost solid sphere, from becoming superheated, through the unthinkable ages that this condition must have existed. The Earth seasons are reflected but slightly in the Moon, there being but a few degrees difference between summer and winter. There are, however, periodic wind-storms, which recur with greater or less regularity once each sidereal month, due, I imagine, to the unequal distribution of crater openings through the crust of the Moon, a fact which must produce an unequal absorption of heat at various times and in certain localities. The natural circulation of the lunar atmosphere, affected as it is by the constantly-changing volume and direction of the sun's rays, as well as the great range of temperature between the valleys and the