The physical phenomena attending eclipses of the moon are no longer of a high order of interest either to the layman or scientific observer. A brief statement of them and their causes will therefore be sufficient. An observer watching such an eclipse from the moon would see the earth, which has nearly four times the apparent diameter of the sun, impinging on the sun's disk and slowly hiding it. The phenomenon would be quite similar to that of an eclipse of the sun seen from the earth, until the sun was completely covered. During the progress of this partial eclipse the moon would be passing into the earth's penumbra. As the moment of total obscuration approached, a red band of light would rapidly form in the neighbourhood of the disappearing limb of the sun, and gradually extend around the earth. This would arise from the refraction of the sun's light by the earth's atmosphere, and the absorption of its blue rays. When the light of the sun was completely hidden, a reddish ring of great brilliancy would, owing to this cause, surround the entire dark body of the earth during the period of the total eclipse. The aspect of the moon, as seen from the earth, corresponds to this view from the moon. The fading of the moon's light, due to its entrance into the penumbra, is scarcely noticeable without direct photometric determination until near the beginning of the total phase. Then, as the limb of the moon approaches the earth's shadow, it begins to darken. When only a small portion has entered into the shadow, that portion is completely hidden. But, as the total phase approaches, the part of the moon's disk immersed in the penumbra becomes visible by a reddish coppery light--that of the sun refracted through the lower parts of the earth's atmosphere. The brightness of this illumination is different in different eclipses, a circumstance which may be attributed to the greater or less degree of cloudiness in those regions of the earth's atmosphere through which the light of the sun passes in order to reach the moon. Its colour is due to absorption in passing through the earth's atmosphere. III. _Laws and Cycles of Recurrences of Eclipses of the Sun and Moon._ It has been known since remote antiquity that eclipses occur in cycles. These cycles are known now to be determined principally by the motion of the moon's node and the relations between the revolutions of the earth round the sun and the moon round the earth. Eclipse seasons.