70 Things not generally Known. 



with a non- coincidence of its centre of gravity with its centre 

 of symmetry. 



If to this we add the supposition that the substance of the 

 moon is not homogeneous, ani that some considerable pre- 

 ponderance of weight is placed excentrically in it, it will be 

 easily apprehended that the portion of its surface nearer to that 

 heavier portion of its solid content, under all the circumstances 

 of the moon's rotation, will permanently occupy the situation 

 most remote from the earth. 



In what regards its assumption of a definite level, air obeys precisely 

 the same hydrostatical laws as water. The lunar atmosphere would 

 rest upon the lunar ocean, and form in its basin a lake of air, whose 

 upper portions at an altitude such as we are now contemplating would 

 be of excessive tenuity, especially should the provision of air be less 

 abundant in proportion than our own. It by no means follows, then, 

 from the absence of visible indications of water or air on this side of the 

 moon, that the other is equally destitute of them, and equally unfitted 

 for maintaining- animal or vegetable life. Some slight approach to such 

 a state of things actually obtains on the earth itself. Nearly all the 

 land is collected in one of its hemispheres, and much the larger portion 

 of the sea in the opposite There is evidently an excess of heavy mate- 

 rial vertically beneath the middle of the Pacific ; while not very remote 

 from the point of the globe diametrically opposite rises the great table- 

 land of India and the Himalaj^a chain, on the summits of which the air 

 has not more than a third of the density it has on the sea-level, and 

 from which animated existence is for ever excluded. Herschel s Out- 

 5th edit. 



LIGHT OF THE MOON. 



The actual illumination of the lunar surface is not much 

 superior to that of weathered sandstone-rock in full sunshine. 

 Sir John Herschel has frequently compared the moon setting 

 behind the gray perpendicular faQade of the Table Mountain 

 at the Cape of Good Hope, illuminated by the sun just risen 

 from the opposite quarter of the horizon, when it has been 

 scarcely distinguishable in brightness from the rock in contact 

 with it. The sun and moon being nearly at equal altitudes, 

 and the atmosphere perfectly free from cloud or vapour, its 

 effect is alike on both luminaries. 



HEAT OF MOONLIGHT. 



M. Zantedeschi has proved, by a long series of experiments 

 in the Botanic Gardens at Venice, Florence, and Padua, that, 

 contrary to the general opinion, the diffused rays of moonlight 

 have an influence upon the organs of plants, as the Sensitive 

 Plant and the Desmodium gyrans. The influence was feeble 

 compared with that of the sun ; but the action is left beyond 

 further question. 



Melloni has proved that the rays of the Moon give out a 



