SCENES ON THE PLANET MERCURY. 69 



tions and precipitations, I do not know of any decisive arguments 

 that can be opposed to the opinion. The spots are not gathered 

 in large masses, but are disposed in areas and zones of small 

 extent ; are greatly ramified, and alternate with considerable uni- 

 formity with clear spaces. We may, therefore, conclude that no 

 vast oceans or great continents exist on Mercury ; but that land 

 and sea interpenetrate one another and give rise to conditions 

 very different from those which exist on the earth, but which 

 may be more desirable. 



Mercury is a world that differs from ours as much as Mars 

 does. The sun lights it and warms it much more intensely than 

 it does the earth, and in a very different way. If life exists in 

 that world, it is doubtless under conditions so different from ours 

 that we can hardly imagine them. The eternal presence of the 

 sun, darting its rays almost vertically on some regions, and its 

 perpetual absence in the opposite countries, would seem intoler- 

 able to us. And yet, if we reflect upon it, we shall remark that 

 such a contrast would produce a more rapid, more powerful, and 

 more regular atmospheric circulation than that which spreads the 

 elements of life over the earth ; and it possibly is brought about 

 in this way that as complete and even perhaps more perfect equi- 

 librium of temperature is produced on the whole planet than 

 with us. 



Mercury, by directing the same face toward the sun during its 

 whole revolution, is peculiarly distinguished from the other plan- 

 ets, all of which the length of whose rotation has been determined, 

 turn round their axes in a few hours. This mode of rotation, how- 

 ever, which would be unique among the planets, seems common 

 enough among the satellites. All testimony is to the effect that 

 our moon has always conformed to it. The first three satellites 

 of Jupiter probably behave in the same way, and the observations 

 of Auwers and Engelmann demonstrate that the fourth does so. 

 Cassini verified the same fact for Japhet, the eighth satellite of 

 Saturn. It may, therefore, be considered the rule among the sat- 

 ellites, while it is an exception among the planets. 



The exception may probably be attributed to the proximity of 

 Mercury to the sun, and perhaps also to the fact that it has no 

 satellites ; and depends, I think, on the way Mercury was formed 

 when the solar system took its present shape. The peculiarity 

 constitutes a new datum to be added to those which astronomers 

 will have to take account of in studying solar and planetary cos- 

 mogony. — Translated for the Popular Science Monthly from a 

 French version by F. Terby in del et Terre. 



