532 THE POPULAR SCIENCE MONTHLY. 



CHANGES IN THE ASPECT OF MARS. 



Bt STANISLAUS MEUNIEE. 



THE planet Mars has for a long time signalized itself to observers 

 by the remarkable traits of its constitution. In consequence of 

 its relative nearness, the telescope has been able to furnish us with a 

 number of data respecting its physical geography and its meteorology ; 

 and it has been a very rich source of results concerning the philosophy 

 of the solar system and the physical universe in general. 



It is well known that Mars displays some bright spots, and others 

 dark, of which we have every reason to consider the former to be con- 

 tinents, the latter seas. Toward the poles appear large white zones, 

 varying in size at different times, which are caps of ice, susceptible 

 of occasional breakings-up like our icebergs. In the thin and trans- 

 parent atmosphere we can distinguish clouds, currents, and sometimes 

 whirlwinds quite like the cyclones that rage among us. 



Besides these intimate analogies with the earth, the study of Mars 

 reveals especial features, some of which are most satisfactorily ex- 

 plained by considerations of comparative geology. With the tenuity 

 of the atmosphere is associated a much smaller extension of the seas, 

 and the relative repartition of land and water is very different from 

 what prevails on the earth. Astronomers observe, as one of the most 

 remarkable peculiarities of the surface of this planetary neighbor of 

 ours, a large number of long and narrow passages and seas like bottle- 

 necks. In our globe the oceans are of three times the surface of the 

 continents ; and Europe, Asia, and Africa form together a single isl- 

 and, while another island is formed by the union of the two Amei'icas. 

 But, on Mars, an almost complete equality exists between the surfaces 

 occupied by the continents and by the seas. Further, they are mingled 

 with one another in such a complicated manner that a traveler might 

 visit nearly all the quarters of the planet, either by land or by boat, 

 without having to leave the element on which he began his journey. 



This much assumed, it should be recollected that Mars is older in 

 the planetary series than the earth ; that is, having been individualized 

 at a more ancient period, and having a smaller volume, it has reached 

 a more advanced stage in the sidereal evolution. Hence the planet 

 represents now, in its great lines and independent of its individual 

 characteristics, a condition which the earth will ultimately attain. 

 One of the effects of the secular cooling of the earth is to determine 

 the progressive absorption of the waters of the ocean by the successive- 

 ly consolidated rocky masses. Hence a striking comparison might be 

 made between the present Martial seas and the terrestrial oceans after 

 we shall have supposed they have been in a more or less great part 

 absorbed. The results of innumerable soundings have permitted the 



