152 



THE MINOR PLANETS. 



sons, and which divides the earth into zortes and climates, it will be easily in- 

 ferred that the same phenomena prevails in Mars the limits of the seasons 

 being little more extreme than those which prevail in the earth. 



ATMOSPHERE OF MARS. 



The existence of an atmosphere upon Mars is proved by the gradual dimi- 

 nution which the light of a star suffers as his disk approaches it, and by the 

 variable character of the lights and shadows apparent upon the disk. The 

 ruddy appearance of the planet has been explained by the supposition of an 

 atmosphere of great density around it ; but more accurate telescopic observa- 

 tions have led Herschel and others rather to incline to the opinion that this 

 redness must be ascribed to a peculiar color prevailing on the surface of the 

 planet, like that of the red sandstone districts upon the earth. A slight appear- 

 ance of belts has always been noticed on this planet, which affords another 

 indication of an atmosphere, as will be more clearly understood when the belts 

 of Jupiter and Saturn shall be explained. 



PHYSICAL CONSTITUTION OF MARS. 



Telescopic inquiry has been directed to determine the physical condition of 

 this planet, and with a degree of success greater perhaps than that which has 

 attended similar inquiries respecting any other body in the solar system, except 

 the sun and moon. Sir William Herschel, and after him his son, Sir John 

 Herschel, ascertained the form and position of a variety of the features of light 

 and color on the disk ; but it has been reserved for the Prussian astronomers, 

 BEER and MADLER, to carry this inquiry to a much greater degree of detailed 

 accuracy. 



Sir John Herschel made a series of observations on Mars within the last 

 fourteen years, and supplied a telescopic drawing of one hemisphere of the 

 planet. We annex a figure exhibiting this sketch. 



He stated that the outlines here exhibited were found to be permanent and 

 unvariable, and must therefore be regarded as geographical and not atmospheric 

 features. It is true that they were not always visible, being sometimes obscured, 

 or varied by what seems to be clouds ; but when visible they were always the 

 same. Some portions appeared of a rsddish color, while others had a greenish 

 tint. He supposes the red portions to be land whose geological character im- 



