MARS ASTEROIDS JUPITER SATURN URANUS. 



91 



chiefly make their way through the resisting medium. The idea of Sir John Herschel is 

 however more probable, that the fiery aspect of Mars proceeds from the geology of the 



planet, its general soil having this colour, like the 

 red-sandstone districts of the earth, but in a more 

 decided manner. When viewed through a tele- 

 scope, the surface exhibits a variety of spots, of 

 which, as observed by Cassini, Hook, and Maraldi, 

 we have several drawings. Some of the spots are 

 changing and evanescent, and appear to be clouds 

 and vapours floating in the atmosphere ; but others 

 are permanent, and are evidently geographical 

 features of the planet continents, seas, and 

 regions of polar snow. The annexed view of Mars 

 was taken by Sir John Herschel at Slough, August 

 16th, 1830, in the twenty-feet reflector. The darker 

 parts are seas, which appeared of a greenish hue. 

 The zone observable at the polar point is brilliantly white, but of variable brightness, 

 and is conceived to be snow, its luminosity being least after exposure to the sun through 

 the summer season of the planet, and greatest after the darkness of its long wintry night. 

 There are thus points of striking accordance between the Martial and Terrene worlds. 



Their periods of light and darkness, night and day, are 

 nearly equal. Both have a succession of seasons, arising 

 from the obliquity of their respective ecliptics, though 

 of different duration. Both have an atmosphere 

 clouds, rain, snow, continents and seas ; but without 

 an attendant moon, the oceans of Mars must be 

 nearly tideless, only gently undulating like the waters 

 of the Mediterranean and the Baltic. Each planet 

 has also vast fields of ice and snow at its poles. 

 Should the inhabitants of Mars take a view of our 

 world through any far-seeing instrument like that 

 with which we inspect their dwelling, the terrestrial 

 aspect, viewed from that distance, in one of its phases 

 will not be very remote from the sketch now given. 

 Proceeding farther on an outward-bound course through the system, we arrive at the 

 cluster of four small bodies, whose existence is a modern discovery. They present a 

 variety of anomalies which distinguish them from the older planets ; and received from 

 Herschel the distinctive appellation of Asteroids, a Greek compound signifying the ap- 

 pearance of stars, but by others they are called Planetoids, and extra-zodiacal planets. 

 Taking them in the order of their mean distances from the sun, VESTA is the first to be 

 noticed, discovered by Olbers at Bremen in Lower Saxony on the 29th of March 1807, 

 in the wing of the constellation Virgo. The orbit of this body is computed to be 225 

 millions of miles from the sun, which is performed in rather more than three and a half 

 years. Its diameter is supposed to be only 270 miles. Vesta shines with a very pure 

 white and intense light, as a brilliant point in the heavens, and has been observed by 

 the naked eye on a clear evening, the only one of the asteroids that can be thus dis- 

 covered. JUNO, the next in succession, was discovered by M. Harding of Gottingen on 

 the 2nd of September, 1804, appearing like a star of the eighth magnitude near the tail 

 of Cetus. Her mean distance from the sun is 254 millions of miles, but the orbit is so 

 elliptical that her greatest distance is nearly double the least, so that, when in her peri- 



