82 Things not generally Known. 



TEMPERATURE OF THE PLANET MERCURY. 



Mercury being so much nearer to the Sun than the Earth, 

 he receives, it is supposed, seven times more heat than the 

 earth. Mrs. Somerville says: "On Mercury, the mean heat 

 arising from the intensity of the sun's rays must be above that 

 of boiling quicksilver, and water would boil even at the poles." 

 But he may be provided with an atmosphere so constituted as 

 to absorb or reflect a great portion of the superabundant heat ; 

 so that his inhabitants (if he have any) may enjoy a climate as 

 temperate as any on our globe. 



SPECULATIONS ON VESTA AND PALLAS. 



The most remarkable peculiarities of these ultra-zodiacal 

 planets, according to Sir John Herschel, must lie in tin's condi- 

 tion of their state : a man place i on one of them would spring 

 with ease sixty feet high, and sustain no greater shock in his 

 descent than he does on the earth from leaping a yard. On 

 such planets, giants might exist ; and those enormous animals 

 which on the earth require the buoyant power of water to coun- 

 teract their weight, might there be denizens of the land. But 

 of such speculations there is no end. 



IS THE PLANET MARS INHABITED ? 



The opponents of the doctrine of the Plurality of Worlds 

 allow that a greater probability exists of Mars being inhabited 

 than in the case of any other planet. His diameter is 4100 

 miles ; and his surface exhibits spots of different hues, the 

 seas, according to Sir John Herschel, being green, and the laud 

 red. " The variety in the spots," says this astronomer, " may 

 arise from the planet not being destitute of atmosphere and 

 cloud ; and what adds greatly to the probability of this, is the 

 appearance of brilliant white spots at its poles, which have 

 been conjectured, with some probability, to be snow, as they 

 disappear when they have been long exposed to the sun, and are 

 greatest when emerging from the long night of their polar 

 winter, the snow-line then extending to about six degrees from 

 the pole." " The length of the day," says Sir David Brew- 

 ster, " is almost exactly twenty-four hours, the same as that 

 of the earth. Continents and oceans and green savannahs 

 have been observed upon Mars, and the snow of his polar re- 

 gions has been seen to disappear with the heat of summer. " 

 We actually see the clouds floating in the atmosphei-e of Mars, 

 and there is the appearance of land and water on his disc. 

 In a sketch of this planet, as seen in the pure atmosphere of 

 Calcutta by Mr. Grant, it appears, to use his words, " actually 



