752 THE UNIVERSE. 



brought to so great perfection, we can pry into the minutest 

 details of our satellite, and examine them with as much ac- 

 curacy as if it were some distant view on earth; hence we 

 can to a certain extent make out its geological disposition. 

 The precision of our glasses has been carried to such a 

 pitch, that we could with them easily perceive large build- 

 ings, if any existed on the lunar surface; we could even 

 make out troops of animals moving about. It would, it is 

 true, be impossible to perceive one of its inhabitants travers- 

 ing the valleys of its silver crescent; but if the much spoken 

 of Selenites existed, we should certainly perceive their 

 movements when they Avere collected into dense masses. 

 According to Hnmboldt, however, there is only a noiseless, 

 silent desert there. ^ 



CHAPTER IV. 



COMETS. 



Among the myriads of stars scattered through the 

 vault of heaven, there are none which have so much 

 taxed the imagination of the learned as comets. They 

 have often given rise to the most opposite and most 



1 Mr. Harrison seems to have shown that the moon really gives out heat, and 

 that the heat which it receives and radiates to the earth is what Professor Tyn- 

 dall calls dark heat, or what would be almost wholly absorbed by our atmospheric 

 vapour. This, by raising the temperature of the air above the clouds, would 

 diminish their density, and raise or disperse them. In either case there would 

 be a fall in the temperature near the earth ; and the tabulated results of tem- 

 perature at Oxford, CJreeuwich, aud Berlin, taken for several years at each place, 

 agree in showing that at the time when, by calculation, the moon must have ac- 

 c^uired the greatest heat, the average temperature on the earth's surface was lower, 

 accompanied by a dispersion of cloud. — Tr. 



