Curiosities of Science. 83 



as a little world," and as the earth would appear at a distance, 

 with its seas and continents of different shades. As the dia- 

 meter of Mars is only about one half that of our earth, the 

 weight of bodies will be about one half what it would be if they 

 were placed upon our globe. 



DISCOVERY OF THE PLANET NEPTUNE. 



This noble discovery marked in a signal manner the matu- 

 rity of astronomical science. The proof, or at least the urgent 

 presumption, of the existence of such a planet, as a means 

 of accounting (by its attraction) for certain small irregularities 

 observed in the motions of Uranus, was afforded almost simul- 

 taneously by the independent researches of two geometers, 

 Mr. Adams of Cambridge, and M. Leverrier of Paris, who were 

 enabled from theory alone to calculate whereabouts it ought 

 to appear in the heavens, if visible, the places thus indepen- 

 dently calculated agreeing surprisingly. Within a single de- 

 gree of the place assigned by M. Leverrier's calculations, and 

 by him communicated to Dr. Galle of the Royal Observatory 

 at Berlin, it was actually found by that astronomer on the very 

 first night after the receipt of that communication, on turning 

 a telescope on the spot, and comparing the stars in its imme- 

 diate neighbourhood with those previously laid down in one of 

 the zodiacal charts. This remarkable verification of an indica- 

 tion so extraordinary took place on the 23d of September 1846.* 

 Sir John Herschels Outlines. 



Neptune revolves round the sun in about 172 years, at a 

 mean distance of thirty, that of Uranus being nineteen, and 

 that of the earth one : and by its discovery the solar system 

 has been extended one thousand millions of miles beyond its 

 former limit. 



Neptune is suspected to have a ring, but the suspicion has 

 not been confirmed. It has been demonstrated by the obser- 

 vations of Mr. Lassell, M. Otto Struve, and Mr. Bond, to be 

 attended by at least one satellite. 



One of the most curious facts brought to light by the dis- 

 covery of Neptune, is the failure of Bode's law to give an ap- 

 proximation to its distance from the sun ; a striking exempli- 

 fication of the danger of trusting to the universal applicability 

 of an empirical law. After standing the severe test which led 



* Professor Challis, of the Cambridge Observatory, directing the Northum- 

 berland telescope of that, institution to the place assigned by Mr. Adams's calcu- 

 lations and its vicinity on the 4th and 12 th of August 1846, saw the planet on 

 both those days, and noted its place (among those of other stars) for re-observa- 

 tion. He, however, postponed the comparison of the places observed, and not 

 possessing Dr. Bremiker's chart (which would at once have indicated the pre- 

 sence of an unmapped star), remained in ignorance of the planet's existence as a 

 visible object till the announcement of such by Dr. Galle. 



