The Moon. 



Just as the sun possesses in the planets its satellites, 

 so also the majority of the planets have satellites of 

 their own. Of such minor orbs the telescope has reveal- 

 ed 3 attached to Mars 5 to Jupiter, 8 to Saturn *) 4 to 

 Uranus, 1 to Neptune, and finally one, Belonging to our 

 own earth, is sufficiently visible to the naked eye. This 

 last-named is our moon. 



As the number of a planet's satellites is in direct pro- 

 portion to its distance from the sun We must suppose 

 that Uranus and Neptune possess more satellites than 

 are yet known to astronomy, but that, owing to their 

 great distance from our earth they evade scientific rese- 

 arch. The sphere of such research is however widening. 

 Till 1892 only 4 moons had been discovered round Jupi- 

 ter, but in that year a fifth was added. This was closer 

 to its planet than the others and was only revealed 

 accidentally thanks to an eclipse of Jupiter by Mars. 

 Jupiter is separated from the earth by 580.000,000 versts, 

 and it took thousands of years to disclose its fifth satel- 

 lite; but Neptune is distant from us 4,030.000,000 versts, 

 and it is scarcely to be wondered at that astronomical 

 investigation directed across such an inconceivable inter- 

 val should have failed to detect multitudes of bodies 

 swimming in that vast space. 



For a long time the question, What is the moon? con- 

 stituted the pium desiderium of the learned astro- 



*) A ninth and more remote satellite of this planet was discove- 

 red according to an announcement of the Lick Observatory 

 in 1904. 



