GALILEO AND HIS JUDGES. 61 



Another suggestion, and a rather amusing one, on 

 the opposition side, was that all things in motion 

 require occasional rest, as we see to be the fact with 

 animals ; therefore the Earth, if it were constantly 

 moving, would stand in need of rest an argument, 

 I suppose, which needs no very elaborate answer. 



In the third day's dialogue a question is raised, 

 and sifted at great length, as to whether a certain 

 newly observed star in the constellation Cassiopeia 

 was in the firmament among the distant fixed stars, 

 or "sublunar," i.e. nearer to the Earth than the Moon. 

 This star was probably the same as the very re- 

 markable one first observed by Tycho Brahe in 1572, 

 which attained a brilliancy so extraordinary, that 

 it is said to have been equal to the planet Venus, 

 and to have been visible to good eyes in full daylight ; 

 in about a month's time it appeared to grow smaller, 

 and gradually faded away until it disappeared entirely 

 about six months after it was first discovered. This 

 was some years before the invention of the telescope, 

 and the observations were deprived of any assistance 

 they might have gained from that source. The star 

 was one of the most noteworthy of all the variable 

 stars on record. 



There followed upon the mention of this star, a 

 dissertation on the method of finding the distances 

 of the heavenly bodies by parallax. The principle 

 of this method was, as we may suppose, well known 

 to Galileo ; but he probably did not allow sufficiently 

 for the great difficulty in taking accurate obser- 



