178 SCENERY OF THE HEAVENS. 



movements they might have. This bold and original thinker suffered death at Eome, for 

 apostatising from the Komish church ; but it is believed that his rebellion against the 

 physics of Aristotle contributed to his committal to the flames. " This sentence," said he, 

 on being condemned, " pronounced in the name of a God of mercy, terrifies you more than 

 it does me." Hooke, our own countryman, in the following century, surmised the 

 improbability of the stars being absolutely fixed with respect to each other, and suggested 

 that not only might these bodies be in a state of continual motion, but the whole solar 

 system likewise. But Halley is the first person who, from observation, suspected the 

 proper motion of the stars. In a paper of the year 1718, he stated, that since the days of 

 the Alexandrian astronomers, the stars Aldebaran, Arcturus, and Sinus, must have slowly 

 advanced to the south. A few years later, J. Cassini demonstrated, by the most conclusive 

 evidence, that Arcturus had sensibly shifted in latitude since the time of Tycho Brahe. 

 Bradley soon afterwards remarked, that the apparent motions of the stars might arise either 

 from a movement of the solar system in space, or from a real change in the positions of 

 the stars themselves ; but he avowed the opinion, that many ages must elapse before it 

 would be possible to come to a definite conclusion on the subject. In 1750, the remarkable 

 " Theory of the Universe," published by Wright, assumed the motion of the solar system 

 in space, as well as that of all the stars of the firmament. 



At last, in 1783, Herschel addressed himself to the resolution of the great problem, by 

 forming a catalogue of stars situated in all parts of the heavens, in which an appreciable 

 amount of proper motion had been detected and measured. He justly reasoned, that in 

 case this apparent motion of the stars could be attributed to the movement of the solar 

 system through space, a close scrutiny of the directions in which the stars appear to move, 

 would indicate the direction in which the sun, with its train of planets, is moving. In 

 illustration of the principle of investigation, it has been aptly remarked, that in the instance 

 of a person travelling on a railway, in a direct line through a forest, as he advances, the 

 trees towards which he is moving will appear to open out or separate from each other, 

 while those left behind will appear to close up. " If, then, the astronomer, borne along by 

 the movement of the sun through the vast forest of stars by which he is surrounded, 

 desires to ascertain the direction in which he is progressing, let him search the heavens 

 until he finds a point where the stars seem to be increasing their distance from each other. 

 Should he find such a point, let him confirm his suspicions by looking in the direction 

 precisely opposite, and in case he finds the stars located in this region closing up on each 

 other, he may fairly conclude that he has found the direction in which he is moving, and 

 a rigid coincidence of all the phenomena wotild demonstrate the accuracy of his conclusions." 

 After an extended examination of the subject, Herschel announced his belief that a part of 

 the proper motion of the stars must be attributed to the effect of systematic parallax, or to 

 the movement of the solar system itself ; and that this movement is directed towards a 

 point in the heavens somewhat to the north of the star y Hercules. 



This theory was not supposed in general by the astronomers of the day to be founded on 

 well-determined observations. It was received, therefore, with hesitation and doubt ; it 

 fell into disrepute ; and Herschel died before any confirmation of it had been obtained. 

 But the recent researches of Argelander, Lundahl, Otto Struve, and Peters, on the stars of 

 the northern hemisphere, combined with those of Mr Galloway on the stars of the southern 

 sky, have demonstrated, in the most undeniable manner, not only the fact of the solar 

 motion, but its direction, in close agreement with Herschel's announcement, and its rate. 

 The results of perfectly independent observations have been thus summed up by the elder 

 Struve : " The motion of the solar system in space is directed to a point in the celestial 

 sphere, situated on the right line, which joins the two stars of the third magnitude, . and 

 /^ Hercules, at a quarter of the apparent distance between these stars, measured from *> 





