THE FIXED STARS. 5 ! 3 



ences of climate and of individual eye-sight affect this considerably. 

 Argelander, and after him Heis, catalogued all the stars visible to 

 their eyes ; their numbers, for the whole northern hemisphere, Avere 

 2,350 and 3,936 respectively. Heis, must therefore, have seen stars 

 at least four tenths of a magnitude fainter than Argelander's faintest. 

 La Caille's eye must also have been sharper than the average ; and, if 

 Mr. Proctor had thought to apply the test of enumeration to the dif- 

 ferent magnitudes in different parts of the sky, this explanation would 

 doubtless have occurred to him, and nothing have been heard of his 

 remarkable " rich region." His observation is valuable, certainly ; but 

 only by showing the undeveloped state of the whole subject, and the 

 precautions necessary before venturing conclusions on it. 



The search for a common center, about which the uncounted mil- 

 lions of stars composing the galactic cluster may revolve, has tempted 

 many investigators, but it can not be said as yet to have proved alto- 

 gether successful. Madler, by calculations from the proper motions 

 of stars in different parts of the heavens, sought to locate it among 

 the Pleiades ; some later astronomers have preferred the Sword of 

 Perseus ; Mr. Maxwell Hall has just decided, and informed the As- 

 tronomical Society of England, that the universe turns about the 

 South Elbow of Andromeda. The proof advanced is always incom- 

 plete, resting on assumptions not generally admitted ; and when we 

 remember that the gravitative force exerted by the fixed stars on one 

 another is so small that to keep the nearest of them from falling to 

 the sun, supposing no counterbalancing attractions, an angular velocity 

 of but one second of arc in eighty years is needed ; that the proper 

 motions to be explained are often far larger than this ; that the dis- 

 tance of the attracting center must be many times that of the near- 

 est fixed star ; and that the heavens give no sign of any preeminent 

 body or group of bodies to which we may ascribe the enormous attrac- 

 tive power necessary to control these motions the skepticism of many 

 astronomers as to the universal center seems excusable. 



It must be admitted, then, that but little of the true character of 

 our sidereal system is known to us, and that all speculation upon it 

 rests as yet on a very insecure foundation. But, as the sudden devel- 

 opment of spectrum analysis has shown, matters of pure conjecture 

 to-day may become entirely settled to-morrow ; and it may reasonably 

 be hoped that the secrets of this domain, if due interest be taken in 

 them, will not much longer elude the search of scientific explorers. 



TOL. xv. 33 



