CHAPTER III. 



ADDITIONS TO OUR KNOWLEDGE OF THE FIXED STARS 

 AND NEBULJG. 



SECTION I. 



DETERMINATION OF THE PARALLAX OF FIXED STARS. 



UNTIL recently, astronomers had been unable to meas- 

 ure the distance of a single fixed star. The parallax 

 arising from the motion of the earth in its orbit, even for 

 the nearest fixed star which had been examined, remained 

 concealed among the small errors to which all astronomical 

 observations are liable. Nevertheless, it was generally 

 agreed among astronomers that no star visible in north- 

 ern latitudes, to which attention had been directed, mani- 

 fested an amount of parallax exceeding a single second of 

 arc. An annual parallax of one second implies a distance 

 of about twenty millions of millions of miles, a distance which 

 light, traveling at the rate of 192,000 miles per second, 

 requires 3 years to traverse. This being the inferior limit 

 which the nearest stars exceed, it is not unreasonable to 

 suppose that among the innumerable stars which the 



