4 THE BORDERLAND OF SCIENCE. 



wish rather to present results than to consider 

 methods. 



Yet the first of Herschel's researches was so full of 

 interest, and led to a result so strange, that it will be 

 well briefly to consider its purport. 



When Herschel began his labours he hoped not 

 merely to determine the general arrangement of the 

 stars throughout the spaces around us, but also to as- 

 certain the real architecture (if one may so speak) of 

 the stellar system. To this end it was necessary that 

 the distances of the stars should be ascertained ; and, 

 accordingly, one of the first subjects to which Herschel 

 applied his powers was the amazingly difficult one of 

 measuring the stars' distances. A method of extreme 

 ingenuity, but also (as was commonly the case with 

 Herschel's devices) of extreme simplicity, suggested 

 itself to his mind. Of course the only real means of 

 determining any star's distance must depend upon the 

 effects of the earth's motion round the sun. If the 

 earth were at rest we should see the star always in a 

 certain direction, but how far off it lay in that direction 

 we could never know. It is because the earth takes up 

 different positions, so that we see a star at different 

 times in different directions, that we have a means of 

 estimating the star's distance. But the earth's path, 

 despite the 180,000,000 of miles of its diameter, is so 

 minute compared with the spaces which separate our 

 sun from the nearest stars, that astronomers had des- 

 paired in Herschel's time of measuring the change 

 of seeming direction due to the earth's motion. An 



