SIDEREAL ASTRONOMY. 341 



tion increasing and diminishing precisely as ought to happen 

 in relation to the annual motion of the earth in its orbit. 

 The variation, thus certain in proof, was so small in itself as 

 to be measured by an angle of scarcely more than one-third 

 of a second a striking example of what is common in every 

 part of astronomy, the attainment of results sublime in their 

 magnitude by methods of the most exquisite minuteness and 

 refinement. Even in this very minuteness of means there is 

 something of grandeur to the thought, seeing what are the 

 objects thus attained. He must be a man of obtuse mind 

 who can regard with indifference the slender lines of spider- 

 web intersecting the field of the telescope, to mark the exact 

 moment when the star passes its axis; or listen without 

 emotion, in the otherwise silent Observatory, to the measured 

 beats of the clock which records with unerring truth these 

 moments of transit.* 



Other astronomers were at work at the same time, and with 

 the same object as Bessel; and the labours of the last fifteen 

 years, combined and compared with those of Struve of an 

 earlier date, have given the parallax and distance of upwards 

 of thirty Stars ; not with equal certainty in every case, but 

 continually approximating to it. Henderson and Maclear 

 obtained a parallax of nearly one second for a Centauri, the 

 finest double star of the southern hemisphere, thus placing it 

 three times nearer to us than 61 Cygni ; while a Lyrse, another 

 bright star, yielded to Struve a parallax of little more than a 

 quarter of a second, indicating thereby a distance of 771,400 

 times that of the earth from the Sun, and a time of twelve 



* We may mention here that Mr. Bond, by a happy adaptation of one science 

 to another, has applied an electrical apparatus of admirable construction to the 

 still more instantaneous and perfect registration of astronomical events. 



Another eminent American astronomer, Mr. Mitchel of the Albany Observa- 

 tory, has given us what he terms a personal equation for astronomical ob- 

 servers, founded on the different capacity of different persons for receiving and 

 recording instantaneous impressions on the eye. 



