VENUS ON THE SUN'S FACE. 59 



nor unreasonable, since we find implanted in our very 

 nature and not merely in the nature of scientific 

 men a quality which causes us to take interest in a 

 variety of matters that do not in the least concern our 

 personal interests. Nor is this quality, rightly con- 

 sidered, one of the least noble characteristics of the 

 human race. 



That the determination of the sun's distance is im- 

 portant, in an astronomical sense, will be seen at once 

 wnen it is remembered that the ideas we form of the 

 dimensions of the solar system are wholly dependent 

 on our estimate of the sun's distance. Nor can we 

 gauge the celestial depths with any feeling of assur- 

 ance, unless we know the true length of that which is 

 our sole measuring-rod. It is, in fact, our basis of 

 measurement for the whole visible universe. In some 

 respects, even if we knew the sun's distance exactly, 

 it would still be an unsatisfactory gauge for the stellar 

 depths. But that is the misfortune, not the fault of 

 the astronomer, who must be content to use the mea- 

 suring-rod which nature gives him. All he can do is 

 to find out as nearly as he can its true length. 



When we come to consider how the astronomer is to 

 determine this very element the sun's distance we 

 find that he is hampered with a difficulty of precisely 

 the same character. 



The sun being an inaccessible object, the astronomer 

 can apply no other methods to determine its distance 

 directly than those which a surveyor would use in 

 determining the distance of an inaccessible castle, or 



