O^ THE MAGNITUDE OF THE SOLAR SYSTEM. 



By William Haekness. 



Nature may be studied in two widely different Avays. On the one 

 hand we may employ a powerful microscope which will render visible 

 the minutest forms and limit our field of view to an infinitesimal frac- 

 tion of an inch situated within a foot of our own noses ; or, on the other 

 hand, we may occupy some commanding position, and from thence, 

 aided j)erhaj)s by a telescope, we may obtain a comprehensive view of 

 an extensive region. The first method is that of the specialist, the 

 second is that of the i^hilosopher, but both are necessary for an ade- 

 quate understanding of nature. The one has brought us knowledge 

 wherewith to defend ourselves against bacteria and microbes, which 

 are among the most deadly enemies of mankind, and the other has made 

 us acquainted with the great laws of matter and force uijou which rests 

 the whole fabric of science. All nature is one, but for convenience of 

 classification we have divided our knowledge into a number of sciences 

 which we usually regard as quite distinct from each other. Along cer- 

 tain lines, or, more properly, in certain regions, these sciences neces- 

 sarily abut on each other, and just there lies the weakness of the 

 specialist. He is like a wayfarer who always finds obstacles in cross- 

 ing the boundaries between two countries, while to the traveler who 

 gazes over them from a commanding eminence the case is quite differ- 

 ent. If the boundary is an ocean shore, there is no mistaking it; if a 

 broad river or a chain of mountains, it is still distinct; but if only a 

 line of posts traced over hill and dale, then it becomes lost in the 

 natural features of the landscape, and the essential unity of the whole 

 region is apparent. In that case the border land is wholly a human 

 conception of which nature takes no cognizance, and so it is with the 

 scientific border land to which I x>ropose to invite your attention this 

 evening. 



To the popular mind there are no two sciences farther apart than 

 astronomy and geology. The one treats of the structure and mineral 



'Presidential address delivered before the American Association for the Advance- 

 ment of Science, at its Brooklyn meeting, Angiist 16, 1894. Printed in Astronomy and 

 Astro Physics, Vol. XIII, No. 8; also in American Journal of Science, Vol. XLVIII, 

 September, 1894. 



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