230 W. Harkness — Magnitude of the Solar System. 



A junction of two very thin bars of bismuth with two per 

 cent antimony, and bismuth with ten per cent tin (which on 

 the whole seem to be the best combination) exhibited the fol- 

 lowing properties: 



Mean temp, of junctions 7 0, 3 17°'0 22°-0 31°*5 36 0i 7 

 E. M. F. per degree 11150 11670 12050 12410 12630 



Plotting these points we find them to lie nearly upon a 

 straight line, from the slope of which we get, for ordinary 

 temperature, the electromotive force of this junction : — 

 10700+412. C. G. S. units. 



Bismuth and Selenium. 



Melted - 5 gm selenium and 15 gm bismuth at first formed a 

 pasty mass which became fluid only above a red heat. It was 

 easily cast into leaves ; extremely brittle and soldered with 

 difficulty. The combination was evidently a mixture rather 

 than a true alloy, for when allowed to cool slowly most of the 

 selenium separated. Several of these mixtures were tested but 

 were found to exhibit but feeble electromotive force, — less 

 than half that of the iron-copper junction. 



Bowdoin College, May, 1894. 



Art. XXXIII. — On the Magnitude of 'the Solar System • being 

 the address delivered before the American Association for 

 the Advancement of Science at its Brooklyn meeting, August 

 16, 1891, by the retiring president, Wm. Harkness. 



Nature may be studied in two widely different ways. 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 infinitessimal fraction 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 perhaps 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 philosopher, but both are necessary for an adequate 

 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 upon which rests the whole fabric of science. All 

 nature is one, but for convenience of classification we have 



