BURGESS AND WALTENBERG: MELTING POINTS 371 



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a priori that it should; and this effect has been clearly traced 

 back to 1750, or to the time of the earliest reliable records. 

 Hence it is safe to say that such a relation between volcanic 

 dust in the upper atmosphere and average temperatures of the 

 lower atmosphere has always obtained, and therefore that vol- 

 canic dust must have been a factor, possibly a very important 

 one, in the production of many, perhaps all, past climatic changes, 

 and that thru it, at least in part, the world is yet to know many 

 another climatic change in an irregular but well-nigh endless 

 series — usually slight tho always important, but occasionally it 

 may be, as in the past, both profound and disastrous. 



PHYSICS. — Melting points of the refractory elements. I. Ele- 

 7nents of atomic weight from 4-8 to 59. G. K. Burgess and 

 R. G. Waltenberg, Bureau of Standards. To appear in 

 The Bulletin of the Bureau of Standards. 



The elements included in this list are the iron group: nickel, 

 cobalt, iron, manganese and chromium, and also vanadium and 

 titanium. In subsequent papers results will be given on other 

 refractory elements now being studied, and it is hoped eventually 

 to include all the available refractory elements in this series of 

 melting point determinations. The method mainly used is that 

 of the micropyrometeri which, with substances that melt sharply 

 as nickel, cobalt and iron, permits working to a precision of 1 or 

 2 degrees with a few thousandths of a milligram of the material. 



An estimation of the melting points of the iron group elements^ 

 was made some years ago by a similar but less sensitive method 

 at a time when none of these melting points was well known. 

 The object of these earlier measurements was primarily to demon- 

 strate the convenience and reliability of the method especially for 

 those elements which can be obtained pure only in minute quan- 

 tities. It is believed that the present series of determinations, 

 with the improved apparatus, will contribute to a more exact 



1 A micropyrometer, by G. K. Burgess, Jl. Washington Academy of Sciences, 

 3:7. 1913. Phys. Zs., 14: 158. 1913. Bull. Bureau of Standards, 9: 475. 1913. 



2 Melting points of the iron group elements by a new radiation method, by 

 G. K. Burgess. Bull. Bureau of Standards, 3: 345. 1907. 



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