60 HENRY A. KOWLAXD 



cobalt at ordinary temperatures, and of iron, nickel, and cobalt at high 

 temperatures. 



The rings of nickel and cobalt which I have used in the experiments 

 of this paper were all turned from buttons of metal obtained by fusing 

 under glass in a French crucible, it having been found that a Hessian 

 crucible was very much attacked by the metal. The crucibles were in 

 the fire three or four hours, and when taken out were very soft from 

 the intense heat. As soon as taken out, the outside of the crucible was 

 wet with water, so as to cool the metal rapidly and prevent crystalliza- 

 tion; but even then the cooling inside went on very slowly. As the 

 physical and chemical properties of these metals exercise great influence 

 on their magnetic properties, I will give them briefly. A piece of nickel 

 before melting was dissolved in HC1; it gave no precipitate with H 2 S , 

 and there were no indications of either iron or cobalt. A solution of 

 the cobalt gave no precipitate with H 2 S, but contained small traces of 

 iron and nickel. After melting the metals no tests have been made up 

 to the present time; but it is to be expected that the metals absorbed 

 some impurities from the crucibles. They probably did not contain 

 any carbon. One button of each metal was obtained, from each of 

 which two rings were turned. The cobalt was quite hard, but turned 

 well in the lathe, long shavings of metal coming off and leaving the 

 metal beautifully polished. The metal was slightly malleable, but fin- 

 ally broke with a fine granular fracture. The rings when made were 

 slightly sonorous when struck; and the color was of a brilliant white 

 slightly inclined to steel-color, but a little more red than steel. The 

 nickel was about as hard. as wrought iron, and was tough and difficult 

 to turn in the lathe, a constant application of oil being necessary, and 

 the turned surface was left very rough; the metal was quite malleable, 

 but would become hard, and finally fly apart when pounded down thin if 

 not annealed. When the rings were struck, they gave a dead sound as 

 if made of copper. In both cases the specific gravity was considerably 

 higher than that generally given for cast metal ; but it may be that the 

 metal to which they refer contained carbon, in which case it would be 

 more easily melted. There is great liability to error in taking the 

 specific gravity of these metals, because they contract so much on cool- 

 ing, and unless this is carried on rapidly crystals may form, between 

 which, as the metal contracts, vacant spaces may be left. As the 

 specific gravity of my rings approaches to that of the pure metals pre- 

 cipitated by hydrogen, I consider it evidence of their purity. The 

 dimensions of the rings and their other constants are as follows: 



