of an Electric Current by Magnetic Action. 129 
CoBALT. 
In the Philosophical Magazine for September, 1881, I said, 
“No thin strips of the metal [cobalt] being at band, a slice was 
sawn from a small block of moderately pure cast cobalt and 
worked into the form of a cross. To the extremity of each 
arm of this cross was soldered a thin strip of copper... . for 
the purpose of making the electrical connections. The cross of 
cobalt with the copper strips attached was now fastened with 
hard cement {beeswax and rosin] to a strip of glass,” ete. It 
fogether with certain other particulars which may have intro- 
ped & constant error of several per cent into the values 
tained for the rotatory power. 
No, of Exp, Date. Temp. M. C. R.P. 
1, Deo. 22; 89, 8° 34638 1251 +2092x10~" 
3. « 13° 1243 42061 
9° 2076 
2. « 18° «“ 1238 «+2441 
4, ce c “ 1244 +2390 
18 . Pals 
Decrease of R. P. for fall of 1° 0. is approximately 7; per cent. 
BisMUTR. 
thy can only confirm what Prof. Righi* has already published 
neerning the rotational effect in this metal. The rotational 
i. appeared to be about 260 times as great numerically as 
me tempered steel and of the opposite sign. 
. _4€ slice of bismuth used was obtained, shaped and mounted 
Much the same manner as the slice of cobalt already de- 
The length and breadth of the bismuth cross were 
greater than the corresponding dimensions of the 
the thickness was about 1 mm. : 
* Acc. dei Lincei Transunti, June, 1883. 
Somewhat 
cobalt and 
