of an Electrie Current by Magnetic Action. 133 
be about 12700 10-", for a’field of intensity 1660. In looking 
about for an explanation of this disagreement I found that the 
thickness of the strip had been called -00104 cm. in 1881, and 
‘0012 cm.in the later experiments. The former estimate was 
obtained by weight, the latter by measurement with calipers. 
The difference accounts well enough for the different values 
obtained for the R. P. Which estimate of the thickness is the 
more reliable I will not undertake to decide. 
Summary. 
Tron +7850 
_R. P. nearly constant through wide range of magnetic inten- 
ity but apparently decreasing slightly at high intensities. 
No ascertained permanent effect. 
OL Re a ea aan +12060 
Permanent effect about 5 per cent of temporary effect. 
Steel, tempered,.......-.-.------ .-.----- $+ 33000 
Permanent effect about 14 per cent of temporary effect. 
Gold (no new test of magnitude of R. P.) .. —660 
No ascertained permanent effect. 
NOUN i ils seu bce ied Rok +2460 
Nickel _.  —14740 
Me es —8580000 
AIO 6 oc Sedna ant eon es +114000 
A fall of 1° C. in temperature causes 
in the R.P. of Iron, a fall of } per cent approx. 
Steel, soft, ~ oe : 
Steel,temp’d, “ 4 S 
obalt, we. a 
Nickel 8 
Non-magnetic metals, apparently a small 
Au, Jour, Sor—Turep Serres, Vor. XXIX, No. 170.—Fxs., 1885. 
9 
