392 Scientific Intelligence . 
If a third of the needle, reckoning from its middle, is sur- 
rounded in a spiral manner, with waxed taffetas, then the poles 
appear at the points where the spiral begins and ends. If, in- 
stead of a spiral wire, a rod of metal is extended along the glass 
tube, the steel needle placed within becomes feebly magnetic af- 
ter several strong electrical discharges. 
The poles of a magnetic needle were entirely reversed by 
several electrical discharges along the spiral. 
9. Experiments of M. Bockman on the intensity of Magne- 
tism produced by Electricity.'— Dr Bockman of Carlsruhe has 
obtained the following curious results respecting the production 
of magnetism by electricity : 
(1.) Electrical shocks from a plate machine 26 inches in dia- 
meter, gave to a steel rod a repulsive 
force upon the magnetic 
needle of 7°. 
(2.) The following repulsions were 
obtained by ’the charge of 
a Leyden phial of 3.7 square inches of interior coating : 
Repulsion on the N, 
Repulsion on the S. 
No. of discharges. 
pole of the Needle. 
pole of the Needle. 
1 
9* 
12° 
2 
15 
16 
6 
18 
18 
24i 
21 
21.5 
36 
20.5 
21.5 
With a Leyden 
phial of 48 square inches of interior coating. 
the effects were : 
1 
n°.5 
19° 
2 
22.5 
24 
6 
27 
29 
14- 
27 
30 
24- 
27 
30 
With a Leyden 
phial of 300 square inches : 
2 
21^.5 
23° 
4 
29 
33 
6 
29 
34> _ j 
18 
29 
34a 
With a battery 
of five jars, with about 300 square inches 
each : 
X 
25°. 5 
26°.5 
2 
29 
30 
3 
30.5 
32 
- 
4 
31.5 
32 
5 
34.5 
35 
6 
34 
QJi 
36 
