169 
, Ma^'fietim and Galvanism. 
3. If, when the magnetic needle is rendered horizontal by a 
counterpoise, we place the uniting wire in the same horizontal 
plane, and parallel with it, no declination takes place, but the 
needle dips^ so that the pole where the negative electricity en-* 
ters^ is depressed, when the wire is situated on the west side^ 
qjnd RAISED when it is situated on ihe east side. 
4> If the uniting wire is placed at right angles to the mag- 
netic meridian, the needle remains at rest, whether it is placed 
above or below the uniting wire ; excepting in the case when 
it is very near the pole of the needle, and then the pole will be 
raised, if the negative electricity enters from the west, and de-. 
pressed when it enters from the east. 
5. When the uniting wire is placed vertically, and receives 
the negative electricity at its upper end, then, if it is op- 
posite the pole of the needle^ it will turn to the east, but if it is 
opposite a point between the pole- and the centre of the needle.^ it. 
will turn to the west. When the negative electricity enters at 
the lower end, the phenomena are reversed. 
6. If the uniting wire is bent into the form of Z, so as to 
form two parallel legs, it attracts or repels the poles of the needle 
according to certain circumstances of position. If we place the 
wire opposite one of the poles of the needle, the plane of the 
legs being perpendicular to the magnetic meridian, the nega- 
tive electricity entering by the east leg, and the positive by the 
west leg, the pole will be repelled to the east or to the west, ac- 
cording to the situation of the plane of the legs. But if the 
negative electricity enters by the west leg, and the positive by 
the east leg, the pole will be attracted. If the plane of the. 
legs is perpendicular to the magnetic meridian, and opposite a 
point situated between the extremity and the centre of the needle, 
all these effects will be inverted. 
The nature of the uniting wire has no influence on the above 
phenomena. Wires of platina, gold, silver, brass, iron, plates 
of lead and tin, and even mercury, may be employed with the 
same success. Several wires twisted together, or metallic rib- 
bons, may also be used. The uniting wire does not lose its 
effect when interrupted by water, unless when the intemiptioo 
ainounts to several inches in length. 
