OBSERVED IN THE WIRES OF THE ELECTRIC TELEGRAPH. 
63 
is suspended, of which the lower end is made to preponderate, so that the natural 
position of the needle is vertical. The only alteration made to adapt this instrument 
to the purpose was supporting the needles on knife edges instead of circular bearings, 
and diminishing the gravitating preponderance of the lower end of the needles, which 
alterations increased the sensitiveness in a high degree. 
The preliminary experiments were directed towards ascertaining whether the de- 
flections were attributable to the electricity passing from the atmosphere along the 
wire to the earth. The observations were frequently repeated on wires from forty 
to fifty miles in length, and their results may be briefly stated as follows: — 
Wires insulated from the earth throughout their entire length produced no deflec- 
tion in either instruments. 
Wires having an earth connection only at one extremity produced no deflection, 
A complete circuit made by uniting both extremities of two wires, each forty-one 
miles long, and insulated from the earth throughout their length, produced no de- 
flection. 
But in every case deflections were obtained from a wire having an earth connec- 
tion at both extremities. 
Two wires having earth connections at both extremities produced a larger deflec- 
tion than one wire. 
A later experiment on the same subject showed that a wire having an earth con- 
nection at one extremity, and another earth connection near the middle of its length, 
gave a deflection on the part of the wire between the two earth connections, but 
none on the part beyond. 
In watching the operations of the galvanometers when in circuit with a wire having 
two earth connections, it was observed that the needle was rarely found to remain 
in the same position many minutes, large variations taking place sometimes in a few 
seconds, and it became interesting to ascertain if these changes coincided at both 
ends of the wire. 
In order to submit this to experiment, simultaneous observations were made at 
intervals of five minutes for twenty-four hours on two galvanometers, one at Derby 
and the other at Birmingham, each connected to the same wire. 
Mr. CuLLEY took the observations at Birmingham, while I took those at Derby, 
each being assisted by an intelligent telegraph clerk. In addition to the galvano- 
meters, the wet and dry thermometers were also noted at every observation. 
The results of these observations are given in diagram No. 1, and allowing for the 
differenee in delicacy of the two galvanometers, there is enough to show that the 
currents were simultaneous in all their changes ; it was also evident from this experi- 
ment that the direction of the current was the same at both extremities of the wire. 
This fact, together with those previously mentioned, indicates that the currents 
which produce deflections do not arise from the transit of electricity between the 
atmosphere and the earth, but that from whatever cause the currents originate, they 
