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VI. On the Spontaneous Electrical Currents observed in the Wires of the Electric 
Telegraph. By W. H. Barlow, Esq., M. Inst. C.E. 
Communicated by Peter Barlow, Esq., F.R.S. 
Received May 15, — Read May 25, 1848. 
The observations described in the following pages were undertaken in consequence 
of eertain spontaneous deflections having been noticed in the needles of the electric 
telegraph on the Midland Railway, the erection of which was carried out under my 
superintendence as the Company’s engineer. 
The telegraph is on the principle patented by Professor Wheatstone and Mr. Cooke, 
and the signals are given by deflecting a magnetic needle suspended in a coil of fine 
wire, to the right or left, by means of a galvanic battery. 
Eaeh wire has an earth connection at its two extremities, and when a current is 
made to pass along the wire by means of the galvanic battery, it returns by the con- 
ducting power of the earth. 
When the telegraph instruments are not working, the batteries are put out of 
circuit, and the wires remain with a simple earth connection at both extremities. 
It was in this condition of the wires that spontaneous currents were observed to 
arise in them, producing occasionally large deflections in the needles. These deflec- 
tions were sometimes to the right and sometimes to the left ; at times they changed 
rapidly from right to left, at others they continued in one direction for periods varying 
from a few minutes to one or more hours. 
The system of telegraphs which centres at Derby, consists of four main lines, 
viz. — 
1st. From Derby in a southerly direction to Rugby. 
2nd. From Derby to Birmingham, which approaches a south-westerly direction. 
3rd. From Derby in a northerly direction to Leeds. 
4th. From Derby in a north-easterly direction to Lincoln. 
When these four telegraphs were brought into operation, it was observed that the 
spontaneous deflections were almost invariably simultaneous on all the instruments, 
and that when in the Birmingham telegraph the deflection was such as to indicate 
that the current was passing from the telegraph wires to the earth at Derby, the 
current in the Rugby wires was also passing towards the earth at Derby, while the 
two other telegraphs showed the current to be passingyrom the earth at Derby along 
the wires proceeding in a northerly and north-easterly direction. It was also found 
that when the current took a reversed direction in one telegraph, it was reversed in 
