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XXXVIII. Exjperimental Besearches on the Transmission of Electric Signals through 
Submarine Cables. — Part I. Laws of Transmission through various lengths of one 
Cable. By FLEEMmG Jenkin, Esg. Communicated by C. Wheatstone, Esq., F.R.S. 
Eeceived May 20, — Eead June 19, 1862. 
In a paper by Professor W. Thomson “ On the Theory of the Electric Telegraph,” com- 
municated to theEoyal Society in 1855*, the peculiar circumstances affecting submarine 
wires were especially analysed, and it is probable that all the laws regulating the trans- 
mission of signals could, by further development, be deduced from the mathematical 
theory there stated, if the necessary constants were known. 
It is hoped that some account of an experimental research into the same subject may 
be found interesting, especially as the experiments not only confirmed the conclusions 
arrived at by Professor W. Thomson, but led also to the discovery of several facts of 
considerable practical importance. 
With the view of elucidating the present subject, many experiments have been made 
on the charge and discharge observable at the near end of a cable ; but although this 
charge is intimately connected with the retardation of signals, the connexion is compli- 
cated, and many false deductions have been drawn from the facts observed. 
The author preferred to make his experiments on the signal or current actually 
received at the far end of the wire, the object being to establish a direct relation between 
the causes operating at one end and the effects observed at the other. Some experi- 
ments of this kind have also been made, but the instruments used have been such as 
could only indicate some one point of the complete phenomenon, such as the presence 
or absence of a given current, and the conclusions so arrived at vary with the nature of 
the instrument employed. 
The author used an instrument by which he was able to follow the phenomena 
throughout, observing the nature and magnitude of every change produced in the received 
current. An attempt was first made to obtain by experiment, from various lengths of cable, 
and with various battery power, the curve given by Professor Thomson in the above- 
named paper, and called by him “ the curve representing the gradual rise of the current 
in the remote instrument when the end operated on is kept permanently in connexion 
with the battery.” This curve will in the present paper be called the arrival-curve. 
The effect of continually repeated signals of various kinds was next studied, with 
various lengths of cable and various arrangements of battery, in order to determine in 
each case the practicable speed f of signalling. 
* Vide Proceedings of the Eoyal Society, May 1855, and Philosophical Magazine, S. 4. vol. xi. p. 146. 
t In this paper, where the words “speed of signalling” or “rate of transmission” are used, the author 
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