OF ELECTEIC SIGNALS THEOEGH SUBMAEINE CABLES. 
989 
were wanted, one noting by the seconds hand of a watch the interval between the sound 
of the contact made by the Morse key, and the sound of a little blow struck by the 
other at the moment when the spot passed the given division. 
Only one observation could in general be made each time the current entered the 
cable. The results of the observations are given in Table I. 
The maximum current from a battery of 72 Daniell’s cells caused a deviation of 130 
divisions. The strength of this pennanent current depends simply on the electromotive 
force of the battery and the resistance of the various parts of the circuit, being quite 
independent of the inductive phenomena. 
The first column shows the number of seconds during which the current had been 
flowing into the cable when the spot had reached the division of the scale entered 
immediately beneath in the second column. The third column shows the percentage 
of the maximum deviation, or strength of current, to which the figures in the second 
column correspond. Thus, when the Morse key had been pressed down for eight 
seconds, the spot of light was just passing the 100th division of the scale, showing that 
the current had attained 77 per cent, of its maximum strength. One part of the arrival- 
curve might be constructed by using the entries in the first and third columns as 
coordinates. 
The whole cmwe could not be obtained because the movement of the spot of light 
during the first four seconds was too rapid to allow of observation. 
Table II. contains a similar set of observations made with 36 Daniell’s cells instead 
of 72. By comparing the third lines of the two Tables, it is seen that the same percent- 
age of the maximum strength is reached in the same time with both batteries, or, in 
other words, that the electromotive force of the battery has no appreciable effect on the 
velocity with which the current is transmitted. 
All the variations of the received current are therefore in the Tables reduced to 
percentages, or to the variations which would have been observed if the permanent 
current due to the battery used had produced a maximum deviation of 100 divisions in 
each case. This condition could have been practically fulfilled, but was thought 
unnecessary, as no change of the battery would have altered the percentage of variation 
observed in the received current. 
Table III. shows some observations for the arrival-curve with 1500 knots of cable in 
circuit. 
Table VII. contains the result of a similar investigation for 1006 knots. The first 
and second columns of this Table contain similar entries to those in Table I. ; the third 
column shows the division passed by the spot when the current was falling, after the 
Morse key had been released for the number of seconds entered above in the first 
column. 
Thus, after the end A of the charged cable had been put in connexion with the earth- 
plate E (fig. 1) for 14^ seconds, the spot was just falling past the 15th division of the 
scale. As the maximum deviation had been 277 divisions, the spot had, during these 
6 T 2 
