990 ME. F. JENKIN’S EXPEEIMENTAL EESEAECHES ON THE TEANSMISSION 
14^ seconds, traversed 262 divisions of the scale, or the received current had diminished 
94‘6 per cent, in that time. The fourth and fifth columns give these two numbers. It 
will be seen from these columns that, measuring from the starting-point, the spot of 
light traversed the same distance on the scale in the same time when the current was 
falling as when it was rising. From this we conclude that the rate of decrease in the 
current received at X after the contact had been made for a given time with earth at A, 
was the same as the rate of increase observed after making contact with the battery at A 
for an equal time. 
Table XII. contains a very perfect set of similar observations with 2192 knots in 
circuit. The arrival-curves for 1006 knots and 2192 knots constructed from Tables YII. 
and XII. are shown in fig. 7, Plate L. 
The same connexions (fig. 1) were used to test the efiect of practical signals, the 
Morse key being moved up and down in time with a metronome. The signals sent 
were the dot and dash, or dot and line, singly and combined. These signals are the 
simplest of all, but the conclusions drawn from them are applicable to all other signals 
depending on the time during which a given strength of current flows. 
The headings of the several columns explain the contents of Table IV., which shows 
the observations made when various signals were sent at various speeds through 1500 
knots of cable. Tables VI., XIII., and XIV. contain similar observations made with 
other lengths of cable in circuit. It should be observed that the effects recorded are 
those which occur when the same cycle of operations has been constantly repeated for 
some time, and are quite distinct, as will presently be shown, from the effects produced 
when signals of the same kind are for the first time sent through the cable. 
The first set of observations recorded in Table IV. may be explained as follows. The 
metronome was set so as to beat 130 times in the minute. The Morse key alternately 
connected the cable at A vsuth a battery of 72 Daniell’s cells, and with the earth-plate 
for 0’462 second. The signals sent are called dots, because the sixty-five short con- 
tacts with the battery, each followed by an equal contact with the earth, would, through 
a short cable or air line, have transmitted sixty-five distinct currents, each capable 
of printing on the common Morse receiving instrument sixty-five equally spaced dots. 
While the contacts were regularly repeated, the spot of light moved steadily back and 
forward from the 85th to the 80th division of the scale. By reducing these deviations 
to a percentage of the maximum deviation (200 divisions), we obtain the numbers 42‘5 
and 40. The variation of the strength of the received current was therefore 2^ per cent. 
All these numbers are entered in the several columns of the Table. 
The figures annexed to the Tables show by curves the changes of the received cmrent. 
The abscissae of the curves correspond to intervals of time, and are taken from the fourth 
column. The ordinates correspond to the strength of the received current at each 
moment, reduced to a percentage, and are taken from the eighth column. The ordi- 
nates, instead of being measured from a true base-line, are measured from a horizontal 
dotted line, of which the ordinate is 50. 
