996 BIE. F. JENKIN’S EXPEEIMENTAL EESEAECHES ON THE TEANSMISSION 
were a little above the zero-line, those sent by the single currents were, as usual, near the 
middle of the range. This was the only difference observed ; the amplitudes and relative 
position of the dot and dash were identical. The use of reverse currents, therefore, 
does not alter the limit set hy the gradual diminution of the received signals^ nor that set 
by their interference. 
It is just possible that some small effect may be produced by a difference in the insu- 
lation when reversals are used, but there is no reason to suppose that this difference 
would be in their favour. 
Abandoning reverse currents, the author was led to seek some other remedy for the 
confusion observed. One phase of this confusion might be described by saying that 
the mean strength of the current rose above 50 when dashes were sent, and fell below 
it when dots were sent, so that the dots and dashes appeared on different parts of the 
scale. The high position of the dash was due, as has been shown, to the comparatively 
short contact at A with earth after the long battery-contact. By making the second or 
earth-contact longer, the dash would be brought down in the scale. If the earth- 
contact were made equal to the battery-contact, the dash would simply become a dot 
sent at a slower rate. The mean strength of the current during the slow or long dots 
would be the same as that during the quick or short dot. The bottom of the long dot 
curve would be lower than the bottom of the short dot curve, and therefore, when the 
long and short dot were combined, there would still be considerable confusion. More- 
over, if a Morse receiver or analogous instrument were used, the spaces separating the 
long dots would be twice as long as those separating the short dots, and this unequal 
spacing would cause fresh confusion. 
These effects, consequent on making the second contacts always equal to the first, 
were well seen when the signals called A® were sent The tendency observed in the 
original dot and dash was over-corrected. The dash now fell too low, and the dot not 
low enough, so that the confusion was nearly as bad as before ; but the required cor- 
rection was clearly enough pointed out. If, instead of keeping the mean strength of 
the current constant, the current at the end of each signal could be kept the same, the 
passage from one signal to another would cause no confusion, for the beginning or end 
of a dot would be exactly like the beginning or end of a dash. It was plain that the 
current at the end of a dash could be brought to any required point (and therefore to 
the point at which dots finished) by simply altering the proportion of the second to 
the first contact. Experiment had shown that the second contact was too short when 
made only half the length of the first, and too long when made equal to the first ; no 
doubt some intermediate length would fulfil the required condition that the dashes 
should begin and end at the same division of the scale as the dots. The experiment 
required to prove this could clearly not be tried by aid of the metronome, and the appa- 
ratus shown in fig. 8 was therefore arranged so as to make contacts of any required 
proportion. 
* So called because tbe dot and dash, followed by a short pause, represent the letter A in the Morse alphabet. 
