POPULAR SCIENCE REVIEW. 
424 
battery employed is capable of sending through the cable. 
After a further period of five times the same interval (or alto- 
gether ten intervals from the moment of first making con- 
nection with the battery), the strength of the current has 
risen to about 89 per cent, of its greatest possible strength ; 
but by this time, although the current is still getting stronger 
and stronger, its rate of increase has begun perceptibly to 
diminish, so that after another period of five times the interval 
above mentioned its strength is still only about 97 or 98 per 
cent, of the maximum. If at this moment the sending end of 
the wire is disconnected from the battery and connected with 
the earth, the changes which occur in the strength of the 
current at the arrival end are precisely similar to those we 
have just described, though, of course, of the opposite kind. 
At first no diminution occurs in the strength of the current ; 
then a diminution begins and soon becomes very rapid, but 
after a short time again becomes slower and slower ; so that 
when the battery-connection has been broken for a period 
equal to that during which it was maintained, the current at 
the arrival end has diminished by exactly the same proportion 
of its previous highest amount, as that amount bore to the 
greatest current the battery could send through the cable. 
For instance, if the near end of the cable is kept connected 
with the battery until the current at the distant end has 
acquired 90 per cent, of the strength which it would ultimately 
attain if the connection were continued for an indefinite time, 
the diminution in the strength of the current which will occur 
during the same period, after disconnecting the near end of the 
cable from the battery and connecting it with the earth, will 
be to the extent of 90 per cent, of the current which was 
passing at the moment the battery- connection was broken. 
That is to say, after a battery- contact of a certain time, 
followed by an earth-contact of the same length, the current 
at the arrival end, instead of having disappeared, will still 
possess 9 per cent, of the strength of the greatest current 
the battery can send through the cable. 
Hence we see that not only are sudden changes in the elec- 
trical condition of the sending end of the wire not perceived 
immediately at the receiving end, but when they do show 
themselves there, it is as more or less gradual changes of 
smaller extent than those produced at the sending end. It is 
not difficult to conceive how these facts must affect the 
transmission of signals through the wire. The signals all 
consist of changes in the strength of the current passing 
through the receiving instrument, and their distinctness or 
legibility depends on the extent of these changes and on the 
suddenness with which they take place. If the sending end of 
