2 l8 
THE TELEGRAPH. 
continues insulated at each end. The terrestrial currents that 
tend to pass through it then cease to affect either the trans¬ 
mission or the reception of messages, for they are stopped by 
the condenser. In this case, the connections of the apparatus 
are those represented in fig. 156. 
The condenser or accumulator is the name given to an 
Fig. 154 
apparatus consisting of alternate layers of metallic paper, and 
paper saturated with wax or paraffin, or films of mica or of 
gutta-percha arranged so as to form a Ley den-jar of great 
extent of surface, and so constructed as to have a given electro¬ 
static capacity, a , a 17 a 2 , b, b 19 b 2 , fig. 157, are square 
sheets of tin-foil separated by thin leaves of paper soaked in 
paraffin or some other insulating substance. The series a, a 19 
# 2 , are connected together, and so are the series b, b 19 & 2 . a 
and b are likewise connected with what may be termed the 
