PNEUMATIC TELEGRAPHY, 
77 
give here a representation of one of Walcker’s compressed- 
air bells, as an example of this kind of pneumatic apparatus. 
A tube 11 transmits the pressure produced by the hand 
on an india-rubber ball p. 
The little bellows A is blown 
up, and its upper part b in 
rising lifts the lever attached 
to the bell de f and causes the 
hammer g to strike the bell. 
When the india-rubber ball 
is inches in diameter and 
the leaden conducting tube ^ 
in. in diameter, the signals can 
be transmitted to a distance 
of 270 yards. This system 
may be used instead of the 
ordinary door-bell, as the 
tube has, in certain circum¬ 
stances, distinct advantages 
over communications by bell- 
wires. 
M. Guattari, of Berlin, has 
constructed a compressed-air 
telegraph perfectly resembling 
in its signals the Morse tele¬ 
graph. 
He fills a reservoir with 
compressed air by means of 
a hand-pump or by any other machine, and this reservoir is kept 
at a pressure suitable for producing the signals. By his appa¬ 
ratus, which was exhibited at Naples in 1870, very rapid and 
clear signals could be transmitted to a distance of eight miles. 
M. Guattari considers that his non-electrical telegraph offers 
great advantages for employment in mines, oil stores, &c. 
The apprehensions which have been entertained as to the inflam¬ 
mable power of sparks produced by the present electric tele¬ 
graph apparatus are no doubt exaggerated ; but, nevertheless, 
the pneumatic telegraph may be advantageously employed over 
distances not exceeding certain limits. 
