VARIOUS APPLICATIONS OF TELEGRAPHY. 277 
A certain number of secondary circuits, with their centre at 
the fire-stations, are arranged in each circle. In general 
these secondary circuits are provided with automatic alarms 
only ; but this rule is not absolute. There is also a suburban 
circle with overhead wires ; the other circuits being connected 
by underground wires. There are thus three principal 
circles, thirteen secondary circles, and one suburban circle, 
fifty Morse instruments, and one hundred and thirty-five 
automatic fire-alarms. All the lines work with a closed 
circuit. The Morse apparatus is mounted in the same way 
as at Hamburg, and the communications are made in the same 
manner. Loud bells fixed on the banks of the canals give the 
alarm to vessels. At the central station there is an electro¬ 
magnet which gives the alarm to all the stations, and by means 
of combinations of bells the central station can call any 
station separately, or all together. The machinery of the 
bell-alarm is set in motion by a weight, the current having 
only to liberate a detent, precisely as in the system of railway 
calls we have described above. 
The third system of fire telegraphs is that used at Frank- 
fort-on-the-Maine. Like the first, it is radiating, but the 
sectional lines are provided with branches. There are eight 
principal circuits and thirty-six branch circuits. The former 
connect stations furnished with apparatus for transmitting 
messages ; the latter have only calls or alarms. In all there 
are twenty-five Morse stations, thirty-one instruments, and 
fifty automatic alarms. 
No house is more than 600 yards from an alarm; and at all the 
stations officials are on duty night and day. The whole of the 
principal lines which connect the Morse apparatus and the 
alarms with the central station present a length of 3,300 yards, 
and are laid underground with insulated iron-wire. Besides 
the underground lines there are 2,000 a yards of overhead wires, 
connected only with bells fixed in the dwellings of the regular 
or volunteer captains of brigades, and in the police-offices. 
These lines work with a closed circuit, as at Hamburg and 
Amsterdam. 
The fire telegraphs in America resemble those we have just 
described, except that in cities an automatic arrangement 
acts at a central station, and at the same time as the alarm is 
