82 On the Municipal Electric Telegraph, 
This very useful and ingenious instrument can be best described 
as the converse of a rotary pump. I have satisfied myself that _ 
the falling arm liberated by the electro-magnet, could be made to 
open the water-valve, and that a meter supplied by an inch or 
inch and a half pipe, would furnish ample power to lift the ham 
mer required for any of the City bells. For this purpose an arm 
may be placed across the axis of a meter, each end of which, m 
revolving, would raise the lever connected with the hammer hat 
dle above. The hammer would thus be raised at every hall 
revolution of the meter. As the pressure of the water is liable 
to vary, or as it may be completely withdrawn, an intermediate 
reservoir of water under the pressure of air, condensed by the 
previous entrance of water from the pipes, the return of which 
Is prevented by a valve, would seem to be necessary. This 8 
the chief objection to its use. Greater electro-magnetic powel 
would be required to work a water-valve, than the air-valve rep | 
resented in the last figure. ) 
The principal instruments employed in the Fire Alarm System 
are included under no existing patent, although Mr. Farmer lt 
serves to himself the right to those parts of the mechanism which 
he has originated. The electro-magnetic Register, patented by 
Professor Morse, constitutes, however, an exception. — It is desil® 
ble to use this instrument for the record at the Central Office, ® 
its principle is in harmony with the rest of the System. Ont 
account, and also to set at rest any other claim under the patent 
‘the electro-magnetic Telegraph, I should recommend, in ® 
cases of construction the purchase of the right to the use of the — 
Morse instruments in connection with the System. ‘This has a 
cordingly been done by the City of Boston. —_ 
The following table furnishes an approximation to the cost of 
different parts of the System, erected in Boston, which is of I _ 
terest in connection with future constructions. 2s 
Average cost per mile of 49 miles wire, (erected) . $68 ” 
e “of wire No.8, permile, . .  . 730 
N ée 
‘ 62 50 
te ec Ge ce oO. 10, ‘ : : sed | 
Striking machine, fig. 9, (including 800 Ibs. weight,) 165 00 | 
Signal Box, apparatus and connections, complete, . 10 00 
District Key-board, fig. 6, (with 12 Keyay, .. : 75 00 
Alarm Bell Register, fig.7, . .  , 10 00 
Office Alarm, fig. 5, . : : Be g 00 
The estimate, furnished by me to the City Government of Bos 
ton, of the cost of construction of the System, was about ] 
not including superintendence or the right to the use of the 
Morse instruments. It is believed that this estimate has not bee? 
exceeded by the actual cost of the parts included in it. An addi- 
tion has been made to the number of Signal Stations and to thé 
