80 On the sreetpel Electric Telegraph, 
ters I, IL. This Signal is forthwith struck and repeated a few 
times on all the bells. The engines in various and perhaps dis 
tant parts of the me, tu 1 ba na A different signal might be 
employed to order back the South Boston or North End engines, 
and two spare keys, having | connection with only a single cireult, 
may be added to the Key-board for this purpose; or the Agent 
may send such a signal over any Alarm Circuit by means of the | 
Alarm Key. 
10. 
Thei inconvenience of using very heavy 
weights in the Striking Machines hee 
— Which thence arise, as to the 
force of the blow or number of strokes, 
Rk | make it desirable to employ other eet 
Fag) 8 powes such as the pressure of wats 
| confined in pipes within cities, and a's0 
~ | the pressure of condensed air. Fig. 101P | 
kd _| resents an a paratus contrived by Mr. 
; ~ Farmer and myself, by which the pressure 
“y’ [RG of the water in the pipes is made to fur 
“nish a constant su pply of condensed aif; 
| either to operate the air whistle’ : 
" air-engine C, carrying the hammer of the — 
bell. G is the section of a stout metalli¢ 
¢  eylinder—F is a cylindrical float upon ® 
sliding rod. A three-way valve V screws | 
on to the bottom of G by a cap, and is — 
operated by the handle and rod inside. 
vii-""| When the water rises to the upper of the 
two dotted lines, the top of the float raise? | 
the tail-piece t of a small lever, carrying 
an opi arm, with a heavy ball on the top. This or 
beyond the perpendicular and falls over on the other side, as se” 
