64 
THE TELEGRAPH, 
and intended to gather the water that condenses in the pipes. 
These wells are formed of a cast-iron box (Fig. 26) terminated 
by a pipe of the same diameter as the tube. A pipe, closed by a 
screw at the upper part, communicates between the well and a 
cast-iron box placed on the level of the pavement, and by this 
pipe the water can be removed when required. 
The carriers are similar to those used with Clark’s tubes, 
but differ by their greater size, and by having a gutta-percha 
cover, kept in its place by an elastic band. A second covering 
of felt with a funnel-shaped ending is also added at the 
extremity of the carrier. 
Fig. 27 . 
The receiving and transmitting valves are represented in 
Figs. 27, 28, 29, and 30. The valve is formed by two lengths 
of tube, t and r, of the same diameter as the conveying tube, 
fitted on a frame that revolves on the axis A. One or the 
other of these lengths of tube is thrown into the circuit 
according as it is required to transmit or to receive. 
The tube t being open throughout its whole length, the 
carrier that has to be despatched is simply placed in it, and t 
is then brought into continuity with the circuit by pulling the 
handle j?; the air-current bears off the carrier the moment t 
comes into the position shown by the dotted lines in Fig. 29. 
Figs. 29 and 30 show the apparatus in the receiving 
position. The tube r, then in the line of the conveying tube, 
is closed at one end by a disc pierced by small openings. 
