CHAPTER III. 
PNEUMATIC TELEGRAPHY. 
History—Arrangement of the Tubes—Carriers—Apparatus and Engines for 
condensing and exhausting air—Utilizing the compressed air—Motion of 
the Carriers—Accidents—Continuance of the service during derange¬ 
ments—Systems of Tubes in Paris and Berlin—Bell for compressed air. 
The first sending of despatches by air pressure was, according 
to the Abbe Moigno, accomplished by Ador in 1852, at the Parc 
de Monceau. In 1854, M. GalvCazalat in France, and Mr. L. 
Clark in England, took out patents for a system of forwarding 
letters in tin cases. About the same time, Mr. Clark fixed in 
the central telegraphic office in London (Telegraph Street), 
some short lengths of tube in which he caused the cases to move 
in either direction by exhausting the air. 
In 1863, Mr. C. F. Varley completed this arrangement, by 
making use of compressed air for sending the cases in one direc¬ 
tion, and of rarefied air for sending them in the other direction. 
Mr. Varley also contrived various kinds of valves which we 
shall presently describe. 
In 1865, Messrs. Siemens and Halske laid down a peculiar 
arrangement of pneumatic tubes between the telegraph office 
and the Exchange at Berlin. Two tubes were placed side by 
side and connected together at one end so as to form a complete 
circuit. The two free extremities terminating at the telegraph 
office were connected with two reservoirs, one of compressed, 
and the other of rarefied air, furnished by the continuous 
operation of a double-action piston, driven by a steam engine. 
In this way a current of air constantly passed through the 
tubes in the same direction ; and v hile one of these tubes 
served to convey the cases in one direction, the other conveyed 
them in the opposite direction. The length of the current was 
