Nov. 27, 1873] 



NATURE 



65 



The system of Pneumatic Despatch, or " Atmospheric 

 Telegraph," as the French call it, is utilised to a much 

 greater extent in Paris than in London, though with 

 some important differences in construction and object. 

 We have thought that some details concerning the 

 working of this system in Paris might be useful and 

 interesting at the present time, and we therefore give an 

 abstract of some articles on the subject which have re- 

 cently appeared in La Nature. 



The question of the distribution of messages in 

 the interior of towns has revived the systems of pneu- 

 matic transport, which, after having had their day of 

 celebrity, seemed for twenty years doomed to oblivion. 



In following the aspects of this question, we shall show 

 in what way the atmospheric telegraph is a result of the 

 electric telegraph ; we shall afterwards consider the 

 former more specially, and after having shown its present 

 condition, shall inquire what future is irt store for it. 



The telegraphic despatch has become an article of every- 

 day use ; as the age is a fast one, it is natural that it 

 should utilise with eagerness so handy a means of trans- 

 mitting almost instantaneously its impressions or its 

 wishes to all distances. It is necessary to remember that 

 a city like London or Paris sends out and receives every 

 day an immense number of telegrams. The wires which 

 serve as conductors of electricity are multiplied in all 

 directions for the purpose of meeting the demands of this 

 traffic. They meet in the interior at the central office. 

 This central station speaks iiybi ct orhi ; in other words, 

 it receives the messages of the city for the purpose of 

 spreading them over the entire world, and it accomplishes 

 also an inverse movement. The aspect with which we 

 are here concerned is the distribution throughout the city 

 itself ; let us see what has been done in Paris to accom- 

 plish this purpose. 



As each house cannot be put in immediate communica- 

 tion with the telegraphic network, it became necessary to 

 adopt some other convenient plan. In the case of Paris, 

 the city is divided into districts of a mean radius of 500 

 metres in order to limit the journeys of the foot-messen- 

 gers. The application of this rule gave fifty points, 

 distant one kilometre from each other, where are esta- 

 blished so many branches of the chief office. 



This system was found, however, not to work well, and 

 was moreover very expensive, for reasons which we need 

 not detail here ; and after I'oituics were tried for some 

 time as a means of sending despatches from the head 

 office to the more important branches, it was resolved to 

 have recourse to the pneumatic tube. We have just 

 referred to the extent to which it has been carried in 

 London. Paris and Berlin followed the example of 

 London in 1865 : we shall speak here of the system of 

 Paris. 



In Paris there are fifty stations, distant from each other 

 about a kilometre, connected by an iron tube, which is 

 interrupted at each station. The central station, by which 

 the transit of messages is effected with the interior, is in 

 the Rue de Crenelle ; there are seventeen district stations, 

 in the Rue Boissy-d'Anglas, Grand- Hotel, Bourse, &c. 



How is this network managed? Like a diminutive 

 subterranean railway, in which the waggons are cylindri- 

 cal boxes and the motive power compressed air prepared 

 in the stations. At the central bureau the trains are 

 formed, composed of as many boxes as there are branch 

 offices to supply. The trains are omnibus when they stop 

 at the intermediate stations, express when they shoot past 

 them. 



Every quarter of an hour an omnibus train leaves the 

 Rue de Crenelle, and accomplishes the distance which 

 separates it from the Rue Boissy-d'Anglas (1,500 metres) 

 in a minute and a half. There it is received in a ver- 

 tical column, and the box which carries the mes- 

 sages to be distributed in the district having been taken 

 out, the others are put into the section of the line which 



runs towards the Crand Hotel, a new box having been 

 added containing messages to be transmitted, which have 

 been deposited since the last train. The train again takes 

 its departure, composed of as many boxes as before ; it 

 goes through the same operations at the Grand Hotel, 

 the Bourse, the Theatre Fran^ais, and at the Rue des 

 Samts-Peres. It re-enters the Rue de Crenelle twelve 

 minutes after its departure, having changed all its boxes 

 and carried back messages for distribution. 



Besides this there is a secondary network, the details 

 of which, however, we need not now enter upon. There 

 is a direct line which goes from the Rue de Crenelle to 

 the Bourse, and to branches in the Champs-Elysdes, the 

 Place du Havre, and the Rue des Halles. On the first 

 run the express trains going and returning, the depar- 

 tures of which are intercalated between those of the 

 omnibus trains, for the purpose of supplying those stations 

 which are busiest, twice every quarter of an hour. The 

 departure is accomplished by pressure, the return by 

 aspiration. The same method of working is applied to 

 the branches, which correspond with the omnibus trains 

 of the principal network. 



The tubes which compose the hnes are of iron, the in- 

 terior diameter being 0-065 metre. They are connected 

 by bridle joints [el brides), and admit of curves having a 

 radius of from 5 to 20 metres. 



Various systems for the production of compressed 

 or rarified air are employed. The first in date 

 is an application of the principles of the apparatus 

 known as Hiero's Fountain. Atmospheric air is decanted 

 from a first receiver B (Fig. i) into a second receiver com- 

 municating with the first by means of the tube bb, by the 

 introduction of water into the receiver B. The air thus 

 forced is drawn into the receiver for the purpose of being 

 dispersed in the tubes. Where the machines are not 

 allowed to be used, the employment of steam is much 

 more economical for the compression of air. Recourse 

 is then had to ordinary pumps, which insure an active 

 service and are subject to fewer causes of irregularity. 

 The latter method has been preferred in recent estab- 

 lishments. 



Trains composed of ten boxes weigh about four 

 kilograms, they are either pushed or sucked along by a 

 difference of pressure of three-fourths of an atmosphere, 

 which gives a mean speed of a kilometre per minute. 



The travellers which take their places on the Lillipu- 

 tian carriages already described are closed envelopes 

 containing messages ; they are piled in groups of thirty 

 or forty in a eurseiir, or box. This box is formed of two 

 cylinders, the interior one of sheet-iron, the outer one, 

 enveloping the former, of leather. To make up a train, a 

 piston must be affixed after the last box, for the purpose 

 of enabling the compressed air to take effect. The piston 

 is a piece of wood provided with a leather collarette, 

 which assumes the shape of the interior of the tube, and 

 forms an almost hermetical joint, without much friction. 



The apparatus at first adopted for receiving and des- 

 patching the boxes having been found neither sufficiently 

 rapid nor convenient, a much more complete system, 

 shown in Fig. 2, is now employed. The figure explains 

 itself : two lines enter the office, each attached to separate 

 apparatus. In the first place, for the purpose of despatch- 

 ing messages, a man opens the doof A by means of the 

 lever ^; the boxes and the piston are thrown into the 

 tube, and await at the bottom the current of air which 

 will propel them. This current is produced as soon as 

 the cock c is opened, which commands the head of the 

 apparatus opposite to the tube. The cock c' distributes 

 the air upon the second fine. In the second place, the 

 receiving door B is opened by a second attendant, who 

 finds the train at the station, and takes out the boxes in 

 order to bring the telegrams to light. The entire appara- 

 tus has somewhat the form of a cannon, only the effect is 

 more blessed, the artillerymen are not exposed to death ; 



