252 PLYMOUTH BRKTHKKN 



PNEUMATIC DESPATCH 



therefore for any member to lead in prayer or praise 

 or to exhort or teach as he may judge to be for 

 edification, guided by spiritually enlightened under- 

 standing of what U fitting and in harmony with 

 what has gone before. Women are not allowed to 

 take public part in the assembly. Persons proved 

 to have been guilty of the sins mentioned in 1 Cor. 

 v. 11 are excluded from the fellowship, as well 

 as those who deny foundation truths 01 Christian 

 doctrine, until evidence of repentance satisfactory 

 to all is forthcoming. The Plymouth Brethren 

 reject every distinctive appellation but that of 

 Christiana, although a special denomination is 

 found necessary to designate them ; no one not 

 holding their views could remain associated with 

 them. A schism took place among them in con- 

 sequence of doctrines preached at Plymouth con- 

 cerning the human nature of Christ ; Darby vigor- 

 ously opposing what he deemed a dangerous error, 

 and he and his adherents utterly separating from 

 the fellowship of those who maintained it, or re- 

 fused to condemn it, and also from all who, even 

 though personally clear of the error, refused to 

 endorse the extreme form of separation demanded 

 by Darby. The Darbyite section since Darby's 

 death has been more than once divided about 

 various questions of doctrine and discipline. The 

 leas exclusive principles have attracted many 

 earnest Christians out of all denominations, and 

 the meeting^ continue to multiply and increase 

 in Great Britain and Ireland, Canada, the United 

 States, Australia, New Zealand, and elsewhere. 

 The increase is mainly the result of evangelistic 

 work. In the United Kingdom there are almut 

 800 meetings ; in Canada, over 100 ; in the United 

 States, about 100; in Germany, 200 ; in France, 150; 

 in Switzerland, 80 ; and in Holland, some 40. 



See the works of Darby, Kelly, C. H. Mackintosh, and 

 J. G. Bellett; and books for or against the doctrines 

 of the Brethren by Trotter (1856), Groves (1867), Reid 

 (1875), Miller (187'J), Teulon (1883). 



Pneumatic Despatch, the name given to a 

 method of sending written documents, chiefly tele- 

 graphic despatches, through a comparatively narrow 

 tul>e by means of compressed air and by a partial 

 vacuum. Early in the 19th century Mr Medhurst 

 proposed to construct a railway on this principle 

 with carriages moving through an air-tight tunnel 

 (see MURDOCK). But Mr La tinier Clark, C.E., was 

 the first to carry out a plan for the transmission of 

 telegrams by pneumatic power. In I8T>3 he got a 

 tube laid between the central station of the Inter- 

 national Telegraph <'Mi|>aiiy and the Stock IX 

 change, London, through \vhicli a carrier containing 

 despatches was propelled by a current of air pro- 

 i! need by connecting the tube with a vacuum holder. 

 An improvement on this was made in IH.'iS by Mr 

 Varley, C.E., who introduced compressed air for 

 the outward and retained the vacuum method for 

 tin' inwiinl trallic. This method is still in use. 



The essentials of a pneumatic despatch are the 

 exhausting and compressing pumps worked by a 

 steam-engine or other motor ; a metal tube, which 

 in England is usually a lead pipe, since it is easily 

 made air tight by soldering the joints; a small 

 carrier of gutta-percha or other material to contain 

 tin- despatches ; anil a suitable arrangement of 

 valves at the stations for connecting the till* or 

 tubes with the compressed air or vacuum mains. 

 It has IMM-II found by experience that with heavy 

 traffic, such as that at the telegraphic department of 

 the London Pont-oflice, a h-ml pipe 2J inches in dia- 

 meter iff a convenient size, and tlii- i- en< -In-ed in 

 an iron pipe for protection. The method of working 

 i this : At the central station end of the t nbe there 

 is a double sluice valve, and when the carrier is 

 inserted into the message chamber (the widened 

 end of the pipe) the lower slide of the valve U 



drawn so as to close the mouth of the pipe, but on 

 the rod of the slide there is a stop which actuates a 

 lever and rack, and this open* the upper slide in 

 front of the carrier. At the same time, by a separate 

 arrangement, a valve is opened to admit compressed 

 air, which forces the carrier forward. Wuea it 

 arrival at the other end of the tube is signalled 

 electrically, the slide is moved so as to cut otl' the 

 air from the pressure main, and then the chamber 

 at the mouth of the pipe is ready for another carrier. 

 From the distant end of the pipe the carrier is 

 drawn or sucked to the central station by making 

 a connection at that station with the vacuum 

 main instead of the pressure main. For a distance 

 of 1000 yards with a 'JJ im-li tube the time of transit 

 is one minute when the air pressure is ]() II.. per 

 square inch or with an equivalent effective vacuum 

 of 64 Ib. per square inch. With the air pressure 

 and vacuum usually employed, a speed of from 25 

 to 35 miles per hour is attained in tulies not exceed- 

 ing a mile in length. The speed varies inversely 

 as the square root of the length of the tube. 

 According to an official statement prepared in 1887, 

 the pneumatic service of the British post-office has 

 been gradually increasing until the system, which 

 in 1854 was represented in London by one 6 horse- 

 power engine working a single tube of a few hun- 

 dred yards in length, comprised, thirty-three years 

 later, in London alone, four 50 horse-power engines 

 (each indicating 130 bone-power), and 81 tubes of 

 an aggregate length of nearly 3-1 miles. In 1887 

 there were in London and the provinces 128 tubes 

 of a total length of 46 miles, requiring fifteen 

 engines with a total of 379 horse-power nominal to 

 work them; 86,000 messages a day were then 

 passed through these post-oHice tulies. The news- 

 paper otlices in several of our large towns have 

 pneumatic despatches in connection with the tele- 

 graphic instrument rooms of their respective poot- 

 ollices. In Paris and some other towns on the 

 Continent, instead of several tubes radiating from 

 a central to outlying stations as in London, one 

 tube or tulies alongside each other from the 

 central telegraph oflice form a continuous ciicular 

 line with intermediate stations, and several carrieis 

 linked together are sent at one time. In the I'nited 

 Males jHistal sen ice, pneumatic despatch M~l"in- 

 are employed in New- York, Philadelphia, and Hus- 

 ton, giving gmxl results in expedition and cconomv. 



PNEUMATIC RAILWAYS AND TRAMWAYS. It 

 has been several times proposed to construct 

 pneumatic railways, one plan being to propel 

 carriages through a large tube or tunnel by ni< 

 of compressed or raielied air. A piece of rail- 

 way of this kind was laid down in the Crystal 

 Palace grounds in 1865 by Mr Kammel. It con 

 si-ted of a single line of rails in a tunnel 600 yards 

 in length, along w hich a carriage conveyed passen- 

 gers. Motion was given to the carriage by using a 

 fan or hollow disc 22 feet in diameter, which either 

 condensed or rarefied the air as required according 

 to the adjustment of certain valves. This railway 

 did not continue long in operation. The driving of 

 t ramvars by compressed air appears more likely to 

 In' a commercial success. At the town of Nantes 

 in France tramcars have Keen propelled by the 

 Mekarski system of air pressure and local heating 

 since IS7II. and a tramway line worked on this prin- 

 ciple was in 1XS9 opened at Paris. In 1890 trac- 

 tion by compressed air was tried at Chester, the 

 tramcar carrying it* own reservoir and engine for 

 a '2 miles' journey, hut having means of recharg- 

 ing the reservoir, if necessary, at intervals along 

 the line. See TRAMWAYS. 



PNEUMATIC I'OWKK (TRANSMISSION OK). The 

 plan of laying down an extensive system of pipes 

 through a city to supply compressed air for motors, 

 elevators, cranes, and other purposes in Kmall, ami 



