,transcrib]'s ,notes3 ,! spell+1 punctuation & hyph5ation are z ! orig9al1 ) ! exception ( app>5t typographical errors :i* h be5 correct$4 ,italic text is d5ot$ ?us4 ,bold text is d5ot$ ?us4 ,illu/ration3 ,,! ,,ma9 ,,po/-,,(fice1 ,,philadelphia4 ,,! ,,pneumatic ,,despat* ,,tube ,,sy/em ,,( ,,! ,,bat*ell] ,,pneumatic ,,tube ,,co4 ,,also ,,facts ,,& ,,g5]al ,,in=mation ,,relat+ ,,to ,,pneumatic ,,despat* ,,tubes ,,by ,b4 ,c4 ,,bat*ell]1 ,b4,sc4 ,,me*anical ,,eng9e] ,illu/ration ,,philadelphia ,,press ,,( ,j4 ,b4 ,,lipp9cott ,,company #ahig ,,copyright1 #ahif1 ,,by ,b4 ,c4 ,,bat*ell]4 ,,cont5ts4 ,,*apt] ,i4 ,a ,,brief ,,hi/orical ,,sket*4 ,,page ,,e>ly ,,records #i ,,practical ,,beg9n+ ,,( ,,! ,,art--,,! ,,london ,,pneumatic ,,telegraph #aj ,,! ,,siem5s ,,circuit ,,sy/em #ad ,,rec5t ,,improvem5ts ,,9 ,,! ,,london ,,sy/em #af ,,an ,,und]gr\nd ,,pneumatic ,,railway ,,= ,,transportation ,,( ,,mail #ai ,,! ,,b]l9 ,,pneumatic ,,telegraph #bj ,,! ,,p>is ,,pneumatic ,,telegraph #bb ,,! ,,pneumatic ,,telegraph ,,( ,,o!r ,,cities #be ,,pneumatic ,,tubes ,,9 ,,am]ica #be ,,*apt] ,,ii4 ,,! ,,pneumatic ,,transit ,,company ,,& ,,! ,,fir/ ,,pneumatic ,,tubes ,,= ,,! ,,transportation ,,( ,,unit$ ,,/ates ,,mail4 ,,organization #bh ,,aim ,,& ,,object ,,( ,,! ,,company #bh ,,! ,,clay-,,lieb ,,pat5ts #cj ,,fran*ises ,,& ,,fir/ ,,gov]nm5t ,,contract #cc ,,se>* ,,= ,,tubes #cd ,,me?od ,,( ,,manufactur+ ,,tubes #ce ,,lay+ ,,& ,,op5+ ,,! ,,tubes ,,= ,,traffic #cg ,,description ,,( ,,! ,,tubes1 ,,me?od ,,( ,,lay+1 ,,etc4 #ch ,,! ,,air-,,compressor--,,me?od ,,( ,,circulat+ ,,! ,,air #dj ,,t]m9al ,,app>atus #db ,,! ,,s5d] #dc ,,sub-,,po/-,,(fice ,,receiv] #dd ,,ma9 ,,po/-,,(fice ,,receiv] #dg ,,! ,,c>ri] #ej ,,op]ation ,,( ,,! ,,tubes #eb ,,b5efits ,,( ,,! ,,sy/em #ed ,,*apt] ,,iii4 ,,! ,,sy/em ,,& ,,app>atus ,,( ,,! ,,bat*ell] ,,pneumatic ,,tube ,,company4 ,,g5]al ,,arrangem5t ,,& ,,adaptability ,,( ,,! ,,sy/em #eg ,,! ,,size ,,( ,,tubes #fd ,,sy/em ,,( ,,v ,,l>ge ,,tubes #fe ,,g5]al ,,arrangem5t ,,( ,,app>atus ,,9 ,,! ,,/ations--,,two-,,/ation1 ,,two-,,compressor ,,l9e #fi ,,two-,,/ation1 ,,"o-,,compressor ,,l9e #gb ,,?ree- ,,to ,,eight-,,/ation ,,l9e #gd ,,s5d+ ,,app>atus #gi ,,s5d+ ,,"t-,,lock #hd ,,int]m$iate ,,/ation ,,"t-,,lock #hh ,,electro-,,pneumatic ,,circuit-,,clos] #ia ,,! ,,op5 ,,receiv] #id ,,! ,,clos$ ,,receiv] #ii ,,! ,,int]m$iate ,,/ation ,,receiv+ ,,& ,,transf] ,,app>atus #ajf ,,c>ri]s #aae ,,air ,,supply #aag ,,fans #aag ,,bl[]s #aag ,,air ,,compressors #aah ,,! ,,tube1 ,,l9e ,,con/ruction1 ,,etc4 #abb ,,*apt] ,,iv4 ,,facts ,,& ,,g5]al ,,in=mation ,,relat+ ,,to ,,pneumatic ,,tubes4 ,,def9itions #abd ,,int]mitt5t ,,& ,,con/ant ,,air-,,curr5t #abe ,,laws ,,gov]n+ ,,! ,,fl[ ,,( ,,air ,,9 ,,long ,,tubes #abf ,,law ,,( ,,pressure #abh ,,uses ,,( ,,pressure ,,curves #acj ,,law ,,( ,,velocity #acj ,,*>act]i/ics ,,( ,,! ,,velocity ,,curve #acb ,,uses ,,( ,,velocity ,,curves #acc ,,quantity ,,( ,,air ,,us$ #acd ,,temp]ature ,,( ,,! ,,air #ace ,,horse-,,p[] #acf ,,effici5cy #acg ,,pressure ,,& ,,exhau/ ,,sy/ems #ach ,,laws ,,express$ ,,9 ,,ma!matical ,,=mul #ada ,,moi/ure ,,9 ,,! ,,tubes #adb ,,location ,,( ,,ob/ructions ,,9 ,,tubes #adc ,,preface4 ,i h be5 prompt$ to prep>e ?is book by ! frequ5t inquiries made reg>d+ ! details ( our sy/em ( pneumatic tubes4 ,^! inquiries h come f p int]e/$ 9 our company1 f o!rs int]e/$ 9 companies t h pur*as$ ! "r to use our app>atus1 f p desir\s ( becom+ int]e/$ 9 a pneumatic-tube bus9ess1 f w\ld-be pur*as]s ( pneumatic tubes1 & f p int]e/$ 9 pneumatic tubes f a sci5tific1 eng9e]+1 or me*anical po9t ( view4 ,?is book is n int5d$ to be a treatise on pneumatic tubes4 ,9 ! fir/ *apt] ,i h giv5 a brief sket* ( :at has be5 done 9 ! application ( pneumatic tubes f ! e>lie/ records to ! pres5t "t4 ,! second *apt] conta9s a description ( ! po/al tubes 9 ,philadelphia1 & ! ?ird *apt] describes our sy/em 9 detail4 ,foll[+ ?is is a %ort *apt] expla9+ ! !ory ( pneumatic tubes1 or ! !ory ( ! fl[ ( air 9 long pipes1 /at+ ! m int]e/+ facts & relations 9 z pla9 & simple a mann] z possible4 ,ma!matical =mul h be5 purposely avoid$4 ,sev]al plates %[+ ! ,philadelphia po/al l9e h be5 k9dly loan$ to me by ! ,eng9e]s' ,club ( ,philadelphia4 ,!y =m]ly appe>$ 9 a pap] read by ,mr4 ,a4 ,falk5au be=e t club4 ,i h also to ?ank ! & ,drill ,co41 ! ,b4 ,f4 ,/urtevant ,co41 ! ,wilbraham-,bak] ,bl[] ,co41 & ,j4 ,b4 ,/ew>t = ! use ( electrotypes ( _! ma*9es4 ,b4 ,c4 ,b4 ,octob] #f1 #ahif4 ,,! ,,bat*ell] ,,pneumatic ,,tube ,,sy/em4 ,,*apt] ,i4 ,a ,,brief ,,hi/orical ,,sket*4 ,e>ly ,records4--,! e>lie/ ref]5ce to pneumatic transmission ( :i* we f9d any record is a pap] pres5t$ to ! ,royal ,society ( ,london1 by ,d5is ,pap91 9 ! ye> #affg1 entitl$ 8,d\ble ,pneumatic ,pump40 ,8 plan 0 to exhau/ ! air f a long metal tube by two l>ge cyl9d]s4 ,! tube 0 to conta9 a pi/on1 to :i* a c>riage 0 atta*$ by means ( a cord4 ,! 8,am]ican ,cyclopdia0 goes on to say1 8,m ?an a c5tury elaps$ be=e any fur!r ef=t 9 ?is direction 0 made4 ,paucbr\ke's #8,dictionnaire ,encyclopdique des ,amusem5ts des ,sci5ces' 7#agib7 gives a description ( a ma*9e by ,m4 ,van ,e/91 by means ( :i* a holl[ ball hold+ a small package 0 propell$ by a bla/ ( air ?r\gh a tube sev]al hundr$ feet 9 l5g?1 & hav+ _m curves4 ,?is plan seems1 h[ev]1 to h be5 m an amusem5t ?an an attempt to introduce an indu/rial s*eme4 ,) m reg>d to practical results1 ,m$hur/1 an eng9e] ( ,london1 publi%$ a pamphlet on ! subject 9 #ahaj4 ,he propos$ to move small c>riages on rails 9 air-tight tubes or tunnels1 by compress$ air beh9d1 or by creat+ a p>tial vacuum 9 front4 ,9 #ahab he publi%$ ano!r pamphlet2 b ! plan 0 n put into successful op]ation1 pr9cipally f insuffici5t means ( exhau/ion4 ,ab\t #ahcb he propos$ to connect ! c>riage inside su* a tube ) a pass5g] c>riage runn+ on ! top ( ! tube2 &1 al?\gh ! latt] project has nev] be5 comm]cially successful1 x 0 ! fir/ to be practically attempt$4 ,m ?an a score ( pat5ts 7 tak5 out on ! ,cont95t & 9 ,engl& & ,am]ica1 none ( :i* met ) any practical success4 ,return+ to ! orig9al idea ( ,d5is ,pap91 inv5tors attempt$ to accompli% pneumatic transmission by mov+ ! load inside ! tube1 & 9 c\rse ( "t a*iev$ success4 ,9 ,france ,,mm4 ,j>r\x & ,taisseau pres5t$ a project = atmosph]ic telegraphy be=e ! ,academy ( ,sci5ces1 & !y 7 succe$$ 9 ! same direction by ,,mm4 ,bro*et & ,ardor40 ,practical ,beg9n+ ( ! ,art4 ,! ,london ,pneumatic ,telegraph4--,london has ! honor ( be+ ! fir/ city to h a practical sy/em ( pneumatic telegraphy4 ,! fir/ tubes 7 in/all$ by ! ,electric & ,int]national ,telegraph ,company1 ! "w be+ plann$ & c>ri$ out by _! eng9e]1 ,mr4 ,josiah ,latim] ,cl>k1 9 #ahec & #ahed4 ,! fir/ tube to be laid 0 "o & "o-half in*es 9 diamet]1 & ext5d$ f ! c5tral /ation1 ,f\nd]'s ,c\rt1 ,lo?bury1 to ! ,/ock ,ex*ange1 ,?rogmorton ,/reet1 a di/ance ( two hundr$ & tw5ty y>ds4 ,! tube 0 op]at$ int]mitt5tly by connect+ x to a vacuum *amb] at ! c5tral /ation4 ,c>ri]s 7 s5t only 9 "o direction4 ,a /eam-pump 0 us$ to ma9ta9 ! vacuum4 ,mu* exp]i5ce 0 ga9$ f ! use ( ?is fir/ tube4 ,9 #aheh "s improvem5ts 7 made by ,mr4 ,c4 ,f4 ,v>ley1 & ,i c be/ describe !m by quot+ f ! discussion ( ,mr4 ,c>l ,siem5s's pap] on 8,pneumatic ,despat* ,tubes3 ,! ,circuit ,sy/em0 be=e ! ,in/itution ( ,civil ,eng9e]s1 z record$ 9 ! m9utes ( t society4 8,lat]1 ab\t ! ye> #aheh1 :5 a pipe two & "o-f\r? in*es int]nal diamet] 0 ext5d$ f ,telegraph ,/reet to ,m9c+ ,lane1 ?irte5 hundr$ & =ty y>ds 9 l5g?1 ! traffic 0 s consid]able t x 0 f\nd desirable to h ! p[] ( s5d+ messages 9 bo? directions4 ,to effect t a small] pipe1 "o & "o-half in*es 9 int]nal diamet]1 0 laid betwe5 ,telegraph ,/reet & ,m9c+ ,lane1 ) a view to c>ry+ ! vacuum to ! latt] /ation1 s z to take messages 9 ! opposite direction4 ,?is small] pipe 0 f\nd to s wir$raw ! curr5t t ! pipe w\ld n "w1 ! leakage pa/ ! c>ri] be+ too consid]able2 & accord+ly a l>ge *amb] 0 built 9 ! basem5t floor or kit*5 at ! corn] ( ,m9c+ ,lane & ,lead5hall ,/reet to collect p[] or vacuum = br++ ! messages f ,telegraph ,/reet to ,m9c+ ,lane4 ,?is *amb] 0 con/ruct$ ( timb]1 f\rte5 feet by twelve feet broad & t5 feet high1 & 0 cov]$ ) lead4 ,x 0 n /rong en\gh to )/& ! pressure2 = "o day1 a c>ri] hav+ /uck half-way1 & :5 !re 0 a high] vacuum ?an usual1--viz41 tw5ty-?ree in*es ( m]cury1--x collaps$ ) a l\d report4 ,at ! "t ! l&lord ( ! h\se happ5$ to be d9+ 9 ! next room1 & he sudd5ly f\nd himself1 8 table1 d9n]1 & ! door1 :i* 0 wr5*$ (f its h+es1 precipitat$ into ! room among/ ! dbris ( ! *amb]4 ,! w9d[s 7 =c$ inw>ds1 & ^? on ! opposite side ( ,m9c+ ,lane & ,lead5hall ,/reet 7 drawn outw>ds4 ,! damage 0 consid]able4 ,?is accid5t put an end1 = a "t1 to ! attempt to s5d telegraph messages by means ( a vacuum convey$ ?r\gh ?is small] pipe4 ,ab\t t "t he 7,mr4 ,v>ley7 became ! eng9e]-9-*ief ( ! ,electric ,telegraph ,company1 & got p]mission f ! directors to introduce a new sy/em1--viz41 compress$ air1--?\gh _m p]sons cont5d$ t x w\ld be impossible to bl[ messages ?r\gh a pipe1 because all attempts to bl[ air ?r\gh long pipes _h utt]ly fail$2 :ile o!rs said t1 if messages 7 s5t1 !y w\ld g mu* sl[] ?an ) ! vacuum4444 ,9 8 7,mr4 ,v>ley's7 app>atus1 = he 0 ! fir/ to introduce compress$ air1 ! rev]se 0 f\nd to be ! case1 & = ?is reason3 ! tube did n consume p[] until a message 0 ab\t to be =w>d$2 & 9 a tube ?irte5 hundr$ y>ds 9 l5g?1 & two & "o-f\r? in*es 9 diamet]1 fifte5 seconds elaps$ be=e ! vacuum 0 felt at ! di/ant end aft] communication _h be5 e/abli%$ ) ! exhau/$ *amb] at ! eng9e end ( ! tube1 consequ5tly ! c>ri] did n />t until aft] fifte5 seconds _h elaps$4 ,:5 a message 0 s5t by compress$ air1 x 0 s5t f ! end at :i* ! p[] 0 appli$1 & ! c>ri] />t$ at once1 ?us ga9+ a />t ( fifte5 seconds2 n[1 inasmu* z ! air 9 ! tube _h to be compress$1 x />t$ at a v high velocity1 & :5 x rea*$ ! o!r end ! compress$ air 9 exp&+ gave x a high] velocity4 ,! result 01 9 ?irte5 hundr$ & =ty y>ds1 f ,telegraph ,/reet to ,m9c+ ,lane1 ! c>ri]s 7 drawn by vacuum1 on an av]age1 9 f sixty to sev5ty seconds1 & 7 propell$ by compress$ air 9 ab\t fifty or fifty-five seconds1 ! diff]5ce ( pressure 9 ea* case be+ ne>ly equal40 ,! fir/ "o & "o-half in* tubes laid "u ! direction ( ,mr4 ,cl>k 7 ( iron ) screw$ jo9ts4 ,!y gave mu* tr\ble f r\ghness ^u ! int]ior1 :i* wore ! c>ri]s v rapidly1 & f wat] t 0 drawn 9 ?r\gh leaky jo9ts4 ,:5 ! ext5sions 7 made 9 #aheh & aft]w>ds1 two & "o-f\r? in* lead tubes 7 us$ ) plumb]'s jo9ts made ov] a heat$ m&rel1 :i* made ! jo9ts v smoo? ^u ! int]ior4 ,! c>ri]s 7 ( gutta p]*a 9 ! =m ( a cyl9d] clos$ at "o end & fitt$ ) a cap at ! o!r4 ,! outside 0 cov]$ ) felt or drugget4 ,:5 a c>ri] 0 to be despat*$1 a signal 0 s5t to an att5dant at ! pump end ( ! tube1 :o clos$ t end & connect$ ! tube to an exhau/$ *amb] by op5+ a valve4 ,z soon z ! c>ri] arriv$1 he clos$ ! valve & op5$ ! tube1 :i* all[$ ! c>ri] to drop out4 ,mr4 ,v>ley improv$ ! me?od ( op]at+ ! valves by mak+ ! air pressure d ! "w by means ( cyl9d]s & pi/ons :5 ! att5dant press$ a button4 ,he also improv$ ! c>ri]s by do+ away ) ! cap & us+ 9 its place an ela/ic b& to hold ! messages 9 place4 ,we h se5 t ,mr4 ,cl>k design$ ! fir/ tube us$ 9 connection ) ! telegraph1 & t x 0 a s+le tube1 op]at$ 9 "o direction only by vacuum1 be+ op]at$ only :5 !re 7 messages to s5d4 ,?is 0 ext5d$ & improv$ by ,mr4 ,v>ley1 :o increas$ ! diamet] ( ! tubes f "o & "o-half in*es to two & "o-qu>t] in*es1 & op]at$ !m 9 bo? directions1 us+ vacuum = s5d+ 9 "o direction & compress$ air = s5d+ 9 ! o!r4 ,! air curr5t 0 ma9ta9$ 9 ! tubes only :5 messages 7 s5t4 ,great cr$it is due to ,sir ,r[l& ,hill1 :o1 9 #ahee1 _h a propos$ me?od ( convey+ mails 9 ! city ( ,london1 ?r\gh n9e- & ?irte5-in* tubes1 ?or\ghly inve/igat$4 ,x 0 decid$ at ?is "t t ! sav+ 9 "t ov] t consum$ by mail c>ts w\ld n w>rant ! exp5se ( in/all+ su* a sy/em4 ,! ,siem5s ,circuit ,sy/em4--,! next progressive /ep 0 made by ,siem5s ,bro!rs1 ( ,b]l91 :o propos$ a new sy/em call$ ! 8circuit sy/em10 9 :i* two tubes 7 us$1 ! up tube be+ connect$ to ! d[n tube at ! di/ant end4 ,! air 0 compress$ into "o end ( ! circuit & exhau/$ f ! o!r1 &1 fur!rmore1 x 0 kept 9 con/ant circulation4 ,c>ri]s 7 despat*$ by ins]t+ !m into ! air-curr5t )\t /opp+ x1 9 "o direction 9 "o tube or 9 ! opposite direction 9 ! o!r4 ,ano!r feature ( ! ,siem5s sy/em 0 ! plac+ ( ?ree or m /ations on "o d\ble l9e ( tubes4 ,c>ri]s c\ld be /opp$ at an int]m$iate /ation by ins]t+ 9 ! tube an ob/ruct+ scre5 :i* ! air w\ld pass b :i* w\ld /op a c>ri]4 ,?is sy/em is describ$ 9 detail 9 a pap] read by ,mr4 ,c>l ,siem5s be=e ! ,in/itution ( ,civil ,eng9e]s1 ,london1 ,novemb] #ad1 #ahga1 ,vol4 ,,xxxiii4 ( ! ,proce$+s4 ,! ,siem5s app>atus = s5d+ & receiv+ c>ri]s consi/$ ( two %ort sections ( tube atta*$ to a rock+ frame s t ei!r c\ld be swung by h& into l9e ) ! ma9 tube4 ,"o ( ! tube sections 0 op5 at bo? ends1 & 0 us$ = despat*+ c>ri]s4 ,a c>ri] 0 plac$ 9 x1 !n x 0 swung into l9e ) ! ma9 tube1 :5 ! air-curr5t pass+ ?r\gh swept ! c>ri] along4 ,! o!r tube section conta9$ a p]=at$ scre5 9 "o end & 0 us$ to receive c>ri]s4 ,:5 x 0 9 l9e ) ! ma9 tube & a c>ri] arriv$1 ! c>ri] 0 /opp$ by /rik+ ! scre51 !n ! tube section 0 swung to "o side & ! c>ri] pu%$ out ) a rod4 ,a by-pass 0 provid$ = ! air ar\nd ! app>atus s t its fl[ 0 n *eck$ :5 ! tube section 0 swung4 ,:5 a c>ri] 0 despat*$ to an int]m$iate /ation1 a signal 0 s5t1 & !n ! section ( tube conta9+ ! scre5 0 int]pos$ 9 ! l9e ( ! tube to /op ! c>ri] ^u its arrival4 ,! c>ri]s us$ by ,mr4 ,siem5s 7 made ( gutta-p]*a1 papi] ma*1 or t91 clos$ at "o end & fitt$ ) a cov] at ! o!r4 ,!y 7 cov]$ ) felt1 drugget1 or lea!r4 ,! front ends ( ! c>ri]s 7 provid$ ) ?ick disks ( drugget or lea!r fitt+ ! tube loosely1 & ! opposite ends 7 surr\nd$ ) pieces ( ! same mat]ial atta*$ to !m l ! lea!r ( an ord9>y lift+ pump4 ,9 #ahfi ,messrs4 ,siem5s ,bros4 receiv$ an ord] f ! ,briti% gov]nm5t to in/all an exp]im5tal l9e ( tubes betwe5 ! c5tral telegraph /ation & ! g5]al po/-(fice4 ,?is 0 complet$ 9 #ahgj1 & aft] a half-ye>'s te/ x 0 ext5d$ to ,fleet ,/reet1 & f9ally to ,*>+ ,cross4 ,! tubes 7 ( iron1 ?ree in*es 9 diamet]1 ) flang$ & bolt$ jo9ts4 ,x 0 f\nd1 aft] "s exp]i5ce1 t !re 0 no advantage 9 ! circuit1 s ! up & d[n tubes 7 sep>at$ at ,*>+ ,cross ,/ation & work$ indep5d5tly4 ,rec5t ,improvem5ts 9 ! ,london ,sy/em4--,9 #ahgj ,mr4 ,j4 ,w4 ,wilmot design$ a d\ble sluice-valve by means ( :i* c>ri]s c\ld be despat*$ cont9u\sly )\t /opp+ ! fl[ ( air 9 ! tubes4 ,mr4 ,wilmot fur!r increas$ ! work+ capacity ( pneumatic tubes :51 9 #ahhj1 he inv5t$ an int]m$iate automatic signall]1 by means ( :i* a c>ri] signals ! passage ( a giv5 po9t on its j\rney1 %[+ t ! section ( ! tube trav]s$ is cle>1 ?us all[+ a second c>ri] to be despat*$ be=e ! fir/ has rea*$ its de/9ation4 ,illu/ration3 ,,fig4 #b4 ,,diagram ,,illu/rat+ ,,! ,,pneumatic ,,tube ,,sy/em ,,london ,,radial ,,sy/em4 ,,london ,,radial ,,sy/em4 ,f ?is beg9n+ ! ,engli% sy/em develop$ into :at has be5 t]m$ a 8radial sy/em20 t is to say1 "o pr9cipal & sev]al m9or c5tral pump+ /ations h be5 e/abli%$1 & f ^! radiate tubes to num]\s sub-/ations 7see ,fig4 #b74 ,"s ( ! /ations are connect$ ) d\ble l9es = s5d+ 9 opposite directions4 ,! out-go+ tube f ! pump+ /ation is work$ by compress$ air1 & ! incom+ tube by exhau/ion4 ,o!r /ations are connect$ by s+le tubes1 & !y are op]at$ alt]nately by compression & exhau/ion4 ,int]m$iate /ations are locat$ on "s ( ! l9es4 ,= ! c5tral /ation ! ,v>ley valves 7 f\nd too exp5sive & tr\blesome to keep 9 ord]1 s !y 7 replac$ by ! ,wilmot d\ble sluice-valves1 :i* are op]at$ manually4 ,9 rec5t ye>s ! sluice-valves h be5 9 turn replac$ by :at are t]m$ ,d-boxes1 a simpl] =m ( app>atus4 ,at ! sub-/ations ! tube t]m9ates 9 a box into :i* ! c>ri]s drop4 ,z ! sy/em has be5 gradually ext5d$1 tubes two & ?ree-sixte5?s in*es inside diamet] h be5 us$ = %ort l9es1 & ?ree-in* tubes = long l9es4 ,! tubes are ( lead laid inside a ca/-iron pipe :i* s]ves z a %ield1 protect+ !m f injury4 ,!y are laid 9 tw5ty-n9e foot sections1 ! jo9ts be+ made by sold]+ ov] a /eel m&rel1 :i* is aft]w>ds drawn out by a *a94 ,! jo9ts 9 ! ca/-iron protect+ pipe are made by caulk+ ) y>n & lead4 8,electric signals are us$ betwe5 ! c5tral & sub-/ations1 consi/+ ( a s+le /roke bell & indicator1 giv+ notice ( ! arrival & dep>ture ( c>ri]s1 & to answ] ! necess>y que/ions requir$ 9 work+4 ,:]e !re are int]m$iate /ations ! tubes are work$ on ! block sy/em1 z if x 7 a railway4 ,exp]i5ce %[s t1 :]e great exactness ( manipulation _c be obta9$1 x is necess>y to all[ only "o tra9 9 ea* section ( a tube1 :e!r work$ by vacuum or pressure4 ,b :]e !re is no int]m$iate /ation1 & :]e ! tube c be c>efully work$1 c>ri]s may be all[$ to foll[ "o ano!r at %ort int]vals 9 a tube work$ by vacuum1 al?\gh x is n p]fectly safe to d s 9 "o work$ by pressure4 ,9 work+ by pressure x has be5 f\nd t1 not)/&+ a fair int]val may be all[$1 c>ri]s are apt to ov]take "o ano!r1 = no two c>ri]s travel 9 ! same times1 because ( diff]5ces 9 fit1 unless !y are plac$ end to end4 ,if signall+ be neglect$ & a c>ri] happ5s to /ick fa/1 be+ foll[$ by sev]al o!rs1 a block w ensue :i* x w be difficult to cle>1 :ile ! s+le c>ri] c\ld readily h be5 dislodg$40 7,proce$+s ,in/itute ( ,civil ,eng9e]s1 ,london1 ,vol4 ,,xliii4 p4 #fa47 ,no *anges h be5 made 9 ! c>ri]s f ^? us$ 9 ! e>ly exp]im5ts :i* h already be5 describ$4 ,! ,london sy/em has gr[n until x n[ includes no less ?an =ty-two /ations & ?irty-f\r miles ( tubes4 ,simil> sy/ems h be5 e/abli%$ 9 connection ) ! telegraph 9 ,liv]pool1 ,man*e/]1 ,birm+ham1 ,glasg[1 ,dubl91 & ,new ,ca/le4 ,! tubes give a *eap] & m rapid means ( despat*+ telegrams betwe5 sub-/ations & c5tral /ations ?an transmission by telegraph1 & local telegrams c be deliv]$ 9 ! s5d]'s h&writ+4 ,an ,und]gr\nd ,pneumatic ,railway = ,transportation ( ,mail4--,be=e describ+ ! sy/ems us$ 9 ! cities on ! ,cont95t ( ,europe1 we mu/ notice a v l>ge pneumatic tube1 or m prop]ly call$ a pneumatic tunnel railway1 con/ruct$ 9 ,london = ! transportation ( mail f "o ( ! railway /ations4 ,! fir/ railway ( ?is type 0 con/ruct$ 9 #ahfc by ! ,pneumatic ,despat* ,company ( ,london1 & ext5d$ f ,eu/on to ! di/rict po/-(fice 9 ,ev]%olt ,/reet1 a di/ance ( ab\t eighte5 hundr$ feet4 ,! tunnel 0 flat on ! bottom1 hav+ a ,d-%ap$ cross-section two feet eight in*es by two feet eight in*es4 ,! c>ri]s or c>riages 7 cradle-l boxes fitt+ ! tunnel1 & !y mov$ at a spe$ ( sev5te5 miles p] h\r1 c>ry+ fifte5 mails daily4 ,9 #ahgb two simil> b l>g] tunnels 7 built f ,eu/on ,/ation to ! g5]al po/-(fice1 a di/ance ( f\rte5 ?\s& two hundr$ & f\r feet1 or two & ?ree-qu>t]s miles4 ,"o 0 = ! up traffic1 & ! o!r = ! d[n4 ,! tunnels 7 f\r & a half feet wide by f\r feet high1 ! /raight "p be+ built ( ca/ iron & ! b5ds ( brick4 ,! l9e 0 op]at$ by a fan tw5ty-two feet 9 diamet]1 :i* =c$ ! air into "o tunnel & exhau/$ x f ! o!r1 produc+ a vacuum ( t5 in*es ( wat]1 or six ounces p] squ>e in*4 ,! c>riages occupi$ twelve m9utes 9 trav]s+ ! tunnels1 & !re 0 "o gradi5t ( "o to f\rte54 ,! c>riages 7 t5 feet f\r in*es long & weigh$ tw5ty-two hundr$weight4 8,! sy/em 0 able to transport ov] ! :ole l9e1 all[+ = delays1 an av]age ( a ton p] m9ute40 ,! sy/em 0 us$ to transport ! mails 9 bulk1 b x 0 f\nd to be sl[ & unsatisfactory1 & 0 v soon ab&on$4 ,! ,b]l9 ,pneumatic ,telegraph4--,9 #ahfc ! ,prussian gov]nm5t appli$ to ! firm ( ,siem5s & ,halske1 ( ,b]l91 = a proposition to e/abli% a sy/em ( pneumatic tubes 9 t city = ! transmission ( telegraph messages4 ,a proposition 0 accord+ly submitt$1 & ! "w 0 complet$ 9 #ahfe4 ,?is fir/ l9e consi/$ ( two p>allel wr\ght-iron tubes1 two & "o-half in*es 9 diamet]1 "o tube be+ us$ exclusively to s5d 9 "o direction1 & ! o!r 9 ! opposite direction4 ,!y ext5d$ f ! telegraph /ation to ! ,ex*ange1 requir+ a total l5g? ( five ?\s& six hundr$ & sev5ty feet ( tube4 ,! two tubes 7 loop$ toge!r at ! ,ex*ange1 & a cont9u\s curr5t ( air 0 made to circulate 9 !m by a d\ble-act+ /eam air-pump1 locat$ at ! telegraph /ation4 ,air 0 compress$ into "o end ( ! tube & exhau/$ f ! o!r4 ,) n9e in*es ( m]cury pressure & vacuum ! passage 0 made 9 n9ety-five seconds to ! ,ex*ange1 & sev5ty-five seconds f ! ,ex*ange4 ,x 0 simil> to ! l9e e/abli%$ 9 ,london by ! same firm "s ye>s lat]1 :i* we h already describ$1 except t !re 0 no int]m$iate /ation4 ,aft] ! l9e _h be5 9 use = a ye> & a half1 ! ,prussian gov]nm5t _h x ext5d$1 fir/1 f ! telegraph /ation to ! ,potsdam gate1 ) an int]m$iate /ation at ! ,br&5burg gate4 ,aft] ^! prelim9>y exp]im5ts1 fur!r ext5sions 7 made until a net-"w ( tubes ext5d$ ov] ! city ( ,b]l91 includ+ no less ?an ?irty-eight /ations & ov] tw5ty-eight miles ( tubes2 b 9 lay+ d[n ?is net-"w a dep>ture 0 made f ! ,siem5s sy/em4 ,air 0 no long] kept con/antly circulat+1 b p[] 0 /or$ up 9 l>ge tanks1 "s be+ exhau/$ & o!rs fill$ ) compress$ air1 :i* 0 us$ :5 requir$ to s5d messages1 usually at int]vals ( five or fifte5 m9utes4 ,! exhau/$ tanks 7 p]man5tly connect$ ) ! clos$ tubes1 :i* 7 op5$ :5 requir$ = use4 ,! tanks conta9+ compress$ air 7 connect$ to ! tubes :5 messages 7 s5t4 ,! int]nal diamet] ( ! tubes 0 #b4eei in*es4 ,!y 7 laid 9 circuits1 includ+ sev]al /ations 9 a circuit1 & ! c>ri]s travell$ only 9 "o direction ar\nd ! circuit4 ,"s outly+ /ations 7 connect$ by a s+le tube ) c5tral pump+-/ations1 ^! s+le tubes be+ work$ 9 bo? directions4 ,ye>s ( exp]i5ce h %[n ! disadvantages ( ?is circuit-sy/em1 & x has gradually be5 *ang$ to ! radial sy/em1 su* z is us$ 9 ,london1 until n[ ne>ly all ! /ations are gr\p$ ar\nd ! c5tral pump+-/ations1 to :i* !y are connect$ directly by radiat+ tubes4 ,! ,siem5s app>atus has be5 replac$ by simpl] & less exp5sive valves & receiv+-boxes1 ! late/ =m ( :i* 0 design$ & pat5t$ by ,mr4 ,josef ,wildemann4 ,illu/ration3 ,,fig4 #c4 ,,diagram ,,( ,,"p ,,( ,,p>is ,,pneumatic ,,tube ,,sy/em4 ,,p>is ,,circuit ,,sy/em4 ,! ,p>is ,pneumatic ,telegraph4--,we w n[ glance at ! sy/em us$ 9 ,p>is1 :i* has "s novel features4 ,9 #ahfe x 0 decid$ to e/abli% a sy/em1 & ! fir/ exp]im5tal l9e1 f ,place de la ,b\rse to ! ,gr& ,htel1 on ! ,b\lev>d des ,capuci5s1 0 laid 9 #ahff4 ,in/ead ( us+ a /eam-eng9e to drive an air-compressor or exhau/-pump1 air 0 compress$ 9 tanks by displacem5t ) wat] f ! city ma9s4 ,9 #ahfg ?is l9e 0 ext5d$ to ,rue de ,gr5nelle ,/4 ,g]ma91 ) an int]m$iate /ation at ! ,rue ,boissy d',anglais1 & ano!r l9e ) /ations at ,rue ,jean ,jacques ,r\sseau1 ,htel du ,l\vre 9 ! ,rue de ,rivoli1 ! ,rue des ,sa9ts ,pres1 & t]m9at+ 9 ! c5tral /ation4 ,9 #ahfh ! sy/em 0 *ang$ to a polygonal or circuit sy/em by remov+ ! /ation 9 ! ,rue de ,rivoli to ! ,place du ,?tre ,franais & connect+ ! latt] directly ) ! ,b\rse4 ,o!r *anges & ext5sions 7 made 9 #ahgj & #ahga1 until ?ree polygons or circuits 7 =m$1 ) five or six /ations 9 ea* circuit1 & sev]al outly+ /ations 7 connect$ by indep5d5t tubes4 ,9 ! middle ( ! ye> #ahge sev5te5 /ations _h be5 connect$ & plans 7 made = tw5ty-"o m4 ,in/ead ( ma9ta9+ an air-curr5t ar\nd ea* circuit by ma*9]y locat$ at "o ( ! /ations on ! circuit1 at lea/ ?ree ( ! five or six /ations compris$ 9 ! circuit h means ( supply+ compress$ air or ( exhau/+ x1 & ea* side ( ! polygon1 or section ( ! circuit betwe5 two /ations1 is op]at$ indep5d5tly ( ! re/ ( ! circuit 7see ,fig4 #c74 ,c>ri]s are s5t on f /ation to /ation ar\nd ! circuit1 ei!r by compress$ air f ! la/ /ation f :i* !y 7 s5t or by means ( exhau/ion at ! next /ation t[>ds :i* !y are mov+4 ,! c>ri]s are made up 9 tra9s ( f six to t51 ) a pi/on beh9d !m t fits ! tube closely & =ces !m ahead4 ,ea* c>ri] is address$ by means ( a label = its de/9$ /ation4 ,tra9s are despat*$ ar\nd ! circuits at /at$ times1 usually at fifte5-m9ute int]vals4 ,z !y arrive at ! v>i\s /ations1 c>ri]s are tak5 out & o!rs put 91 & ! tra9s s5t on _! way4 ,! c>ri]s consi/ ( iron cyl9d]s1 clos$ at "o end1 ) a lea!r case t slides ov] !m & closes ! op5 end4 ,!y weigh1 :5 fill$ ) ?irty-five messages1 twelve & "o-half ounces1 & !y w travel ab\t twelve hundr$ miles be=e ! lea!r cov] is s worn t x mu/ be ?r[n away4 ,! pi/ons are made ( a wood5 cone1 cov]$ ) iron1 & hav+ a 8cup-lea!r0 ^u ! re> end t fits ! tube closely4 ,! s5d+ & receiv+ app>atus consi/s ( sections ( tube clos$ at "o end1 hav+ a door on ! side1 ?r\gh :i* c>ri]s are ins]t$ or despat*$4 ,a peculi> =m ( =k is us$ = pick+ !m out4 ,! air is controll$ by valves op5$ & clos$ by h&4 ,sev]al me?ods are us$ to compress & exhau/ ! air4 ,! mo/ novel me?od consi/s 9 hav+ tanks 9 :i* a p>tial vacuum is produc$ by all[+ wat] to fl[ out ( !m into ! sew]1 or 9 hav+ ! air compress$ by all[+ wat] f ! city ma9s to fl[ into ! tanks & displace ! air4 ,wat] jets h also be5 us$1 op]at+ simil> to a /eam-injector4 ,at "s ( ! /ations wat] turb9es drive ! air-pumps1 & at o!rs /eam-eng9es are us$4 ,! tubes ( ! ,p>is sy/em are ( wr\ght iron1 9 l5g?s ( f fifte5 to tw5ty feet1 ! jo9ts be+ made ) flanges & bolts4 ,! int]ior diamet] is #b4eei in*es ) a maximum v>iation to #b4eai in*es4 ,! b5ds are made ) a radius ( f six to "o hundr$ & fifty feet4 ,wat] frequ5tly gives tr\ble by accumulat+ 9 ! tubes4 ,traps are plac$ at l[ po9ts to dra9 x (f4 ,! spe$ ( ! tra9s ( c>ri]s 9 ! ,p>is tubes is f fifte5 to tw5ty-?ree miles p] h\r1 & ! av]age "t t elapses f ! receipt ( a message until its deliv]y is f =ty to =ty-five m9utes4 ,! ,pneumatic ,telegraph ( o!r ,cities4--,a sy/em simil> to ! "o j describ$ is us$ 9 ,vi5na4 ,x diff]s "s 9 details ( app>atus1 b ! c>ri]s are despat*$ ar\nd circuits 9 tra9s1 /opp+ at ea* /ation1 :]e "s c>ri]s are remov$ & o!rs ins]t$4 ,brussels also is n )\t its sy/em ( pneumatic tubes = ! transmission ( telegrams4 ,pneumatic ,tubes 9 ,am]ica4--,turn+ our att5tion n[ to our own c\ntry1 we _c pass )\t m5tion "s exp]im5ts ( ,alfr$ ,e4 ,bea* ) pneumatic railways1 made ne>ly ?irty ye>s ago4 ,8 fir/ exp]im5t ^u a l>ge scale 0 made at ! ,am]ican ,in/itute ,fair held 9 ,new ,york ,city 9 #ahfg4 ,"h he _h con/ruct$ a circul> wood5 tube1 "o hundr$ & sev5 feet long & six feet 9 diamet]4 ,a c> t w\ld seat t5 p ran ^u a track laid d[n inside ! tube1 & 0 propell$ by a helix fan t5 feet 9 diamet]1 mak+ two hundr$ revolutions p] m9ute4 ,he next tri$ 8 railway ^u a practical scale1 con/ruct+ an eight-foot tunnel = two hundr$ feet "u ,broadway1 />t+ at ! corn] ( ,w>r5 ,/reet4 ,a c> 0 propell$ by a l>ge rot>y bl[] locat$ 9 ! basem5t ( a build+ ne> by4 ,! bl[] 0 kept con/antly runn+1 & ! c> 0 s5t alt]nately 9 "o direction & !n ! o!r by *ang+ valves at ! bl[]4 ,few p "k t ?is exp]im5tal l9e /ill exi/s "u ,broadway z ,mr4 ,bea* left x4 ,! mo/ ext5sive use ( small pneumatic tubes 9 ?is c\ntry has be5 9 our l>ge retail dep>tm5t /ores = despat*+ ca% to & f a c5trally locat$ ca%i]'s desk4 ,seamless brass tubes are usually us$1 &1 s9ce ! tubes are %ort1 ! air is ei!r compress$ or exhau/$ by means ( positive rot>y bl[]s4 ,at ! outly+ /ations ! tubes are usually op5 to ! atmosph]e1 :ile at ! c5tral /ation simple =ms ( valves are us$ = s5d+ & receiv+4 ,an outgo+ & a return tube are always us$1 & ! air is kept 9 con/ant circulation4 ,! c>ri]s are ( metal ) felt pack+ r+s & op5 on ! side4 ,^! ca%-c>ry+ sy/ems h come into use dur+ ! pa/ tw5ty-five ye>s4 ,! ,we/]n ,union ,telegraph ,company uses small tubes to transmit its messages to a consid]able ext5t 9 "s ( our l>ge cities4 ,9 #ahgf f\r l9es 7 laid 9 ,new ,york ,city f ! ma9 (fice on ,broadway3 two to ! bran* (fice at ,no4 #ad ,broad ,/reet1 "o to #acd ,pe>l ,/reet1 & "o to ! ,cotton ,ex*ange4 ,s9ce !n ?is company has laid a d\ble l9e ab\t two miles 9 l5g? "u ,broadway to its up-t[n (fice4 ,x also uses tubes to s5d messages f ! receiv+ desks to ! op]at+ rooms )9 ! build+s4 ,_m ( our l>ge hotels use pneumatic tubes to transmit messages to ! diff]5t floors & (fices ( ! build+s1 tak+ ! place ( mess5g]1 or bell boys1 :o =m]ly did ?is s]vice4 ,we call especial att5tion to ! fact t 9 all ! sy/ems t we h m5tion$ :i* are 9 use bo? 9 ?is c\ntry & 9 ,europe1 none ( ! tubes are l>g] ?an ?ree in*es int]nal diamet]2 also t 9 all ! sy/ems1 except 9 ,p>is :]e ! c>ri]s are despat*$ 9 tra9s1 ! c>ri]s are s light & move s sl[ly t !y c be /opp$ by all[+ !m to come 9 contact ) "s solid object1 su* z a box into :i* ! c>ri]s drop4 ,v few ( ! tubes are m ?an two miles 9 l5g?1 & mo/ ( !m are less ?an "o mile4 ,a spe$ ( m ?an ?irty miles p] h\r has seldom be5 attempt$1 & usually x is mu* less ?an ?is4 ,,*apt] ,,ii4 ,,! ,,pneumatic ,,transit ,,company ,,& ,,! ,,fir/ ,,pneumatic ,,tubes ,,= ,,! ,,transportation ,,( ,,unit$ ,,/ates ,,mail4 ,organization4--,e>ly 9 ! ye> #ahib sev]al ,philadelphia g5tlem5 organiz$ a corporation & obta9$ a *>t] 9 ! ,/ate ( ,new ,j]sey to con/ruct1 lay1 & op]ate pneumatic tubes = ! transmission ( ,unit$ ,/ates mail1 packages1 m]*&ise1 messages1 etc41 )9 ! ,/ates ( ,new ,j]sey & ,p5nsylvania4 ,! corporation 0 /yl$ ! ,pneumatic ,transit ,company4 ,mr4 ,william ,j4 ,kelly 0 elect$ presid5t1 & ! company is /ill "u 8 managem5t4 ,illu/ration3 ,,wm4 ,j4 ,,kelly1 ,presid5t ( ! ,pneumatic ,transit ,co4 ,aim & ,object ( ! ,company4--,:5 ! ,pneumatic ,transit ,company 0 =m$1 x 0 ! aim & object ( its promot]s to con/ruct an ext5sive sy/em ( und]gr\nd tubes 9 ! ,city ( ,philadelphia :i* w\ld s]ve1 fir/1 = ! rapid transmission ( mail1 second1 = ! quick deliv]y ( m]*&ise f ! l>ge retail /ores1 ?ird1 = ! transmission ( telegrams or messages )9 ! city limits1 &1 f\r?1 to conduct a g5]al local express bus9ess ) great] spe$ ?an c be done 9 any o!r mann]4 ,to accompli% ?is result sub-/ations 7 to be locat$ six or eight blocks ap>t ?r\gh\t a l>ge portion ( ! city1 & a c5tral /ation 0 to be e/abli%$ 9 ! c5tre ( ! bus9ess section4 ,/ations 7 also to be e/abli%$ 9 ! m important retail /ores & l>ge (fice build+s1 & all ( ! /ations 7 to be connect$ by tubes =m+ "o l>ge sy/em4 ,= ! transmission ( mail x 0 plann$ to connect ! ma9 po/-(fice ) ! sub-po/-(fices by tubes ( a size l>ge en\gh to c>ry all ( ! fir/-class & mo/ ( ! o!r classes ( mail matt]4 ,! sub-po/-(fices w\ld be divid$ into gr\ps1 all ( ! (fices 9 "o gr\p be+ connect$ to ! same l9e1 :i* w\ld t]m9ate at ! ma9 po/-(fice4 ,mo/ ( ! bus9ess w\ld be betwe5 ! ma9 & individual sub-(fices2 9 addition to ?is !re w\ld be "s local mail s5t betwe5 ! sub-(fices :i*1 = (fices 9 ! same gr\p1 c\ld be despat*$ directly )\t pass+ ?r\gh ! ma9 (fice4 ,! advantages to be ga9$ by ! use ( ^! tubes ov] ! pres5t wagon s]vice are v app>5t4 ,x places all ! sub-po/-(fices 9 almo/ in/ant communication ) ! ma9 (fice & ) ea* o!r4 ,x 0 a "p ( ! g5]al plan to lay tubes f ! ma9 po/-(fice to ! railway /ations1 !reby ha/5+ ! despat* & receipt ( mails to & f ! tra9s4 ,x 0 expect$ t ! bulk ( ! bus9ess w\ld consi/ 9 ! deliv]y ( p>cels f ! retail /ores to ! private h\ses 9 ! resid5ce sections ( ! city4 ,( c\rse x w\ld n be practicable to lay a tube to ea* h\se1 b ) a /ation n m ?an f\r or five blocks away1 ! p>cels w\ld be s5t ?r\gh ! tube to ! ne>e/ /ation1 & !n deliv]$ by mess5g]s to ! h\ses ) a m9imum loss ( "t4 ,ladies c\ld d _! %opp+ & f9d _! pur*ases at home :5 !y return$4 ,! same tubes us$ = p>cel deliv]y w\ld also be us$ = a di/rict mess5g] s]vice4 ,) num]\s public /ations 9 conv5i5t locations1 all ! advantages ( ! ,european sy/em w\ld be realiz$ 9 ! quick despat* ( lett]s & telegrams4 ,e "o kn[s h[ mu* "t is consum$ by di/rict mess5g]-boys 9 ! deliv]y ( messages1 especially :5 !y h to g long di/ances1 & no argum5t is requir$ to %[ t ?is "t w\ld be v mu* r$uc$ by ! use ( pneumatic tubes1 besides prompt deliv]y w\ld be made mu* m c]ta94 ,! tubes ( ?is sy/em 7 to be six or eight in*es 9 diamet]1 ) a few small tubes 9 localities :]e ! message s]vice is v heavy4 ,)\t go+ m into detail1 su* 7 9 brief ! plans ( ! promot]s ( ?is new company2 b be=e laun*+ su* an ent]prise1 involv+ a l>ge am\nt ( capital1 !re 7 _m eng9e]+ & me*anical problems to be solv$4 ,x 0 n simply a "q ( obta9+ tubes & lay+ !m 9 ! /reets1 b ways & means = op]at+ !m mu/ be devis$4 ,up to ?is "t only small tubes _h be5 us$ = ! transmission ( telegrams1 messages1 ca%1 & o!r light objects4 ,n[ x 0 propos$ to transmit heavy & bulky mat]ial4 ,!re 0 no exp]i5ce = a guide4 ,! ,clay-,lieb ,pat5ts4--,! ,pneumatic ,transit ,company at ?is "t turn$ to ! ,electro-,pneumatic ,transit ,company1 ( ,new ,j]sey1 a national company t _h be5 9 exi/5ce s9ce #ahhf1 & :i* claim$ to own valuable pat5ts1 = ! ways & means to c>ry out its new ent]prise4 ,! pat5ts 7 ^? ( ,h5ry ,clay & ,*>les ,a4 ,lieb1 & ! rights to use !m 9 ! ,/ate ( ,p5nsylvania 7 procur$ by ! ,pneumatic ,transit ,company1 "u a contract ent]$ into betwe5 ! two companies4 ,! pat5ts claim$ to cov] a practical work+ sy/em by :i* a l>ge numb] ( /ations c\ld be connect$ to a sy/em ( ma9 & bran* tubes1 ) electrically-op]at$ swit*es at ! junctions ( ! bran*es ) ! ma9 l9es4 ,any p]son :o gives ! subject a little ?\ght w at once see ! advantages ( su* a sy/em if x c\ld be made to op]ate4 ,up to ! pres5t "t only s+le- or d\ble-l9e tubes h be5 us$1 )\t bran*es4 ,9 ! ,european sy/ems1 frequ5tly sev]al /ations are locat$ along a l9e1 b ! c>ri]s mu/ /op at ea* /ation1 be exam9$1 & if !y are de/9$ = ano!r /ation1 !y mu/ be r$espat*$4 ,! ca% sy/ems us$ 9 _m ( our l>ge /ores h indep5d5t tubes runn+ f ! c5tral ca%i]'s desk to ea* /ation ab\t ! /ore4 ,x is pla9 to be se5 t1 if sev]al ( ^! /ations c\ld be connect$ by bran*es to a ma9 tube1 a l>ge am\nt ( tub+ w\ld be sav$--a mo/ desirable result4 ,! advantages ( su* a sy/em w\ld be /ill great] = long l9es ( tube laid "u ! pavem5ts1 ext5d+ to /ations locat$ 9 diff]5t p>ts ( a l>ge city4 ,x 0 su* a result t ! pat5ts ( ,clay & ,lieb aim$ to accompli%4 ,9 ord] to demon/rate ! practicability ( ! sy/em1 ! ,electro-,pneumatic ,transit ,company _h con/ruct$ 9 ! basem5t ( ! ,mills ,build+1 on ,broad ,/reet1 ,new ,york1 a %ort l9e ( small brass tub+1 ab\t two or ?ree in*es 9 diamet]1 ) "o bran*1 ?us connect+ ?ree /ations toge!r4 ,! tube 0 v %ort1 probably n m ?an two hundr$ feet 9 l5g?4 ,! air-pressure requir$ 0 v slight1 probably n m ?an an ounce or two1 be+ suppli$ by a small bl[] run by an electric motor4 ,at ! junction ( ! bran* & ! ma9 tube 0 locat$ a swit* t c\ld be mov$ across ! ma9 tube & s deflect ! approa*+ c>ri] into ! bran*4 ,?is swit* 0 mov$ by an electro-magnet1 or sol5oid1 t c\ld be excit$ by press+ a button at ! /ation f :i* ! c>ri] 0 s5t4 ,:5 ! c>ri] pass$ into ! bran* tube x set ! swit* back into its normal position1 s t a second c>ri]1 foll[+ ! fir/1 w\ld pass along ! ma9 tube1 unless ! swit* 0 aga9 mov$ by press+ ! button at ! s5d+ /ation4 ,?is tube 9 ! ,mills ,build+ work$ well1 b x 0 ( a size only suit$ to ! transmission ( ca% 9 a /ore or o!r simil> s]vice4 ,x c\ld n be said1 because ?is tube work$ well1 t a l>g] & long] tube ) num]\s bran*es w\ld "w equally well4 ,9 fact1 !re are sev]al reasons :y su* a tube w\ld n op]ate satisfactorily4 ,! me?od ( op]at+ ! swit*es 0 impracticable4 ,suppose ! bran* tube _h be5 locat$ two miles away f ! s5d+ /ation & t x w\ld take a c>ri] f\r m9utes to travel f ! s5d+ /ation to ! junction ( ! bran* tube4 ,aga91 suppose t we h j despat*$ a c>ri] de/9$ = a /ation on ! ma9 l9e beyond ! junction1 & t we wi% to despat* ! second c>ri] to be swit*$ (f into ! bran* tube1 we mu/ wait at lea/ f\r m9utes1 until ! fir/ c>ri] has pass$ ! junction1 be=e we c press ! button & set ! swit* = ! second c>ri] :i* may be on its way4 ,h[ are we to "k :5 ! fir/ c>ri] has pass$ ! junction1 & :5 ! second w arrive !re1 9 ord] t we may ?r[ ! swit* at ! prop] "t8 ,mu/ we hold our wat* & "t ea* c>ri]8 ,x is pla9 t ?is is n practical4 ,i take ?is z an illu/ration ( ! impracticability ( ! ,clay-,lieb ,sy/em z con/ruct$ 9 ! ,mills ,build+ :5 ext5d$ to practical dim5sions4 ,i w n describe ! me*anism & details ( ! sy/em1 :i* are +5i\s1 b w say 9 pass+ t ! automatic sluice-gates1 :i* "w v well 9 a ?ree-in* tube ) c>ri]s weigh+ an ounce or two & air-pressures ( only a few ounces p] squ>e in*1 w\ld be useless & c\ld n be made to op]ate 9 a six-in* tube ) c>ri]s weigh+ f eight to tw5ty-five p\nds & an air-pressure ( f five to tw5ty-five p\nds p] squ>e in*4 ,= fur!r in=mation ! read] is ref]r$ to ! pat5ts ( ,clay & ,lieb4 ,fran*ises & ,fir/ ,gov]nm5t ,contract4--,9 ! spr+ ( #ahib an ord9ance 0 pass$ by ,common & ,select ,c\ncils1 & sign$ by ! ,mayor ( ! ,city ( ,philadelphia1 p]mitt+ ! ,pneumatic ,transit ,company to lay pneumatic tubes 9 ! /reets ( t city4 ,at ! "t ?is fran*ise 0 grant$ negotiations 7 9 progress ) ! po/-(fice dep>tm5t1 9 ,wa%+ton1 = ! con/ruction ( a six-in* pneumatic tube1 connect+ ! ,ea/ ,*e/nut ,/reet sub-po/-(fice1 at ,?ird & ,*e/nut ,/reets1 ) ! ma9 po/-(fice1 at ,n9? & ,*e/nut ,/reets1 = ! transmission ( mail4 ,?is sub-po/-(fice 0 select$ because m mail passes ?r\gh x daily ?an any o!r sub-(fice 9 ! city1 x be+ locat$ ne> ! c5tre ( ! bank+ di/rict4 ,negotiations 7 delay$ by v>i\s causes1 s t ! contract ) ! gov]nm5t 0 n sign$ until ,octob]1 #ahib4 ,illu/ration3 ,,fig4 #d4 ,illu/ration3 ,,fig4 #e4 ,,six-,,in* ,,pneumatic ,,tubes ,,9 ,,process ,,( ,,bor+ ,,at ,,! ,,%op ,,( ,a4 ,,falk5au1 ,,philadelphia1 ,,pa4 ,se>* = ,tubes4--,x 0 at ?is "t t ! writ] 0 fir/ employ$ by ! ,pneumatic ,transit ,company1 z eng9e]1 to sup]9t5d ! con/ruction ( ?is l9e4 ,! company comm5c$ at once to c>ry out its contract ) ! ,unit$ ,/ates gov]nm5t1 bo? ! po/-(fice dep>tm5t & ! company be+ v desir\s ( hav+ ! "w complet$ be=e w9t]4 ,! "t 0 v %ort = su* an und]tak+1 b wr\ght-iron tubes _h already be5 ord]$ ( a well-kn[n firm :o manufacture pipe & tub+ ( all k9ds4 ,aft] wait+ f\r or five weeks ! fir/ lot ( tubes 7 f9i%$1 b ^u inspection x 0 f\nd t !y 7 n suffici5tly accurate & smoo? on ! int]ior to p]mit ( _! be+ us$ = ! purpose int5d$4 ,! next ?+ t sugge/$ itself 0 seamless drawn brass tubes4 ,:ile !y w\ld be v exp5sive1 ! process ( manufacture makes !m em95tly suit$ = ! purpose1 b !y c\ld n be obta9$ 9 "t4 ,a city ord9ance prohibits ! op5+ ( ! /reets ( ,philadelphia dur+ ! w9t] mon?s except 9 extreme cases4 ,accurate tubes mu/ be _h1 & _h quickly4 ,x !n occurr$ to ! writ] t x might be possible to bore a suffici5t quantity ( ord9>y ca/-iron wat]-pipe & fit ! ends accurately toge!r to answ] our purpose4 ,inquiry 0 made at ne>ly all ! ma*9e-%ops 9 ! city1 to asc]ta9 h[ _m bor+-ma*9es c\ld be put ^u ?is "w ( bor+ ne>ly six ?\s& feet ( six-in* pipe4 ,x 0 f\nd impossible to get ! "w done 9 "t1 if x 0 to be done 9 ! usual mann] ( bor+ ) a rigid b>4 ,at la/ a man 0 f\nd 9 ,mr4 ,a4 ,falk5au1 eng9e] & ma*9i/1 :o 0 prep>$ to contract = ! con/ruction ( twelve special bor+-ma*9es & to bore all ! tub+ requir$4 ,suffice x to say1 t ! ma*9es 7 built1 & ab\t six ?\s& feet ( tubes 7 bor$1 betwe5 ,novemb] #h & ,decemb] #ca4 ,illu/ration3 ,,fig4 #f4 ,,pipe ,,bor+ ,,app>atus4 ,me?od ( ,manufactur+ ,tubes4--,! process ( bor+ 0 novel 9 "s respects1 & might be t]m$ ream+ r ?an bor+4 ,figs4 #d & #e %[ ! int]ior ( ! %op & ! twelve ma*9es4 ,fig4 #f is a draw+ ( "o ( ! ma*9es4 ,a long flexible b> rotat$ ! cutt]-head1 :i* 0 pull$ ?r\gh ! tube1 9 di/9ction f be+ pu%$4 ,9 ord] to give ! fe$+ motion1 a screw 0 atta*$ to ! cutt]-head & ext5d$ ?r\gh ! tube 9 advance ( x4 ,! fe$-screw 0 drawn =w>d by a nut atta*$ to a h&-:eel locat$ at ! opposite end ( ! tube f :i* ! bor+ began4 ,s9ce x 0 n necess>y t ! tubes %\ld be p]fectly /raight1 a me?od ( ?is k9d 0 p]missible1 9 :i* ! cutt]s c\ld be all[$ to foll[ ! cor$ axis ( ! tube4 ,air f a ,/urtevant bl[] 0 =c$ ?r\gh ! tubes dur+ ! process ( bor+1 = ! d\ble purpose ( cle>+ ! *ips f ! cutt]s & keep+ !m cool4 ,aft] ! tubes 7 ream$1 ea* piece _h to be plac$ 9 a la!1 h a c\nt]-bore turn$ 9 ! bottom ( ! bell1 & h ! o!r end squ>$ (f & turn$ = a %ort di/ance on ! outside to fit ! c\nt]-bore ( ! next section4 ,lay+ & ,op5+ ! ,tubes = ,traffic4--,! fir/ tubes 7 laid ab\t ! middle ( ,novemb]1 b ,decemb] #a came be=e ! "w 0 complet$ & special p]mission _h to be obta9$ f ! city to c>ry on ! "w aft] t date4 ,all "w 0 susp5d$ dur+ ! holidays 9 ord] n to int]f]e ) ! holiday trade ( ! /ores on ,*e/nut ,/reet4 ,sev]e fro/s prevail$ at t season1 s t :5 ! "w 0 begun aga91 aft] ! holidays1 bonfires _h to be built 9 ! /reets to ?aw out ! gr\nd 9 ord] to take up ! pav+-/ones & dig ! tr5* = ! tubes4 ,sev]al times ! tr5* 0 fill$ ) sn[ by unusually heavy /orms4 ,not)/&+ all ^! delays & annoyances1 ! "w 0 pu%$ =w>d1 :5 a less det]m9$ company w\ld h giv5 x up1 & 0 f9ally complet$4 ,a =mal op5+ took place on ,febru>y #ag1 #ahic1 :5 ,hon4 ,john ,wanamak]1 !n ,po/ma/]-,g5]al1 s5t ?r\gh ! tube ! fir/ c>ri]1 conta9+ a ,bible wrapp$ 9 ! ,am]ican flag4 ,x 0 c]ta9ly a cr$it to ! ,pneumatic ,transit ,company & its manag]s t !y 7 able to complete ?is fir/ l9e ( tubes s quickly & successfully "u su* try+ circum/ances4 ,! tubes h be5 9 successful op]ation f ! op5+ until ! pres5t "t1 a p]iod ( ne>ly f\r ye>s1 & ! repairs t h be5 made dur+ t "t h n requir$ its /oppage = m ?an a few h\rs4 ,9 ! summ] ( #ahie ! sub-po/-(fice 0 remov$ f ,*e/nut ,/reet to ! basem5t ( ! ,b\rse 7see ,fig4 #g74 ,?is requir$ ! ab&onm5t ( a few feet ( tube on ,*e/nut ,/reet & ! lay+ ( a slightly great] am\nt on ,f\r? ,/reet1 ?us increas+ ! total l5g? ( ! tubes a little4 ,wr\ght-iron tube1 coat$ ) "s alloy1 probably compos$ l>gely ( t9 or z9c1 0 us$ = ?is ext5sion4 ,! wr\ght-iron tube is n z good z ! bor$ ca/ iron4 ,illu/ration3 ,,fig4 #g4 ,,b\rse ,,build+1 ,,philadelphia4 ,illu/ration3 ,,fig4 #h4 ,,pneumatic ,,tubes ,,susp5d$ ,,9 ,,! ,,basem5t ,,( ,,! ,,ma9 ,,po/-,,(fice4 ,description ( ! ,tubes1 ,me?od ( ,lay+1 etc4--,?is ,*e/nut ,/reet l9e consi/s ( two tubes1 "o = despat*+ c>ri]s f & ! o!r to ! ma9 po/-(fice4 ,! di/ance betwe5 ! two /ations is two ?\s& n9e hundr$ & sev5ty-f\r feet1 requir+ five ?\s& n9e hundr$ & =ty-eight feet ( tube4 ,! inside diamet] ( ! tube is six & "o-eigh? in*es1 & x 0 made 9 sections ea* ab\t elev5 feet long1 ) 8bells0 ca/ ^u "o end1 9 ord] to jo9 ! sections ) lead & oakum1 calk$ 9 ! usual mann] ( mak+ jo9ts 9 wat]- & gas-pipes1 ) ?is exception1 t at ! bottom ( ! bell a c\nt]-bore 0 turn$ to receive ! f9i%$ end ( ! next section4 ,by ?us ma*9+ ! ends ( ea* section ( tube & hav+ !m fit accurately toge!r1 male & female1 a practically cont9u\s tube 0 =m$ ) no %\ld]s ^u ! int]ior to ob/ruct ! smoo? passage ( ! c>ri]s4 ,jo9ts made 9 ?is way possess ano!r great advantage ov] flang$ & bolt$ jo9ts1 9 t !y are slightly yield+ )\t leak+1 & s all[ = expansion & contraction due to *anges ( temp]ature4 ,ea* jo9t takes c>e ( ! expansion & contraction ( its section1 :i* is v slight1 b if all 7 add$ toge!r w\ld am\nt to a v l>ge movem5t4 ,ano!r advantage ( ! 8bell0 jo9t is t x p]mits slight b5ds to be made 9 ! l9e ( tube )\t requir+ special b5t sections4 ,:]e %ort b5ds _h to be made1 at /reet corn]s1 9 ent]+ build+s1 & o!r simil> places1 brass tubes 7 us$1 b5t to a radius ( n less ?an six feet1 or ab\t twelve times ! diamet] ( ! tube4 7,"o ( ! brass b5ds may be se5 9 ,fig4 #aj47 ,! b5ds 7 made ( seamless tub+1 b5t to ! desir$ =m & radius 9 a hydraulic ma*9e4 ,to prev5t !m f be+ flatt5$ 9 ! process ( b5d+1 !y 7 fill$ ) res91 :i* 0 aft]w>ds melt$ out4 ,flanges 7 screw$ & sold]$ to ! ends ( ! b5t brass tubes1 & !y 7 bolt$ to special flang$ sections ( ! iron tube4 ,! tubes 7 laid 9 ! tr5* & support$ by hav+ ! gr\nd firmly tamp$ ab\t !m4 ,usually "o tube 0 laid above ! o!r1 ) an iron bracket betwe51 b frequ5tly ?is arrangem5t _h to be dep>t$ f 9 ord] to avoid ob/ructions1 su* z gas- & wat]-pipes1 sew]s1 man-holes1 etc4 ,! dep? ( ! tubes bel[ ! pavem5t v>i$ f two to six feet1 & 9 "o place1 9 ord] to pass "u a sew]1 ! extreme dep? ( ?irte5 feet 0 rea*$4 ,at ! /reet cross+s x 0 frequ5tly difficult to f9d suffici5t space to lay ! tubes4 ,at ! int]section ( ,fif? & ,*e/nut ,/reets a six-in* wat]-ma9 _h to be cut & a b5d put 94 ,a sev5-/r& electric cable1 us$ = telephon+ & signall+1 0 laid ^u ! top ( "o ( ! tubes1 protect$ by a /rip ( 8vulcaniz$ wood10 groov$ to fit ov] ! cable4 ,! cable & protect+ /rip ( wood 7 fa/5$ to ! tube by wr\ght-iron /raps & bolts4 ,! tubes ent] ! ma9 po/-(fice on ! ,*e/nut ,/reet side1 ?r\gh "o ( ! w9d[s1 & are susp5d$ f ! ceil+ along ! corridor 9 ! basem5t = a di/ance ( ne>ly two hundr$ feet4 ,fig4 #h %[s ! tubes ?us susp5d$4 ,!y t]m9ate ^u ! gr\nd floor ab\t ! c5tre ( ! build+1 & ne> ! cancell+ ma*9es4 ,illu/ration3 ,,fig4 #i4 ,,duplex ,,air-,,compressor ,,9 ,,! ,,basem5t ,,( ,,! ,,ma9 ,,po/-,,(fice4 ,illu/ration3 ,,fig4 #aj4 ,,tanks ,,& ,,tube ,,9 ,,! ,,basem5t ,,( ,,! ,,ma9 ,,po/-,,(fice4 ,air-,compressor--,me?od ( ,circulat+ ! ,air4--,! curr5t ( air t op]ates ! tubes is suppli$ by a duplex air-compressor locat$ 9 ! basem5t ( ! ma9 po/-(fice4 ,?is ma*9e is %[n 9 ,fig4 #i1 & requires no detail$ description1 z x does n diff] mat]ially f air-compressors us$ = o!r purposes4 ,! /roke is tw5ty-f\r in*es1 ! diamet] ( ! /eam-cyl9d]s t5 in*es1 & ! air-cyl9d]s eighte5 in*es4 ,! air-cyl9d]s are d\ble act+1 ) poppet-valves1 & h a clos$ suction4 ,! spe$ ( ! ma*9e v>ies slightly1 be+ controll$ by a pressure-regulator t ma9ta9s a practically con/ant pressure 9 ! tank t fe$s ! tube4 ,! eng9es develop a little ov] ?irty horse-p[] "u normal conditions4 ,! pressure ( ! air z x leaves ! compressor is usually six or sev5 p\nds p] squ>e in*4 ,compress+ ! air heats x to ab\t #aef ,f41 b ?is is n suffici5t to require wat]-jackets ab\t ! air-cyl9d]s4 ,f ! compressor ! air fl[s to a tank1 %[n on ! "r 9 ,fig4 #aj1 :]e any oil or dirt conta9$ 9 ! air is deposit$4 ,! pr9cipal purpose ( ! tank is1 h[ev]1 to =m a cu%ion to r$uce ! pulsations 9 ! air caus$ by ! p]iodic dis*>ge f ! cyl9d]s ( ! compressors1 & make ! curr5t 9 ! tube m /eady4 ,f ?is tank ! air fl[s to ! s5d+ app>atus on ! gr\nd floor ( ! po/-(fice & !nce ?r\gh ! outgo+ tube to ! sub-po/-(fice4 ,at ! sub-po/-(fice1 aft] fl[+ ?r\gh ! receiv+ & s5d+ app>atus1 x ent]s ! return tube & fl[s back to ! ma9 (fice1 pass+ ?r\gh ! receiv+ app>atus !re & !n to a tank 9 ! basem5t1--! left tank 9 ,fig4 #aj4 ,! air-compressor draws its supply f ?is tank1 s t ! air is us$ ov] & ov] aga94 ,?is return tank has an op5+ to ! atmosph]e1 :i* all[s air to ent] & make up = any leakage or escape at ! s5d+ & receiv+ app>atus1 !reby ma9ta9+ ! atmosph]ic pressure 9 ! dis*>ge end ( ! tube & 9 ! suction ( ! compressor4 ,! tank s]ves to cat* any moi/ure & dirt t come out ( ! tube4 ,fig4 #aa is a diagram %[+ ! direction & c\rse ( ! air-curr5t4 ,x w be notic$ t bo? ! out-go+ & return tube are op]at$ by pressure1 9 di/9ction f exhau/4 ,! air is =c$ ar\nd ! circuit by ! air-compressor4 ,!re is no exhau/+ f ! return tube4 ,! pressure ( ! air :5 x ent]s ! tube at ! ma9 po/-(fice is1 say1 sev5 p\nds p] squ>e in*2 :5 x arrives at ! sub-po/-(fice ! pressure is ab\t ?ree & ?ree-qu>t]s p\nds1 & :5 x gets back to ! ma9 (fice & ent]s ! return tank1 ! pressure is z]o or atmosph]ic4 ,?us x w be se5 t ! pressure becomes less & less z ! air fl[s along ! tube4 ,?is is n ! pressure t moves ! c>ri]s1 b ! pressure ( ! air 9 ! tube1 a pressure t exi/s :5 !re are no c>ri]s 9 ! tube4 ,x is ! pressure t w\ld be indicat$ if y %\ld drill a hole into ! tube & atta* a gauge4 ,illu/ration3 ,,fig4 #aa4 ,t]m9al ,app>atus4--,:5 ! con/ruction ( ?is l9e 0 begun1 x 0 ! int5tion ( ! ,pneumatic ,transit ,company to use ! app>atus ( ! ,electro-,pneumatic ,transit ,company1 at bo? /ations1 = s5d+ & receiv+ c>ri]s1 & s-call$ work+-draw+s 7 obta9$ = ?is purpose4 ,! s5d+ app>atus 0 con/ruct$ accord+ to ! designs furni%$1 b1 ^u exam9ation ( ! draw+s ( ! receiv+ app>atus1 x 0 s app>5t t x w\ld n "w z int5d$ t x 0 nev] con/ruct$4 ,! writ] 0 ask$ to design an automatic receiv] to /op ! c>ri]s )\t %ock ^u _! arrival at ! /ations1 & to deliv] !m ^u a table )\t appreciable escape ( air1--some?+ t w\ld answ] ! requirem5ts ( ! pres5t plant4 ,illu/ration3 ,,fig4 #ab4 ,,transmitt]4--,,phila4 ,,s5d+ ,,app>atus4 ,! ,s5d]4--,! s5d+ app>atus is = ! purpose ( enabl+ ! op]ator to place a c>ri] 9 ! tube )\t all[+ ! air to escape4 ,9 o!r words1 x is a means ( despat*+ c>ri]s4 ,! app>atus = ?is purpose1 already ref]r$ to1 is simply a valve4 ,a side view & section ( x are %[n 9 ,fig4 #ab4 ,fig4 #ae is a view ( ! app>atus 9 ! ma9 po/-(fice4 ,! s5d+ app>atus is se5 on ! left4 ,fig4 #ac is a view ( ! sub-po/-(fice app>atus1 & "h a man may be se5 9 ! act ( despat*+ a c>ri]4 ,ref]r+ to ! section1 ,fig4 #ab1 x w be se5 t ! s5d+ app>atus consi/s ( a %ort section ( tube support$ on trunnions & enclos$ 9 a circul> box4 ,normally ?is %ort section ( tube /&s 9 l9e ) ! ma9 tube1 & ! air-curr5t passes directly ?r\gh x4 ,x is %[n 9 ?is position 9 ! figure4 ,:5 a c>ri] is to be despat*$1 ?is %ort section ( tube is rotat$ by a h&le until "o end comes into co9cid5ce ) an op5+ 9 ! side ( ! box4 ,9 ?is position ! air fl[s ?r\gh ! box ar\nd ! movable tube4 ,a c>ri] c !n be plac$ 9 ! %ort section ( tube & be rotat$ by ! h&le into l9e ) ! ma9 tube4 ,! c>ri] w !n be c>ri$ along ) ! curr5t ( air4 ,a circul> plate cov]s ! op5+ 9 ! box :]e ! c>ri] is ins]t$ :5 ! s5d+ app>atus is clos$4 ,at ! sub-po/-(fice ?is s5d+ app>atus is plac$ 9 a horizontal position1 b its op]ation is ! same4 ,illu/ration3 ,,fig4 #ac4 ,,receiv+ ,,& ,,s5d+ ,,app>atus ,,9 ,,! ,,sub-,,po/-,,(fice4 ,illu/ration3 ,,fig4 #ad4 ,,app>atus ,,at ,,sub-,,/ation--,,phila4 ,illu/ration3 ,,fig4 #ae4 ,,t]m9als ,,( ,,! ,,tube ,,9 ,,! ,,ma9 ,,po/-,,(fice4 ,sub-,po/-,(fice ,receiv]4--,we h already expla9$ t ! air-pressure 9 ! tube at ! sub-po/-(fice is ab\t ?ree & ?ree-qu>t]s p\nds p] squ>e in*4 ,) su* a pressure we _c op5 ! tube to all[ ! c>ri]s to come out4 ,!y mu/ be receiv$ 9 a *amb] t c be clos$ to ! tube aft] ! arrival ( a c>ri] & !n op5$ to ! atmosph]e4 ,fur!rmore1 ?is *amb] mu/ act z an air-cu%ion to *eck ! mom5tum ( ! c>ri]s4 ,fig4 #ac %[s ! sub-po/-(fice app>atus :5 a c>ri] is be+ deliv]$ f ! receiv+ app>atus1 or1 z we w "n x = conv5i5ce1 ! receiv]4 ,fig4 #ad is a draw+ ( ! same app>atus1 p>tly 9 section1 t %[s m cle>ly its me?od ( op]ation4 ,?is draw+ %[s ! s5d+ app>atus 9 a diff]5t position f ,fig4 #ac1 b t is immat]ial4 ,! receiv] consi/s ( a movable section ( tube1 ab\t twice ! l5g? ( a c>ri]1 clos$ at "o end1 support$ ^u trunnions1 & normally 9 a position to =m a cont9uation ( ! ma9 tube f :i* ! c>ri]s are receiv$4 ,:5 a c>ri] arrives x runs directly into ! receiv]1 :i* be+ clos$ at ! end =ms an air-cu%ion t /ops ! c>ri] )\t %ock or injury4 ,j be=e rea*+ ! receiv+ *amb] ! curr5t ( air passes out ?r\gh slots 9 ! walls ( ! tube into a jacket t conducts x to ! s5d+ app>atus1 z %[n 9 ,fig4 #ad4 ,at ! clos$ end ( ! receiv+ *amb]1 or air-cu%ion1 is a relief valve1 normally held clos$ by a spr+4 ,z ! c>ri] compresses ! air 9 front ( x1 ?is valve op5s & all[s "s ( ! air to escape1 :i* prev5ts ! c>ri] f reb\nd+ into ! tube4 ,"u ! out] end ( ! receiv+ *amb] is a v]tical cyl9d]1 ,e1 ,fig4 #ad1 support$ ^u ! base-plate conta9+ a pi/on4 ,! pi/on ( ?is cyl9d] is connect$ by a pi/on- & connect+-rod to ! receiv+ *amb]4 ,:5 air is admitt$ to ! cyl9d] "u ! pi/on1 ! latt] rises & tilts ! receiv+ *amb] to an angle ( ab\t =ty degrees1 :i* all[s ! c>ri] to slide out4 ,! receiv+ *amb] c>ries a circul> plate1 ,c1 t cov]s ! end ( ! ma9 tube :5 x is tilt$4 ,a small pi/on slide-valve1 ,f1 locat$ ne> ! trunnion ( ! receiv+ *amb]1 controls ! admission & dis*>ge ( air to & f ! cyl9d] ,e1 ^u ! arrival ( a c>ri]4 ,:5 a c>ri] arrives & compresses ! air 9 ! air-cu%ion or receiv+ *amb]1 a small portion ( ?is compress$ air is =c$ ?r\gh pipe ,g1 to a small cyl9d] conta9+ a pi/on & locat$ j above ! pi/on slide-valve ,f4 ,! increas$ pressure act+ on ! pi/on moves x d[nw>d1 & x 9 turn moves ! slide-valve ,f4 ,?us x w be se5 t ! /opp+ ( ! c>ri] causes ! receiv+ *amb] to be tilt$ & ! c>ri] slides out on to an incl9$ plat=m1 ,k4 ,?is plat=m is h+$ at "o end1 & support$ at ! angle se5 9 ! figure by a c\nt]weight4 ,:5 a c>ri] re/s ^u x1 ! weight ( ! c>ri] is suffici5t to be> x d[n into a horizontal position2 9 ?is position ! c>ri] rolls (f on to a table or %elf4 ,! plat=m1 ,k1 is connect$ by rods1 bell-cranks1 etc41 to ! pi/on slide-valve1 s t :5 x sw+s d[nw>d by ! weight ( a c>ri]1 ! slide-valve is mov$ upw>d into its normal position1 & ?is causes ! receiv+ *amb] to tilt back into a horizontal position ready to receive ! next c>ri]4 ,! "t t elapses f ! arrival ( a c>ri] until ! receiv+ *amb] has return$ to its horizontal position is n m ?an ?ree or f\r seconds4 ,no?+ c\ld op]ate 9 a m satisfactory mann]4 ,ma9 ,po/-,(fice ,receiv]4--,at ! ma9 po/-(fice we h a receiv] ( a diff]5t type4 ,x w be rememb]$ t ! pressure 9 ! return tube at ! ma9 po/-(fice is ne>ly d[n to z]o or atmosph]ic1 s t we c op5 ! tube to all[ ! c>ri]s to pass out )\t noise or an annoy+ bla/ ( air4 ,figs4 #ae & #af %[ ! ma9-(fice app>atus1 & ,fig4 #ag is a draw+ ( ! same4 ,"h ! receiv] consi/s ( a section ( tube clos$ by a sluice-gate1 locat$ at ,b1 ,fig4 #ag4 ,! air-curr5t passes out ?r\gh slots 9 ! tube into a bran* pipe lead+ to ! return tank 9 ! basem5t4 ,^! slots are locat$ ab\t f\r feet back ( ! sluice-gate1 s t ! portion ( ! tube betwe5 ! slots & ! sluice-gate =ms an air-cu%ion to *eck ! mom5tum ( ! c>ri]s4 ,! sluice-gate is rais$ & l[]$ by a pi/on mov+ 9 a cyl9d] locat$ j above ! gate4 ,! movem5t ( ?is pi/on is controll$ by a pi/on slide-valve 9 a mann] simil> to ! app>atus at ! sub-po/-(fice4 ,air = op]at+ ! pi/on is convey$ ?r\gh ! pipe ,d1 ,fig4 #ag1 f ! pipe lead+ f ! air-compressor to ! s5d+ app>atus4 ,?is air is at ab\t sev5 p\nds pressure p] squ>e in*4 ,illu/ration3 ,,fig4 #af4 ,,receiv+ ,,app>atus ,,at ,,! ,,ma9 ,,po/-,,(fice4 ,illu/ration3 ,,fig4 #ag4 ,,app>atus ,,at ,,! ,,ma9 ,,(fice--,,phila4 ,:5 a c>ri] arrives1 aft] pass+ ! slots t all[ ! air-curr5t to fl[ into ! bran* pipe1 x compresses ! air 9 front ( x aga9/ ! gate4 ,?is compression *ecks its mom5tum1 & x comes gradually to re/4 ,! air compress$ betwe5 ! c>ri] & ! sluice-gate op]ates to move ! pi/on slide-valve1 !reby admitt+ air to ! gate cyl9d] "u ! pi/on1 :i* rises1 c>ry+ ) x ! sluice-gate4 ,! tube is n[ op5 to ! atmosph]e1 & !re is j suffici5t pressure 9 ! tube to pu% ! c>ri] out on to a table arrang$ to receive x4 ,z ! c>ri] passes out ( ! tube x lifts a f+] out ( its pa?4 ,?is f+] is locat$ at ,e1 ,fig4 #ag1 & :5 x is lift$ by ! pass+ c>ri] x moves ! pi/on slide-valve1 & ! sluice-gate is clos$4 ,a valve is locat$ 9 ! bran*-pipe t conducts ! air to ! return tank 9 ! basem5t4 ,if ! pressure 9 ! tube is n suffici5t to pu% ! c>ri] out on to ! table1 ?is valve is p>tially clos$1 !reby increas+ ! pressure to a desir$ am\nt4 ,illu/ration3 ,,fig4 #ah4 ,,c>ri]4 ,illu/ration3 ,,fig4 #ai4 ,,c>ri]4 ,! ,c>ri]4--,we h frequ5tly spok5 ( ! c>ri]1 :i* conta9s ! mail & o!r p>cels t are transport$ f "o (fice to ! o!r4 ,9 ,fig4 #ac1 %[+ ! sub-po/-(fice app>atus1 we see "o ( ^! c>ri]s be+ despat*$ by ! att5dant & ano!r be+ deliv]$ f ! tube4 ,9 ,fig4 #ae sev]al c>ri]s may be se5 /&+ on ! floor4 ,fig4 #ah %[s a c>ri] ) ! lid op51 ready to receive a *>ge ( mail1 & ,fig4 #ai %[s ! same clos$1 ready = despat*+4 ,! con/ruction ( ! c>ri] is %[n by ! draw+1 ,fig4 #bj4 ,! body ( ! c>ri] is /eel1 ab\t "o-?irty-second ( an in* 9 ?ickness4 ,x is made f a flat %eet1 b5t into a cyl9d]1 rivet$1 & sold]$4 ,! l5g? outside is eighte5 in*es1 & ! inside diamet] is five & "o-qu>t] in*es4 ,! front end is made ( a convex disk ( /eel1 /amp$ 9 ! desir$ =m1 & secur$ to ! body ( ! c>ri] by rivets1 ) ! convex side inw>d4 ,x is necess>y to h a buff] ^u ! front end ( ! c>ri] to protect x f bl[s t x might receive1 & ?is buff] is made by fill+ ! concave side ( ! front head ) felt1 held 9 place by a disk ( lea!r & a c5tral bolt4 ,! lea!r disk is made ( two pieces1 rivet$ toge!r1 ) a /eel wa%] betwe54 ,! /eel wa%] is atta*$ to ! head ( ! bolt4 ,! c>ri] is support$ 9 ! tube on two be>+-r+s1 locat$ on ! body ( ! c>ri] a %ort di/ance f ea* end4 ,! location ( ^! r+s is s *os5 t x p]mits a c>ri] ( maximum l5g? to pass ?r\gh a b5d 9 ! tube ( m9imum radius )\t becom+ w$g$4 ,?is is a v important feature 9 ! con/ruction ( c>ri]s1 b does n appe> to h be5 utiliz$ 9 o!r sy/ems4 ,illu/ration3 ,,fig4 #bj4 ,,mail ,,c>ri]4--,,phila4 ,! be>+-r+s are made ( fibr\s wov5 mat]ial1 especially prep>$1 & held 9 place by be+ clamp$ betwe5 two metal r+s1 "o ( :i* is rivet$ to ! body ( ! c>ri]4 ,( c\rse ^! r+s we> out & h to be replac$ occasionally1 b _! usual life is ab\t "o ?\s& miles4 ,! re> end ( ! c>ri] is clos$ by a h+$ lid & secur$ by a special lock4 ,! lock consi/s ( ?ree radial bolts t pass ?r\gh ! body ( ! c>ri] & ! rim ( ! lid4 ,^! bolts are ?r[n by ?ree cams1 atta*$ to a %ort %aft t passes ?r\gh ! lid & has a h&le or lev] atta*$ to x ^u ! outside ( ! lid4 ,?is cam-%aft is locat$ out ( ! geometrical c5tre ( ! lid 9 su* a position t :5 ! lev] or h&le is swung ar\nd 9 ! unlock$ position1 x projects beyond ! p]iph]y ( ! lid1 & 9 ?is position ! c>ri] w n ent] ! tube4 ,:5 ! lid is clos$ & lock$1 ! lev] lies across ! lid 9 ! position %[n 9 ,fig4 #ai1 & :5 ! c>ri] is 9 ! tube x _c become unlock$1 = ! lev] _c sw+ ar\nd )\t com+ 9 contact ) ! wall ( ! tube4 ,?is insures aga9/ ! possibility ( ! c>ri]s op5+ dur+ transit ?r\gh ! tube4 ,! empty c>ri]s weigh ab\t n9e p\nds1 & :5 fill$ ) mail1 f twelve to fifte5 p\nds4 ,!y h a capacity = two hundr$ ord9>y lett]s1 pack$ 9 ! usual mann]4 ,op]ation ( ! ,tubes4--,! tubes are kept 9 con/ant op]ation dur+ ! day1 & six days ( ! week4 ,! air-compressor is />t$ at n9e o'clock 9 ! morn+ & runs until sev5 9 ! ev5+1 except dur+ ! noon h\r1 ! air fl[+ 9 a con/ant /eady curr5t ?r\gh ! tubes4 ,:5 a c>ri] is plac$ 9 ! tube x is c>ri$ along 9 ! curr5t )\t appreciably affect+ ! load on ! compressor4 ,c>ri]s may be despat*$ at six-second int]vals1 & :5 !y are despat*$ ?us frequ5tly at ea* (fice1 !re w be eighte5 c>ri]s 9 ! tube at ! same "t4 ,if t5 c>ri]s p] m9ute are despat*$ f ea* (fice1 & ea* c>ri] conta9s two hundr$ lett]s1 ! tube has a c>ry+ capacity ( two hundr$ & =ty ?\s& lett]s p] h\r1 :i* is f> beyond ! requirem5ts ( ?is (fice4 ,ab\t five hundr$ c>ri]s a day are despat*$ f ea* (fice4 ,?is v>ies consid]ably on diff]5t days & at diff]5t seasons ( ! ye>4 ,exp]i5ce has taught t a c]ta9 p]iod ( "t %\ld elapse betwe5 ! despat*+ ( c>ri]s1 9 ord] t !y may n come 9 contact ) ea* o!r1 & t ! receiv]s may h "t to act4 ,) ! pres5t plant ?is p]iod is made ab\t six seconds4 ,9 ord] to make x impossible = c>ri]s to be despat*$ m frequ5tly ?an ?is1 "t-locks are atta*$ to ! s5d+ app>atus4 ,"o ( ^! locks may be se5 9 ,fig4 #ac1 connect$ to ! h&le ( ! s5d+ app>atus4 ,x is s arrang$ t :5 a c>ri] is despat*$ a weight is rais$ & all[$ to fall1 c>ry+ ) x a pi/on 9 a cyl9d] fill$ ) oil4 ,:ile ! weight is ris+ & fall+ ! s5d+ app>atus is lock$1 b becomes unlock$ :5 ! weight is all ! way d[n4 ,a by-pass 9 ! cyl9d] p]mits ! oil to fl[ f "o side ( ! pi/on to ! o!r1 & ! size ( ?is by-pass c be regulat$1 ?us det]m9+ ! "t t ! weight %all take 9 desc5d+4 ,?is makes a simple & effective "t-lock t does n get out ( ord]4 ,! "t requir$ = a c>ri] to travel f ! ma9 to ! sub-po/-(fice is sixty seconds1 & f ! sub- to ! ma9 po/-(fice1 fifty-five seconds4 ,?is diff]5ce ( "t 9 go+ & return+ is due to ! expansion ( ! air 9 ! tube1 z w be expla9$ m fully 9 ano!r place4 ,! di/ance betwe5 ! (fices be+ two ?\s& n9e hundr$ & sev5ty-f\r feet1 gives an av]age spe$ ( ab\t fifty-two feet p] second1 or #ce4bg miles p] h\r4 ,( c\rse ! spe$ c be increas$ by increas+ ! air-pressure1 b ?is spe$ is f\nd 9 practice to be ample = all requirem5ts4 ,9 ord] to give "s idea ( ! en]gy possess$ by "o ( ^! c>ri]s travell+ at ?is spe$1 x may be said t if ! end ( ! tube 7 left op5 & turn$ upw>d1 an em]g+ c>ri] w\ld rise ab\t =ty feet into ! air4 ,x is easy to imag9e h[ app>atus1 dep5d+ = its op]ation ^u impact ) a mov+ c>ri]1 w\ld be soon de/roy$1 z well z ! c>ri]s !mselves4 ,?is is :y receiv+ app>atus us$ ) small tubes & light c>ri]s _c be appli$ to l>ge tubes ) heavy c>ri]s4 ,no s]i\s tr\ble has ev] be5 exp]i5c$ f c>ri]s gett+ w$g$ 9 any "p ( ^! tubes4 ,b5efits ( ! ,sy/em4--,! advantages to ! po/-(fice dep>tm5t by ! adoption ( ?is sy/em h be5 num]\s1 & ! po/-(fice (ficials :o are famili> ) ! op]ation ( ! tubes frequ5tly speak 9 high t]ms ( _! usefulness4 ,=m]ly ! mail 0 transport$ f "o (fice to ! o!r by a wagon mak+ a trip e half-h\r4 ,consid]able "t has be5 sav$ by ! great] spe$ ( transit1 b ev5 m "t is ga9$ by keep+ ! mail mov+ in/ead ( all[+ x to accumulate & !n despat*+ x 9 bulk4 ,) ! pneumatic sy/em a lett] po/$ 9 ! sub-po/-(fice w rea* its de/9ation j z quickly z if po/$ at ! ma9 (fice1 & sometimes m quickly4 ,let u take an example1 fir/1 ) ! old wagon s]vice4 ,suppose t y drop a lett] 9 ! sub-po/-(fice2 x lies !re1 say1 fifte5 m9utes wait+ = ! dep>ture ( ! next wagon2 x is put into a p\* ) hundr$s ( o!r lett]s1 & t5 m9utes are consum$ 9 transport+ x to ! ma9 (fice4 ,:5 x arrives !re ! p\* is ?r[n on ! floor at ! entrance ( ! build+2 9 a few m9utes1 m or less1 a cl]k takes ! p\*1 ?r[s x on a truck & :eels x ar\nd to ! cancell+ ma*9es1 :]e x may lie = five or t5 m9utes m be=e be+ op5$1 & !n p]haps five m9utes w elapse be=e y\r lett] rea*es ! cancell+ ma*9e4 ,x w\ld n be unusual = ?ree-qu>t]s ( an h\r to elapse f ! "t y dropp$ y\r lett] 9 ! (fice until x 0 cancell$4 ,n[ ) ! pneumatic tube s]vice =ty m9utes ( ?is "t w be sav$2 = imm$iately aft] y drop y\r lett] 9 ! (fice x w be despat*$ ?r\gh ! tube & deliv]$ on ! table 9 front ( ! cancell+ ma*9es4 ,soon aft] ! tubes 7 in/all$ ! po/ma/]'s att5tion 0 call$ to an in/ance :]e lett]s f ! sub-(fice 7 s5t ?r\gh ! tube & 7 despat*$ to ,new ,york ,city "o tra9 e>li] ?an !y c\ld h be5 _h ! old wagon s]vice be5 9 use4 ,p frequ5tly po/ lett]s reque/+ t !y be s5t ?r\gh ! tube2 ( c\rse !y w\ld be s5t 9 t way if ! reque/ 0 n made1 b x %[s t ! public recognize ! bett] s]vice4 ,=m]ly mail 0 collect$ f ! /reet boxes 9 ! bank+ section ( ! city & ! collectors c>ri$ x to ! ma9 (fice4 ,aft] ! tubes 7 in/all$ ?is mail 0 c>ri$ to ! sub-po/-(fice to be s5t ?r\gh ! tube1 & ! "t =m]ly occupi$ 9 walk+ to ! ma9 (fice 0 !n utiliz$ 9 hav+ ! m5 face up ! lett]s ready = ! cancell+ ma*9es1--a d\ble sav+ 9 "t besides mak+ _! labor mu* light] & enabl+ !m to d m useful "w4 ,s9ce ! sub-(fice has be5 e/abli%$ 9 ! ,b\rse1 x has be5 made a di/ribut+ z well z receiv+ (fice4 ,at lea/ two m deliv]ies ( mail are made ea* day 9 ! ,b\rse build+ ?an 9 any o!r (fice build+ 9 ! city4 ,all lett]s mail$ 9 ! sub-(fice ) a special deliv]y /amp are despat*$ ?r\gh ! tube imm$iately4 ,x is n[ ne>ly f\r ye>s s9ce ! sy/em 0 put into op]ation4 ,dur+ t "t m ?an ?irty-five million lett]s h be5 transport$1 & all ! repairs to ! sy/em h n requir$ x to be /opp$ = m ?an a few h\rs4 ,dur+ ! fir/ ye> ! ,pneumatic ,transit ,company op]at$ ! tubes at _! own exp5se1 agree+ at ! end ( t "t to take !m out if ! gov]nm5t s reque/$4 ,s9ce ! fir/ ye> ! gov]nm5t has paid ! runn+ exp5ses4 ,su* is ! hi/ory ( ! fir/ ,unit$ ,/ates pneumatic po/al sy/em4 ,su* is ! hi/ory ( ! fir/ pneumatic tubes ( suffici5t size to c>ry all ! fir/ class & mo/ ( ! l[] classes ( mail1 9 ?is or any o!r c\ntry1 s f> z ! writ] kn[s4 ,,*apt] ,,iii4 ,,! ,,sy/em ,,& ,,app>atus ,,( ,,! ,,bat*ell] ,,pneumatic ,,tube ,,company4 ,g5]al ,arrangem5t & ,adaptability ( ! ,sy/em4--,! exp]i5ce ga9$ 9 ! con/ruction & op]ation ( ! ,philadelphia po/-(fice tubes has naturally sugge/$ improvem5ts t c be made 9 future con/ruction1 &1 fur!rmore1 x has taught u :at ! requirem5ts w be ( an ext5sive sy/em ( tubes laid 9 ! /reets ( our cities1 bo? = ! transmission ( mail & = a g5]al comm]cial bus9ess4 ,s9ce ! ,philadelphia po/-(fice tube 0 complet$1 we h be5 busily engag$ 9 work+ out all ! details ( a sy/em ( _m /ations s connect$ toge!r t c>ri]s c be despat*$ 9 ! mo/ direct mann] possible f any /ation to any o!r4 ,x is ! purpose ( ! pres5t *apt] to describe ?is sy/em4 ,:ile ! ,pneumatic ,transit ,company has ample field 9 ! ,/ate ( ,p5nsylvania to c>ry out ! "w :i* x has mapp$ out1 a field broad en\gh to yield a good pr(it = ! capital inve/$1 !re is no reason :y ! sy/em %\ld be limit$ to "o ,/ate4 ,s1 9 ord] to obta9 a broad] *>t]1 cov]+ all places :]e pneumatic s]vice may be ne$$1 a new corporation 0 =m$ & /yl$ ! ,,bat*ell] ,,pneumatic ,,tube ,,company4 ,x is impossible to lay d[n a rigid sy/em equally well adapt$ to all places & purposes4 ,we mu/ accommodate ourselves some:at to circum/ances4 ,= example1 ! po/-(fice dep>tm5t may require "o size ( tube1 arrang$ to op]ate 9 a p>ticul> way1 :ile ! requirem5ts ( a p>cel deliv]y bus9ess w\ld be utt]ly diff]5t4 ,! geographical location ( ! /ations w h mu* to d ) ! g5]al arrangem5t2 also ! condition ( ! /reets4 ,"s ( ! /reets ( our l>ge cities are s fill$ ) wat]- & gas-pipes1 electrical conduits1 sew]s1 /eam-pipes1 etc41 etc41 t x is almo/ impossible to f9d space = pneumatic tubes1 especially ( l>ge diamet]4 ,railway or wat] facilities h mu* to d ) ! location ( a c5tral pump+ /ation1 on acc\nt ( ! coal supply4 ,all ( ^! & _m o!r ?+s h to be tak5 into consid]ation 9 plann+ a sy/em = any locality4 ,we h an example ( a peculi> location & conditions 9 a propos$ l9e ( tubes ov] ! ,new ,york & ,brooklyn bridge connect+ ! ma9 po/-(fices ( ^? cities4 ,?is w\ld be 9 _m respects a unique plant4 ,two air-compressors w\ld be us$1 "o at ea* (fice4 ,9 ord] to give a g5]al idea h[ a l>ge numb] ( /ations c be connect$ into "o sy/em1 ! diagram ,fig4 #ba has be5 drawn4 ,we h already ref]r$ to ! attempts ( ,clay & ,lieb to devise means :]eby sev]al /ations c\ld be locat$ along a ma9 l9e & c>ri]s be s5t f any /ation to any o!r ?r\gh ! ma9 l9e4 ,_! me?od 0 to use bran* tubes lead+ (f f ! ma9 l9e ) swit*es at ! junctions4 ,!y deflect$ ! air-curr5t into ! bran* by plac+ an automatic clos$ valve 9 ! ma9 l9e j beyond ! junction1 return+ ! air f ! bran* to ! ma9 l9e j beyond ! valve4 ,! c>ri]s 7 to op5 & close ?is valve automatically z !y pass$4 ,! bran* & swit* sy/em has _m attractions = ! inv5tor1 & ^u fir/ ?\ght x w\ld seem ! mo/ feasible solution ( ! problem4 ,x has be5 ! dream ( m ?an "o inv5tor1 z ! records ( ! pat5t-(fice %[1 b no "o has succe$$ 9 work+ x out4 ,! curr5t ( air _c be divid$2 c>ri]s pass+ f ! bran* into ! ma9 l9e mu/ n collide ) o!r c>ri]s runn+ 9 ! ma9 l9e2 a c]ta9 m9imum di/ance mu/ always be ma9ta9$ betwe5 ! c>ri]s 9 ! same tube2 :5 a c>ri] is despat*$ x mu/ g directly to ! /ation = :i* x is int5d$ )\t fur!r att5tion f ! s5d] & x mu/ n int]f]e ) o!r c>ri]s2 exp5se ( manufacture prohibits ! use ( any b r\nd smoo? tubes up to eight in*es 9 diamet]1 h5ce projections _c be plac$ ^u ! c>ri] to give x an individuality & cause x to op]ate a swit* at any p>ticul> po9t along ! l9e2 ! c>ri] is free to rotate 9 a r\nd tube ab\t its longitud9al axis1 !re=e1 its individuality mu/ be indicat$ by "s symmetrical m>k+ ab\t ?is axis1 if x is to be automatic 9 its op]ation2 ! spe$ ( ! c>ri] is s high t electrical contacts plac$ 9 di/9ctive positions on ! c>ri]s _c be us$ :ile x is 9 motion1 = me*anism hav+ in]tia c\ld n be mov$ dur+ ! %ort "t t ! electric circuit w\ld be clos$2 only ! simple/ atta*m5ts c be made to ! c>ri]1 = con/ructional reasons & because ( ! r\gh usage t !y receive4 ,^! & num]\s o!r reasons make ! problem mo/ difficult4 ,we h n attempt$ to solve x by ! use ( bran* tubes & electrically op]at$ swit*es1 b h adopt$ ! simpl] & equally effective me?od ( c>ry+ ! ma9 l9e ?r\gh ea* ( ! /ations t x unites4 ,9 our sy/em ea* c>ri] has an individuality det]m9+ ! /ation at :i* x w be dis*>g$ f ! tube4 ,by a simple atta*m5t to1 ! front end ( ! c>ri]1 consi/+ ( a circul> metal disk1 ! s5d] s m>ks ! c>ri] t x w pass all /ations until x arrives at ! /ation = :i* x 0 de/9$ & w !re pass out ( ! tube4 ,9 addition to ?is a me?od has be5 devis$ :]eby c>ri]s c be ins]t$ into ! tube )\t ! possibility ( collision ) c>ri]s already runn+ 9 ! tube4 ,illu/ration3 ,,fig4 #ba4 ,a ,,diagram ,,%[+ ,,v>i\s ,,me?ods ,,( ,,connect+ ,,! ,,/ations ,,( ,a ,,l>ge ,,sy/em ,,) ,,pneumatic ,,tubes4 ,ref]r+ n[ to ! diagram1 ,fig4 #ba1 we h "h an imag9>y sy/em :i* we w suppose to be locat$ 9 "s l>ge city4 ,! two l>ge squ>es ,i & ,,ii indicate c5tral pump+ /ations1 & ! small squ>es ,a1 ,b1 ,c1 ,d1 etc41 indicate receiv+ & s5d+ /ations4 ,"s ( ! /ations1 su* z ,a1 ,b1 ,c1 ,d1 ,e1 ,f1 & ,y1 :i* d a l>ge am\nt ( bus9ess & may be suppos$ to be l>ge retail /ores1 are connect$ directly ) ! c5tral /ation by d\ble tubes1 "o = s5d+ & ! o!r = receiv+ c>ri]s4 ,two small] /ores1 su* z ,g & ,h1 may be locat$ on ! same l9e4 ,at ,i1 ,j1 ,k1 & ,l we h f\r /ations1 all connect$ by ! same d\ble l9e ( tubes4 ,^! /ations we w imag9e to be locat$ 9 ! resid5ce section ( ! city4 ,c>ri]s conta9+ p>cels ( m]*&ise or o!r matt] de/9$ = private resid5ces w\ld be s5t f ! /ores ,a1 ,b1 ,c1 etc41 to ! c5tral /ation ,i1 :]e !y w\ld be transf]r$ to ! l9e #b & be adju/$ to /op at ! /ation ne>e/ ! resid5ce to :i* ! p>cels 7 address$4 ,f ?is /ation ! p>cels w\ld be deliv]$ by mess5g]s to ! resid5ces4 ,if a c>ri] is to be s5t f ! c5tral /ation ,i to /ation ,k1 x w be s adju/$ be=e x is put into ! tube t x w pass /ations ,i & ,j1 b be dis*>g$ automatically f ! tube :5 x arrives at /ation ,k4 ,9 a simil> mann] c>ri]s c be despat*$ f /ation ,l to /ation ,i or f /ation ,j to /ation ,l4 ,9 pass+ ?r\gh ! c5tral /ation ! c>ri]s are manually transf]r$ f "o l9e to ano!r4 ,9 ano!r "p ( ! city we may h ano!r c5tral pump+ /ation1 ,,ii2 & ! two c5tral /ations may be connect$ by a d\ble trunk l9e1 #c4 ,aga91 we h l9es radiat+ f ?is c5tral /ation1 z %[n by /ation ,y4 ,!re w be "s localities :]e x w be an advantage to arrange ! /ations ^u a loop1 z %[n 9 circuit #d1 :]e /ations ,s1 ,t1 ,u1 ,v1 ,w1 & ,x are connect$ toge!r 9 ?is way4 ,or we c comb9e ! two arrangem5ts ( loop & direct l9e1 z %[n 9 circuit #e4 ,/ations ,o & ,r are on ! d\ble l9e1 b f ,o a loop is =m$ includ+ /ations ,n1 ,m1 ,p1 & ,q4 ,"h x is suppos$ t ! /ations ,o & ,r d a mu* l>g] bus9ess ) ! c5tral /ation ,,ii ?an ! /ations ,n1 ,m1 ,p1 & ,q1 ?is be+ ! pr9cipal reason = plac+ !m on ! d\ble l9e4 ,all c>ri]s mu/ be return$ to ! /ation f :i* !y 7 s5t1 or o!rs to replace !m1 o!rwise !re w be an accumulation ( c>ri]s at "s ( ! /ations4 ,x is l a railway3 !re mu/ be z _m tra9s despat*$ 9 "o direction z ! o!r1 ea* day4 ,/ation ,o c receive a c>ri] f ! c5tral /ation & return x directly1 b :5 /ation ,n receives "o x mu/ be return$ via ,m1 ,p1 ,q1 ,o1 & ,r1 a mu* long] r\te ?an t by :i* x 0 receiv$4 ,?is disadvantage is comp5sat$1 :5 /ations ,n1 ,m1 ,p1 & ,q d only a small am\nt ( bus9ess1 by ! less co/ ( lay+ a s+le l9e4 ,if a c>ri] is to be s5t f ,m to ,n1 x mu/ g via ,p1 ,q1 & ,o1 be+ manually transf]r$ at ,o f ! 8d[n0 to ! 8up0 l9e4 ,p c s5d directly to ,q1 b ,q mu/ s5d to ,p via ,o1 ,n1 & ,m4 ,r c s5d directly to ,o & ,o to ,r4 ,simil>ly 9 circuit #d ! c>ri]s mu/ all travel ar\nd ! loop 9 ! same direction1 %[n by ! arr[s4 ,/ation ,s c receive c>ri]s directly f ! c5tral /ation1 b !y mu/ return via ,u1 ,w1 ,x1 ,v1 & ,t4 ,aga91 we may h a d\ble-loop l9e1 z indicat$ 9 ! diagram by circuit #f4 ,"h five /ations1 a1 b1 c1 d1 & e1 are connect$ by a loop consi/+ ( two l9es ( tube1 9 :i* ! air circulates 9 "o direction 9 "o l9e & 9 ! opposite direction 9 ! o!r4 ,"h b c s5d directly to c1 c directly to b1 & e to b via d & c1 or via c5tral & a4 ,?is is an arrangem5t t w\ld be us$ :]e !re is a l>ge am\nt ( bus9ess betwe5 ! /ations on ! loop4 ,z /at$ be=e1 ! be/ arrangem5t = any p>ticul> locality dep5ds entirely ^u circum/ances4 ,size ( ,tubes4--,! pneumatic-tube sy/em t we are describ+ is n limit$ to any p>ticul> size ( tube4 ,! size is usually det]m9$ by ! numb] & size ( packages to be transport$4 ,a small tube1 two or ?ree in*es 9 diamet]1 is be/ suit$ = telegrams & messages2 mail1 p>cels1 etc41 require a six- or eight-in* tube1 :ile mail p\*es & bulky mat]ial1 a ?irty-six in* or possibly l>g] tube4 ,we divide tubes into ?ree classes1 accord+ to _! size1 nam+ !m small1 l>ge1 & v l>ge tubes4 ,by small tubes we mean ^? n l>g] ?an ?ree or possibly f\r in*es 9 diamet]4 ,l>ge tubes are ^? hav+ a diamet] m ?an f\r in*es & n m ?an eight in*es4 ,v l>ge tubes include all t are m ?an eight in*es4 ,?is classification is = conv5i5ce1 b x has a deep] significance4 ,= example1 9 ! transportation ( mail1 x mu/ ei!r be h&l$ 9 bulk1 t is1 9 p\*es1 or 9 brok5-bulk1 t is1 loose or ti$ up 9 small packages4 ,!re are _m advantages 9 transport+ x 9 brok5-bulk1 9 fact1 !re are v few places :]e x c\ld be h&l$ 9 any o!r way4 ,= ?is s]vice six- or eight-in* tubes--n l>g]--are be/ suit$4 ,! c>ri]s are light en\gh to be easily h&l$2 !y are n s l>ge 9 capacity z to make x necess>y to wait = an accumulation ( mail to fill !m2 !y c be deliv]$ f ! tube on to tables at any po9t 9 ! build+ :]e ! mail is want$1 = cancell+1 di/ribution1 or p\*+1 ?us r5d]+ a v rapid s]vice2 ! mail is kept mov+ 9 an almo/ con/ant /ream1 keep+ ! po/al employees m uni=mly employ$2 special c>ri]s c be despat*$ ) 8special deliv]y0 lett]s4 ,9 o!r words1 ! mo/ rapid s]vice c be r5d]$ by ?is size ( tube4 ,if a l>g] ?an eight-in* tube is to be us$ = mail s]vice1 x %\ld be n less ?an ?irty-six in*es4 ,c>ri]s l>g] ?an eight in*es _c be h&l$3 !y are too heavy4 ,!y are also too heavy to slide ?r\gh ! tube1 h5ce1 mu/ be m\nt$ ^u :eels4 ,x is n practical to make a c>ri] on :eels less ?an eighte5 or tw5ty-f\r in*es1 & ! c>ri] mu/ be at lea/ tw5ty-f\r in*es to conta9 a l>ge mail-p\*4 ,n[1 if we are go+ to despat* mail-p\*es ?r\gh a pneumatic tube we mu/ s5d m ?an "o 9 a c>ri]1 o!rwise ! s]vice w be too sl[4 ,su* l>ge c>ri]s c\ld n be despat*$ (t5] ?an once or at mo/ twice 9 a m9ute4 ,suppose we 7 to transport ! mail f a railway /ation to a ma9 po/-(fice4 ,a tra9 arrives )1 say1 sixty p\*es4 ,if only "o p\* c\ld be put into a c>ri] & ! c>ri]s c\ld be despat*$ at half-m9ute int]vals1 x w\ld take ?irty m9utes to despat* all ! p\*es4 ,n[1 suppose we make ! tube ?irty-six in*es4 ,! c>ri]s w be eight feet long & w conta9 f twelve to fifte5 p\*es4 ,five c>ri]s w\ld conta9 ! entire tra9-load ( mail1 & !y c\ld be despat*$ 9 f\r or five m9utes4 ,illu/ration3 ,,fig4 #bb4 ,,cross-,,section ,,( ,a #cf-;,,in* ,,tube4 ,illu/ration3 ,,fig4 #bc4 ,,c>ri] ,,= ,a #cf-;,,in* ,,tube4 ,sy/em ( ,v ,l>ge ,tubes4--,! cross-section ( a ?irty-six-in* tube is %[n 9 ,fig4 #bb4 ,x is built flat on ! bottom & sides1 ) an ar*$ top4 ,! floor is ( concrete conta9+ creosot$ ties2 ! side walls & top are ( brick1 pla/]$ ) cem5t ^u ! int]ior4 ,! two tubes may be built "o above ! o!r or side by side1 dep5d+ ^u ! condition ( ! /reets1 b "o common sep>at+ wall w s]ve = bo?4 ,! c>ri]s1 "o ( :i* is %[n 9 ,fig4 #bc1 run on two rails laid close to ! sides ( ! tube4 ,at curves a gu>d-rail is plac$ ^u ! side wall1 mak+ x impossible = a c>ri] to leave ! track4 ,! c>ri]s are made ( h>d wood ) an iron frame1 & are z light z consi/5t ) ! s]vice requir$ ( !m4 ,!y are op5 on top4 ,_! outside dim5sions are ?irty-f\r in*es by ?irty-f\r in*es by eight feet4 ,! s5d+ & receiv+ app>atus = ^! v l>ge tubes h to be specially design$ = ea* p>ticul> /ation1 s no attempt w be made "h to describe !m4 ,! air-pressure requir$ dep5ds ^u ! l5g? ( ! l9e4 ,if x 7 n m ?an six or eight ounces a fan w\ld be us$ to ma9ta9 ! air-curr5t1 b = pressures above ?is1 up to a p\nd or two p] squ>e in*1 "s =m ( positive bl[] w\ld be us$4 ,at ! /ations consid]able floor space or 8y>d room0 w\ld be requir$ = side tracks1 swit*es1 etc4 ,usually ! basem5t ( a build+ w\ld h to be utiliz$ = ! t]m9ation ( su* a tube4 ,!re are b few places 9 our l>ge cities :]e ! /reets are s free f pipes1 sew]s1 conduits1 etc41 t x w\ld be practicable to build a ?irty-six-in* pneumatic tube4 ,:5 ! s]vice c be r5d]$ by an eight-in* tube1 ! co/ ( in/allation favors its adoption4 ,/eep grades _c be asc5d$ by ^! v l>ge tubes1 :ile ! eight-in* tubes c be plac$ v]tically4 ,we d n say t !re is no use = eighte5- & tw5ty-f\r-in* tubes1 b ! dem& = !m w\ld be 9 special cases & we w n discuss !m "h4 ,= ord9>y mail & p>cel s]vice we recomm5d ! use ( six- & eight-in* tubes4 ,an eight-in* c>ri] is tw5ty-f\r in*es long1 ab\t sev5 in*es inside diamet]1 & w conta9 five hundr$ ord9>y lett]s4 ,x weighs ab\t ?irte5 p\nds empty1 & "o c be despat*$ e six to t5 seconds4 ,we e/imate t eighty p] c5t4 ( all ! p>cels deliv]$ f a l>ge retail dep>tm5t /ore c\ld be wrapp$ up to g into ^! c>ri]s4 ,! m9imum radius ( curvature ( an eight-in* tube is eight feet4 ,g5]al ,arrangem5t ( ,app>atus 9 ! ,/ations4 ,two-,/ation1 ,two-,compressor ,l9e4--,we w n[ proce$ to a description ( our sy/em 9 detail4 ,figs4 #bd1 #be1 & #bf are diagrams %[+ h[ ! tubes1 air-compressor1 tanks1 s5d+ & receiv+ app>atus are connect$ toge!r at ! /ations4 ,^! diagrams are drawn to repres5t an eight-in* tube1 b ess5tially ! same arrangem5t w\ld be us$ = small] tubes4 ,fig4 #bd repres5ts a l9e ( two /ations ) an air-compressor at ea* /ation4 ,su* an arrangem5t is propos$ = ! l9e ( po/al tubes ov] ! ,new ,york & ,brooklyn bridge1 or = any two /ations locat$ a v long di/ance ap>t1 say six or eight miles4 ,illu/ration3 ,,fig4 #bd4 ,,diagram ,,( ,a ,,two-,,/ation1 ,,two-,,compressor ,,l9e4 ,ref]r+ to ! diagram1 we h at /ation ,a an air-compressor1 c1 :i* draws its supply ( air f ! tank e1 & deliv]s x1 compress$ to ! necess>y pressure1 into ! tank d4 ,f ! tank d ! air fl[s to ! s5d+ app>atus1 a1 & !nce ?r\gh ! tube f to ! /ation ,b4 ,^u arrival at ,b x fl[s ?r\gh ! receiv+ app>atus m1 & !n by ! pipe l to ! tank j4 ,a second air-compressor1 o1 is locat$ at /ation ,b1 & x draws its supply ( air f ! tank j4 ,! tank j has an op5+ to ! atmosph]e1 i1 ?r\gh :i* air c ent] :5 ! air-compressor draws m ?an is suppli$ f ! pipe l4 ,! op5+ i 9 ! tank j s]ves z an escape = air :5 ! air-compressor at /ation ,a is />t$ be=e t at /ation ,b4 ,/ations ,a & ,b are simil> 9 _! arrangem5ts4 ,at ,b ! air-compressor o deliv]s its compress$ air to ! tank k1 f :i* x fl[s to ! s5d+ app>atus n1 & !nce ?r\gh ! tube g back to /ation ,a4 ,^u its arrival at ,a x passes ?r\gh ! receiv+ app>atus & ent]s ! tank e1 :i* is op5 to ! atmosph]e at h4 ,! tanks d & k s]ve z sep>ators to remove f ! air any dirt & oil com+ f ! compressors1 & !y =m a cu%ion1 dead5+1 to "s ext5t1 ! pulsations ( ! compressors & mak+ ! curr5t ( air 9 ! tubes m /eady & uni=m4 ,! tanks e & j =m traps to cat* any moi/ure1 oil1 or dirt com+ out ( ! tubes4 ,c>ri]s are plac$ 9 ! tubes & despat*$ by means ( ! s5d+ app>atus a & n4 ,!y are receiv$ f ! tubes & deliv]$ on to tables by means ( ! receiv+ app>atus b & m4 ,x w be se5 t ! arrangem5t is su* t ! air fl[s ?r\gh "o tube & returns ?r\gh ! o!r1 ! same air be+ us$ ov] & ov] aga94 ,any air t escapes at ! s5d+ & receiv+ app>atus is replac$ by an equal am\nt ent]+ ! tanks e & j f ! atmosph]e4 ,by ?us keep+ ! same air circulat+ 9 ! tubes we prev5t an accumulation ( moi/ure 9 ! tubes4 ,! air is at its maximum pressure 9 ! tanks d & k4 ,! pressure falls gradually z x fl[s along ! tubes & is d[n to atmosph]ic :5 x ent]s ! tanks e & j4 ,! pressure at ! receiv]s1 b & m1 is j suffici5t to pu% ! c>ri]s out on to ! tables4 ,! con/ruction ( ! s5d+ & receiv+ app>atus w be describ$ 9 ano!r place4 ,illu/ration3 ,,fig4 #be4 ,,diagram ,,( ,a ,,two-,,/ation1 ,,"o-,,compressor ,,l9e4 ,two-,/ation1 ,"o-,compressor ,l9e4--,fig4 #be is a diagram %[+ two /ations1 ,a & ,b1 connect$ by a d\ble l9e ( tubes1 bo? op]at$ by "o air-compressor locat$ at /ation ,a4 ,?is is ! arrangem5t us$ 9 ! ,philadelphia po/-(fice l9e1 & is ! arrangem5t t w ord9>ily be us$ = all two-/ation l9es except :]e unusual conditions require some?+ diff]5t4 ,/ation ,a is arrang$ precisely l /ation ,a 9 ,fig4 #bd1 s x ne$ n be describ$ aga94 ,! air fl[s f ! s5d+ app>atus a ?r\gh ! tube f to ! receiv+ app>atus p at /ation ,b4 ,f ! receiv] p x fl[s ?r\gh ! pipe l to ! s5d+ app>atus n & !nce ?r\gh ! tube g back to /ation ,a4 ,! receiv] p at /ation ,b is :at we w call a clos$ receiv]1--i4e41 x deliv]s ! c>ri] f ! tube on to ! table )\t op5+ ! tube to ! atmosph]e4 ,! use ( ?is =m ( receiv] is made necess>y by ! fact t ! air-pressure 9 ! tube at ?is /ation is consid]ably above atmosph]ic4 ,! air-pressure is at a maximum 9 ! tank d4 ,x falls gradually along ! tube f1 & :5 ! air arrives at ! receiv] p1 at /ation ,b1 ! pressure has fall5 ne>ly to "o-half its maximum am\nt 9 ! tank d4 ,on its return j\rney ?r\gh ! tube g ! pressure cont9ues fall+ until x rea*es ! atmosph]ic pressure :5 ! air ent]s ! tank e at /ation ,a4 ,! entire l9e ( tube1 go+ & return+1 is op]at$ by air at a pressure above ! atmosph]ic4 ,!re is no exhau/+ 9 ! return tube4 ,x is di/9ctly a pressure sy/em4 ,illu/ration3 ,,fig4 #bf4 ,,diagram ,,( ,a ,,?ree- ,,to ,,eight-,,/ation ,,l9e4 ,?ree- to ,eight-,/ation ,l9e4--,?us f> we h describ$ only two-/ation l9es4 ,9 ,fig4 #bf we h a diagram ( ?ree /ations connect$ toge!r by a d\ble l9e ( tubes1 & ! arrangem5t w\ld be simil> if x 7 ext5d$ to f\r1 five1 six1 sev51 or eight /ations4 ,! /ations are call$ ,a1 ,b1 & ,h4 ,/ation ,a is arrang$ exactly ! same z /ations ,a 9 ,figs4 #bd & #be1 !re=e1 ne$s no description4 ,/ation ,b1 be+ an int]m$iate /ation1 is q diff]5tly arrang$ f any ( ! prec$+4 ,f /ation ,a ! air fl[s ?r\gh ! tube f to /ation ,b1 :]e x ent]s ! automatic receiv+ & transf]r+ app>atus1 s4 ,f ?is x fl[s ?r\gh ! tube f to ! s5d+ app>atus r1 & !nce ?r\gh ! tube f to ! next /ation1 :i* may be ano!r int]m$iate /ation1 ,c1 or ! t]m9al /ation ,h4 ,/ation ,h is arrang$ l /ation ,b1 ,fig4 #be4 ,! air f ! tube f ent]s ! receiv] p1 & is !n return$1 ?r\gh ! pipe l1 to ! s5d+ app>atus n4 ,f ! s5d+ app>atus n x cont9ues on its return j\rney ?r\gh ! tube g to ! int]m$iate /ation ,b1 :]e x ent]s ! receiv] & transf] app>atus t1 !n passes to ! s5d+ app>atus q1 & ?r\gh ! tube g back to ! receiv] b at /ation ,a4 ,?us we h foll[$ ! air-curr5t out ?r\gh "o tube & back ?r\gh ! o!r4 ,! curr5t is kept circulat+ by ! compressor locat$ at /ation ,a4 ,! pressure is at a maximum 9 ! tank d1 & falls gradually z ! air fl[s along ! tube until x returns to ! tank e1 :5 ! pressure has fall5 to atmosph]ic4 ,a c>ri] is despat*$ f /ation ,a1 & aft] pass+ ?r\gh ! tube f arrives at /ation ,b1 :]e x /ops mom5t>ily 9 ! automatic receiv] & transf] app>atus s4 ,if ! c>ri] is int5d$ = /ation ,b1 & 0 prop]ly adju/$ :5 x 0 despat*$ at ,a1 x w be dis*>g$ f ! app>atus s on to ! table u4 ,b if x 7 int5d$ = "s o!r /ation & 7 s adju/$1 aft] ! delay ( two or ?ree seconds 9 ! app>atus s1 x w be automatically transf]r$ to ! tube f1 pass ?r\gh ! s5d+ app>atus r1 & g on its j\rney ?r\gh tube f to ! next /ation4 ,if x is n dis*>g$ f ! tube at any ( ! int]m$iate /ations1 x w f9ally arrive at ! t]m9al /ation ,h & !re /op4 ,j h[ ! c>ri]s are adju/$ & ! details ( ! receiv+ & transf] app>atus w be describ$ h]eaft]4 ,c>ri]s arrive at /ation ,b f ,h1 or o!r /ations on ! l9e1 ?r\gh tube g1 9 ! app>atus t1 :i* ei!r dis*>ges !m on to ! table u or s5ds !m on ?r\gh ! tube g & g to /ation ,a4 ,c>ri]s are despat*$ f /ation ,b to /ation ,a by means ( ! s5d+ app>atus q1 & f /ation ,b to o!r /ations along ! l9e1 ,c1 ,d1 ,e1 ,f1 ,g1 & ,h1 by means ( ! s5d+ app>atus r4 ,?us1 f ,b c>ri]s c be s5t & receiv$ 9 ei!r direction4 ,9 ord] to prev5t ! possibility ( a collision ( c>ri]s by attempt+ to despat* "o at /ation ,b at ! in/ant ano!r is pass+ ?r\gh ! s5d+ app>atus1 an automatic lock is atta*$ to ea* s5d+ app>atus4 ,j outside ! /ation ,b1 say ?ree hundr$ feet on ea* side1 are locat$ manholes1 & 9 ^! manholes boxes are atta*$ to ! tube conta9+ an electric circuit-clos+ app>atus1 s arrang$ t :5 a c>ri] passes x w close an electric circuit lead+ to ! s5d+ app>atus 9 ! /ation4 ,^! manholes & circuit-clos]s are %[n & locat$ on ! diagram at v & w4 ,wires x & y lead f !m to ! s5d+ app>atus r & q4 ,:5 a c>ri] f /ation ,a passes ! box v1 x closes ! electric circuit x1 :i* sets a "t-lock on ! s5d+ app>atus r1 hold+ ?is app>atus lock$1 s t x is impossible to despat* a c>ri] =1 say1 twelve seconds1 a suffici5t "t = ! c>ri] com+ f ! /ation ,a to pass /ation ,b & get ?ree hundr$ feet beyond x4 ,aft] ! twelve seconds h elaps$ ! s5d+ app>atus is unlock$ & a c>ri] c !n be despat*$4 ,9 a simil> mann] a c>ri] com+ f /ation ,h1 9 pass+ ! box w1 closes ! electric circuit y & locks ! s5d+ app>atus q = a suffici5t l5g? ( "t to let ! c>ri] pass ! /ation4 ,?is resembles1 9 "s respects1 ! 8block sy/em0 z us$ on railroads4 ,a 8block0 ab\t six hundr$ feet 9 l5g?1 dep5d+ ^u ! spe$ ( ! c>ri]s1 is made at ea* int]m$iate /ation ) ! /ation 9 ! c5tre ( ! block4 ,:5ev] a c>ri] ent]s ?is 8block0 ! s5d+ app>atus at ! /ation is lock$1 & a c>ri] _c be ins]t$ into ! tube to collide ) ! "o :i* is pass+4 ,x w be not$ t a c>ri] 9 pass+ out ( ! 8block0 does n unlock ! s5d+ app>atus2 ?is is done automatically at a def9ite "t aft] ! c>ri] ent]$ ! block4 ,! unlock+ is entirely indep5d5t ( ! c>ri] aft] x has ent]$ ! block1 & ! reason x is s arrang$ is ?is3 suppose t a second c>ri] ent]s ! 8block0 be=e ! fir/ "o leaves x2 if ! fir/ c>ri] unlock$ ! app>atus :5 x left ! 8block10 !n x w\ld be unlock$ ) ! second c>ri] 9 ! block & a collision might occur1 b by arrang+ x z we h done1 if a second c>ri] ent]s ! 8block0 be=e ! fir/ has pass$ out1 ! s5d+ app>atus rema9s lock$ = a p]iod ( "t beg9n+ ) ! arrival ( ! fir/ c>ri] 9 ! 8block0 & end+1 say1 twelve seconds aft] ! arrival ( ! la/ c>ri]1 :i* is suffici5t "t = ! la/ c>ri] to pass out ( ! block4 ,( c\rse1 if a c>ri] becomes w$g$ 9 ! tube a collision may occur1 b ?is v seldom if ev] happ5s4 ,! details ( ! lock+ app>atus w be describ$ 9 ano!r place4 ,if /ations ,a1 ,b1 444 & ,h 7 arrang$ on a loop1 z %[n 9 circuit #f1 ,fig4 #ba1 !n /ation ,h1 ,fig4 #bf1 w\ld be at ! c5tral1 or /ation ,a4 ,if x 7 a s+le loop1 l circuit #d1 ,fig4 #ba1 !n !re w\ld be only "o s5d+ app>atus & "o receiv+ & transf]r+ app>atus at ! int]m$iate /ations4 ,a telephone circuit w include all /ations1 9 ord] to give ord]s to ! /ation att5dants & to signal to ! c5tral /ation 9 case ( an accid5t1 :5 x might be necess>y to /op ! air-compressor4 ,! telephone wires1 9 ! =m ( a lead-cov]$ cable1 are laid 9 ! same tr5* ) ! tubes & fa/5$ to !m4 ,illu/ration3 ,,fig4 #bg4 ,,s5d+ ,,app>atus4 ,illu/ration3 ,,fig4 #bh4 ,,s5d+ ,,app>atus4--,,longitud9al ,,section4 ,! ,s5d+ ,app>atus4--,we h1 9 ! prec$+ pages1 frequ5tly spok5 ( ! s5d+ app>atus1 & h describ$ x z me*anism by :i* c>ri]s are ins]t$ into ! tube4 ,9 ! ,philadelphia po/al l9e ?is app>atus consi/$ ( a l>ge valve1 op]at$ by h&4 ,= an eight-in* tube su* a valve w\ld be too l>ge & heavy to be manually op]at$4 ,fur!rmore1 t type ( app>atus is n suit$ to an int]m$iate /ation1 :]e c>ri]s h to pass ?r\gh x4 ,to meet all ( ^! requirem5ts we h design$ an app>atus1 ( :i* ,fig4 #bg is a side elevation1 ,fig4 #bh a longitud9al section1 & ,fig4 #bi a cross-section4 ,ref]r+ to ! longitud9al section1 ,fig4 #bh1 ! s5d+ app>atus is %[n ins]t$ into ! l9e ( a pneumatic tube1 ,a1 ,a4 ,we h a movable section ( tube1 ,b1 t c be swung ab\t ! l>ge bolt1 ,g1 at ! top1 into & out ( l9e ) ! ma9 tube1 ,a1 ,a4 ,:5 ! section ( tube ,b is be+ swung to "o side1 ! air-curr5t has a by-pass ?r\gh ! slots ,e & ,f & ! ,u-%ap$ pipe ,d4 ,! jo9ts at ! ends ( ! movable section ,b are pack$ ) specially-=m$ lea!rs4 ,ref]r+ to ! cross-section1 ,fig4 #bi1 :5 ! movable section ( tube ,b is swung out ( l9e ) ! ma9 tube1 ano!r & simil> tube1 ,c1 takes its place4 ,! two movable tubes1 ,b & ,c1 are made 9 "o piece1 s t !y mu/ always move toge!r4 ,!y are connect$ toge!r at ea* end by plates1 ,m1 t s]ve n only z connect+-plates1 b cov]s = ! ends ( ! ma9-l9e tube :ile ! tubes ,b & ,c are be+ mov$4 ,! tubes ,b & ,c sw+ betwe5 f\r plates or w+s1 ,l1 t ext5d out on ea* side ( ! app>atus4 ,!y s]ve z gu>ds1 &1 at c]ta9 positions ( ! sw++ tubes1 prev5t ! air f escap+4 ,we w1 = conv5i5ce1 call ! sy/em ( sw++ tubes ,b & ,c1 ) _! supports1 etc41 ! sw+-frame or simply ! frame4 ,?is frame is mov$ or swung f "o position to ! o!r by means ( a cyl9d] & pi/on1 ,h1 plac$ 9 an incl9$ position "u x4 ,a lug1 ,n1 is ca/ on ! tube ,b1 to :i* ! connect+-rod1 ,o1 is atta*$4 ,! cross-head1 ,p1 slides ^u an incl9$ guide1 ,q4 ,on top ( ! cyl9d] is plac$ a controll+ valve1 made 9 ! =m ( a pi/on slide-valve4 ,! pi/on 9 ! cyl9d] ,h is mov$ by ! pressure ( ! air tak5 f ! ma9 tube ?r\gh ! pipe ,i4 ,! app>atus is op]at$ by a h&-lev]1 ,k4 ,:5 ?is lev] is pull$1 x moves ! slid+-head ,r1 & ?is1 ?r\gh ! spr+ ,s1 moves ! controll+ valve1 if ! valve is n lock$4 ,if x is lock$1 pull+ ! lev] simply compresses ! spr+ ,s4 ,:5 ! controll+ valve is mov$ to ! "r ! air 9 ! cyl9d] ,h escapes ?r\gh ! passage ,v & ! port ,j to ! atmosph]e1 & compress$ air f ! ma9 tube fl[s ?r\gh ! pipe ,i1 ! passages ,t & ,u1 to ! cyl9d] ,h1 "u ! pi/on1 caus+ ! pi/on to move up ! incl9$ cyl9d] & sw+ ! frame until ! tube ,c is 9 l9e ) ! ma9 tube4 ,c>ri]s are despat*$ by plac+ !m 9 ! tube ,c1 !n pull+ ! lev] ,k1 & sw++ ! frame until ! tube ,c is 9 l9e ) ! ma9 tube4 ,! c>ri] is !n tak5 up & c>ri$ along by ! curr5t ( air 9 ! ma9 tube4 ,illu/ration3 ,,fig4 #bi4 ,,s5d+ ,,app>atus4--,,cross-,,section4 ,replac+ ! h&-lev] ,k 9 its orig9al position returns ! frame to its normal position4 ,illu/ration3 ,,fig4 #cj4 ,,s5d+ ,,"t-,,lock4 ,s5d+ ,"t-,lock4--,9 any sy/em ( l>ge pneumatic tubes a %ort "t %\ld elapse betwe5 ! despat*+ ( c>ri]s1 9 ord] t !y may n collide 9 ! tube1 & to give ! receiv+ app>atus at ! /ations "t to act4 ,to insure ! impossibility ( hav+ c>ri]s despat*$ too rapidly1 we place on ! s5d+ app>atus a "t-lock t w automatically lock x = a det]m9$ l5g? ( "t aft] ea* c>ri] is despat*$1 ! "t-lock be+ adju/able = any desir$ "t4 ,! "t-lock1 ,w1 is %[n atta*$ to ! s5d+ app>atus 9 ,fig4 #bg4 ,:5 ! sw+-frame is swung to despat* a c>ri]1 x pulls up ! rod ,x by means ( a l9k & bell-crank1 ,y1 !reby lock+ ! controll+ valve ( ! cyl9d] ,h & />t+ ! "t-lock ,w1 :i* w unlock ! controll+ valve aft] ! requir$ "t has elaps$4 ,! details ( ?is "t-lock are %[n 9 ,fig4 #cj4 ,x consi/s ( a long v]tical cyl9d]1 ,a1 conta9+ a pi/on1 ,b1 & a spiral spr+1 ,c1 t t5ds to =ce ! pi/on to ! bottom ( ! cyl9d]4 ,! cyl9d] is fill$ ) oil1 & holes1 ,d1 9 ! pi/on all[ ! oil to pass freely ?r\gh x :5 x is mov$ upw>d 9 ! cyl9d]4 ,:5 ! pi/on moves d[nw>d an annul> coll>1 ,e1 =m+ a valve1 closes ! holes 9 ! pi/on & prev5ts ! oil f pass+ ?r\gh4 ,ext5d+ f "o side ( ! pi/on to ! o!r is a by-pass1 ,f1 9 ! wall ( ! cyl9d]4 ,:5 ! pi/on moves d[nw>d ! displac$ oil is =c$ to fl[ ?r\gh ?is by-pass4 ,a small cock1 ,g1 is arrang$ 9 ! by-pass to ?rottle ! /ream ( oil fl[+ ?r\gh x4 ,! op5+ 9 ?is cock1 or ! am\nt ( ?rottl+1 is indicat$ on ! outside by an index & dial1 ,z 7see ,fig4 #bg74 ,:5 ! pi/on ,b is rais$ & all[$ to desc5d by ! =ce ( ! spr+ ,c1 x =ces ! oil ?r\gh ! by-pass ,f & ! cock ,g4 ,if ! latt] is wide op5 ! pi/on w desc5d quickly1 b if x is ne>ly clos$ ! pi/on w desc5d v sl[ly4 ,9 o!r words1 ! "t ( desc5t c be regulat$ by op5+ & clos+ ! cock ,g4 ,! read+ on ! dial ,z c be made seconds ( "t t elapse :ile ! pi/on is desc5d+4 ,above ! cyl9d] is a cross-head1 ,h1 t moves up & d[n betwe5 v]tical guides4 ,?is cross-head is mov$ by ! rod ,x1 also %[n 9 ,fig4 #bg1 t receives its motion f ! sw++ frame ( ! s5d+ app>atus4 ,a pi/on rod1 ,i1 atta*$ to ! pi/on 9 ! cyl9d]1 ext5ds up ?r\gh ! travell+ cross-head b is n atta*$ to x4 ,on ! pi/on-rod are two enl>gem5ts1 ,j & ,k1 "o made a solid "p ( x1 ! o!r =m$ by two nuts4 ,! travell+ cross-head ,h c>ries a pawl1 ,l1 t engages "u ! %\ld] =m$ by ! nuts ,k4 ,?is pawl is kept aga9/ ! pi/on-rod by ! spr+ ,m4 ,! enl>gem5t1 ,j1 on ! pi/on-rod =ms a %\ld] t be>s aga9/ ! bell-crank1 ,n1 t connects ) ! bolt1 ,o1 :i* locks ! controll+ valve4 ,9 ! pres5t d[n position ( ! pi/on & pi/on-rod1 ! enl>gem5t ,j1 by press+ aga9/ ! bell-crank ,n1 holds ! bolt ,o 9 an unlock$ position4 ,:5 a c>ri] is despat*$ ! cross-head ,h is lift$ by ! rod ,x1 & c>ries ) x ! pi/on & pi/on-rod1 compress+ ! spr+ ,c4 ,?is upw>d movem5t ( ! pi/on-rod all[s ! bolt ,o to be ?r[n by a spr+1 n %[n 9 ! figure1 & s lock ! controll+ valve ( ! s5d+ app>atus4 ,z ! cross-head cont9ues its upw>d movem5t1 ! pawl ,l comes 9 contact ) ! end ( ! screw ,p & dis5gages ! pi/on-rod4 ,?is all[s ! pi/on to desc5d z rapidly z ! oil c pass ?r\gh ! by-pass & cock ,g4 ,:5 ! pi/on has rea*$ ne>ly to ! bottom ( ! cyl9d]1 ! %\ld] ,j1 on ! pi/on-rod1 engages ! bell-crank ,n & )draws ! bolt ,o1 !reby unlock+ ! controll+ valve4 ,! "t t ! s5d+ app>atus is lock$ dep5ds ^u ! "t requir$ = ! pi/on to desc5d4 ,:ile ! s5d+ app>atus is lock$ aga9/ ! s5d+ ( ano!r c>ri]1 x is n s lock$ t ! sw+-frame _c be return$ to its normal position & ano!r c>ri] ins]t$ ready to be s5t z soon z ! necess>y "t expires4 ,?is "t is usually n m ?an t5 seconds4 ,n only may ! second c>ri] be plac$ 9 ! tube ,c1 ,fig4 #bi1 ready to be s5t1 b ! h&le ,k may be pull$ & fa/5$ 9 ! not* a1 !reby compress+ ! spr+ ,s1 :i*1 z soon z ! controll+ valve is unlock$1 w move ! valve & automatically despat* ! c>ri]4 ,! controll+ valve is lock$ by ! passage ( a bolt ?r\gh ! hole b1 9 a block c>ri$ on ! end ( ! valve /em1 :5 x returns to ! normal position %[n 9 ! figure4 ,usually little or no "t w be lo/ 9 ?us lock+ ! s5d+ app>atus1 = ! small am\nt ( "t t ! app>atus is lock$ w be ne$$ 9 h&l+ ! c>ri]s4 ,int]m$iate ,/ation ,"t-,lock4--,we h ano!r "t-lock atta*$ to ! s5d+ app>atus t has be5 already ref]r$ to 9 describ+ ! 8block sy/em0 us$ at int]m$iate /ations2 a "t-lock to prev5t c>ri]s be+ ins]t$ into ! tube at int]m$iate /ations :ile ano!r c>ri] is pass+ t /ation4 ,?is "t-lock is %[n 9 ,fig4 #bg at ,w1 & is %[n 9 detail by a sectional draw+1 ,fig4 #ca4 ,:5 a c>ri] closes an electric circuit 9 pass+ "o ( ! boxes locat$ 9 a manhole ab\t ?ree hundr$ feet f an int]m$iate /ation1 x indicates its approa* to ! /ation by excit+ ! electro-magnet ,a1 ,fig4 #ca4 ,?is magnet pulls d[n its armature ,b & raises ! small pi/on valve ,c1 :i* admits compress$ air to a small *amb]1 ,d4 ,! air is suppli$ to ?is *amb] f ! ma9 tube ?r\gh ! pipe ,e4 ,9 "o end ( ?is *amb] is fitt$ a pi/on1 ,f1 held to "o end ( its /roke by a spr+1 ,g4 ,:5 compress$ air is admitt$ to ! *amb] ,d1 ?is pi/on is mov$ to ! left1 & by su* movem5t ?r[s ! controll+ valve ( ! s5d+ app>atus into its normal position 7%[n 9 ,fig4 #bi7 & holds x !re4 ,?is =ms a positive lock1 &1 no matt] 9 :at position ! s5d+ app>atus may be1 x puts ! tube ,b1 ,fig4 #bi1 into l9e ) ! ma9 tube s t ! approa*+ c>ri] c pass ?r\gh ! app>atus4 ,! pi/on-rod ,h1 ,fig4 #ca1 is connect$ to ! f+] d1 ,fig4 #bi1 & by rock+ ?is f+] moves ! controll+ valve1 or prev5ts x be+ mov$ by ! h&le ,k4 ,illu/ration3 ,,fig4 #ca4 ,,int]m$iate ,,/ation ,,"t-,,lock4 ,return+ n[ to ,fig4 #ca1 we h on ! top ( ! *amb] ,d1 9 addition to ! electro-magnet ,a & its armature ,b1 a diff]5tial cyl9d] & pi/on1 ,k1 ,l1 ^: function is to close ! valve ,c :5 ! *amb] ,d is fill$ ) air4 ,! pi/on ,k is small] ?an ! pi/on ,l1 & su/a9s a con/ant air-pressure1 suppli$ ?r\gh ! small pipe ,m ,m1 f ! pipe ,e1 :i* leads to ! ma9 tube4 ,:5 ! *amb] ,d becomes fill$ f ! pipe ,e ?r\gh ! valve ,c1 ! pressure 9 ! *amb] moves ! pi/on ,l upw>d aga9/ ! pressure on ! pi/on ,k1 because ( ! great] area ( ! pi/on ,l4 ,?is movem5t ( ! diff]5tial pi/on raises ! lev] ,i1 :i* passes ?r\gh a slot 9 ! /em ( ! diff]5tial pi/on1 & ?us closes ! valve ,c4 ,! air 9 ! *amb] n[ gradually escapes to ! atmosph]e ?r\gh a small orifice ,q2 9 fact x has be5 escap+ "h all ! "t :ile ! *amb] 0 be+ fill$1 b ! op5+ ?r\gh ! valve ,c is s _m times l>g] ?an ! orifice ,q t ! escape ( air 0 n suffici5t to prev5t ! *amb] f fill+4 ,n[1 h[ev]1 t all supply to ! *amb] is %ut (f1 ! air 9 ! *amb] is gradually be+ dis*>g$ ?r\gh ! orifice4 ,:5 ne>ly all ! air has escap$1 ! pi/on ,f w return to its normal position1 %[n 9 ! figure1 & unlock ! controll+ valve4 ,! "t requir$ = ! air to escape f ! *amb]1 ,d1 is ! "t t ! s5d+ app>atus w be lock$1 & ?is "t c be regulat$ by v>y+ ! size ( ! orifice ,q4 ,! op5+ ( ! orifice1 or ! "t t ! s5d+ app>atus is lock$1 is indicat$ by an index & dial1 ,p4 ,?is lock+ me*anism is secur$ to a bracket on ! side ( ! l>ge cyl9d] ,h1 ,fig4 #bg1 9 a position :]e x c be easily inspect$4 ,! mov+ p>ts ( ! electro-magnetic valve--= su* is ! valve ,c1 ) ! magnet ,a1 ,fig4 #ca--;are made v light1 9 ord] t !y may respond easily & quickly to ! clos+ ( ! electric circuit4 ,x is a disadvantage to h /ations too num]\s ^u ! same l9e1 especially if !y d a l>ge am\nt ( bus9ess1 = ea* /ation w delay ! s5d+ ( c>ri]s f ! o!rs m or less1 & ! int]f]5ce w be greate/ dur+ ! busie/ h\rs ( ! day4 ,?is condition is inh]5t 9 any sy/em ( l>ge tubes :]e c>ri]s h to be run a c]ta9 m9imum di/ance ap>t1 & _c be ov]come by any me*anism4 ,b ! disadvantage is greatly ov]%ad[$ by ! advantage ( be+ able to connect sev]al /ations by "o l9e1 in/ead ( hav+ to run indep5d5t l9es f ea* /ation to ! c5tral1 especially :5 ! bus9ess ( ! individual /ations is n suffici5t to occupy a sep>ate tube all ! "t4 ,x makes x possible to h /ations :]e o!rwise ! bus9ess w\ld n w>rant ! co/ ( in/allation & exp5se ( op]ation4 ,we recomm5d ! e/abli%+ ( n m ?an eight /ations on a l9e1 & usually a small] numb] ?an ?is1 dep5d+1 ( c\rse1 ^u ! am\nt ( bus9ess to be done at ea* /ation4 ,illu/ration3 ,,fig4 #cb4 ,,electro-,,pneumatic ,,circuit-,,clos]4 ,! ,electro-,pneumatic ,circuit-,clos]4--,!re is "o piece ( me*anism us$ 9 connection ) ! s5d+ app>atus t we h yet to describe1 & t is ! circuit-clos+ device locat$ 9 ! manholes 9 ! /reet4 ,s9ce ! c>ri]s travel at a high rate ( spe$1 !y %\ld n be made to op]ate any me*anism by impact ) f+]s or lev]s protrud+ into ! tube :5 x c be avoid$1 ev5 ?\gh ! "w to be done is s slight z ! clos+ ( an electric circuit1 = ! repeat$ impacts _c fail to "w injury to ! c>ri]s & ! me*anism to be op]at$1 no matt] h[ c>efully !y are design$4 ,to avoid su* impacts1 we h design$ ! electro-pneumatic circuit-clos]1 %[n by ! draw+ 9 ,fig4 #cb4 ,x is op]at$ by a pass+ c>ri]1 b pneumatically r ?an me*anically4 ,9 ! figure we h a pneumatic tube1 ,a1 ,a1 9 :i* a c>ri]1 ,b1 is mov+ 9 ! direction indicat$ by ! arr[4 ,at two po9ts1 ab\t tw5ty or ?irty feet ap>t1 two small holes are tapp$ into ! tube & pipes1 ,c & ,d1 are screw$ 94 ,^! pipes lead to two *amb]s 9 a ca/-iron box1 ,f1 sep>at$ by a diaphragm1 ,e4 ,?is diaphragm is insulat$ electrically f ! box support+ x1 & is connect$ ) ! wire ,g4 ,j out ( contact ) ! diaphragm is an insulat$ screw1 ,h1 connect$ ) ! wire ,i4 ,^! wires lead to ! "t-lock1 already describ$1 on ! s5d+ app>atus at ! /ation4 ,:5 no c>ri] is pass+1 ! air-pressure is ! same on bo? sides ( ! diaphragm1 b :5 a c>ri] ent]s t "p ( ! tube betwe5 ! two po9ts :]e ! pipes ,c & ,d are connect$1 ! equality ( pressure on opposite sides ( ! diaphragm is de/roy$4 ,!re is always a slightly great] pressure 9 re> ( ! c>ri] ?an 9 front ( x1 equal to ! frictional resi/ance ( ! c>ri] 9 ! tube4 ,x is ?is diff]5ce ( pressure 9 front & 9 re> ( ! c>ri] t moves x ?r\gh ! tube4 ,:5 ! c>ri] is 9 ! position %[n 9 ! figure1 ! same diff]5ce ( pressure w exi/ on opposite sides ( ! diaphragm1 & x w be deflect$ into contact ) ! screw ,h1 !reby clos+ ! electric circuit4 ,:5 ! c>ri] has pass$1 equality ( pressure on opposite sides ( ! diaphragm is e/abli%$ & ! diaphragm takes its normal position1 out ( contact ) ! screw ,h4 ,?is app>atus is easily atta*$ to ! tube1 & x conta9s no me*anism to get out ( ord]4 ,illu/ration3 ,,fig4 #cc4 ,,op5 ,,receiv]4 ,! ,op5 ,receiv]4--,:]ev] ! pressure 9 ! tube is d[n ne>ly to atmosph]ic1 we c use an op5 receiv] to dis*>ge ! c>ri]s f ! tube4 ,?is is a receiv] t op5s ! tube to ! atmosph]e & all[s ! c>ri] to come out4 ,su* a receiv] is us$ at ! ma9 po/-(fice 9 ! ,philadelphia po/al-l9e1 & 0 describ$ 9 ! la/ *apt]4 ,! pres5t receiv] is simil> 9 op]ation1 b conta9s "s improvem5ts 9 details4 ,fig4 #cc is a side elevation ( ! app>atus1 ,fig4 #cd is a longitud9al section1 & ,fig4 #ce is a cross-section ?r\gh ! cyl9d] & valve1 %[+ ! sluice-gate4 ,illu/ration3 ,,fig4 #cd4 ,,op5 ,,receiv]4--,,longitud9al ,,section4 ,illu/ration3 ,,fig4 #ce4 ,,op5 ,,receiv]4--,,sluice-,,gate ,,me*anism4 ,ref]r+ to ! longitud9al section1 ! app>atus is atta*$ to ! end ( a pneumatic tube1 ,a4 ,! curr5t ( air f ! tube ,a fl[s ?r\gh ! slots ,b into a pipe1 ,c1 t conducts x to a tank ne> ! air-compressor4 ,ab\t ! c5tre ( ! app>atus is a sluice-gate1 ,e1 t is rais$ & l[]$ by a pi/on 9 a v]tical cyl9d]1 ,f1 locat$ j above ! sluice-gate4 ,?is pi/on is mov$ by air-pressure tak5 f "s "p ( ! sy/em4 ,:5 a c>ri] arrives f ! tube ,a1 x passes ov] ! slots ,b & runs into ! air-cu%ion ,d1 :]e x comes gradually to re/4 ,*eck+ ! mom5tum ( ! c>ri] compresses ! air 9 front ( x consid]ably1 & ?is excess ( pressure is utiliz$ to move a small slide-valve t controls ! movem5t ( ! pi/on 9 ! cyl9d] ,f1 s t z soon z ! c>ri] has come to re/ ! sluice-gate rises & all[s ! c>ri] to be pu%$ out ) a l[ velocity on to a table4 ,! small pipe ,g conducts a small portion ( ! air compress$ 9 front ( ! ret>d$ c>ri] to ! controll+ valve1 ,h1 se5 9 ,figs4 #cc & #ce4 ,ref]r+ n[ to ! section ( ! valve & cyl9d]1 ,fig4 #ce1 ! pipe ,g ent]s ! top ( a small valve-cyl9d] conta9+ a hemisph]ical pi/on1 ,i1 t is held up by a spiral spr+1 ,j4 ,?is spr+ has j suffici5t t5sion to hold ! pi/on ,i up aga9/ ! normal pressure ( air 9 ! tube4 ,:5 a c>ri] arrives & compresses ! air 9 ! air-cu%ion1 ! excess ( pressure =ces ! pi/on ,i d[n aga9/ ! spr+ ,j1 & moves ! pi/on slide-valve ,k4 ,?is *ange ( position ( ! slide-valve all[s ! air 9 ! cyl9d] ,f to escape to ! atmosph]e ?r\gh ! passage ,l1 passage ,p1 & pipe ,m1 :ile compress$ air f "s "p ( ! ma9 tube ent]s ?r\gh ! port ,n & passage ,o to ! "u side ( ! pi/on 9 ! cyl9d] ,f4 ,?is moves ! pi/on up1 c>ry+ ) x ! sluice-gate ,e4 ,!re is j suffici5t pressure 9 ! tube 9 re> ( ! c>ri] to pu% ! c>ri] pa/ ! gate & on to ! table4 ,z ! c>ri] moves out x raises a f+]1 ,q1 ,fig4 #cd1 t projects into its pa?4 ,rais+ ?is f+] ext5ds ! spr+ ,r1 ,fig4 #cc1 & rotates ! lev] ,s1 br++ ! pawl ,t "u ! end ( ! controll+ valve-/em4 ,:5 ! c>ri] has pass$ out & ! f+] ,q is free to desc5d1 ! spr+ ,r rotates ! lev] ,s back to its orig9al position1 & !reby raises ! controll+ slide-valve1 :i* causes ! sluice-gate to close4 ,by hav+ ! upw>d motion ( ! f+] ,q simply ext5d ! spr+ ,r1 & ! d[nw>d motion1 by ! =ce ( ! spr+1 move ! valve1 we are enabl$ to h sev]al c>ri]s pass out ( ! tube toge!r )\t hav+ ! sluice-gate close until ! la/ c>ri] has pass$ out4 ,if rais+ ! f+] ,q mov$ ! valve1 !n :5 ! fir/ c>ri] pass$ out1 ! gate w\ld close d[n ^u ! second4 ,atta*$ to ! receiv+ app>atus & ext5d+ beyond x is a tube1 ,u1 cut away ^u "o side s t ! c>ri]s c roll out ( x on to a table1 & hav+ 9 ! end a buff] to /op ! c>ri]s if by any accid5t !y come out ( ! tube ) too mu* spe$4 ,?is buff] consi/s ( a pi/on cov]$ ) sev]al lay]s ( lea!r & hav+ a /iff spr+ beh9d x4 ,! :ole app>atus is support$ f ! floor ^u suitable /&>ds1 &1 = an eight-in* tube1 occupies a floor-space twelve feet long by two feet wide1 n includ+ ! table4 ,?is is ! simple/ =m ( receiv+ app>atus4 ,ow+ to conditions ( pressure already expla9$1 its use is conf9$ pr9cipally to ! pump+ /ations4 ,! only c>e t x requires is an occasional clean+ & oil+4 ,illu/ration3 ,,fig4 #cf4 ,,clos$ ,,receiv]4 ,illu/ration3 ,,fig4 #cg4 ,,clos$ ,,receiv]4--,,longitud9al ,,section4 ,! ,clos$ ,receiv]4--,next we w turn our att5tion to ! clos$ receiv+ app>atus us$ at all t]m9al /ations :]e ! pressure 9 ! tube is consid]ably above ! pressure ( ! atmosph]e1 s mu* s t ! tube _c be op5$ to all[ ! c>ri] to pass out )\t an annoy+ bla/ ( air & a high velocity ( ! c>ri]4 ,?is app>atus is simil> to ! receiv] us$ 9 ! sub-po/-(fice ( ! ,philadelphia po/al l9e1 b conta9s sev]al modifications & improvem5ts t5d+ t[>ds simplification4 ,fig4 #cf %[s x 9 elevation1 & ,fig4 #cg 9 longitud9al section4 ,z 9 ! op5 receiv] j describ$1 ! air f ! tube ,a is deflect$ ?r\gh slots ,b into a bran* pipe1 ,c1 t conducts x f ! receiv+ app>atus to ! s5d+ app>atus & return tube4 ,! c>ri]s arrive f ! tube ,a1 pass ov] ! slots ,b1 :]e ! air makes its exit1 & run into an air-cu%ion1 ,d4 ,?is air-cu%ion is a tube ab\t twice ! l5g? ( ! c>ri]1 clos$ at "o end1 & support$ ^u trunnions4 ,:5 ! c>ri] has be5 br\ght to re/1 ?is clos$ section ( tube is tilt$ by ! movem5t ( a pi/on 9 a cyl9d] to an angle t all[s ! c>ri] to slide out2 ! tube !n returns to its orig9al position4 ,if ! end ( ! air-cu%ion 0 clos$ p]fectly tight ! c>ri]1 aft] com+ to re/1 w\ld reb\nd & might be caught 9 ! jo9t betwe5 ! /ation>y & movable p>ts ( ! app>atus1 :5 ! air-cu%ion tube tilt$4 ,to prev5t ! reb\nd+ ( ! c>ri] a relief-valve1 ,e1 has be5 plac$ 9 ! head ( ! air-cu%ion tube4 ,x is held clos$ aga9/ ! normal pressure 9 ! tube by a spiral spr+1 b ! excessive pressure creat$ by *eck+ ! mom5tum ( ! c>ri] op5s ! valve & all[s a little air to escape ?r\gh ! passage ,f & pipe ,g1 d[n ! p$e/al ,h1 to ! atmosph]e4 ,:5 ! air-cu%ion or receiv+ tube ,d is tilt$ to dis*>ge a c>ri]1 ! circul> plate ,i cov]s ! end ( ! ma9 tube4 ,9 ord] to prev5t c>ri]s /ick+ 9 ! receiv+ tube :5 x is tilt$1 & to insure _! prompt dis*>ge1 ! pipe ,j is provid$4 ,9 ! tilt$ position ( ! receiv+ tube1 ! end ( ?is pipe co9cides ) ! end ( ! ma9 tube1 f :i* x receives air to ha/5 ! dis*>ge ( ! c>ri]4 ,a *eck-valve1 ,k1 prev5ts ! air f fl[+ backw>d 9 ?is pipe :5 a c>ri] is be+ receiv$ 9 ! air-cu%ion *amb]4 ,! op5+ ( ?is *eck-valve c be adju/$ by a screw1 !reby regulat+ ! spe$ ( ejection ( ! c>ri]4 ,illu/ration3 ,,fig4 #ch4 ,,int]m$iate ,,/ation ,,receiv+ ,,& ,,transf] ,,app>atus4 ,illu/ration3 ,,fig4 #ci4 ,,int]m$iate ,,/ation ,,receiv+ ,,& ,,transf] ,,app>atus4--,,v]tical ,,section4 ,! c>ri] is dis*>g$ d[n a *ute1 ,l1 :i* has a buff] at ! bottom1 & f ! *ute x rolls (f on to a table4 ,! buff] is made simil> to ! buff] 9 ! op5 receiv] already describ$4 ,! cyl9d] & pi/on ,m1 t op]ate to tilt ! receiv+ tube ,d1 are support$ ^u ! base ( ! app>atus "u ! clos$ end ( ! receiv+ tube4 ,! cross-head ( ! pi/on- & connect+-rods travels betwe5 guides t are made a "p ( ! upp] cyl9d] head4 ,! movem5t ( ! pi/on 9 ! cyl9d] ,m is controll$ by a pi/on slide-valve exactly simil> to ! "o %[n 9 ,fig4 #ce4 ,! slide-valve is mov$1 9 ! same mann]1 by ! air compress$ ahead ( ! c>ri] :5 x is br\ght to re/ 9 ! air-cu%ion ,d4 ,! air is conduct$ f ! air-cu%ion to ! controll+ slide-valve ?r\gh a small pipe1 ,n1 ,fig4 #cf4 ,?is pipe leads to "o ( ! trunnions1 :]e x has a jo9t to all[ = ! tilt+ ( ! receiv+ tube4 ,:5 ! c>ri] is dis*>g$ f ! receiv+ tube1 x raises a f+]1 ,o1 ,fig4 #cg1 locat$ j outside ! tube4 ,rais+ ?is f+] pulls ! rod ,p1 ,fig4 #cf1 ext5ds ! spr+ ,q1 turns ! lev] ,r1 & cat*es ! pawl ,s1 "u ! end ( ! controll+ valve /em4 ,:5 ! c>ri] has pass$ d[n ! *ute & all[$ ! f+] ,o to drop d[n1 ! spr+ ,q turns ! lev] ,r back to its orig9al position & moves ! controll+ valve4 ,?is causes ! receiv+ tube to return to a horizontal position1 :]e x is ready to receive ! next c>ri]4 ,at fir/ ?is app>atus may seem a little cumb]some1 b no?+ c\ld "w bett]4 ,x is c]ta9 9 its action & almo/ noiseless4 ,c>ri]s are receiv$1 dis*>g$1 & ! receiv+ tube return$ to its normal position 9 f\r seconds1 & x c be done 9 less "t if necess>y4 ,! ,int]m$iate ,/ation ,receiv+ & ,transf] ,app>atus4--,"o o!r =m ( receiv+ app>atus rema9s to be describ$1 & ?is is ! app>atus us$ at int]m$iate /ations to int]cept all c>ri]s int5d$ = t /ation & to s5d ! o!rs on ?r\gh ! tube to ! next /ation4 ,a side elevation ( ! app>atus is %[n 9 ,fig4 #ch & a v]tical section 9 ,fig4 #ci4 ,! tubes are l$ into an int]m$iate /ation1 c>ri$ upw>d1 & !n1 ) a b5d ( "o hundr$ & eighty degrees1 are connect$ to ! top ( ! receiv+ & transf] app>atus1 z %[n 9 ! diagram1 ,fig4 #bf4 ,! object ( ?is arrangem5t w be se5 z we describe ! app>atus4 ,ref]r+ to ! sectional draw+1 ,fig4 #ci1 ! connection ( ! tube ,a is se5 at ! top4 ,z 9 ! o!r receiv]s1 ! curr5t ( air arriv+ f ! tube ,a is deflect$ ?r\gh slots1 ,b1 into a passage1 ,c1 made 9 ! frame ( ! app>atus4 ,f ?is passage x ent]s ! tube ,d ?r\gh ! slots ,e4 ,! tube ,d leads to ! s5d+ app>atus & on to ! next /ation1 z se5 9 ,fig4 #bf4 ,! c>ri]s are receiv$ 9 a clos$ section ( tube ,f1 :i* =ms an air-cu%ion1 simil> to ! clos$ receiv] la/ describ$4 ,?is receiv+ tube ,f is made a "p ( :at we might t]m a :eel4 ,?is :eel fits accurately into a circul> cas+ & is support$ by two trunnions or axles1 ^u :i* x revolves4 ,! :eel has a broad flat rim1 ,g1 t cov]s ! end ( ! tube at ,h :5 ! :eel is revolv$1 &1 9 ! normal position 9 :i* x is %[n 9 ! figure1 cov]s ! int]ior op5+s ,i1 ,j1 ,k1 & ,l1 9 ! cas+4 ,lea!r pack+ is provid$ ar\nd ea* ( ! op5+s to prev5t ! escape ( air betwe5 ! face ( ! :eel & ! int]ior face ( ! cas+4 ,f ! bottom ( ! receiv+ tube ,f a passage1 ,m1 leads pa/ a *eck-valve1 ,n1 to ! tube ,d4 ,:5 a c>ri] arrives f ! tube ,a1 x desc5ds into ! receiv+ tube ,f1 compress+ ! air 9 front ( x4 ,?is compress$ air beg9s to escape ?r\gh ! passage ,m1 b ! high velocity ( x closes ! *eck-valve ,n z mu* z possible4 ,a /op on ! /em ( ! valve prev5ts x be+ clos$ entirely4 ,! small op5+ pa/ ! valve all[s "s ( ! air to pass1 !reby prev5t+ ! c>ri] f reb\nd+ on ! air-cu%ion4 ,z soon z ! c>ri] has come to re/1 ! *eck-valve ,n1 by its own weight1 op5s wide1 & ! c>ri]1 by its weight1 settles gradually d[n to ! bottom ( ! receiv+ tube4 ,! :eel conta9+ ! receiv+ tube & ! c>ri] w !n be revolv$ by ! cyl9d] & pi/on ,o1 :i* is op]at$ by compress$ air tak5 f ! tube ?r\gh ! pipe ,p4 ,if ! c>ri] is = ?is /ation1 ! :eel w rotate ?r\gh an angle ( =ty-five degrees & dis*>ge ! c>ri] ?r\gh ! op5+ ,j1 d[n ! *ute ,q1 f :i* x w roll on to a table arrang$ to receive x4 ,if1 h[ev]1 ! c>ri] is int5d$ = "s o!r /ation1 ! :eel w rotate ?r\gh an angle ( n9ety degrees & dis*>ge ! c>ri] ?r\gh ! op5+ ,k into ! tube ,d1 & x w g on its way to ! next /ation4 ,?is selection ( c>ri]s is br\ght ab\t 9 a comp>atively simple mann]4 ,at ! bottom ( ! receiv+ tube ,f !re are two v]tical ne$les1 ,r & ,s1 %[n ^u a l>g] scale 9 ,fig4 #dj4 ,! ne$les ,r & ,s are conta9$ 9 tubes hav+ an insulat+ l9+ :i* keeps !m out ( electrical contact ) ! frame ( ! app>atus4 ,wires a & b make connection ) ! ne$les ?r\gh metal plugs t =m a guide = ! ne$les1 & ?r\gh ! spr+s ,u & ,v4 ,directly bel[ ! ne$le ,r is an insulat$ spr+ clip1 ,w1 held by two bolts & connect$ to ! wire e4 ,illu/ration3 ,,fig4 #dj4 ,a ,,detail ,,( ,,! ,,int]m$iate ,,/ation ,,receiv+ ,,& ,,transf] ,,app>atus4 ,! end ( a c>ri] is repres5t$ at ,t4 ,z ! c>ri] settles d[n to ! bottom ( ! receiv+ tube1 x comes 9 contact ) ! ends ( ! ne$les & presses !m d[n1 !y be+ support$ by two spr+s ,u & ,v4 ,z ! ne$le ,r is mov$ d[n1 x makes contact ) ! spr+ clip ,w1 locat$ j bel[ x1 & closes an electric circuit t includes ! electro-magnet ,x1 ,figs4 #ch & #ci1 on ! valve ( ! rotat+ cyl9d] ,o4 ,:5 ?is electro-magnet is excit$ x attracts its armature & moves ! pi/on slide-valve ,y1 t admits air to ! top ( ! pi/on 9 ! cyl9d] ,o1 & all[s ! air "u ! pi/on to escape to ! atmosph]e4 ,! pi/on moves d[nw>d & revolves ! :eel by means ( a connect+ rod4 ,^u ! end ( ! c>ri] ,t is plac$ a ?9 circul> metal disk1 f1 :i* may be copp]1 brass1 t9-plate or any metal t is n easily oxidiz$4 ,! diamet] ( ?is disk ( metal det]m9es ! /ation at :i* ! c>ri] w be dis*>g$ f ! tube4 ,disks ( v>i\s diamet]s1 t may be atta*$ to ! c>ri]1 are repres5t$ by da%$ l9es1 g1 9 ,fig4 #dj4 ,:5 ! c>ri] comes 9 contact ) ! two ne$les ,r & ,s1 if ! circul> metal disk on ! front end ( ! c>ri] has a diamet] suffici5t to span ! space betwe5 ! two ne$les1 9 ! position 9 :i* x is held1 !n an electric circuit1 made by ! wires a & b1 w be clos$ ?r\gh ! ne$les & ! metal disk on ! c>ri]4 ,! metal disk makes a %ort-circuit f "o ne$le to ! o!r4 ,if ! metal disk is n l>ge en\gh to span ! di/ance betwe5 ! two ne$les1 !n ! electric circuit rema9s brok54 ,return+ aga9 to ,fig4 #ci1 we h ! op5+ ,j1 :]e ! c>ri]s are dis*>g$1 clos$ by a sluice-gate4 ,?is gate is op5$ & clos$ by a pi/on mov+ 9 a cyl9d]1 h1 %[n 9 ,fig4 #ch4 ,a pi/on slide-valve1 i1 simil> 9 all respects to ! valve on ! cyl9d] ,o1 controls ! movem5t ( ! pi/on 9 ?is cyl9d] & ! sluice-gate to :i* x is atta*$4 ,! slide-valve is mov$ 9 "o direction1 t op5s ! sluice-gate1 by an electro-magnet 9 ! circuit ( ! wires a & b1 ,fig4 #dj4 ,:5 ! electric circuit made by ^! wires is clos$ by a disk on ! front end ( a c>ri]1 %ort-circuit+ ! two ne$les1 ! valve is mov$ by ! electro-magnet 9 ! circuit1 & ! sluice-gate is op5$4 ,z ! :eel1 includ+ ! receiv+ tube & c>ri]1 revolves1 a lug1 j1 ,fig4 #ch1 on ! outside ( ! :eel comes 9 contact ) ! op5 sluice-gate & ! :eel c rotate no f>!r4 ,a bla/ ( air ?r\gh ! valve ,l1 ,fig4 #ci1 assi/$ by gravity1 pu%es ! c>ri] out ( ! receiv+ tube1 ?r\gh ! op5+ ,j & d[n ! *ute ,q1 on to ! receiv+ table4 ,_h ! disk on ! front end ( ! c>ri] be5 too small to span ! di/ance betwe5 ! two ne$les1 ! circuit w\ld n h be5 clos$1 ! sluice-gate w\ld n h be5 op5$1 no ob/ruction w\ld h be5 plac$ 9 ! pa? ( ! lug j1 on ! :eel1 & ! :eel w\ld h cont9u$ its rotation ?r\gh n9ety degrees until ! receiv+ tube ,f came 9 l9e ) ! tube ,d4 ,dur+ ! latt] "p ( ! rotation1 a p9 on ! :eel engages a lev]1 k1 ,fig4 #ch1 & turns a valve1 l1 ,fig4 #ci1 /opp+ ! fl[ ( air ?r\gh ! passage ,c1 compell+ x to take ano!r r\te ?r\gh ! passage m1 & ! receiv+ tube ,f1 tak+ ) x ! c>ri] into ! tube ,d4 ,:5 ! c>ri] leaves ! receiv+ tube & passes ?r\gh ei!r ( ! op5+s ,j or ,k1 x engages "o ( ! f+]s1 n or o1 t lie 9 its pa?4 ,^! f+]s are connect$ by rods & lev]s to ! valves on ! rotat+ & sluice-gate cyl9d]s4 ,! eject$ c>ri] pu%es ^! f+]s to "o side1 & aft] x has pass$ ! f+]s return1 by ! =ce ( a spr+1 to _! =m] position & move ! valves1 caus+ ! sluice-gate to close & ! :eel to rotate backw>d into its normal position ready to receive ! next c>ri]4 ,! connection betwe5 ! f+]s & ! valves is simil> to ! me*anism on ! op5 & clos$ receiv]s1 s ne$ n be describ$ 9 detail "h4 ,! spe$ ) :i* ! c>ri]s are eject$ f ! receiv+ tube ?r\gh ! op5+ ,j & d[n ! *ute ,q is regulat$ by ! valve ,l1 :i* c be op5$ or clos$ by a h&-:eel1 p4 ,be=e ! :eel & receiv+ tube c be rotat$1 ! ne$les mu/ be )drawn f ! receiv+ tube1 & ?is is accompli%$ by a small cyl9d] & pi/on1 q1 %[n 9 ,fig4 #dj4 ,! ne$les & _! encasem5t are atta*$ to a cross-head1 r1 on ! end ( a holl[ pi/on-rod1 s4 ,:5 air is admitt$ to ! top ( ! pi/on 9 ! rotat+ cyl9d] ,o1 ,fig4 #ci1 x is also admitt$ ?r\gh ! pipe t1 ,fig4 #ch1 to ! cyl9d] & upp] side ( ! pi/on q1 ,fig4 #dj4 ,?is moves ! pi/on q d[n aga9/ ! =ce ( a spr+1 u1 & )draws ! ne$les f ! receiv+ tube4 ,?is takes place aft] ! ne$les h s]v$ _! purpose & be=e ! :eel is rotat$4 ,! pi/on q has mu* less in]tia ?an ! :eel1 !re=e x moves mu* quick]4 ,:5 ! :eel beg9s to rotate x closes a valve1 v1 9 ! pipe t1 ,fig4 #ch1 conf9+ ! air 9 ! cyl9d] q1 & prev5t+ ! ne$les f be+ rais$ by ! spr+ u be=e ! :eel returns to its normal position4 ,if by any accid5t ! ne$les %\ld be rais$1 no s]i\s h>m w\ld result1 = _! ends w\ld simply be> aga9/ ! face ( ! :eel4 ,if ?is took place con/antly1 grooves might be worn 9 ! face ( ! :eel2 = ?is reason ! valve v is provid$4 ,9 ord] to facilitate ! inspection ( ! ne$les & electric contact spr+s ,w1 !y are conta9$ 9 a cyl9drical brass case1 w1 t is held 9 place b5ea? ! receiv+ tube by two bolts4 ,by remov+ ! nuts f ^! bolts ! entire me*anism c be remov$1 exam9$1 & clean$4 ,x also gives easy access to ! receiv+ tube4 ,! receiv+ tube is long en\gh to receive two c>ri]s1 if x %\ld ev] happ5 t two arrive at ! same "t4 ,illu/ration3 ,,fig4 #da4 ,,diagram ,,( ,,contact-,,disks ,,& ,,ne$les4 ,to %[ h[ ! app>atus at ! v>i\s /ations is arrang$ to correspond ) ! disks ( v>i\s sizes atta*$ to ! front ( ! c>ri]s1 a diagram1 ,fig4 #da1 has be5 made1 9 :i* ! ne$les at ! bottom ( ! receiv+ tubes ( ! app>atus at six int]m$iate /ations are repres5t$ at ,a1 ,b1 ,c1 ,d1 ,e1 & ,f4 ,six disks ( diff]5t sizes are repres5t$ at a1 b1 c1 d1 e1 & f4 ,! ne$les are plac$ f>!/ ap>t at /ation ,a & ne>] toge!r at ea* succe$+ /ation until we arrive at /ation ,f1 :]e !y are ne>e/ toge!r4 ,if we wi% to s5d a c>ri] to /ation ,a f ! c5tral1 we place ! l>ge/ disk1 a1 ^u ! front end ( x4 ,:5 x arrives at /ation ,a1 x closes ! electric circuit betwe5 ! ne$les & is dis*>g$ f ! tube4 ,%\ld we wi% to s5d a c>ri] to /ation ,d1 !n we place ! disk d ^u ! front end ( x4 ,:5 ! c>ri] arrives at ! /ation ,a1 ! disk is n l>ge en\gh to span ! ne$les2 !re=e ! sluice-gate is n op5$ & ! c>ri] is s5t on 9 ! tube4 ,:5 x arrives at /ations ,b & ,c1 ! same ?+ occurs aga91 b :5 x rea*es /ation ,d1 ! ne$les are suffici5tly close toge!r s t ! disk makes an electric circuit betwe5 !m1 & ! c>ri] is dis*>g$ f ! tube1 z 0 int5d$ :5 despat*$4 ,s9ce ! c>ri]s always travel 9 ! same direction 9 a tube1 ! fir/ /ation at :i* !y arrive :]e ! ne$les are ne> en\gh toge!r to h bo? t\* ! disk1 w be ! /ation at :i* ! c>ri] 0 int5d$ to /op4 ,c>ri]s c be despat*$ f any /ation1 b if we wi% to s5d f say ,d to ,a1 !y mu/ ei!r travel ar\nd a loop or be s5t ?r\gh a return tube 9 :i* ! ne$les are arrang$ 9 ! rev]se ord]4 ,if no disk is plac$ on ! c>ri]1 x w g to ! la/ /ation on ! l9e4 ,!re are o!r atta*m5ts t might be made to ! front end ( ! c>ri]s 9 ord] to h !m /op at any desir$ /ation along a l9e4 ,we h work$ out two o!r sy/ems :i* are entirely me*anical 9 _! op]ation1 n us+ electric circuits & electro-magnets to move ! valves4 ,:ile su* a me*anical sy/em has "s advantages ov] ! pres5t comb9$ me*anical & electrical sy/em1 yet !re is "o great advantage 9 ! latt]1 & t is ! simplicity ( ! atta*m5t made to ! c>ri]4 ,a r\nd flat disk ( t9-plate is atta*$ to ! front end2 x is some?+ t is n 9 ! way2 x does n prev5t /&+ ! c>ri]s on end 9 racks to fill !m2 x is n easily injur$1 & only ^? :o h _h exp]i5ce c realize ! r\gh usage t ! c>ri]s receive2 x is quickly & easily atta*$ to ! c>ri]1 & x is s *eap t :5 b5t x c be ?r[n away4 ,c>ri]s4--,! c>ri]s are simil> 9 all respects to ^? us$ 9 ! ,philadelphia po/al-l9e1 t h be5 describ$ 9 ! prec$+ *apt] & illu/rat$ 9 ,figs4 #ah1 #ai1 & #bj4 ,:5 !re are int]m$iate /ations ^u ! l9es1 means are provid$ = atta*+ disks to ! front end ( ! c>ri]s4 ,! disks h a c5tral /em t secures !m to ! bolt 9 ! c5tre ( ! head1 & are s arrang$ t !y c be quickly atta*$ or remov$4 ,_m exp]im5ts h be5 made to f9d ! be/ mat]ial = be>+-r+s1 b ?us f> no?+ bett] ?an a specially-prep>$ wov5 fabric has be5 f\nd4 ,^! r+s w run ab\t a ?\s& miles1 :5 !y become s r$uc$ 9 diamet] t !y h to be replac$ by new ones4 ,! mo/ ess5tial elem5ts ( a c>ri] are /r5g?1 lightness1 & security ( ! cont5ts4 ,alum9um has frequ5tly be5 propos$ z a suitable mat]ial = ! bodies ( c>ri]s1 b = ! same weight /eel is mu* /rong]1 especially 9 ?9 roll$ %eets1 & = ?is reason x has be5 us$4 ,"o ( ! mo/ p]plex+ problems t pres5t$ itself 9 work+ out ! details ( ! sy/em 0 to design a secure & reliable lock = ! lids ( ! c>ri]s4 ,we believe t ! "o :i* has be5 adopt$ fulfils all requirem5ts 9 a satisfactory mann]4 ,"s exp]im5ts h be5 made ) c>ri]s t op5 on ! side1 b /ructurally !y are weak & unsuit$ to /& ! bl[s t c>ri]s frequ5tly receive4 ,!y are n s easily & quickly fill$ & empti$ z ^? t op5 on ! end4 ,^! rem>ks apply to c>ri]s = l>ge tubes4 ,9 small tubes = ! transportation ( ca% 9 retail /ores1 c>ri]s ) side op5+s are f\nd conv5i5t4 ,:5 ,unit$ ,/ates mail is s5t ?r\gh tubes n us$ exclusively = po/al s]vice1 c>ri]s ) special locks c be us$1 s t !y c be op5$ only by po/-(fice employees4 ,air ,supply4--,?is completes ! description ( ! special app>atus us$ 9 ?is sy/em1 b we h yet to say some?+ reg>d+ ! ma*9es t supply ! air4 ,9 ,p>is ! wat] f ! city ma9s has be5 us$ to compress or exhau/ ! air us$ 9 small tubes1 b to op]ate l>ge tubes 9 mo/ ( our cities /eam is ! only available p[]4 ,except 9 isolat$ cases1 an indep5d5t /eam plant w be erect$ to supply ! air = a sy/em ( tubes4 ,?is plant %\ld be design$ ) a view to obta9+ ! maximum economy 9 coal consumption1 labor1 wat]1 c>tage1 & incid5tal exp5ses4 ,we might say t ! same g5]al rules ( economy :i* gov]n ! design & con/ruction ( electric-light+ plants %\ld be appli$ to ! plans & con/ruction ( air-compress+ plants4 ,?ree types ( bl[+ ma*9es are us$1--viz41 c5trifugal fans1 positive bl[]s1 & air-compressors4 ,fans4--,v l>ge tubes ( mod]ate l5g? c be op]at$ by ord9>y c5trifugal fans4 ,^! fans are capable ( supply+ air "u a pressure n exce$+ t5 or twelve ounces p] squ>e in* ) v good effici5cy4 ,!y are ! simple/ & mo/ inexp5sive ( all bl[+-ma*9es4 ,bl[]s4--,:5 tubes h a l5g? & diamet] t require a pressure f "o to f\r p\nds p] squ>e in*1 "s =m ( positive bl[] ( ! ,root type c be us$ ) economy4 ,_! con/ruction is famili> to ne>ly e "o at all int]e/$ 9 ma*9]y1 s we ne$ give no space to _! description "h4 ,illu/ration3 ,,fig4 #db4 ,,! ,,/urtevant ,,/eel ,,pressure ,,bl[]4 ,illu/ration3 ,,fig4 #dc4 ,,root',s ,,positive ,,pressure ,,bl[]4 ,illu/ration3 ,,fig4 #dd4 ,,section ,,( ,,root',s ,,true ,,circle ,,bl[]4 ,illu/ration3 ,,fig4 #de4 ,,! ,,gre5 ,,bl[]4 ,illu/ration3 ,,fig4 #df4 ,,section ,,( ,,! ,,gre5 ,,bl[]4 ,air-,compressors4--,by f> ! great] numb] ( our tubes require an air-pressure ( m ?an five p\nds p] squ>e in*4 ,= su* air supply we recomm5d "s =m ( air-compressor1 & usually ?is is driv5 by a /eam-eng9e1 :i* =ms a "p ( ! compressor4 ,9 mak+ our selection we %\ld be> 9 m9d ! conditions "u :i* ! compressor w run4 ,usually x mu/ be kept 9 con/ant op]ation at lea/ t5 h\rs p] day1 & frequ5tly = a mu* long] p]iod4 ,?is makes x important t ! compressor be sub/antially built & support$ ^u a solid & firm f\ndation4 ,! be>+s %\ld be broad1 ( good we>+ mat]ial t has a l[ coeffici5t ( friction1 & provid$ at all times ) ample lubrication4 ,if poppet valves are us$ 9 ! air-cyl9d]s1 & !y are mo/ common1 ! spe$ 9 revolutions p] m9ute %\ld n be high4 ,duplex are bett] ?an s+le cyl9d] compressors1 because !y deliv] ! air 9 a m /eady /ream1--! pulsations are less4 ,= con/ant runn+1 economy ( /eam is an important item2 !re=e "s good type ( cut-(f valve %\ld be provid$4 ,! air-cyl9d]s %\ld n be wat]-jacket$ unless ! pressure is above tw5ty-five p\nds p] squ>e in*4 ,x is bett] to use ! air z w>m z possible1 = x w soon be cool$ aft] ent]+ ! tube4 ,a spe$-gov]nor %\ld be provid$ ) compressors :i* are to run at con/ant spe$1 b usually !y w be run to ma9ta9 a con/ant pressure 9 ! tank1 & to ?is end a good & reliable =m ( pressure-gov]nor %\ld be provid$1 toge!r ) "s reliable safety device to /op ! eng9e :5 ! spe$ exce$s a safe limit4 ,b mo/ important ( all is to h ! valves ( ! air-cyl9d]s l>ge 9 area2 o!rwise ! effici5cy ( ! ma*9e w be v l[4 ,) ma*9es work+ "u eighty p\nds pressure1 a diff]5ce 9 pressure ( "o p\nd on opposite sides ( ! valves has b little effect1 b :5 ! ma*9e is only compress+ to five or t5 p\nds1 "o p\nd is a v l>ge proportion ( ! total pressure & r$uces ! effici5cy4 ,besides ^! few sugge/ions1 only ! requirem5ts ( good eng9e]+ ne$ be dem&$4 ,9 ,figs4 #db1 #dc1 #dd1 #de1 #df1 & #dg we %[ a fan1 two bl[]s1 & an air-compressor suit$ to ! requirem5ts ( pneumatic-tube s]vice t c be f\nd 9 ! m>ket1 & t are built by responsible conc]ns4 ,we believe !y are all good ( _! k9d1 b d n recomm5d any p>ticul> make4 ,! ,tube1 ,l9e ,con/ruction1 etc4--,up to ! pres5t "t we h f\nd no mat]ial bett] suit$ = ! /raight p>ts ( pneumatic tubes ?an ca/ iron1 ma*9$ ^u ! int]ior4 ,x gives a smoo? & accurate tube4 ,x c be made 9 mo/ conv5i5t l5g?s4 ,x is /rong & n easily de=m$4 ,! bell-jo9t1 calk$ ) lead & oakum1 hav+ ! tubes fitt$ toge!r male & female at ! bottom ( ! bell1 is ! be/ jo9t yet devis$ = pneumatic tubes4 ,x is slightly yield+1 accommodat+ itself to slight *anges ( l5g? ( tube due to *anges ( temp]ature1 & x all[s slight b5ds to be made at ea* jo9t4 ,! jo9ts are v accurate1 pres5t+ no %\ld]s to ob/ruct ! passage ( c>ri]s4 ,! jo9ts c be made by m5 accu/om$ to lay+ wat]- & gas-pipe4 ,! ca/ iron is s /iff t x is n di/ort$ 9 calk+1 z may be done ) wr\ght-iron tube4 ,! pr9cipal objections to its use are ! exp5se ( bor+ & ! read9ess ) :i* x corrodes ^u ! int]ior4 ,illu/ration3 ,,fig4 #dg4 ,,r& ,,comp\nd ,,compressor ,,( ,,mod]ate ,,size4 ,we are always hop+ t wr\ght-iron or /eel tubes w be s mu* improv$ 9 uni=mity ( dim5sions & smoo?ness ( int]ior t we c use !m1 b our exp]im5ts ?us f> h be5 disc\rag+4 ,x may be t "s ( ! new processes ( mak+ tubes w give u :at we want1 b we h n yet f\nd x4 ,small tubes & ! %ort b5ds ( l>ge tubes are made ( brass1 x be+ ! mo/ suitable mat]ial4 ,x w\ld be v difficult to b5d iron tubes )\t involv+ great exp5se4 ,! ?ickness ( ! b5t portion ( an eight-in* tube is usually ?ree-sixte5?s ( an in* & nev] less ?an "o-eigh? ( an in*4 ,:]e ! gr\nd is firm1 no o!r support is ne$$ = ! tubes ?an to tamp ! e>? solidly ab\t !m4 ,9 ord] to economize space 9 ! /reets1 x is cu/om>y to lay ! tubes "o above ! o!r2 & x is v conv5i5t1 al?\gh n necess>y1 to sep>ate !m by ca/-iron saddle brackets4 ,su* an arrangem5t has to be frequ5tly dep>t$ f 9 ord] to ov]come ob/ructions 9 ! /reets & to get ?r\gh n>r[ passages4 ,at all l[ po9ts 9 a tube l9e1 traps are provid$ to cat* any moi/ure t may accumulate4 ,^! traps are made accessible = frequ5t inspection by means ( man-holes or o!rwise4 ,! tube is usually laid ab\t ?ree feet bel[ ! pavem5t4 ,?is di/ance has frequ5tly to be v>i$1 b x nev] becomes s small z to r5d] ! tubes liable to injury f heavy trucks pass+ ov] ! pavem5t4 ,,*apt] ,,iv4 ,,facts ,,& ,,g5]al ,,in=mation ,,relat+ ,,to ,,pneumatic ,,tubes4 ,we w n[ discuss1 9 an elem5t>y way1 ! !ory ( pneumatic tubes1 9 ord] to und]/& m cle>ly _! modus op]&i & ! pr9ciples ^u :i* !y %\ld be con/ruct$4 ,let u beg9 ) ! def9ition ( a pneumatic tube4 ,def9itions4--,a pneumatic tube is a tube conta9+ air4 ,?is is p]haps ! broade/ & mo/ compreh5sive def9ition t c be giv51 b we usually associate ) ! idea ( a pneumatic tube ! use to :i* x is put4 ,if we 7 to embody ?is idea 9 our def9ition we might def9e a pneumatic tube z a tube ?r\gh :i* mat]ial is s5t by means ( a curr5t ( air4 ,?is is /ill a v broad def9ition1 includ+ all k9ds ( mat]ial = transportation1 = e conceivable purpose4 ,x places no limit ^u ! dim5sions ( ! tube nor ! mann] ( its op]ation4 ,?is def9ition w\ld include ! toy commonly kn[n z a putty-bl[]1 & ! pneumatic gun4 ,^! in/rum5ts are n usually pictur$ 9 our m9ds :5 we he> or see ! t]m pneumatic tube us$4 ,in/ead ( ^!1 we ?9k ( ! brass tubes t we h se5 9 ! l>ge retail /ores 9 "s ( our cities = convey+ ca% f ! v>i\s c\nt]s to ! c5trally locat$ ca%i]'s desk4 ,aga9 n>r[+ our def9ition to con=m m ne>ly ) ! m5tal picture pres5t$1 we w def9e a pneumatic tube z a long tube = ! purpose ( transport+ mat]ial 9 c>ri]s by means ( a curr5t ( air 9 ! tube4 ,?is1 l all def9itions1 is n entirely satisfactory1 if we exam9e x critically1 b x w answ] our pres5t purpose4 ,int]mitt5t & ,con/ant ,air-,curr5t4--,hav+ ?us def9$ a pneumatic tube1 !re are two ways 9 :i* we may op]ate x to transport our c>ri]s conta9+ mail1 packages1 or o!r matt]4 ,! fir/ me?od consi/s 9 /or+ our compress$ air 9 a suitable tank1 or by exhau/+ ! air f ! tank2 !n1 :5 we wi% to despat* a c>ri] we place x 9 ! tube & connect ! tube ) ! tank by op5+ a valve4 ,z soon z ! c>ri] arrives at ! di/ant end ( ! tube ! valve is clos$ & ! air soon ceases to fl[4 ,:5 a long int]val ( "t elapses betwe5 ! despat*+ ( c>ri]s1 ?is is ! mo/ economical me?od ( op]ation1 b usually c>ri]s h to be despat*$ s frequ5tly t a great deal ( "t w\ld be lo/ if ! air-curr5t _h to be />t$ & /opp$ = ea* c>ri]4 ,! second & m usual me?od ( op]ation consi/s 9 ma9ta9+ a con/ant curr5t ( air 9 ! tube & 9 hav+ ! c>ri]s ins]t$ & eject$ at ! ends ( ! tube )\t /opp+ ! curr5t ( air = any appreciable l5g? ( "t4 ,x is analog\s to laun*+ boats 9 a rapidly fl[+ /ream1 all[+ !m to float d[n /ream & !n )draw+ !m4 ,:5 ! boats are 9 ! /ream !y pres5t little ob/ruction to ! fl[ ( wat] & *eck its spe$ b v little4 ,9 ord] to compute ! spe$ ) :i* ! boat w pass f "o po9t to ano!r1 we only h to "k ! spe$ ( ! /ream betwe5 ^? po9ts :5 no boat is 9 x4 ,! pres5ce ( ! boat does n *ange ! spe$ appreciably4 ,s x is ) c>ri]s 9 a pneumatic tube3 !y are c>ri$ along ) ! curr5t ( air4 ,! air fl[s ne>ly z rapidly :5 a c>ri] is 9 ! tube z :5 !re is none4 ,! friction ( ! c>ri] aga9/ ! inn] surface ( ! tube creates a slight drag1 b x *ecks ! spe$ ( ! air only a little4 ,!re=e1 9 ord] to "k ! spe$ ) :i* a c>ri] w be transport$ f "o /ation to ano!r ?r\gh a pneumatic tube1 we ne$ only to "k ! velocity ) :i* ! air fl[s ?r\gh ! tube :5 no c>ri] is pres5t4 ,( c\rse !re are special cases ( heavy c>ri]s1 or c>ri]s hav+ a l>ge am\nt ( friction f _! pack+1 or ( tubes n laid horizontally1 :]e ! resi/ance ( ! c>ri] mu/ be tak5 into consid]ation1 b = our pres5t purpose we w neglect all ( ^! conditions4 ,laws ,gov]n+ ! ,fl[ ( ,air 9 ,long ,tubes4--,?is leads u to /udy ! laws gov]n+ ! fl[ ( air 9 long tubes1 omitt+ = ! pres5t ! pres5ce ( a c>ri]4 ,s9ce tubes op]at$ int]mitt5tly h become obsolete1 we w only consid] ! case ( a con/ant curr5t ( air1 ?is be+ :at we h to deal ) 9 practice4 ,illu/ration3 ,,fig4 #dh4 ,,pressure ,,& ,,velocity ,,curves4 ,9 ord] to make our ideas & ?\ghts z cle> z possible let u repres5t !m by a diagram1 ,fig4 #dh4 ,we w suppose t a tank1 ,a1 is kept con/antly fill$ ) compress$ air at a pressure ( t5 p\nds p] squ>e in*1 f "s s\rce ( supply4 ,we w suppose t ! pressure ( ! air 9 ?is tank nev] *anges1 air be+ suppli$ z fa/ z x fl[s away4 ,next1 let u assume t a tube eight in*es 9 diamet] inside & "o mile long 7five ?\s& two hundr$ & eighty feet7 is connect$ to ! tank at "o end & left op5 to ! atmosph]e at ! o!r4 ,! air w fl[ 9 a con/ant /ream f ! tank into ! atmosph]e1 = ! reason t air is be+ suppli$ to ! tank z fa/ z x fl[s away4 ,law ( ,pressure4--,fir/1 let u consid] ! pressure ( ! air at v>i\s po9ts 9 ! tube4 ,we w1 = conv5i5ce1 repres5t ! pressure 9 ! tank by a v]tical l9e1 ,d ,e1 t5 units 9 l5g?1 s9ce ! pressure is t5 p\nds p] squ>e in*4 ,n[ let u g to a po9t on ! tube "o qu>t] ( a mile 7"o ?\s& ?ree hundr$ & tw5ty feet7 f ! tank1 drill a hole 9 ! tube1 atta* a pressure-gauge & measure ! pressure ( ! air at ?is po9t4 ,we %all f9d x to be ab\t #g4ia p\nds p] squ>e in*2 or1 #b4ji p\nds bel[ ! pressure 9 ! tank4 ,we w repres5t ?is on our diagram by ano!r v]tical l9e1 ,f ,g1 hav+ a l5g? ( #g4ia units4 ,aga9 let u measure ! pressure 9 ! tube at a po9t "o-half a mile 7two ?\s& six hundr$ & =ty feet7 f ! tank4 ,"h we f9d x to be ab\t #e4fa p\nds p] squ>e in*1 & we repres5t x by ! v]tical l9e1 ,h ,i1 hav+ #e4fa units ( l5g?4 ,we note t ! pressure is #d4ci p\nds bel[ ! pressure 9 ! tank4 ,we are at ! middle po9t ( ! tube & ! pressure has fall5 to ne>ly1 b n q1 "o-half ! pressure 9 ! tank4 ,we w n[ g to a po9t ?ree-qu>t]s ( a mile 7?ree ?\s& n9e hundr$ & sixty feet7 f ! tank1 & "h ! pressure is ab\t #c4ja p\nds p] squ>e in*4 ,we repres5t x by ! v]tical l9e1 ,j ,k4 ,la/ly1 we measure ! pressure v ne> ! end ( ! tube1 "o mile f ! tank1 & f9d x to be ab\t z]o1 or ! same z ! pressure ( ! atmosph]e4 ,all ( our measurem5ts h be5 9 p\nds above ! atmosph]ic pressure2 to express !m 9 absolute pressure1 we %\ld add to ea* ! pressure ( ! atmosph]e1 :i* is #ad4fi p\nds1 ne>ly4 ,n[ we w draw a smoo? curve ?r\gh ! tops ( all our v]tical l9es1 & we h a curve1 ,e1 ,g1 ,i1 ,k1 ,l1 repres5t+ ! pressure 9 ! tube at e po9t4 ,x falls gradually f t5 p\nds to z]o1 b x does n fall 9 exact proportion to ! di/ance f ! tank4 ,su* a fall ( pressure w\ld be repres5t$ by ! /raight da%-l9e1 ,e1 ,l4 ,! reason :y ! true pressure-curve is n a /raight l9e1 & lies above a /raight l9e1 is because air is an ela/ic fluid & exp&s1 becom+ l>g] 9 volume z ! pressure dim9i%es4 ,! /raight da%-l9e repres5ts ! fall ( pressure ( an inela/ic fluid1 l wat]1 :5 fl[+ 9 ! tube4 ,! fall ( pressure along ! tube is analog\s to ! fall ( level along a fl[+ /ream4 ,9 fact1 we frequ5tly speak ( ! desc5t ( a /ream z ! 8head ( wat]0 :5 x is us$ = p[] purposes1 & we mean by ?is ! pressure ! wat] w\ld ex]t if x 7 conf9$ 9 a pipe4 ,! desc5t1 or *ange ( level1 9 ! b$ ( a /ream is necess>y to keep ! wat] fl[+ aga9/ ! friction ( ! banks4 ,! desc5t ( ! wat] imp>ts en]gy to ov]come ! friction4 ,9 a simil> mann]1 we mu/ h a fall ( pressure along ! pneumatic tube to ov]come ! friction ( ! air aga9/ ! int]ior surface ( ! tube4 ,we f9d ano!r analogue 9 ! fl[ ( ! electric curr5t along a wire2 "h !re is a fall ( pot5tial necess>y to ov]come ! resi/ance ( ! wire4 ,s9ce p[] has to be exp5d$ to compress ! air & imp>t to x its pressure1 :5 ?is pressure disappe>s we "k t ! air mu/ be los+ its en]gy or do+ "w1 & we look to see :at becomes ( x4 ,9 ! pres5t case1 we f9d t mo/ ( ?is "w is exp5d$ 9 ov]com+ ! friction betwe5 ! air & ! surface ( ! tube4 ,uses ( ,pressure ,curves4--,! pressure curve tea*es u _m ?+s4 ,suppose we 7 to e/abli% /ations on ?is tube at ! qu>t]1 half1 ?ree-qu>t]1 & mile po9ts2 we see at once t int]m$iate-/ation or clos$ receiv]s1 describ$ 9 ! la/ *apt]1 mu/ be us$ at all ( ! /ations except ! mile po9t at ! end ( ! tube1 because ! pressure 9 ! tube is s high above ! pressure ( ! atmosph]e t we c\ld n op5 ! tube to let ! c>ri]s come out1 b at ! end ( ! tube we c\ld use ! op5 receiv]4 ,9 design+ our s5d+ & receiv+ app>atus = ea* /ation1 we look to ?is pressure curve to tell u ! pressure :i* we %all h on ! pi/ons 9 our cyl9d]s1 & are !reby enabl$ to make !m ) prop] proportions = ! "w t !y h to d4 ,law ( ,velocity4--,next let u see :at ! velocity ( ! air is 9 ! tube4 ,suppose t we h "s conv5i5t means ( measur+ ! velocity ( ! air at any po9t1 9 feet p] second or miles p] h\r1 ) "s =m ( anemomet]4 ,we w h our measurem5ts tak5 at ! five po9ts :]e we measur$ ! pressure1--viz41 at ! tank1 "o-qu>t]1 "o-half1 ?ree-qu>t]s & "o mile f ! tank4 ,we w repres5t ! velocities by a diagram simil> to ! "o us$ = pressures4 ,at ! tank we f9d ! air ent]+ ! tube ) a velocity ( #ei4e feet p] second 7#dj4f miles p] h\r74 ,we draw ! v]tical l9e ,m ,n1 to repres5t ?is4 ,at ! qu>t] mile po9t ! velocity is sixty-five feet p] second 7#dd4d miles p] h\r7 an increase 9 ! fir/ qu>t] ( a mile ( #e4e feet p] second4 ,we con/ruct ! v]tical l9e ,o ,p4 ,at ! half-mile po9t ! velocity is #gb4d feet p] second 7#di4d miles p] h\r72 at ! ?ree-qu>t] mile po9t x is eighty-?ree feet p] second 7#ef4h miles p] h\r72 & at ! end ( ! tube1 "o mile f ! tank1 ! air comes out ( ! tube ) a velocity ( #ajj4d feet p] second 7#fh4e miles p] h\r71 ab\t #a4g times fa/] ?an x ent]$ ! tube at ! tank4 ,draw+ all ! v]tical l9es to repres5t ^! velocities1 & draw+ a smoo? curve l9e ?r\gh ! tops ( our v]tical l9es1 we h ! curve ( velocities1 ,n1 ,p1 ,r1 ,t1 ,v1 = all po9ts along ! tube4 ,x is an increas+ velocity & increases m rapidly z we approa* ! end ( ! tube4 ,?is is %[n m cle>ly by draw+ ! /raight da%$ l9e ,n ,v4 ,if ! fluid fl[+ 9 ! tube 7 inela/ic1 l wat]1 !n ! curve ( velocities w\ld be a /raight horizontal l9e1 = ! wat] w\ld n come out ( ! tube any fa/] ?an x w5t 94 ,b we are deal+ ) air1 :i* is an ela/ic fluid1 &1 z we /at$ be=e1 x exp&s z ! pressure is r$uc$ & becomes l>g] 9 volume4 ,x is ?is expansion t increases its velocity z x fl[s along ! tube4 ,x mu/ g fa/] & fa/] to make room to exp&4 ,s9ce ! same actual quantity ( air 9 p\nds mu/ come out ( ! tube ea* m9ute z ent]s ! tube at ! o!r end 9 ! same "t1 to prev5t an accumulation ( air 9 ! tube1 & s9ce x increases 9 volume z x fl[s ?r\gh ! tube1 x foll[s t its velocity mu/ increase4 ,*>act]i/ics ( ! ,velocity ,curve4--,?is velocity curve is bo? int]e/+ & surpris+1 if we h n giv5 ! subject any previ\s ?\ght4 ,x might occur to u t ! air exp&s 9 volume 9 ! tube1 & we might reason f ?is fact t ! velocity ( ! air w\ld increase z x fl[$ ?r\gh ! tube1 b v few ( u w\ld be able to see t ! rate ( increase ( velocity also increases4 ,t is to say1 x ga9s 9 velocity m rapidly z x approa*es ! op5 end ( ! tube4 ,if ! velocity 7 repres5t$ on ! diagram by a /raight horizontal l9e1 we %\ld "k t x 0 con/ant 9 all p>ts ( ! tube1 :i* w\ld be ! case if wat] 7 fl[+ in/ead ( air4 ,if x 7 repres5t$ by a /raight incl9$ l9e1 l ! da%$ l9e ,n ,v1 !n we %\ld "k t ! velocity increas$ z ! air fl[$ along ! tube1 b t x increas$ at a uni=m rate4 ,! slope ( ! l9e w\ld indicate ! rate ( increase4 ,nei!r ( ^! suppositions repres5t correctly ! velocity ( ! air at all po9ts 9 ! tube2 ?is c only be done by a curv$ l9e su* z we h %[n4 ,! slope ( ! curve at any po9t repres5ts ! rate ( increase ( velocity ( ! air at t po9t4 ,if ! curve is ne>ly horizontal1 !n we "k t ! velocity does n increase mu*2 b if ! curve is /eep1 !n we "k t x is increas+ rapidly1 ! actual velocity be+ indicat$ by ! v]tical height ( ! curve above ! horizontal l9e ,m ,u4 ,use ( ,velocity ,curves4--,besides be+ int]e/+1 a k ( ! velocity ( ! air at all po9ts 9 a tube is ( mu* practical value4 ,x gives u ! "t a c>ri] w take 9 go+ f "o /ation to ano!r4 ,usually ! fir/ que/ions ask$1 :5 x is propos$ to lay a pneumatic tube f /ation ,a to /ation ,b1 are1 ,h[ quickly c y s5d a c>ri] betwe5 ^! po9ts8 ,h[ mu* "t c be sav$8 ,^! que/ions are answ]$ by con/ruct+ a velocity curve4 ,s9ce ! velocity *anges at e po9t along a tube1 to get ! "t ( transit betwe5 two po9ts we mu/ "k ! av]age velocity ( ! air betwe5 ^? po9ts4 ,we c f9d ?is approximately f our curve by measur+ ! height ( ! curve above ! horizontal l9e ,m ,u at a l>ge numb] ( po9ts1 & !n tak+ ! av]age ( all ^! heights2 b !re is a m exact & easi] me?od by means ( a ma!matical =mula4 ,z su* =mula w\ld be out ( place "h1 we w n give x2 suffice x to say1 t ! av]age velocity ( ! air betwe5 ! tank & ! end ( ! tube1 9 ! case we h assum$1 is ab\t sev5ty-?ree feet p] second 7#di4g miles p] h\r71 a little less ?an "o-half ! sum ( ! velocities at ! two ends1 & a little m ?an ! velocity at ! half-mile po9t4 ,kn[+ ! av]age velocity1 we c tell h[ long x takes = a p>ticle ( air1 & x w be ne>ly ! same = a c>ri]1 to travel f ! tank to ! end ( ! tube1 by divid+ ! di/ance 9 feet by ! av]age velocity 9 feet p] second4 ,?is we f9d to be "o m9ute #ab4c seconds4 ,s9ce ! air moves m rapidly z x approa*es ! op5 end ( ! tube1 a c>ri] w consume a great] p]iod ( "t 9 go+ f ! tank to ! qu>t] mile po9t ?an 9 go+ f ! ?ree-qu>t] mile po9t to ! op5 end4 ,! la/ qu>t] ( a mile w be cov]$ 9 a little m ?an f\rte5 seconds1 :ile ! fir/ qu>t] w require a little m ?an tw5ty-"o seconds4 ,?is diff]5ce is surpris+1 & x becomes ev5 m m>k$ 9 v long tubes ) high initial pressures4 ,?is expla9s :y ! s]vice betwe5 /ations locat$ ne> ! end ( ! tube is m rapid ?an betwe5 /ations on o!r p>ts ( ! l9e4 ,?is velocity curve %[s u ! velocity ( ! c>ri]s at ea* /ation along ! l9e & enables u to regulate our "t-locks & to locate ! man-holes & circuit-clos]s connect$ ) ea* int]m$iate /ation4 ,x gives u ! l5g? ( ! 8blocks0 9 our 8block sy/em40 ,:5 we "k ! velocity & weight ( our c>ri]s1 we c compute ! en]gy /or$ up 9 !m1 & f ?is ! l5g? we ne$ to make our air-cu%ions s z n to h ! air too highly compress$4 ,x w\ld be impossible to design our app>atus prop]ly if we did n "k ! laws t gov]n ! fl[ ( air 9 ! tubes4 ,quantity ( ,air ,us$4--,! next important fact t we le>n f ! velocity curve is ! quantity ( air t fl[s ?r\gh ! tube ea* second or m9ute4 ,if we multiply ! velocity ) :i* ! air escapes f ! op5 end ( ! tube by ! area ( ! end ( ! tube 9 squ>e feet1 we h ! numb] ( cubic feet ( air at atmosph]ic pressure dis*>g$ f ! tube p] unit ( "t4 ,! same quantity ( air mu/ be suppli$ to ! tank 9 ord] to ma9ta9 a con/ant fl[ 9 ! tube4 ,9 ! pres5t case t we h assum$1 ! tube is eight in*es 9 diamet]2 !re=e ! cross-sectional area is #j4cdi squ>e foot4 ,! velocity ( ! air z x comes out ( ! end ( ! tube is #ajj4d feet p] second2 !re=e ab\t ?irty-five cubic feet ( air are dis*>g$ f ! tube ea* second1 or two ?\s& "o hundr$ cubic feet p] m9ute4 ,?is same am\nt mu/ be suppli$ to ! tank ,a 9 ord] to ma9ta9 ! pressure con/ant1 b :5 x is compress$ s t x ex]ts a pressure ( t5 p\nds p] squ>e in*1 ! two ?\s& "o hundr$ cubic feet w only occupy a space ( "o ?\s& two hundr$ & fifty cubic feet1 if its temp]ature does n *ange4 ,?is leads u to consid] ! effect ( temp]ature *anges4 ,temp]ature ( ! ,air4--,if ! air is all[$ to become heat$ by compression1 z is ! case 9 practice1 we h a new set ( conditions4 ,if ! air 9 ! tank ,a is hot1--t is1 w>m] ?an ! surr\nd+ atmosph]e1--x w by radiation cool some:at be=e x ent]s ! tube1 & x w be /ill fur!r cool$ :5 x exp&s 9 ! tube4 ,aga91 if its temp]ature falls bel[ ! temp]ature ( ! gr\nd 9 :i* ! tube is laid1 x w absorb heat f ! gr\nd1 & ?is w t5d to keep up its temp]ature2 s 9 practice we h v complicat$ relations betwe5 ! temp]ature1 pressure1 & volume ( ! air4 ,^! relations _c be exactly express$ by ma!matical =mul1 & we w make no attempt s to express !m1 b w be cont5t ) say+ t 9 practice we f9d t ! temp]ature ( ! air 9 ! tubes is ne>ly con/ant aft] ! fir/ few hundr$ feet1 s t we c )\t appreciable error compute ! pressures & velocities z if x 7 con/ant4 ,n[1 if ! air 9 ! tank ,a is hot1 we mu/ raise ! pressure a little above t5 p\nds p] squ>e in* to obta9 ! velocities giv5 on our diagram4 ,:5 ! air cools x contracts 9 volume1 or1 if ! volume _c *ange1 be+ fix$ by ! limits ( ! conta9+ vessel1 !n ! pressure is r$uc$1 s by rais+ ! pressure 9 ! tank ,a a little above t5 p\nds1 we comp5sate ! loss ( pressure4 ,horse-,p[]4--,hav+ %[n h[ ! quantity ( air c be comput$ we are n[ 9 a position to e/imate ! horse-p[] ( ! air-compressor necess>y to op]ate ! tube4 ,i say e/imate1 because we h to take into consid]ation ! effici5cy ( ! air-compressor1 & t is n an absolutely fix$ quantity3 x v>ies ) diff]5t types ( ma*9es & ) _! con/ruction4 ,:5 work+ ) pressures ( less ?an t5 p\nds1 ! friction ( ! ma*9e is an important factor4 ,! area & con/ruction ( ! valves 9 ! air-cyl9d]s is ano!r v important factor4 ,if ! valves are n l>ge en\gh or d n op5 promptly1 our cyl9d]s w n be fill$ ) air at ea* /roke2 ?is w r$uce ! effici5cy ( ! ma*9e4 ,9 practice we g to a manufactur] ( air-compressors & tell him h[ mu* air mu/ be compress$ p] m9ute1 & ! pressure to :i* x mu/ be compress$1 ) o!r conditions1 & !n he tells u :at size ( ma*9e we %all require & ! horse-p[] ( ! ma*9e approximately4 ,he is suppos$ to "k ! effici5cy ( 8 own ma*9es4 ,we may endeavor to prove 8 e/imate by computations ( our own4 ,to give "s idea ( ! horse-p[] requir$ to supply ! air ne$$ to op]ate our eight-in* tube "o mile long1 ,i w say t ! /eam-eng9es ( ! air-compressor w h to develop 9 ! vic9ity ( "o hundr$ & tw5ty-five actual horse-p[]4 ,f ! horse-p[] ( ! /eam-eng9e we c easily compute ! coal t w be consum$ "u boil]s ( ! usual type4 ,effici5cy4--,x w be not$ t mo/ ( ! p[] is n us$ prim>ily 9 mov+ ! c>ri]s1 b to move ! air ?r\gh ! tube4 ,v ne>ly z mu* p[] is us$ to keep ! air fl[+ 9 ! tube :5 no c>ri]s are 9 x z :5 c>ri]s are be+ despat*$4 ,if we %\ld def9e ! effici5cy ( a pneumatic tube z ! ratio ( ! p[] consum$ 9 mov+ ! c>ri]s to ! p[] consum$ 9 mov+ ! c>ri]s & ! air1 we %\ld f9d ?is s-call$ effici5cy to be v l[4 ,x is analog\s to pull+ ! c>ri] ) a long rope & dragg+ ! rope on ! gr\nd4 ,mu* m p[] w\ld be consum$ by ! rope ?an by ! c>ri]4 ,b a bus9ess man w\ld def9e ! effici5cy ( a pneumatic tube z ! ratio ( ! co/ ( transport+ 8 lett]s1 p>cels1 etc41 to ! co/ ( transport+ !m ) equal spe$ 9 any o!r way4 ,def9$ 9 ?is practical mann] ! effici5cy ( a pneumatic tube is high4 ,we d n c>e :at becomes ( ! p[] s long z x accompli%es our purpose4 ,pressure & ,exhau/ ,sy/ems4--,we h notic$ t pneumatic tubes h n always be5 op]at$ by compression ( ! air1 b t "s ( ! small tubes us$ 9 ! telegraph s]vice ( ,european cities h be5 op]at$ by exhau/+ ! air4 ,! two sy/ems are sometimes di/+ui%$ by call+ "o a pressure sy/em & ! o!r an exhau/ sy/em4 ,^! t]ms are v mislead+1 = an exhau/ sy/em is a pressure sy/em4 ,! curr5t ( air is kept fl[+ 9 a tube by ma9ta9+ a diff]5ce ( pressure at ! two ends1 & ! result is ! same :e!r we raise ! pressure at "o end above ! atmosph]ic or l[] x at ! o!r bel[ ! atmosph]ic4 ,9 ei!r case x is pressure t causes ! air to fl[4 ,x happ5s t we are liv+ 9 an atmosph]e ( ab\t fifte5 p\nds pressure p] squ>e in*1 & x is v conv5i5t (t5times 9 our computations to take ! pressure ( ! atmosph]e z our z]o1 & reckon all o!r pressures above & bel[ ?is4 ,if all our pressure scales read f absolute z]o1 ! pressure ( a p]fect vacuum1 !n all ?is confusion w\ld be avoid$4 ,we h n us$ ! absolute z]o 9 our diagram1 because all our gauges are graduat$ ) _! z]o at atmosph]ic pressure1 & x is cu/om>y to speak ( pressures above & bel[ ! atmosph]ic4 ,x is v natural to ask ! "q1 :y are tubes sometimes op]at$ by compress+ ! air & at o!r times by exhau/+ x8 ,we answ] by say+ t x is usually a "q ( simplicity & conv5i5ce t det]m9es :i* sy/em %all be us$4 ,"s ( ! ca% sy/ems 9 ! /ores use compress$ air 9 ! out-go+ tubes f ! ca%i]'s desk & exhau/ ! air f ! return tubes4 ,bo? ends ( ! tubes are !n left op5 at ! c\nt]s1 no s5d+ or receiv+ app>atus be+ requir$ !re4 ,! c>ri]s are s light1 _! velocity s l[1 & ! air-pressure v>ies s little f ! pressure ( ! atmosph]e t ! c>ri]s c be all[$ to drop out ( ! tubes on to ! c\nt]s1 & !y c be despat*$ by simply plac+ !m at ! op5 end ( ! tube into :i* ! air is fl[+4 ,! curr5ts ( air ent]+ & leav+ ! tubes are n s /rong z to cause any special annoyance4 ,at ! ca%i]'s desk "s simple receiv+ & s5d+ app>atus has to be us$1 b x is bett] to conc5trate all ( ! app>atus at "o po9t r ?an h x di/ribut$ ab\t ! /ore1 z w\ld be ! case if ! d\ble sy/em 7 n us$4 ,9 ! ,london pneumatic telegraph bo? me?ods ( op]ation h be5 9 use4 ,d\ble l9es 7 laid1 & ! eng9es exhau/$ ! air f "o tube & =c$ x into ! o!r4 ,! exhau/$ tube 0 !re=e us$ to despat* 9 "o direction1 :ile ! o!r tube1 op]at$ by ! compress$ air1 s]v$ = despat*+ 9 ! opposite direction4 ,s f> z ,i "k1 bo? "w equally well4 ,9 op]at+ l>ge tubes1 t is to say1 tubes six or eight in*es 9 diamet]1 !re is an advantage 9 us+ compress$1 r ?an exhau/$ air1 9 ! con/ruction ( ! s5d+ & receiv+ app>atus1 especially :5 ! tubes are v long4 ,) an ample supply ( compress$ air always at h&1 ! air-cu%ions c be made %ort] & m effective 9 br++ ! c>ri]s quickly to re/4 ,) exhau/$ air ! cu%ions are ineffective1 & consequ5tly mu/ be made v long 9 ord] to /op ! c>ri] be=e x /rikes ! clos$ end ( ! tube4 ,?is does n apply to small tubes :]e ! c>ri]s are s light t !y c be /opp$ )\t injury by all[+ !m to /rike solid buff]s4 ,aga91 :5 compress$ air is us$1 we h a l>g] diff]5ce 9 pressure betwe5 ! pressure 9 ! tube & ! atmosph]e to op]ate our me*anism by cyl9d]s & pi/ons4 ,) an exhau/ sy/em c>ri]s are n s easily eject$ f ! tubes ( ! receiv+ app>atus2 we c\ld n use ! simple =m ( op5 receiv]4 ,aga91 if ! tubes are laid 9 wet gr\nd1 & a leak occurs 9 any ( ! jo9ts1 wat] w be drawn 9 if air is be+ exhau/$ f ! tube1 :ile x w be kept out if compress$ air is us$4 ,9 reg>d to ! "q ( relative economy ( ! two sy/ems1 we w say t :5 long tubes are us$1 requir+ high pressures1 or1 m /rictly speak+1 a l>ge diff]5ce ( pressure1 to ma9ta9 ! desir$ velocity ( air-curr5t1 !re seems to be "s advantage 9 us+ an exhau/ sy/em4 ,! reason is ?is3 ! friction ( ! air 9 ! tube1 :i* absorbs mo/ ( ! p[]1 increases z ! air becomes heavi] & m d5se4 ,:5 ! air is exhau/$ f ! tube1 we are us+ a curr5t ( r>efi$ air1 & ?is moves ?r\gh ! tube ) less friction &1 consequ5tly1 a high] velocity1 = ! same diff]5ce ( pressure1 ?an ! m d5se compress$ air4 ,b = %ort tubes t require only a small diff]5ce ( pressure1 ?is advantage becomes v small1 & is ov]balanc$ by o!r advantages ( a compress$ air sy/em4 ,s1 tak+ ev]y?+ into consid]ation1 !re is n s mu* to be said 9 favor ( an exhau/ sy/em4 ,laws ,express$ 9 ,ma!matical ,=mul4--,:ile we h h]et(ore purposely avoid$ all complicat$ ma!matical =mul1 x may n be out ( place "h to give a few ( ! m simple relations t exi/ betwe5 ! pressure1 velocity1 l5g? & diamet] ( ! tubes1 etc4 ,9 two tubes hav+ ! same diamet]1 ) ! same pressures ma9ta9$ at ea* end1 b ( diff]5t l5g?s1 ! mean velocities ( ! air 9 ! tubes w be> ! inv]se ratio to ! squ>e roots ( ! l5g?s ( ! tubes4 ,?is is express$ by ! foll[+ proportion3 u 3 ,u 33 ,l 3 l u & ,u repres5t ! mean velocities ( ! air 9 ! two tubes & l & ,l ! respective l5g?s ( tubes4 ,a simil> b direct ratio exi/s betwe5 ! mean velocities & ! diamet]s ( ! tubes1 ?us3 u 3 ,u 33 d 3 ,d ,?is relation1 h[ev]1 is only approximately true = tubes diff]+ greatly 9 diamet]4 ,! relation ( ! pressure to o!r factors is n s simply express$4 ,= example1 9 two tubes ( ! same l5g? & diamet]1 ! relation betwe5 ! pressures at ! ends & ! mean velocity ( ! air may be express$ z foll[s3 7p - p7_/ 7,p - ,p7_/ u 3 ,u 33 -------------------------- 3 ------------------ 7p - p7 7,p - ,p7 :]e u & ,u are ! respective mean velocities1 p#j & ,p#j ! respective pressures at ! initial ends ( ! tubes1 & p#a & ,p#a ! respective pressures at ! f9al ends ( ! tubes1--! pressures be+ measur$ above absolute z]o4 ,!re are o!r relations t c be simil>ly express$1 b = !m we mu/ ref] ! read] to a ma!matical treatise on ! subject4 ,moi/ure 9 ! ,tubes4--,:5 pressures ( m ?an five p\nds p] squ>e in* are us$1 x is n unusual to f9d "s moi/ure on ! int]ior ( ! tube & ^u ! outside ( ! c>ri]s :5 !y come out ( ! tube4 ,x is seldom m ?an a slight dampness1 or at mo/ a degree ( wetness equal to t se5 on ! outside ( a pit*] ( ice-wat] on a w>m day4 ,a slight am\nt ( moi/ure 9 ! tube is n objectionable1 = x s]ves z a lubricant to ! c>ri]s2 b :5 x is pres5t 9 consid]able quantity x becomes objectionable & ev5 annoy+4 ,?is moi/ure is br\ght into ! tube ) ! air1 & is deposit$ ^u ! walls ( ! tube :5 _! temp]ature is suffici5tly bel[ t ( ! atmosph]e4 ,! atmosph]e always conta9s m or less moi/ure 9 ! /ate ( vapor4 ,! capacity ( air = wat]-vapor dep5ds ^u its temp]ature1 be+ great] ! high] ! temp]ature1 b x is a fix$ & def9ite quantity at any giv5 temp]ature4 ,:5 ! air conta9s all ! wat]-vapor x c hold at a c]ta9 temp]ature1 x is said to be saturat$4 ,if x is n saturat$1 we express ! am\nt t x conta9s 9 p] c5t4 ( ! am\nt x w\ld conta9 if x 7 saturat$1 & ?is is t]m$ ! 8relative humidity40 ,= example1 if ! air is ?ree-f\r?s saturat$1 we say ! 8relative humidity0 is sev5ty-five2 b if ! temp]ature *anges1 ! 8relative humidity0 *anges also4 ,suppose ! temp]ature to-day is sev5ty-five degrees ,fahr5heit1 & t ! 8relative humidity0 is eighty1 a cubic foot ( air !n conta9s #j4jjajg p\nd ( wat]-vapor4 ,n[ suppose ?is air ent]s a pneumatic tube & is cool$ by expansion & contact ) ! cold] walls ( ! tube to sixty degrees4 ,at ?is temp]ature a cubic foot ( air c conta9 only #j4jjjhb p\nd ( wat]-vapor :5 x is saturat$4 ,n[1 ea* cubic foot ( air br\ght into ! tube br+s ) x #j4jjajg p\nd ( vapor1 & aft] x is cool$ d[n to sixty degrees x _c hold x all1 consequ5tly ! diff]5ce1 or #j4jjjbe p\nd1 mu/ be deposit$ 9 ! tube4 ,"u ^! conditions "o hundr$ ?\s& cubic feet ( air w deposit tw5ty-five p\nds ( wat] 9 ! tube4 ,9 ! sy/em ( pneumatic tubes built & op]at$ by ! ,bat*ell] ,pneumatic ,tube ,company1 ! pres5ce ( a l>ge quantity ( moi/ure 9 ! tube is prev5t$ by us+ ! same air ov] & ov] aga94 ,a little moi/ure may be deposit$ :5 ! tube />ts into op]ation1 b ! am\nt does n increase appreciably1 z v little fre% air is admitt$ aft] />t+4 ,location ( ,ob/ructions 9 ,tubes4--,9 reg>d to ! removal ( ob/ructions 9 ! tubes1 ,i h _h little or no exp]i5ce2 !re=e "u ?is head+ ,i am satisfi$ to quote f ! 8,m9utes ( ! ,proce$+s ( ! ,in/itution ( ,civil ,eng9e]s10 ,london1 ,volume ,,xliii4 8,intimately connect$ ) ! work+ ( ! tubes is ! removal ( ob/ructions :i* occur f "t to "t1 caus+ n unfrequ5tly s]i\s inconv5i5ce & delay4 ,! mo/ g5]al cause ( ob/ruction is a /oppage ( ! tra9 aris+ f accid5t to ! tube1 to ! c>ri]s or pi/on1 or to ! transmitt+ app>atus4 ,9 su* cases ! delay is g5]ally v brief1 x be+ = ! mo/ "p suffici5t to rev]se ! pressure on ! tra9 f ! next /ation1 & to drive x back to ! po9t x />t$ f4 ,if "o or m ( ! c>ri]s break 9 ! tube1 rev]se pressure is also g5]ally suffici5t to remove ! ob/acle2 b :]e ?is fails1 ! po9t ( ob/ruction mu/ be asc]ta9$4 ,?is is done by c>efully obs]v+ ! v>iations ( air pressure 9 ! res]voir :5 plac$ 9 connection1 fir/ ) a l9e ( kn[n l5g?1 & !n ) ! ob/ruct$ tube4 ,by ?is means ! position ( ! ob/ruction c be asc]ta9$ )9 "o hundr$ feet4 ,or ! tube may be prob$ ) a long rod up to a l5g? ( two hundr$ feet4 ,a v +5i\s app>atus1 by ,m4 ,*4 ,bontemps1 is %[n 9 ,figs4 #di & #ej1 & is employ$ to asc]ta9 ! exact position ( ! ob/ruction4 ,x acts by ! reflection ( s\nd-waves on a rubb] diaphragm4 ,a small metal disk is cem5t$ to ! rubb]1 & above ?is is a po9t$ screw1 ,d4 ,an electric circuit is clos$ :]e ! po9ts ,c & ,d are br\ght 9 contact4 ,to locate an ob/ruction a pi/ol is fir$ into ! tube z %[n1 & ! result+ wave1 trav]s+ ! tube at ! rate ( ?ree hundr$ & ?irty metres a second1 /rikes ! ob/ruction & is !n reflect$ aga9/ ! diaphragm1 :i* 9 its turn reflects x to ! ob/acle1 :5ce x returns to ! diaphragm4 ,by ?is means indications are m>k$ on ! record+ cyl9d]1 & if ! int]val ( "t betwe5 ! fir/ & second indications be record$1 ! di/ance ( ! ob/acle f ! membrane is easily asc]ta9$4 ,! *ronograph employ$ is provid$ ) ?ree po9ts2 ! fir/ ( ^! is plac$ 9 a circuit1 :i* is clos$ by ! successive vibrations ( ! diaphragm2 ! second corresponds to an electric regulator1 m>k+ seconds on ! cyl9d]2 & ! ?ird subdivides ! seconds !re m>k$4 ,fig4 #ej indicates a record ?us made4 ,9 ?is case ! ob/acle is situat$ at a di/ance ( sixty-two metres1 & ! vibration m>ks ?irty-?ree oscillations p] second4 ,! int]val occupi$ by two successive m>ks f ! diaphragm on ! pap] corresponds to twelve oscillations1 & ! di/ance ( ! ob/ruction is !n calculat$ by ! foll[+ =mula3 ,d #j4e #ccj #ab_/cc #fj metres2 s t ! di/ance ( ! ob/acle is record$ )9 two metres4 ,illu/ration3 ,,fig4 #di4 ,,ob/ruction-,,record+ ,,app>atus4 ,illu/ration3 ,,fig4 #ej4 ,,ob/ruction-,,record+ ,,app>atus4 8,among/ ! special causes ( accid5t may be m5tion$ ! accid5tal abs5ce ( a pi/on to ! tra91 break+ ( ! pi/on1 ! freez+ up ( a pi/on 9 ! tube1 & ev5 =gett+ ! pres5ce ( a tra91 :i* has caus$ ! entire s]vice to be "o tra9 late ?r\gh\t ! day4 ,f9ally1 ! tubes !mselves are sometimes brok5 or di/urb$ dur+ /reet repairs1 result+ ( c\rse 9 a complete cessation ( traffic 9 ! sy/em till ! damage is made good40