aeroplanes and dirigibles of war- 第29部分

distance　between　the　gun　and　the　target　cannot　be　utilised

directly　for　the　back　sight。　　On　the　other　hand；　it　is　essential

that　in　proportion　as　the　angle　from　the　horizontal　increases；

the　back　sight　should　be　lowered　progressively　in　a　manner

corresponding　to　the　distance。



To　assist　the　range…finder　in　his　task　of　sighting　it　is

necessary　that　he　should　be　provided　with　firing　tables　set　out

in　a　convenient　form；　which；　in　conjunction　with　the　telemeter；

serve　to　facilitate　training　for　each　successive　round。　　In　this

way　it　is　possible　to　pick　up　the　range　quickly　and　to　keep　the

objective　in　the　line　of　fire　until　it　either　has　been　put　hors

de　combat；　or　has　succeeded　in　retiring　beyond　the　range　of　the

gun。



The　sighting　arrangements　of　these　Krupp　anti…aircraft　guns　are

carried　out　upon　these　lines。　　Beneath　the　barrel　of　the

back…sight　is　an　observing　glass　with　an　eye…piece　for　the

artillerist；　while　above　and　behind　the　observing　glass　is

another　eye…piece；　to　be　used　in　conjunction　with　the

manipulation　of　the　back…sight。　　The　eye…piece　of　the　observation

glass　is　so　made　that　it　can　be　turned　through　a　vertical　plane

in　proportion　as　the　angle　of　fire　increases　in　relation　to　the

horizontal。　　The　determination　of　the　distance　from　the　objective

and　from　the　corresponding　back…sight　as　well　as　the　observation

of　the　altitude　is　carried　out　with　the　aid　of　the　telemeter。　

This　again　carries　an　observation　glass　fitted　with　an　eye…piece

which　can　be　turned　in　the　vertical　plane　in　the　same　manner　as

that　of　the　fore…sight。　　By　means　of　this　ingenious　sighting

device　it　is　possible　to　ascertain　the　range　and　angle　of　fire

very　easily　and　speedily。



The　weight　of　the　special　Krupp　anti…aircraft　field…piece；

exclusive　of　the　protecting　shield；　is　approximately　identical

with　that　of　the　ordinary　light　artillery　field…piece。　　It　throws

a　shell　weighing　8。8　pounds　with　an　initial　velocity　of　about

2；066　feet　per　second。



Although　the　German　armament　manufacturers　were　among　the　first

to　enter　the　field　with　an　anti…aircraft　gun　of　this　character

they　were　speedily　followed　by　the　French；　who　devised　a　superior

weapon。　　In　fact；　the　latter　represented　such　a　decisive　advance

that　the　German　artillerists　did　　not　hesitate　to　appropriate

their　improvements　in　sundry　essential　details；　and　to

incorporate　them　with　their　own　weapons。　　This　applies　especially

to　the　differential　recoil　system　which　is　utilised　in　the　small

anti…aircraft　guns　now　mounted　upon　the　roofs　of　high　buildings

of　cities　throughout　Germany　for　the　express　purpose　of　repelling

aerial　attack。



The　French　system　is　admitted　by　the　leading　artillery

technicians　of　the　world　to　be　the　finest　which　has　ever　been

designed；　its　remarkable　success　being　due　to　the　fact　that　it

takes　advantage　of　the　laws　of　Nature。　　In　this　system　the　gun　is

drawn　back　upon　its　cradle　preparatory　to　firing。　　In　some

instances　the　barrel　is　compressed　against　a　spring；　but　in　the

more　modern　guns　it　is　forced　to　rest　against　a　cushion　of

compressed　air　contained　within　a　cylinder。　　When　first　bringing

the　gun　into　action；　the　barrel　is　brought　into　the　preliminary

position　by　manually　compressing　the　air　or　spring　by　means　of　a

lever。　　Thereafter　the　gun　works　automatically。　　When　the　gun　is

fired　the　barrel　is　released　and　it　flies　forward。　　At　a　critical

point　in　its　forward　travel　the　charge　is　fired　and　the

projectile　speeds　on　its　way。　　The　kick　or　recoil　serves　to

arrest　the　forward　movement　of　the　barrel　and　finally　drives　it

back　again　against　the　strong　spring　or　cushion　of　compressed　air

within　the　cylinder　to　its　normal　position；　when　it　is　ready　for

the　introduction　of　the　next　shell。



The　outstanding　feature　of　this　system　is　that　the　projectile　is

given　a　higher　initial　velocity　than　is　possible　with　the　barrel

held　rigid　at　the　moment　of　discharge；　because　the　shell　is

already　travelling　at　the　moment　of　firing。



The　fixed　anti…aircraft　guns　such　as　are　stationed　upon　eminences

and　buildings　are　of　the　quick　firing　type；　the　object　being　to

hurl　a　steady；　con　tinuous　stream　of　missiles　upon　the　swiftly

moving　aeroplane。　　Some　of　the　weapons　throw　a　one…pound　shell

and　are　closely　similar　to　the　pom…pom　which　proved　so　effective

during　the　South　African　war。　　Machine　guns　also　have　been

extensively　adopted　for　this　duty　by　all　the　combatants；　their

range　of　approximately　2；000　yards　and　rapidity　of　fire　being

distinctly　valuable　when　hostile　aircraft　descend　to　an　altitude

which　brings　them　within　the　range　of　the　weapon。



The　greatest　difficulty　in　connection　with　this　phase　of

artillery；　however；　is　not　so　much　the　evolution　of　a　serviceable

and　efficient　type　of　gun；　as　the　determination　of　the　type　of

projectile　which　is　likely　to　be　most　effective。　　While　shrapnel

is　employed　somewhat　extensively　it　has　not　proved　completely

satisfactory。　　It　is　difficult　to　set　the　timing　fuse　even　after

the　range　has　been　found　approximately；　which　in　itself　is　no

easy　matter　when　the　aircraft　is　moving　rapidly　and　irregularly；

but　reliance　is　placed　thereon　in　the　hope　that　the　machine　may

happen　to　be　within　the　cone　of　dispersion　when　the　shell　bursts；

and　that　one　or　more　of　the　pieces　of　projectile　and　bullets　may

chance　to　penetrate　either　the　body　of　the　airman　or　a　vital　part

of　the　mechanism。



It　is　this　uncertainty　which　has　led　to　a　preference　for　a　direct

missile　such　as　the　bullet　discharged　from　a　machine　gun。　　A

stream　of　missiles；　even　of　rifle　calibre；　maintained　at　the　rate

of　some　400　shots　per　minute　is　certain　to　be　more　effective；

provided　range　and　aim　are　correct；　than　shrapnel。　　But　the

ordinary　rifle…bullet；　unless　the　objective　is　within　very　close

range；　is　not　likely　to　cause　much　harm；　at　least　not　to　the

mechanism　of　the　aerial　vessel。



It　is　for　this　reason　that　greater　attention　is　being　devoted；

especially　by　the　French　artillerists；　to　the　Chevalier

anti…aircraft　gun；　a　weapon　perfected　by　a　Swiss　technician

resident　in　Great　Britain。　　It　projects　a　formidable　missile

which　in　fact　is　an　armour…piercing　bullet　1/2…　to　3/4…inch　in

diameter。　　It　is　designed　for　use　with　an　automatic　machinegun；

which　the　inventor　has　devised　more　or　less　upon　the　well…known

French　system。　　The　bullet　has　a　high　velocityabout　2；500　feet

per　secondand　a　maximum　range　of　6；000　to　8；000　feet　at　the

maximum　elevation。　　Should　such　a　missile　strike　the　motor　or

other　mechanism　of　the　vessel　it　would　wreak　widespread　havoc；

and　probably　cause　the　machine　to　come　to　earth。　　This　arm　has

been　designed　for　the　express　purpose　of　disabling　the　aeroplane；

and　not　for　the　subjugation　of　the　airman；　which　is　a　minor

consideration；　inasmuch　as　he　is　condemned　to　a　descent　when　his

craft　receives　a　mortal　wound。



Attempts　have　been　and　still　are　being　made　to　adapt　an　explosive

projectile　to　this　gun；　but　so　far　the　measure　of　success

achieved　has　not　proved　very　promising。　　There　are　immense

difficulties　connected　with　the　design　of　an　explosive　shell　of

this　class；　charged　with　a　high　explosive；　especially　in

connection　with　the　timing。　　So　far　as　dependence　upon　percussive

detonation　is　concerned　there　is　practically　no　difficulty。　

Should　such　a　missile　strike；　say；　the　motor　of　an　aeroplane；　or

even　the　hull　of　the　craft　itself；　the　latter　would　be

practically　destroyed。　　But　all　things　considered；　it　is

concluded　that　more　successful　results　are　likely　to　be　achieved

by　the　armour…piercing　bullet　striking　the　mechanism　than　by　an

explosive　projectile。



The　Krupp　company　fully　reahsed　the　difficulties　pertaining　to

the　projectile　problem　in　attacks　upon　aerial　craft。　　So　far　as

dirigibles　are　concerned　shrapnel　is　practically　useless；

inasmuch　as　even　should　the　bag　be　riddled　by　the　flying

fragments；　little　effective　damage　would　be　wroughtthe　craft

would　be　able　to　regain　its　haven。　　Accordingly　efforts　were

concentrated　upon　the　perfection　of　two　new　types　of　projectiles；

both　of　which　were　directed　more　particularly　against　the

dirigible。　　The　one　is　the　incendiary　shellobus　fumigenewhile

the　other　is　a　shell；　the　contents　of　which；　upon　coming　into

contact　with　the　gas　contained　within　the　gas…bag；　set　up　certain

chemical　reactions　which　precipitate　an　explosion　and　fire。



The　incendiary　shells　are　charged　with　a　certain　compound　which

is　ignited　by　means　of　a　fuse　during　its　flight。　　This　fuse

arrangement　coincides　very　closely　with　that　attached　to　ordinary

shrapnel；　inasmuch　as　the　timing　may　be　set　to　induce　ignition

at　different　periods；　such　as　either　at　the　moment　it　leaves　the

gun；　before；　or　when　it　strikes　the　envelope　of　the　dirigible。　

The　shell　is　fitted　with　a　〃tracer；〃　that　is　to　say；　upon

becoming　ignited　it　leaves　a　trail　of　smoke；　corresponding　with

the　trail　of　a　rocket；　so　that　its　passage　through　the　air　may　be

followed　with　facility。　　This　shell；　however；　was　designed　to

fulfil　a　dual。　　Not　only　will　it　fire　the　gaseous　contents　out　of

the　dirigible；　but　it　has　an　explosive　effect　upon　striking　an

incombustible　portion　of　the　aircraft；　such　as　the　machinery；

propellers　or　car；　when　it　will　cause　sufficient　damage　to　throw

the　craft　out　of　action。



The　elaborate　trials　which　were　carried　out　with　the　obus

fumigene　certainly　were　spectacular　so　as　they　went。　　Two　small

spherical　balloons；　10　feet　in　diameter；　and　attached　to　1；000

feet　of　cable；　were　sent　aloft。　　The　anti…aircraft　guns

themselves　were　placed　about　5；1OO　feet　distant。　　Owing　to　the

inclement　weather　the　balloons　were　unable　to　attain　a　height　of

more　than　200　feet　in　a　direct　vertical　line　above　the　ground。　

The　guns　were　trained　and　fired；　but　the　one　balloon　was　not　hit

until　the　second　round；　while　the　third　escaped　injury　until　the

fifth　round。　　When　struck　they　collap