quadrant-shaped, 4o-round magazine projecting above the gun.
A detachable barrel is provided for the purpose of gaining a
more sustained fire, the system being to replace the barrel, when
it has been excessively heated, by another barrel, and continue
the fire while the first barrel is being cooled. It is claimed that
the barrel may be changed in from 12 to 20 seconds.




FIG. 13. Madsen Machine-Rifle (Russian).

The action of the mechanism is as follows :

When the gun is loaded, as shown in the figure, and the trigger
(76) is pulled, the hammer (77) under the force of the hammer
spring (78) strikes the link (79), which transmits the blow to the
firing pin and so to the cap. On firing, the barrel (80) and bolt
mechanism (81), locked as a unit, recoils, compressing the recoil
spring (82) until the link disconnects the bolt from the barrel lock
and allows the bolt to recoil sufficiently to cock the hammer, extract
and eject the fired cartridge case. The accelerator (83) assists in
driving the bolt to the rear as it engages on the accelerator lug
(84) during the recoil and transmits the momentum of the barrel and
mechanism to the bolt. The accelerator also drives the barrel home
during the forward stroke of the bolt.

A safety device (85) controls the trigger. A change lever (86)
enables the gun to be fired semi-automatically or automatically.

The Madsen light machine-rifle was designed some years before
the war, and for a time all Russian cavalry divisions had automatic
rifle sections armed with it. These were abolished before the out-
break of the World War and replaced by ordinary machine-gun sec-
tions as the lighter weapon was found to be too delicate for the field.
The Madsen was, however, again taken into use by the Russians dur-
ing the war, and under the name of the " Musket " it formed the
armament of the German " Musket battalions "which were created
in 1915. Some of these units with their guns were engaged in the
battle of the Somme 1916 but apparently the result, in the trying



conditions of the trench-warfare battle, was not very successful. 1
Tests have been made of the Madsen gun at different times in the
British and United States armies.

The Lewis Machine-Gun (fig. 14) is a magazine-fed, gas-
operated, and air-cooled machine-gun. The ground type, which
is used as a light machine-gun, weighs 265 lb., and is capable of
firing at the rate of about 600 shots per minute. The ammuni-
tion is fed from a drum-type magazine placed over the receiver,
and which holds 47 rounds for ground use, or 97 rounds for air-
craft use. It was invented by Col. I. N. Lewis of the U.S. army
shortly before the outbreak of the World War, and large numbers
were purchased by the British Government to supplement the
available Vickers (heavy) machine-guns. When the differentia-
tion of light and heavy types began, therefore, the British army
found itself already provided with a gun of what was judged to
be sufficient mobility, handiness and firepower, and the Lewis
gun became and remained the standard type of the light machine-
gun for the fighting unit of infantry. In the United States, on
the other hand, the military authorities determined to adopt the
still lighter Browning, and pending the supply of this, the
Chauchat as above mentioned. The Lewis gun, thus classed
among the heavy machine-guns, was, however, used in large
numbers for aircraft, and a few were employed for training pur-
poses as well, some 39,000 of U.S. rifle calibre being ordered and
produced. For aircraft, the gun was used by the French also,
while in 1918 the Germans, who had a high opinion of it, armed
some newly formed motor-cyclist units with captured weapons.

The principal feature is the cooling system, which consists of
an aluminum radiator having deep longitudinal fins surrounded
by a thin tubular casing which projects several inches beyond
the barrel and is reduced in diameter at the front end. These
parts with the barrel mouthpiece constitute the cooling system.
The mouthpiece deflects the powder gases against the interior
wall of the forward portion of the radiator casing in such a man-
ner as to draw a current of cool air through the open rear end of
the casing and along the thin fins from which it absorbs the heat.
The heat conductivity and low specific gravity of aluminum
combined with the construction described produce a light-weight
cooling mechanism^ The Lewis machine-gun is provided with a
bipod mount. The over-all length is approximately 51 inches.
The muzzle velocity and chamber pressure are approximately
the same with a given ammunition as that of the shoulder rifles
in which the ammunition is used.

Action: To operate the Lewis machine-gun, a loaded magazine
(10-11) is placed in position on top of the gun, and the charging han-
dle (8-4) is pulled to the rear until the sear nose (5-8) engages in the
sear notch in the rack (8-1 ). The gun is then ready to be fired. When
the trigger is pulled and held, the rack and piston (8-6) move forward
under the action of the mainspring (9-9), which in unwinding rotates
its gearwheel (9-7) and rack to carry the bolt (4-4) forward. As the
operating rod moves forward, the front top edge of the bolt strikes
the lower edge of the cartridge which is held in the magazine and
feed-way, and drives the cartridge forward into the chamber. The
locking lugs on the rear of the bolt move clear of the guide slots in the
receiver so that the bolt is free to rotate. The locking of the bolt is
then accomplished by the striker post coming in contact with the left
side of a cam slot in the bolt, which forces the bolt and its lugs to
turn one-eighth of a turn to the right. The extractor springs over
the rim of the cartridge case (or the cannelure if rimless) as the bolt
forces the cartridge in the chamber. The magazine is held by the
rebound pawl (6-8) during the forward move of the bolt and piston.
The feed operating arm (7-5) acted upon by the feed operating stud
(41) on the rear of the bolt, returns to its normal position during the
forward motion of the bolt ready to feed the next cartridge. When
the bolt has been completely locked, the striker is free to drive for-
ward and fire the cartridge. When the cartridge is fired the mech-
anism remains locked until immediately after the bullet has passed
the gas port in the barrel (31). Thereupon a portion of the powder
gases enters the gas regulator cup (38) and thence through a small
aperture 2 reaches the front of the piston (8-6). The force of the ex-
panding gases drives the piston to the rear and through the action of
the rack, rewinds the mainspring (99). During the backward
motion, the striker post, which is also carried on the rack, moves

1 In 1918 the Musketenbataillone were reformed as ordinary heavy
machine-gun units.

* The function of the gas regulator cup is to act as a well for any
solid matter carried in the gas and to prevent fouling of the gas
chamber. The size of the aperture can be adjusted as required.






284



RIFLES AND LIGHT MACHINE-GUNS



about one inch to the rear in a straight s]ot in the bolt, which, there-
fore, it does not affect while the bullet is traversing the final space
between the gas port and the muzzle; but after the striker post has
passed through the straightway of the bolt, it comes in contact with
the right side in the cam slot in the bolt and unlocks the bolt and
drives it to the rear. In unlocking the bolt is rotated and the locking
lugs come into line with the guide slots in the receiver. Lastly the
extractor (4-3) withdraws the empty cartridge case which is thrown
out by the ejector (2-3), a flat lever pivoted in the centre and actuated
by the feed operating stud (4-1) striking its rear end. This stud,

6-6 Stop 6 Rebound Potr/Spr.
6 5 feed Cover
2-3 Qector
S-S EjeccorCot
7-5 Feed Operating Arm



heavy machine-gun (M.G. 08), which is of the Maxim type,
without any change in the essentials of the system (for which
see MACHINE-GUN, 17.237). A serviceable light machine-gun
was made in large quantities and with the least possible delay,
and the German authorities determined to lighten the existing
material, for which manufacturing facilities were already avail-
able, rather than embark on the experiments and tool and gauge
making that would have been necessary if a new type had been



BacMgM 6 ~ 2 * Cartndge Guide



rrel Mouthpiece
4 Radiator Casing
Showing Siphoninq action
of escaping gases



3-aa,s,ulati>,Cvt
3-S 001 Ktftilotor Xy



8-4 Charging Handlt
-1 Fetd Operating Stud




FlG. 14. Lewis Machine-Gun.



which is carried by the bolt, also acts on the underside of the feed
operating arm (75) and moves the arm to the left. By means of this
arm and the feed pawl (7-2) that it carries, a cartridge from the
magazine is brought under the cartridge guide (6-24) and into the
feeding position in the feed-way in the top of the receiver and is
partially turned so as to bring the next cartridge into position, being
held in its new position by the stop pawl (6-7), and by the rebound
pawl (6-8). The rearward motion of the mechanism is arrested
when the bolt comes against the butt tang of the stock, and the bolt,
rack, etc., then again move forward under the action of the main-
spring, and the cycle of operation is repeated for each shot until the
magazine is empty or the trigger is released. When the last cartridge
is fired from the magazine, the bolt goes forward and locks with no
cartridge in the barrel.

The magazine is a round corrugated pan about 8 in. in diameter
carrying 25 upright separator pins. This pan is mounted with an
aluminum centre having annular grooves with a spiral step connect-
ing each groove, into which the front end of the cartridge fits. The
cartridge, being held from rotating by the separator pins, is fed along
these grooves up the steps into the gun when the pan is revolved
around the magazine centre. The pan is loaded by means of a
special loading tool. The feeding of the cartridges being positive
instead of depending on springs or gravity, the gun can be used when
turned at any angle or upsidg down.

The Lewis machine-gun operates automatically, single shots being
fired by quickly releasing the trigger after each shot.

In aircraft the Lewis gun is used as a " flexible gun," i.e., a gun
mounted (usually in the observer's pit) so as to fire in any direction
in elevation or azimuth. The main differences between the ground
type and the aircraft type gun are that the latter has no radiator or
radiator casing, has a spade or stirrup-shaped hand-grip in lieu of the
shoulder stock, and uses a 97-round magazine. A more efficient type
of recoil check is also provided. This consists of a muzzle attachment
which is arranged to deflect the powder gases so that they pass out
practically at right angles to the axis of the bore. In this way a
pressure against the muzzle piece tends to counteract recoil.

No cooling device is provided with the aircraft gun, inasmuch as
the fire is in short bursts only and the speed of the aeroplane and the
temperature at high elevations provide ample cooling. The aircraft
gun fires at a rate of about 750 shots per minute, this higher speed
being gained by increasing the gas pressure acting on the piston and
the strength of the mainspring which returns the mechanism.

German Light Machine-Gnns 08/15 an d 08/18. The German
light machine-gun 08/15 is simply a modification of the standard



sought for. In consequence, the differences between the 08 and
the 08/15 are very few. The diameter and contents of the water-
jacket are considerably smaller in the light gun than in the 08.
Instead of the tripod or sleigh mount, there is a shoulder stock
and bipod, and a trigger release and handgrips replace the twin
handles and firing gear. Ammunition is belt-fed as in the heavy
gun, but the belt (100 rounds) is wound on a reel inside a drum
attached to the right of the gun. The weight of the gun with
water-jacket filled and bipod, is 40^ lb., or in action with drum
and filled belt 515. The Dreyse water-cooled light machine-gun
was also used. Its weight was slightly less than that of the 08/15.

Guns of this weight, however, though they might be sufficiently
mobile for trench warfare battles, were evidently too heavy for
the more open warfare of 1917 and especially 1018, and a new
and lighter model called the 08/18 was brought out. In this
instead of the water-jacket there is a barrel casing with numerous
holes to facilitate air circulation round the barrel. This abolition
of positive cooling by water reduced the possibility of sustained
fire almost to that of an automatic rifle, but independence of
water supply greatly reduced freedom of manoeuvre and the
actual reduction in the weight of the gun was considerable
(32 lb. as against 40^ in the 08/15).

This gun had been introduced only for cavalry and cyclists
when the Armistice was signed. Had the war continued, it
would no doubt have replaced the water-cooled weapons entirely.

The Bergmann Light Machine-Gun (fig. 15) in the German
army, variously called L.M.G. and L.M.G. 15 n A, is a recoil-
operated air-cooled, belt-fed machine-gun, weighing 30 lb. with
bipod mount and sling, and fires about 600 shots a minute.

A barrel casing (91) is provided which carries the barrel and also
serves as a housing in which the barrel recoils. The cooling of the
barrel is assisted by rings which are formed on the barrel to increase
the radiating surface. A handle (92) is provided to facilitate carrying
the weapon short distances. The belt is fed through the feed-box
opening (93) as in the Maxim and other heavy machine-guns.

The principal features of the Bergmann machine-gun are a small
cylindrical service-rifle type of bolt and extractor, which may be



RIFLES AND LIGHT MACHINE-GUNS



285



operated by hand by means of a bolt handle (95) ; and an accelerator
which is in the form of a cam lever, which acts against the bolt and
barrel extension during the forward movement of the bolt, helping
to push the barrel extension and barrel forward as the bolt advances
under the action of the heavy recoil spring.

The gun is provided with a trigger and handgrip, a shoulder butt
and a bipod, which is attached to the trunnion (96).

The front sight (97) is very high, owing to the low position of the
barrel in the receiver and to the feed mechanism in cover. A tubular
sight with a hole about one-fourth of an inch in diameter is attached
by a bracket to the side of the gun for close-range shooting and for
tank work. It will be noted that several features of this gun were
adopted in the L.M.G. 08/18.

In the German army Bergmann guns formed the armament of
the so-called " Light Machine Gun Detachments," mounted units
created in 1916 for the Rumanian campaign. The use of this gun,
however, seems to have been discontinued towards the end of the
war, the weapons remaining serviceable being handed over to Turkey.




FIG. 15. Bergmann Light Machine-Gun.

Machine Carbine-Pistols. The idea of securing more accurate
shooting from a pistol by fitting it with a shoulder stock and
lengthening the barrel is an old one, and one well-known modern
example is the Mauser pistol (for description see 21.657-8).
But while in the pistol proper, from the nature of the arm and its
uses, all modern development has been in the direction of per-
fecting the semi-automatic action (see PISTOL), there arose in the
World War a need for some weapon lighter and handier than the
rifle yet capable of developing an intensely rapid fire at short
ranges. The outcome of this need was a class of firearm which
at present has few representatives and no recognized generic
title, but is very interesting. In the absence of an accepted
designation, these may be called machine carbine-pistols.




Onnir., \_*>frata

Barn! Caiing

\ Portion of II Bin Spring

FIG. 16. Bergmann Pistol-Gun.

In this field the precursors appear to have been the Italians.
The pistola miglialrice Fiat (Fiat mitrailleuse pistol) was largely
used by them as a substitute for the light machine-gun, no
doubt because extreme lightness both in the gun and its am-
munition was essential in an automatic arm for mountain warfare.
The " machine pistol " is fitted with a small shield which also
serves as a mounting, though the weapon can be used in the
hands, if necessary. It is double-barrelled, each barrel having
a separate box magazine of 25 rounds above the receiver. It is
gas-operated and air-cooled. The bolt and its dependent parts
are supported but not positively locked on firing. It weighs 14 Ib.
without shield, takes 9 mm. pistol ammunition, and is sighted
to 500 metres. An outstanding feature is the very high rate
of fire. Both magazines (50 rounds) are fired in two seconds, and
with highly trained loaders and a full supply of magazines it is
said that 1,000 rounds can be delivered in a minute. This ex-
treme rate, in spite of certain advantages, militates against
steadiness and accuracy, especially with so slight a mounting.
Nevertheless, according to the Germans the weapon proved
trustworthy and effective.

The Bergmann Pistol-Gun (fig. 16), on the other hand, was
intended not to replace the light machine-gun but to provide



artillerymen and machine-gunners with a handy personal weapon
capable of intense fire power in emergencies. It originated
in the pistol proper. The German service pistol 08 (Borchardt-
Luger) used by specialists, who were not armed with the rifle,
was fitted with a snail magazine (see PISTOL) allowing of 32 shots,
the wooden holster being attached to the handgrip as a shoulder
piece as in the Mauser pistol above alluded to, if accurate fire
was required. The success of this arrangement led to the intro-
duction of the Bergmann pistol-gun (officially, Machine-Pistol
18 1.), which in spite of its name is rather a carbine than a pistol,
as an infantry weapon pure and simple.

This arm shoots 9 mm. pistol ammunition at the rate-of about
540 shots per minute. The gun weighs 9 Ib. 6 oz. without the maga-
zine drum, which itself weighs I Ib. 8 oz. empty. It is recoil-operated
and air-cooled, and has an 8-in. barrel, protected by a casing per-
forated to allow circulation of air. The magazine (32 shots) is of the
snail type (see PISTOL). The breech mechanism is of the " blow-back "
class in which on firing the inertia of the bolt, the compressing of the
mainspring, and friction of the cartridge in the chamber momentarily
hold the action firm. The gun fires when the bolt reaches its forward
position as the striker projects through the face of the bolt, and is
cocked when the mainspring is compressed and the bolt drawn to the
rear. This has the advantage that the chamber is always left empty,
but the forward movement of the heavy bolt after pulling the trigger
is liable to disturb the aim. The gun is sighted to 200 metres only.

This gun was only brought into use just before the Armistice.




101 ... 103 99 100 102




FIG
FIG



18 I Thompson Sub-Machine-Gun.



The Thompson Sub-Machine-Gun (figs. 17 and 18) is an inter-
esting type of a very light portable automatic weapon which
shoots a -45-calibre pistol cartridge. The action is semi-auto-
matic or automatic at will. The rate of fire when used as an
automatic is 800 to 1,500 shots per minute. The weapon is about
23 in. in length, weighs 7-5 Ib., and uses a straight magazine
(fig. 18) holding 20 cartridges in staggered rows, or drum maga-
zines holding 50 or 100 cartridges (fig. 17).

The novel feature of this weapon is the angular wedge breech
closure which utilizes the force of adhesion developed by the heavy
breech pressure to lock the breech. The principle, developed by
Comm. Blish of the U.S. navy, has been briefly stated as follows:

" In any breech closure consisting of a breech plug in a suitable
housing and having two pressure-resisting surfaces, the forward
surface disposed normally to the axis of the bore, and the rear surface
inclined thereto and bearing upon a suitable surface of the housing,
the force of adhesion will under heavy pressure immovably fix the
breech block, but at a comparatively small pressure (whose value de-
pends upon the inclination of the two surfaces) the force of adhesion
ceases to act and the breech block is rendered free to move under the
influence of the forces then existing."

The principle permits the use of a very simple breech-locking
mechanism, the essential element being a bolt (98) having an angular
slot cut in the under side, into which the lock (99) is free to slide, and a
housing or receiver (loo) having a slot (101) into which a projecting
lug on the lock engages when the bolt is in its firing position. Under
high pressure the lock firmly adheres to the receiver shoulder and



286



RIGHI RISLEY



prevents the bolt from being blown to the rear. When the pressure
is reduced, the adhesion ceases, and the lock, actuated by the remain-
ing pressure, automatically slides upward and clear of its retaining
shoulder while the bolt moves rearward against the recoil spring
(102) and cocks the firing pin.

When the weapon is cocked the entire bolt group is held by the
sear (104) in a retracted position, as shown in fig. 17. On the trigger
being pulled the bolt, driven forward by the recoil spring, pushes a
cartridge into the chamber. During the forward motion of the bolt
the hammer (103) strikes a shoulder of the receiver and rotates on
the hammer pin, its top end strikes the firing pin and the cartridge is
fired. Firing is discontinued by releasing the trigger; the sear (104)
then engages the bolt in its retracted position, leaving the chamber
empty. By means of the disconnector (105) the weapon 'can be made
semi-automatic at will. When the magazine is emptied, the trip
(106) allows the sear to engage the bolt in a rear position ready to
feed and fire again when the trigger is pulled. Sights graduated to
600 yd. are provided.

The sub- machine-gun is intended as an auxiliary weapon for trench
use and for close fighting generally. It has been adopted also by the
police of several American cities for use as a riot weapon, both for
shot and ball cartridges. (H. O'L.)

RIGHI, AUGUSTO (1850-1920), Italian physicist, was born
at Bologna Aug. 27 1850. Details of his experimental work in
magnetism and the problems of electricity and light are given in
1 7-389, 391 and 346, 6.859, 9-206, 21.936. He was specially
noted for his discovery of the electrical conductivity of bismuth
and other metals, and for his pioneer work in wireless telegraphy.
G. Marconi was his pupil. He died at Bologna, June 8 1920.

RILEY, JAMES WHITCOMB (1853-1916), American poet
(see 23.343), died at Indianapolis, Ind., July 22 1916. In 1915,
by proclamation of the governor of Indiana, his birthday, Oct. 7,
was observed throughout the state, in honour of " Indiana's
most beloved citizen." In 1913 he issued in six volumes a
biographical edition of his works.

See Clara E. Laughlin, Reminiscences of J. W. Riley (1916).

RIO DE JANEIRO (see 23.353). According to the census of
1920, the pop. of the independent municipal commune, or
federal district, which contains the city and is detached from
the province of the same name, was 1,157,873 inhabitants.
As the census of 1906 showed 811,443 inhabitants, the pop. has
increased 43% in 14 years, an annual increment of 3-05 per cent.
In 1920 there were 1,265 factories, large and small, with 46,953
operatives, representing a capital of nearly 270,000,000 paper
milreis, and an annual production valued at about 500,000,000
milreis. In 1920 the number of buildings in the municipality was
about 113,000, as against 84,375 m 1906- The federal district
is governed by a prefect appointed by the president of the
republic, and elects three senators and ten deputies to the national
congress. The legislative power of the municipality is vested in
a council consisting of 24 inlendentes elected for three years.

The consolidated debt of the municipality in 1920 was com-
puted at 227,089,200 paper milreis, of which 129,225,450 milreis
was an external debt, and 97,863,750 milreis internal. The
revenue had grown from 29,070,883 paper milreis in 1910 to
51,182,357 paper milreis in 1919.

Education. Primary instruction is provided by the municipality,
which in 1920 maintained 320 day-schools and 68 night-schools,
with a matriculation of 74,111 pupils in the former and 8,662 in the
latter. There are in addition 236 elementary private schools, with
19,825 pupils; over 80 receive a subvention from the Government
on condition that they adopt the official curriculurrrand admit a cer-