VISUAL SIGNALING EQUIPMENT.
THE WAND.
The wand is a stick of light wood about 18 inches long and one-half
inch in diameter. It is held loosely between the thumb and forefinger
and waved rapidly to the right or left to indicate the elements of the
alphabet. It is used for practice purposes and the signals made by it
are only intended to be read at very short distances.
THE FLAG KIT.
Two kinds of flag kits, the 2-foot kit and the 4-foot kit, are issued
by the Signal Corps.
_The 2-foot kit._--This kit consists of one white and one red signal
flag, two three-jointed staffs, and a suitable carrying case to contain
the outfit. The white flag is made of white muslin 2 feet square, with
an 8-inch turkey-red muslin center. The red flag is of similar size
and material, the only difference being an alternation of colors in
the body and center. The means of attachment to the staff consists
of a loop at the center, and two ends of white tape at each edge,
of the back of the flag body. The staff is made of hickory in three
joints, each 23 inches long, and is assembled by telescoping into brass
ferrules. Brass eyes are provided on the first and second joints to
receive the tape ends at the edge of the flag. The carrying case, of
convenient size and shape to contain the two flags and staffs complete,
is made of 8-ounce standard khaki bound with leather and fitted with a
shoulder strap.
The 2-foot kit is essentially a practice kit, although under favorable
conditions of weather and terrain it may be used to advantage as a
short distance service signaling outfit. Two of these kits are issued
to each troop, battery, and company for the purpose of disseminating
general instruction in military signaling throughout the army.
_The 4-foot kit._--This kit is of essentially the same description as
the 2-foot kit except as regards size. The flags are 3 feet 9 inches
square with 12-inch centers and the staffs are considerably heavier,
the joints being each 36 inches long. The 4-foot kit is the standard
field flag kit and the range at which signals can be exchanged with it
depends on a variety of factors, such as the condition of the weather,
the location of stations, the proficiency of signalmen, etc. The speed
for continuous signaling is seldom greater than five to six words per
minute.
_Care of flag material._--Signal flags should be examined at the close
of drill or practice and repairs made to any rents or loose ties
discovered. Flags, when soiled, should be thoroughly washed and dried
in the sun. Signals made by clean flags are much more easily read
than those made by dirty ones. Staffs should be handled with care,
especially when jointing or unjointing. Care should be taken not to
bruise the ends of the brass ferrules. If a ferrule becomes loose on a
staff it should be tightened without delay.
_Powers and limitations of flag signaling._--The advantages which may
be claimed for this method of signaling are portability of apparatus,
adaptability to varied weather conditions, and great rapidity of
station establishment. The disadvantages are the lack of celerity
of the signals, their impenetrability to dust or smoke, and the
comparatively short ranges at which they can be read.
THE HELIOGRAPH.
The heliograph is an instrument designed for the purpose of
transmitting signals by means of the sun's rays.
_Historical._--Experiments with the heliograph with a view to its
adoption as a part of the visual signaling equipment of the United
States Army were commenced as early as 1878. The reported successful
use of the instrument by the British in India about this time led to
the importation of two heliographs of the Mance pattern. A series
of experiments with these machines conducted for the purpose of
eliminating certain objectionable features finally resulted in the
evolution of the present type of service heliograph.
The early English heliograph was not provided with a shutter, the flash
being directed on the distant station by means of a movable mirror
controlled by a key. The great objection to this type of instrument
was the impossibility of maintaining accurate adjustment during the
transmission of signals due to the fact that the manipulation of the
mirror tended to throw the flash constantly out of alignment. To
overcome this, the American heliograph has been provided with a screen
designed to operate as a shutter and control the flash reflected from
an immobile mirror.
_Description._--The service heliograph equipment of the Signal Corps
consists of:
A sole-leather pouch with shoulder strap containing--
1 sun mirror. }
1 station mirror. } Inclosed in a wooden box.
1 screen, 1 sighting rod, 1 screw-driver.
A small pouch, sliding by 2 loops upon the strap of the larger
pouch, containing 1 mirror bar.
A skeleton leather case containing 2 tripods.
[Illustration: FIG. 1.--Heliograph assembled.]
The mirrors are each 4½-inch squares of plate glass supported by
sheet brass and cardboard backings, and mounted in brass retaining
frames. At the center of each mirror there is an unsilvered spot three
thirty-seconds of an inch in diameter and holes corresponding to these
spots are drilled in the backing. The sun mirror differs from the
station mirror only in that it has a paper disk pasted upon its face
covering the unsilvered spot. The mirror frames are carried by brass
supports provided at the bases with conical projections accurately
turned to fit the sockets of the mirror bar and grooved at the ends
to receive the clamping spring. Each support is fitted with a tangent
screw and worm wheel attachment functioned to control the motion of the
mirror frame about its horizontal axis.
[Illustration: FIG. 2.--Mirror and mirror bar case.]
The mirror bar is a bronze casting provided at the center with a clamp
threaded to fit the screw of the tripod. By releasing the clamp the bar
may be moved independently of the screw and adjusted to any desired
position. Conical sockets for the reception of the mirror supports are
provided at the ends of the mirror bar. These sockets work freely in
the bar and, being actuated by a tangent screw and worm wheel, serve
to regulate the motion of the mirror frame about its vertical axis.
Clamp springs, for engaging and securing the ends of the mirror frame
supports, are attached at each end of the bar.
The screen is a brass frame 6½ inches square, in which six segments
or leaves are mounted in such a way as to form a shutter. The leaves
are designed to turn through arcs of 90° on horizontal axes, unanimity
of movement being secured by connections made with a common crank bar.
The crank bar is operated by a key and retractile spring which serve to
reveal and cut off the flash. A set screw and check nut at the lower
edge of the screen frame limits the motion of the crank bar and the
opening of the leaves. A threaded base support furnishes the means of
attaching the screen frame to the tripod.
The sighting rod is a brass rod 6½ inches long, carrying at the
upper end a front sight and a movable disk. About the rod is fitted
a movable bronze collar, coned and grooved to take the socket and
clamping spring of the mirror bar. A milled edged bronze washer serves
to clamp the collar to the rod at any desired point.
[Illustration: FIG. 3.--Heliograph tripods.]
The tripods are similar in all respects, the screw of either threading
into the mirror bar or screen frame. Each tripod is provided with a
hook at the base of the head, allowing the suspension of a weight when
great stability is required.
_Assembling._--There are two ways of assembling the heliograph and
the position of the sun is the guide in determining which of the two
should, in any given case, be employed. When the sun is in front of
the operator (that is, in front of a plane through his position at
right angles to the line joining the stations) the sun mirror only is
required; with the sun in rear of this plane both mirrors should be
used. With one mirror the rays of the sun are reflected directly from
the sun mirror to the distant station; with two mirrors, the rays are
reflected from the sun mirror to the station mirror, and thence to the
distant station.
_With one mirror_: Firmly set one of the tripods upon the ground;
attach the mirror bar to the tripod; insert and clamp in the sockets
the sun mirror and sighting rod, the latter having the disk turned
down. At a distance of about 6 inches, sight through the center of
the unsilvered spot in the mirror and turn the mirror bar, raising or
lowering the sighting rod until the center of the mirror, the extreme
point of the sighting rod, and the distant station are accurately
in line. Firmly clamp the mirror bar to the tripod, taking care not
to disturb the alignment, and turn up the disk of the sighting rod.
The mirror is then moved by means of the tangent screws until the
"shadow spot" falls upon the paper disk in the sighting rod, after
which the flash will be visible at the distant station. The "shadow
spot" is readily found by holding a sheet of paper or the hand about 6
inches in front of the mirror, and should be constantly kept in view
until located upon the disk. The screen is attached to a tripod and
established close to, and in front of, the sighting disk, in such a way
as to intercept the flash.
_With two mirrors_: Firmly set one of the tripods on the ground; clamp
the mirror bar diagonally across the line of vision to the distant
station; clamp the sun mirror facing the sun to one end of the mirror
bar and the station mirror facing the distant station. Stooping down,
the head near and in rear of the station mirror, turn the sun mirror
by means of its tangent screws until the whole of the station mirror
is seen reflected in the sun mirror and the unsilvered spot and the
reflection of the paper disk accurately cover each other. Still looking
into the sun mirror, adjust the station mirror by means of the tangent
screws until the reflection of the distant station is brought exactly
in line with the top of the reflection of the disk and the top of the
unsilvered spot of the sun mirror; after this the station mirror must
not be touched. Now step behind the sun mirror and adjust it by means
of the tangent screws so that the "shadow spot" falls upon the center
of the paper disk on the station mirror. The flash will then be visible
at the distant station. The screen and its tripod are established as
described in the single mirror assembling.
_Alternate method with two mirrors_: Clamp the mirror bar diagonally
across the line of vision to the distant station, with the sun mirror
and the station mirror approximately facing the sun and distant
station, respectively.
Look through small hole in sun mirror and turn the station mirror on
its vertical and horizontal axes until the paper disk on the station
mirror accurately covers the distant station.
Standing behind sun mirror, turn it on its horizontal and vertical axes
by means of the tangent screw attachments until the shadow spot falls
upon the paper disk on station mirror.
_Adjustment._--Perfect adjustment is maintained only by keeping the
"shadow spot" uninterruptedly in the center of the paper disk, and
as this "spot" continually changes its position with the apparent
movement of the sun, one signalman should be in constant attendance
on the tangent screws of the sun mirror. Movement imparted by these
screws to the mirror does not disturb the alignment, as its center (the
unsilvered spot) is at the intersection of the axes of revolution.
Extra care bestowed upon preliminary adjustment is repaid by increased
brilliancy of flash. With the alignment absolutely assured and the
"shadow spot" at the center of the disk, the axis of the cone of
reflected rays is coincident with the line of sight and the distant
station receives the greatest intensity of light. Remember the distant
observer is unquestionably the better judge as to the character of the
flash received; and if therefore, adjustment is called for when the
"shadow spot" is at the center of the disk, the alignment is probably
at fault and should be looked after at once. In setting up the tripods
always see that the legs have a sufficient spread to give a secure base
and on yielding soil press firmly into the ground. Keep the head of the
tripod as nearly level as possible and in high wind ballast by hanging
a substantial weight to the hook. See that the screen completely
obscures the flash; also that the flash passes entire when the screen
is opened. This feature of the adjustment is partially regulated by
the set screw attached to the screen frame. The retractile spring
should sharply return all the leaves of the screen to their normal
positions when the key is released. Failure to respond promptly is
obviated by strengthening or replacing the spring.
_Operation._--It is of the utmost importance that uniformity in
mechanical movement of the screen be cultivated, as lack of rhythm in
the signals of the sender entails "breaks" and delay on the part of the
receiver. Dark backgrounds should, when practicable, be selected for
heliograph stations, as the signals can be most easily distinguished
against them.
To find a distant station, its position being unknown, reverse the
catch holding the station mirror and with the hand turn the mirror
very slowly at the horizon over the full azimuth distance in which
the distant station may possibly lie. This should be repeated not
less than twice, after which, within a reasonable time, there being
no response, the mirror will be directed upon a point nearer the home
station and the same process repeated. With care and intelligence it
is quite probable that, a station being within range and watching for
signals from a distant station with which it may be desired to exchange
messages, this method will rarely fail to find the sought-for station.
The exact direction of either station searching for the other being
unknown, that station which first perceives that it is being called
will adjust its flash upon the distant station to enable it when this
light is observed to make proper adjustments. If the position of each
station is known to the other, the station first ready for signaling
will direct a steady flash upon the distant station to enable the
latter to see not only that the first station is ready for work, but to
enable the distant station to adjust its flash upon the first station.
Smoked or colored glasses are issued for the purpose of relieving the
strain on the eyes produced by reading heliograph signals.
_Care of apparatus._--Minor parts of the instrument should be
dismounted only to effect repairs, for which spare parts are furnished
on requisition. Steel parts should be kept oiled and free from rust.
Tangent screws and bearings should be frequently inspected for dust or
grit. Mirrors should invariably be wiped clean before using. In case of
accident to the sun mirror, the station mirror can be made available
for substitution therefor by removing the paper disk. If the tripod
legs become loose at the head joints, tighten the assembling screws
with the screw-driver.
_Powers and limitations of the heliograph._--Portability, great range,
comparative rapidity of operation, and the invisibility of the signals
except to observers located approximately on a right line joining the
stations between which communication is had, are some of the advantages
derived from using the heliograph in visual signaling.
The principal disadvantage results from the entire dependence of the
instrument upon the presence of sunlight. The normal working range
of the heliograph is about 30 miles, though instances of its having
attained ranges many times greater than this are of record. The
heliograph can be depended upon to transmit from five to twelve words
per minute.
THE ACETYLENE LANTERN.
The signal lantern is an instrument designed for the purpose of
transmitting signals by means of intermittent flashes of artificial
light. It is the standard night visual signaling equipment furnished by
the Signal Corps and depends for its illumination upon the combustion
of acetylene gas.
_Acetylene._--Acetylene is a pure hydrocarbon gas, producible in
various ways, the commoner of which are: (_a_) By dropping calcium
carbide into water; (_b_) by dropping water upon calcium carbide.
This gas gives, when burning, high penetrative power, and was first
described by Mr. Edmund Davy, professor of chemistry to the Royal
Dublin Society, in 1836.
_Calcium carbide._--In the manufacture of calcium carbide for
commercial purposes the best quality of coke and quicklime are
used. These two substances are powdered thoroughly, mixed in proper
proportions, and then placed in an electrical furnace. Under the action
of the intense heat (5,500° F.) these two refractory substances unite
and form calcium carbide. Calcium carbide is of a grayish-white color,
crystal in appearance, and is nonexplosive and noncombustible, being,
except for its affinity for water, an absolutely inert substance. A
pound of commercial carbide will produce approximately 5 cubic feet
of gas. When water is brought in contact with calcium carbide, the
generation of acetylene is rapid; owing to its strong affinity for
water it will become air slacked and slowly lose its strength if
exposed to the action of the moisture in the atmosphere; consequently,
when stored or being transported it should be kept in air-tight cans.
When calcium carbide is brought in contact with water, the following
occurs:
As is known, the principal components of water are oxygen and hydrogen,
and calcium carbide is calcium and carbon. When brought in contact,
the oxygen in the water decomposes the calcium in the carbide, and in
this decomposition the hydrogen in the water is liberated and unites
with the carbon of the carbide, forming a hydrocarbon gas which is
acetylene. It is a pure white light of intense brilliancy and high
candlepower. The spectrum analysis of acetylene shows that it is almost
identical with sunlight, and in consequence delicate shades of color
appear according to their true value as under the light of the sun,
consequently it penetrates fog to a greater distance than other lights.
Acetylene is like other gases--explosive when mixed with air in proper
proportions, confined, and ignited--and the same precautions should
therefore be taken in its use as would be in the handling of coal or
water gas, gasoline vapor, etc. As acetylene is very rich in carbon,
it will not burn in its pure state without smoking. To avoid this,
burners have been constructed so that the gas is mixed with the proper
proportion of air at the burner tip, to insure perfect combustion. The
burners for acetylene are different from those for other gases. In
order to get a flat flame, the gas is brought through two perfectly
round holes at an angle which causes the two flames to impinge upon
each other and thus form a flat flame.
_Method of gas generation._--The method employed for producing
acetylene in the signal lantern is by bringing water into contact
with calcium carbide. The disadvantage of this method is that when
the water is not in excess and does not entirely surround and touch
each piece of carbide the heat of generation will so change the
chemical properties of the gas that combustion at the burners is not
satisfactory.
This change is technically known as "polymerization," or the breaking
up of acetylene into other hydrocarbons, such as vapors of benzine,
benzole, etc. These form a tarry substance which is apt to condense
at the burner tip and clog the openings. Also they deposit carbon on
the burners, as they require more air for perfect combustion than does
pure acetylene. Another disadvantage of this system is that after the
carbide and water are in contact, generation of gas will continue
until all the water is absorbed. Where, however, portability of the
generating apparatus is desired and resort to this method is necessary,
the objections are not important, if the apparatus is well constructed
and care is taken in its use.
_Description._--This equipment consists of a signal lantern with
cartridge generator attached. The lantern is equipped with a special
aplanatic lens mirror, 5 inches in diameter and about 3 inches focus.
The lantern is packed complete in a wooden case with shoulder straps
and the following extra parts are included, each part having its own
receptacle in the case: 2 burners; 1 cover glass; 3 cartridges of
calcium carbide of 5 ounces each; 1 pair of gas pliers; 1 tube white
lead; 1 extra filter bag; 1 screw-driver.
[Illustration: FIG. 4.--The signal lantern.]
The lantern is made of brass, all parts of which are riveted. The
burner is of the double tip form, consuming three-quarters of a cubic
foot per hour. The lantern is fitted with a hood to provide proper
ventilation and at the same time to prevent the flickering of the
light by the wind. The front door of the lantern is hinged and fastens
with a spring clasp; it is so arranged that it can be entirely removed
if necessary. The cover glass is made in three sections and is not
affected by the expansion and contraction of the metal due to changes
in temperature. The glass is fastened by the aid of a spring wire, so
that it can be readily removed if it is necessary to replace a broken
section. In the base of the lantern is a key and the adjustment for
regulating the height of the flame. The key is so arranged that when
not depressed but little gas is admitted through the by-pass to the
burner and the flame is low. By depressing the key as much gas as can
be entirely consumed is admitted to the burner, which gives a bright
flash. At the back of the lantern there is an adjustable handle, so
that the equipment can be used as a hand lantern if desired. This
form of lantern can be used with the regular heliograph tripod,
the generator being either attached to the back of the lantern or
suspended, as shown in figure 4. When practicable it is better to
attach the generator to the lantern, as shown in figure 5. The
candlepower of this lantern is about 1,900.
[Illustration: FIG. 5.]
_The generator_ used is known as "the cartridge generator," and while
constructed on the water-feed principle, the disadvantages incident to
this method are eliminated as far as possible. It is constructed of
brass and has a removable top. Attached to the inside of the top is
a flexible frame with a spring latch, the spring latch being hinged.
(Fig. 8.) At the top of the frame is a tube or cylinder, the bottom of
which is conical in shape and covered by a rubber plug. At the bottom
of the frame is a hollow tube, which is the water inlet. The cartridge
proper consists of a tin cylinder, having an opening at either end. A
small cylinder of wire mesh extends from and connects these openings.
The carbide lays around this mesh on the inside of the cartridge. The
rubber plug before mentioned fits into the upper opening, and the water
tube into the lower opening. (See figs. 7, 8, and 9.) Inside the tube,
at the top of the frame, is a filter, the function of which is to
remove the dust and moisture from the gas. The outlet from this chamber
is by a brass bent tube having a stopcock attached thereto.
Figure 6 gives a sectional view of the generator with the cartridge
in place. _D F G H_ represent the valve frame and _I_ the cartridge
attached. The reservoir _A_ is filled with water, and when the frame is
immersed, with the valve _R_ closed, the air contained in the cartridge
and tubing can not escape, the water seal preventing, while the
confined air prevents the water from rising in the tube _N_. When the
valve at _R_ is opened and the air is allowed to escape, part of the
water from the reservoir rises into the tube _N_ and then out through
the small hole _O_ to the carbide. Gas is immediately generated, the
pressure of which prevents further ingress of the water from the tube
_N_, and the generation of gas is suspended.
As the gas passes out through the valve at _R_ the pressure decreases,
permitting the water to again rise in the tube and flow through _O_.
Gas is again generated, which at once exerts its pressure and cuts off
the supply of water. This is the automatic action by which water is
brought in contact with the calcium carbide. Thus it will be observed
that the use or escape of the gas regulates the generation by the
simple device of the rise and fall of a water column. There is a cap
_M_ screwed over the tube _N_. This is used to deflect the course
of the water downward, so that the carbide in the lower part of the
cartridge is first attacked. There is a needle inside of cap _M_,
which can be used for cleaning the hole _O_. When the gas is generated
it passes through the filter _D_ on its way to the burner through
_R_. This filter consists of a tube loosely packed with ordinary
nonabsorbent cotton, which should never cover the escape pipe leading
to the valve _R_. In passing through this cotton filter moisture and
dust are removed from the gas. In the latest model a felt filter is
used instead of cotton.
[Illustration: FIG. 6.--Signal lantern generator.]
The escape pipe _F_ provides a means for the escape of gas generated
and not used or generated more rapidly than consumed. Should an excess
be generated, it passes down through the tube _F_, and, finding its
way through some small holes in the bottom of this tube, escapes
through the water seal and the opening at _C_. It will be noted that
if escaping gas at _C_ should become accidentally lighted, the flame
can not strike back into the filter and cartridge because of the
water seal. The principal things to observe in the operation of this
generator are the following:
(1) To see that the rubber plugs _fit tightly_ into the openings of the
cartridge.
(2) That the tube _N_, the cap _M_, and water hole _O_ are not stopped
up.
(3) That the cotton in the filter is changed frequently.
(4) That the _stopcock R is closed before inserting the frame in the
water_. If this latter instruction is not complied with, it can be
readily seen that the water will have free access to the carbide and
excessive generation will occur.
When the charge is exhausted, the entire cartridge is taken out
and thrown away. This eliminates the handling of carbide and the
disagreeable task of cleaning out the residuum after the gas has been
extracted.
Connection is made from the stopcock _R_ to the hose connection on
the lantern proper, and this is the passageway of the gas from the
generator to the burner. As soon as the stopcock is opened the water
rises through the tube and flows to the carbide. The advantage of the
cartridge being submerged in the water is to reduce and absorb as much
of the heat liberated by generation as is possible. These lanterns have
been tested up to a distance of 10 miles with the naked eye, and under
favorable conditions can be used over a range somewhat in excess of
this. With a 30-power telescope the flash can be read at a distance of
30 miles.
_Operation and care._--Take the lamp and generator from the case by
aid of the handle attached to the lamp; screw the complete outfit on
a heliograph tripod, or stand the outfit on a level object; remove the
cover of generator, to which is attached the flexible frame (fig. 9);
detach spring from the catch of the flexible frame; tear off flaps from
the ends of carbide cartridge (or pry off small caps) and attach the
cartridge as shown in figure 9. Then attach to frame as shown in figure
10, being careful to see that both rubber plugs fit tightly into the
holes in the cartridge; fasten the latch of the spring over the metal
catch; close stopcock _R_ on service pipe; completely fill the outer
can of generator with water, the object being to have the generator
level full of water when the lamp is in service, then immerse the frame
and cartridge, pressing the top of the generator down tight. In doing
this the water will overflow the sides of the generator tank. Now
connect by rubber tubing the stopcock with the gas inlet at the bottom
of the lamps, as shown in figure 4; then (1) open front door of the
lamp, (2) light a match, (3) open stopcock, and (4) light the gas at
the burner. In doing this hold the key open. In the new model the key
and hose connection are on the side of bottom of lamp.
When the gas is ignited, the lamp is ready for signaling, and the key
can be operated as is the Morse telegraph instrument, but of course not
so rapidly.
In the event of the flame being too high when the key is closed,
adjustment can be made by loosening the set screw (fig. 4, indicated
by an arrow) and adjusting the light by turning screw _b_. When at the
proper height, tighten the set screw which locks the by-pass in its
proper position. In the new model this is accomplished by aid of the
regulator by-pass valve at the left-hand side of bottom of lamp. The
lamp is properly adjusted when shipped and should not be changed unless
absolutely necessary. Connect the rubber tube to the burner before
opening the stopcock on the generator.
To recharge the generator, take the frame and the old cartridge from
the case, throw away the old case and replace with a fresh one,
proceeding as before. See that fresh water is put in the generator each
time a new cartridge is used.
[Illustration: FIG. 7.]
In the tube through which the service pipe passes is a felt filter for
taking the dust out of the gas. If the filter clogs, unscrew the cap to
which the service pipe is attached, clean the felt, or replace it with
a new filter, binding it in place by a stout thread or string.
If the burner of the lamp does not produce a perfectly flat flame
it has become clogged and should be cleaned with the burner cleaner
furnished, or a new burner should be substituted, care being taken to
put a little white lead on the nipple, if practicable, so as to insure
a tight joint.
In repacking the outfit in the case, throw out the water and wipe the
can and generator parts dry. You can not be too careful to keep the
apparatus clean. This is especially true of the small pipe that passes
up through the bottom of the cartridge, with a cap over it. The cap
should always be screwed in place, as its object is to prevent the
water from squirting to the top of the cartridge.
[Illustration: FIG. 8.]
[Illustration: FIG. 9.]
The back of the lamp can be removed by turning the small thumbscrew on
the top and drawing out the pin which holds the shell into which is
fitted the lens. It is not necessary to take the back out except to
replace a lens, as the latter can be cleaned by opening the front door.
If it is desirable to use the lamp as a hand lantern the flame can be
turned on full by turning the button in a vertical position; this locks
the key open. In the new model depress the key and lock it with the
latch above the key.
One charge of calcium carbide will supply gas to burn about one hour
with the light turned on full, or for approximately three hours'
signaling.
[Illustration: FIG. 10.]
If signaling is to be suspended for some hours, empty the water out of
the generator and close valve _R_.
The glass front can be replaced by taking out the wire spring. The
glass cuts should be mounted in a horizontal position and, to prevent
breaking, should be protected from rain when the lamp is hot. If a
glass should be broken and an extra one is not available to replace it,
signaling can be continued by turning the flame on full and using the
heliograph shutter, a cap or piece of board in front of the lantern to
obscure and reveal the flash. Without the protection of the cover the
flame is easily blown out when turned low, but will not be extinguished
even in a strong wind if the gas is turned full on.
Old model lamps are serially numbered from 1 to 200, inclusive; the new
model lamps are serially numbered from 201 upward.
_Powers and limitations of the acetylene signal lantern._--As
conditions are usually more uniform at night than in the daytime, the
signal lantern is probably the most reliable of all visual signaling
outfits. The advantages of this form of apparatus are its portability,
speed of operation, and comparatively great range. The principal
disadvantages are due to the interference caused by rain, fog, and
moonlight. The speed attainable with the lantern is about the same as
that attainable with the heliograph.
ROCKETS AND SHELLS.
Two distinct kinds of rockets and shells are issued, one of which is
adapted to day and the other to night signaling. Shells and rockets of
the amber smoke type with parachutes are used in the daytime, while
shells (red and white) and sequence rockets are used at night.
[Illustration: FIG. 11.--Signaling rocket and accessories.]
[Illustration: FIG. 12.--Signaling shells.]
_Description._--The shells are all single shot and are fired from a
5-inch portable mortar, attaining a height of about 550 feet. The
report of explosion can be heard at varying distances up to 5 miles,
depending on weather conditions. The parachute attached to the smoke
shell suspends a small light wooden tube which, after ignition,
emits smoke for from four to six seconds. The red and white shells,
on bursting, discharge a shower of red and white fire which can be
observed for some time, in fact almost until the sparks fall to the
ground.
Rockets for both day and night signaling are equipped with parachutes.
The smoke rocket is of similar construction to the smoke shell. The
sequence rocket is so arranged at the base that threaded sections of
combustible material burning either red or white can be attached to it.
Rockets ascend about 700 feet.
Each rocket and shell is supplied in a cylindrical sealed tin can,
which also contains a port fire, wind matches, and for the rockets
a stick in four sections. On the outside of the can is a label
designating the kind of shell or rocket therein contained. These cans
are easily opened by pulling a ring and require no special opening tool.
_Operation._--In firing shells the mortar should be surrounded by earth
or sand, preferably placed in sacks. The fuse for all shells is very
rapid and should be ignited by attaching the port fire to a long stick.
All of the old type Signal Corps mortars, originally designed to
withstand a pressure of 1,000 pounds per square inch, and made of
ordinary iron pipe, are considered unsafe and should be immediately
destroyed. The new mortars, recently made for the Signal Corps by
the Ordnance Department, are of cold-drawn steel having a tensile
strength of 6,000 pounds per square inch, which is more than the
maximum pressure for firing any of the Signal Corps bombs. They are
stamped "Signal Corps, U. S. A., Model 1907," or "Rocket Gun, Watertown
Arsenal, 1907."
The sequence rocket is prepared for use by attaching red or white
sections to the base in such a combination as to form letters of the
alphabet which it is desired to use. Letters containing the same color
in sequence are very difficult to read and should be avoided whenever
possible. If necessary to use them, blank sections furnished for the
purpose should be inserted between the units. The base of the rocket
will secure six units.
When rockets are to be fired the sticks must be firmly attached, the
rocket placed upright in a trough, upon a frame, or against a post.
If the fuse is beneath the paper covering the "choke" orifice, the
paper should be torn off and the rocket ignited by a port fire. In
the rockets now used the fuse extends through the covering and can
be lighted direct. If the night be damp this fuse should be exposed
only a moment before the rocket is fired. If several rockets are to
be fired in succession it is well to prepare them all at the same
time, and to have them all stood upright, but each separated from the
other at a distance of at least 6 feet, else one may ignite the other
accidentally. In firing for chronosemic signals, one rocket ought to be
kept ready upon the frame and in reserve, to be fired in place of one
that fails.
If a rocket misses fire it is to be taken from the stand and laid on
the ground. Its place is at once supplied by a similar rocket, fired
in its stead. The failing rocket is laid on the ground pointed away
from the station in order that if it has only hung fire and should
afterwards ignite it may not disarrange the signal shown or injure any
one of the party. If the wind blows freshly the rocket to be fired
should be inclined slightly against the wind.
Signal rockets and shells are furnished in sealed cans and should not
be removed therefrom until ready for use. Strict economy should be
observed in the use of these articles and on no account should they be
used for purposes of display.
_Employment._--Rockets and shells are especially valuable in making
preconcerted or emergency signals. On account of the great amount
of ammunition required it is impracticable to spell out messages
with them. These articles should be supplied to outposts, detached
stations, etc., to be used for signaling the approach of the enemy or
the happening of unexpected events, the necessity for promptly knowing
which is important.
THE SEMAPHORE.
If signal stations are to be permanently occupied, and it is
impracticable to electrically connect them, communication may be
facilitated by erecting semaphores.
Semaphores, while primarily used for day signaling, can be
advantageously used at night by attaching lights to the arms.
The navy semaphore consists of four arms pivoted at the ends, three
on one side of the upright, or pole, and one on the other side. These
arms have three positions: Horizontal; upward at an angle of 45° to the
horizontal; downward at an angle of 45° to the horizontal.
Full instructions for the operation of the semaphore, and also for the
use of balls, cones, drums, pennants, and whefts as distant signals,
are given in the International Code of Signals.
THE SEARCHLIGHT.
The electric searchlight, when available, can often be successfully
employed for night signaling, frequently affording efficient means of
communication between ships and shore stations, when wireless working
is impracticable. This system of visual signaling is practicable and
especially valuable where the stations are, on account of the terrain,
not intervisible.
_Methods of employment._--In signaling with the searchlight the usual
method of handling the shaft or beam is identical with that employed
with the flag. In the first position the beam is shown vertically,
while motions to the right, the left, and directly serve to indicate
the elements of the alphabet. Chronosemic signals may also be used in
searchlight signaling, the shaft of light being directed intermittently
on some conspicuous object, such as a cloud, balloon, or high mountain
top.
COSTON SIGNALS.
These signals are pyrotechnic compositions which burn with great
intensity of light and color. The colors red, white, and green are
found best suited for signaling. The signals are prepared in the form
of cartridges and are burned from a holder. The colors burned may
indicate the elements of any alphabet, or such other special signals as
may be desired.
VERY'S NIGHT SIGNALS.
The Very system employs projected red, white, and green stars, which
are shot from pistols held in the hand.
_Description._--The Very pistol is a breechloading, single-shot pistol
with an 8-inch steel barrel chambered to receive a 12-gauge commercial
shotgun shell. Brass shells are used and are packed in boxes colored
to indicate the character of stars employed in loading. The color of
the star fired may indicate an element of any alphabet or any special
signal which may be desired. The stars rise to a height of about 200
feet and remain visible for some time.
THE ARDOIS SYSTEM.
The Ardois system is a special system of night signaling designed
to utilize combinations of red and white signal lights in forming
the elements of any desired alphabet. Four signal lamps capable of
displaying either red or white lights are attached at convenient
intervals to a vertical cable or staff rigged between the top of a mast
and the deck, if on shipboard, or the ground, if on shore. Illumination
is furnished by electrical means and any desired combination of lights
is automatically obtainable by operating a keyboard.
This system is valuable on vessels or at permanent shore stations, but
the great expense of installation precludes its general use. Wiring
diagrams and technical instructions relative to this apparatus are in
all cases furnished when the same is issued.
[Illustration: FIG. 13.--The Very pistol.]
SOUND SIGNALS.
When recourse to any method of sight signals can not be had on account
of weather conditions or lack of suitable apparatus, sound signals
may often be advantageously used. The commoner means of furnishing
sound signals are the horn and the whistle, though many other kinds of
apparatus are practicable. The necessary elements of any system can be
indicated by one short, two shorts, and a long blast. The advantage
of this system of signaling is that it can be used in any kind of
weather, both in daytime and at night. On the other hand, sound signals
are generally more difficult to read than sight signals and tend to
disclose the presence of stations to hostile forces.
IMPROVISED SIGNALING METHODS.
The object of this chapter has been to describe only the standard
visual signaling equipment issued and generally utilized. Besides the
methods detailed, there are many others which may be successfully
employed by the ingenious signalman when the necessity for them arise.
The use of any means of transmitting signals whatever is justifiable
when for any reason the regular apparatus is not available. Special
conventional scout signals are given in paragraph 82, Field Service
Regulations.
In the field many instances will occur where it will be necessary
to transmit information rapidly without recourse to the authorized
equipment. This will be especially true of outposts, detached stations,
patrols, and other small bodies of troops, and it will devolve upon
individual commanders to improvise methods of signaling best suited to
the occasion and the conveniences at hand.