The sun., 1919-01-19


chant vessels were often outranged The
latest U-boats even dared to attack an
Allied cruiser
II, on the other hand for tactical rea-
tons the torpedo Is selected as the
weapon TO use, the submarine subnlerges
when still out of sight and proceeds 80
the firing position. This is abreast or
slightly ahead of the victim and about
1000 yards off. German L boats have
endeavored to come as close as 800 yards
before launching the torpedo. If the
ship Is part OF a convoy the U-boat
Will either attack the convoy flank or
seek to rise in the center. In case of
such attack no particular ship Is selected
curing the early approach.
While submerged the submarine COM
mander takes from six to eight perisco-
pic observations in order to obtain the
coarse. range and speed OF the mer-
chairman or convoy. These data enable
him to calculate where the firing posi-
ton, will nc against n single vessel or
where to attack a convoy. The duration
of the periscopic sights is from thirty
seconds 20 five seconds. In ordinary
periscopes. ali but about a third of the
light is lost by reflection or absorption
II there be dust or moisture on the
lenses the loss of light is even greater.
This defect in the Instruments is largely
ever. by the natural dilation OF the pupil
| of the eye to admit more light.
Normally the vessels image is en-
lsrged from IL to Is times, but
ma gnification three TO six times is not
unusual To ascertain range from peri
| scopic observations there are only two
| available methods. Telemeter scales or
cross hairs graduated vertically and
horizontally In hundredths are generally
4 l. Ia
image micrometer. Two images Of the
same object are made to cut each other
| In the lens. and are shifted with refer
| ence to one another until the irasts. fun
nels or other high parts OF the vessel un-
der observation are on a level with the
water line or deck line Of tho second
image. The angle OF shift determines
the distance.
The range OF vessel at the various
times that she is observed will give an
idea of her course unless she is zig
Tagging. AT close range the apparent
perspective Of the ship. her bow position
and alignment OF mssts are TIE course
indices used. Speed calculation H. also
approximate only. II should be cmpha-
I sized that course, range and speed eSu-
mated from perlscopic observation is ny
| no means an exact science. The human
eye may be deceived when its view is SO
| limited and brief.
! With respect to protective Camouiage
there are two purposes which may be
/ subserved-nameiy. reduction III the
| visibility of vessels in order that they
| may traverse the danger zone unob-
served or Hss we'll observed by subma-
! rlnes, ana a cnalee VI '''' aPp. OF H'.''
OF the vessel so that II oeSt' yea u, .,t..
culation or her course sPetu an" l"ne
may he tnereoE renuertn ma ma, u. ",
While C-boatS are equinPeu WIN S'utu
detection apparatus or 'uhs'ue'apl
hearing radius, the low Nis'oiIlNS pu'
pose Is well worth securing because t'te
hearing radius Of sound .detec'ors Goes
| not i'll every case extend a" Tar as N'S'on
at sea. Sound, furthermore docs hoS
give the precise dirc,o"h' distance i'Iu
course OF vessel which are ne'eSS"
for an approach 20 torpeH" l1rl"- ios'-
ton.
Hard TO sec, nara 10 NM
.n,r, ,h.. &c hard 10 sec is hard
,,ii, ,Tsrcrorc real adj.
,.a,,aco for s1in 10 he as nearly in
! ,iitS &c ross;blc This ia cspec,allv
,r,,, 60, ,bc MONT Of view o. naval
s.r.,tery Tho area that U-boat can
I ,,,,.o, Ird .till no sure OF meeting ships
~ iou. ,.isihtIitv Is much smaller than II
IAN natrol and be sure of meeting ves-
so,s more readily seen.
We're low visibility secured, 10 cover
~ ~ SEA aroa with n submarine
cordon wound -snt,ire more suha mrires
re q werc nossiblo so 10 dazzle" the
ave as "a render il incapabIe or partly
incanable Of observing the image 81 the
tsrsrt This dazzle" effect would he
de- r.,h,a As howeycr in taking the
ro innortart noriscoric observations
tho vessels outline. masts and tunnels
are chiefly noticed. the programme OF
llov ,.isibility and Of disturbing range
sneed and course estimate - preferred
II - a serious matter to decide the
nature Of the deception to he sought
Decention as TO range can affect guufirc
lees than torpeIo fire. as with tho
former "spot firing" is resorted 70. In
nearly always i, close r"nsc, ,s decor ,,I