Year: 1861




rifle shot, and of large and small calibers,
that seem to indorse the American system,
and limit the uses of rifled cannon. That long
range and great accuracy depend on spin
ming the projectile upon its own axis, is Ger.
tainly proved. Hence the value of the rifle
she'll in the field, and on shipboard, and ia
Notifications, when directed against bodies
of men; but the long range and precision of
shot, and the whirling contents and frag.
ments of shells, never 30 accurately planted
are of limited destructiveness if directed
against objects that they can neither smash
nor tear into pieces-the iron sheathed sides
of ships.


Wooden walls do not require smashing or
splintering; hot shot and shells, filled with
molten iron, will take care of them. Nor
will thin iron sheeting, upon wooden walls,
nor the plates of ordinary iron ships keep
out any thing but the lighter shells What
we have to provide for in our coast defense
is mailed ships-vessels only destructible by
a tremendous and extraordinary force, that
old-fashioned and usual forms of cannon shot
are not capable of exerting.


In the first place, il is not necessary to
make long range an element of defense, even
If sufficient living force of proectile could be
secured with it, for an assaulting fleet eau
not do much damage at arms length but
when it attempts to run the gauntlet and
OANNA bhC bOIy buo uRubluk Dc dL Close
quarters. At close quarters, then, there are
Two methods of destroying all such mailed
ships as have yet been put ahoat. The first
Is by punching them with projectiles Of small
diameter; the second is by smashing them
with masses of immense size and weight. AS
to the first method, it singuIarly appears,
from recent experiments in England, that
the round shot is, on the whole the most
effective. At the late meeting of the British
Aclngiatinn Fai 4oI kl,ot A.
initial velocity of the rihed shot fred in test
ing the iron targets at Shoeburyness was
eleven hundred feet per second. That of the
eighty pound Armstrong and Whitworth
shot is found TO be one thousand aud eighty
and thirteen hundred feet, respectively. The
initial velocity of a sixty-eight pound spheri-
cal shot, however, averages above two thou.
sand feet per second.


AS the living forces of the two are as the
squares of their velocities, the spherical shot
would therefore have nearly three and half
times the penetrating power of the rifed
shot OF equal weight. But the cross Sec
tional area of the rihed bolt being seventeen
and half to nineteen inches, against fifty
five inches for the round shot, the effect of
the latter would be reduced to probably
about twice that of the former. This is con-
hrmed by the practice. At the late meeting
of Mechanical Engineers, four and q half





rddled by sixty. eight pound round shot,
while we constantly hear that heavier rifle
bolts indent similar plates, but do not often
pass through them. The rife bolt certainly
retains its velocity longer by reason of its
smaller area presented to the atmosphere;
but we are now speaking of short range, as
to which that consideration is not of great
importance. The London Engineer, discuss
ing this subject, attributes a part of this loss
pf fhn It'd fA a. al. ~.
leakages of the breech. loading guns iu which
they are used. But most Of it is probably
due to the immense friction of the projectile
while being rotated in the gun. To give a
mass weighing eighty pounds a spinning
motion of four hundred revolutions per
second, certainly deducts largely from a
force which would have only to propel a
round shot without rotating it.


There is another important consideration
here. Supposing the rifle shot and the round
to leave the gun with equal resistance from
friction, the strain upon the gun, for given
weight and velocity of shot, would be Very
much less in case of the spherical proiectile.
The area that the powder acts upon is about
one-half in case of the Armstrong eighty
pound rifle bolt, what it is in case OF round
shot weighing eighty pounds, the diameter5
being about six and eight and one-halfinc
respectively. Hence to exert given force

square inch of the bore of the gun must be
twice as much for the Armstrong as for the
round shot. But the number of square
inches, and hence, the total rupturing force
for a given pressure, is greater in Case of the
large bore required by the round shot, SC
that, in this case, the actual bursting strain
would not be one half but one third less fol
the round shot than for the rife bolt. But
the resistance by friction, which we suppose
10 VanAo al htrtf far ,t
the rifle shell, so that it practically require;
a gun of at least twice the strength required
by the round shot to propel it at an equ3
velocity.


Surprising the living force OF the two shots
| to be equal, which is giving the rifle bolt au
| advantage that it does not possess in prac
| tice, as already stated, the shape of the rount
shot still gives it an advantage. If the rifle
bolt, in virtue of its smaller cross sectiona
area would just 90 through the armor, the
| round shot, OF twice the area, would not &C
through, indeed, but it would do far more
damage by smashing and cracking the plates
and making much more dangerous fracture
| A clean hole can be plugged, but a ragged
crumbling fracture can hardly be stopped
at all.


This leads us to the second method o
destroying the mail of ships-by smashing
with globes of extraordinary size and weight
The initial velocity of the ffteen.inch she
of the Rodman gun is as great as that of th
Armstrong and WbitwOrth eightY-poun
bolts. Their living force therefore varies a
their weight, that of the fifteenth inch sho
being over five times that of the eighty
FOUNDER, and hence it would start frsctur
in plate five times as strong as one that tn
rife bolt would break, because, although it
Cross sectional area is above six times that G
the bolt, it would strike, theoretically, on
mere point, and practically on about tn
same space that the bolt would cover.


Ifeighty- pound shot, therefore, can pene
trate such plates as the English frigates ar
covered with, the fifteen-inch shot are sur
TO smash great chasms in them every tim
they hit. But these globes are shells witha
having a fve-inch cavity within; so when the
once get on the inside of the srmor they ar
as good as so many broadsides in woode
ship. This cavity is found not TO impai
their strength, as compared with solid she
Of the same diameter. ftl


The success of the guns that carry thes
globes is complete. Captain ROdman
method of casting them-coOling and hard
ening the bore first, and preventing th
permanent strains due to the unequal shrink
age of ordinary castings-and the use Of b
large grained, slow burning powder TO owe
come the inertia of the mass, at low pres
ure first, and then get up the velocity, 8
as to reduce initial strain, have rendered
probable-almost certain-that twenty-five
shots shots Weighing oVer half a tIl-ca
be employed. III the Government will d.
velop. the resources we have, in due time "
need stand in no fear Of any foreig