The evening telegraph. [volume] (Philadelphia [Pa.]) 1864-1918, 1870-05-30

which is equal with the weight of the
water it displaces: is not affected by the
earths attraction; and that consequently,
| if put in motion under the surface of O uui-
escent fluid of unlimited extent, such body
| will continue to move in a straight line until
the motive energy which propels it becomes
less than the resisting force of the surround
| ing medium.
In virtue of the first part of this general
proposition, heavy body may be projected
in such manner that the termination of its
trajectory shall make any desirable angle,
less than 45 deg, with the horizontal line,
Independently of the length of the chord of
the trajectory. In other words, the body
may be projected at variable distances over
water, and yet strike its surface at any desirable
angle. This important result is effected simply
! by varying the relative proportion between
elevation and strength of charge The second
part of the stated general proposition is of
! equal Importance. 1t points to the fact
that the trajectory may be extended in a
straight line under water, to any desirable
distance, irrespective of the speed of the pro-
! jectile. Accordingly, a shell may be projected
| from one vessel towards another within mode
rate ranges, in such manner that it shall dip
into the water at a considerable distance from,
or close to, the vessel assailed, independently
of the distance between the two vessels
Also that the shell may be projected at such
an angle that the prolongation of its trajec-
tory in straight line, after contact with the
water, shall strike the hull of the vessel
assailed, at any desirable depth below the
surface. .
That a certain relation between charge
and elevation enables us to project
| spherical shot, with considerable accuracy,
in such manner as to strike the water at
any desirable distance from an opponents
vessel, at angles with Is degrees, will be ad-
mltted. Hence, if the trajectory be such
that its extension in straight line from
the point of contact with the water leads
to the hull of the vessel assailed, the latter
will be hit-on condition, however, that the
shot is not diverted on entering the water
and provided its vis gtoa be sufficient to
overcome the resistance encountered during
its passage through the water. These indis-
pensable conditions, which apparently cannot
be complied with, point to the difficulty of
hitting q vessel below the water line. And
if we suppose that the projectile is not sphe-
rical, another serious difficulty presents ITSELF
An elongated body will not bend to the
curvature of the trajectory, but
same inclination as the gun from
which it has been projected; hence it will fall
nearly fiat on the surface of the water at the
end of its course.
Agreeable to our general proposition a
regular body, weighing as much as the water
1t displaces, is independent of the earths
attraction; but there is another force which,
notwithstanding the absence of any gravi-
tating tendency, will cause body of regular
form moving under water to deviate from
straight line and rise to the surface. A cone
moving in the direction of its apex and in the
line OF its axis horizontally, or on an incline,
will, owing to the inertia and the nearly in
compressible nature of water more readily
displace the column which rests upon and
deprssses its upper half, than the column
from below with its lifting tendency. Con-
sequently, the course of the conical body
will be diverted from the straight line up
wards, describing curve nearly elliptical,
and quite sudden, if the speed be great. A
cylinder with semispherical ends will, from
| the same cause, ascend to the surface if
moved in the line of its axis; while cylinder
with flat ends will take downward course,
| gradually increasing its inclination until at
last the axis assumes a vertical position. OBJ
viously, the lower part of the forward flat end
encounters a greater resistance than the
upper part; hence the lower half of the trans
verse section of the cylinder suffers an excess
of retardation, which occasions the down.
ward course described.
The question whether the apparently
insuperable difficulties thus pointed out
may be overcome by mechanical expedients
has, as already stated, occupied my attention
for long time; and numerous experiments
have been made to test the efficacy of devices
resorted to on theoretical considerations.
But it is not my purpose to enter on a de-
seription of these devices at present, on
grounds that will appear hereafter. Accord
ingly, will assume that the axis of the elon-
gated prejectile during its fight through the
air is parallel with the trajectory, and that on
entering the water the projectile will not be
diverted, but continue to move under the
surface, with the same inclination it had
on coming in contact with the dense me-
dunn.
II may be we'll to state that the elongated
shell is charged with dynamite and provided
with percussion lock and trigger, to be
actuated as described in my former commu-
nication relative to the self-acting torpedo
1t is well known that numerous plans have
been suggested during the last few years for
firing under water, for the purpose Of pierre
ing the hull of iron-clad vessels below the
point protected by the armor. In several in
stances these plans have been carried into
practice with the invariable result that the re-
sistance of the water has been found SO great,
even at very short distances, that an ordi-
nary wooden hull has proved to be impene-
trable. The plan now under consideration
bears no resemblance to these projects. In
the first place, the attack is made at dis
tance; and, secondly, the force of the missile
on reaching its destination need only be suf-
ficient to aetuate the trigger which causes the
ignition of the explosive charge.
Apart from the theoretical considerations
relating to the course of the elongated shell
under water, the practical question of motive
power to propel the same presents itself at
the first step in the investigation. 1t is hardly
necessary to state that the force relied upon
is the 0ts 0toa possessed by the shell on COM