The Portland daily press., 1862-12-11
REPORT OF CAPT. DAnLGREN.

The report from the Ordnance Department,
by Capt j. A. Dahlgren, abounds in interest
ing and important matter. He first urges that
suitable provision of ordnance material be
made for the probable future necessities of the
navy, and after suggesting various other steps
which should at once be taken to increase the
efficiency Of his department, turns to the dis
cussion of Z" iron-clads and Ordnance He
sketches the progress made by our own, as
well as by the French and English govern
ments in the construction and the improve
ment Of ordnance, discusses the difficulties in
constructing a ship impregnable to the hea-
West shot, and working gun of the largest
calber. In the experiments which have been
made in England, he acknowledges that the
advantages remain with the guns, and there,
he thinks, they will continue for the present.
He notes the different circumstances under
which the English, French and American IRON
clads have been constructed; showing that
while England and France were compelled to
make iron ships fit for deep water service, the
depth of water on our own coast is generally
adapted to vessels of moderate draft, and only
few OF our ports are at all accessible TO hea-
Wy iron-clads. He continues
The solution of the question Is, therefore,
In its immediate requirements, comparatively
easy and Inexpensive to us.
Ii .Es rRoyEcrrIEs.
+ A careful summary OF the experiments which
have been made abroad with proiectiles and
arufor plates leads Captain Dahlgren TO the
conclusion that the best method OF attack or
defenceis still an open question. He says:
1t was inferred that the Warrior was i'm
pregnable to the effort Of any ordnance that
could be then used safely against her.
The triumph of the defence was, however,
of short duration; for the rupture of the Arm
strong gun left the way open TO other compet-
itors, and long neglected piece that had lain
remote from view for several years was sug-
gested as deserving of an opportunity to try
its powers.
This was the Horsfall 13-inch, of wrought
iron, Its first blow, with shot Of $50 pounds,
was decisive. The plate was pierced and bad
ly injured, while the endurance of the gun was
untouched.
As if to complete the entire failure of the
defence, and to puzzle its advocates, Mr. Whit
worth undertook to drive a shell through a
stout iron-plated target, which he accomplish
ed.
So that the system of armor that had been
relied on was proved to be vulnerable by shells,
as well as by shot, which was unhoped for ad-
vantage on the side OF the attack.
Here it will probably rest for the while un-
til the defence shall be able to devise some
plan of greater efficacy.
1t would be unwise, however, to rush to the
conclusion that armor is needless, because the
most powerful ordnance should, under skill
ful guidance, be able to pierce it.
For even against such cannon ship may de-
lay the conclusive difficulty long enough to
make its own guns of avail; and when oppos-
ed to any but. these heaviest pieces, will still
be in effect ID kegnable.
The case of the Monitor and Merrimac is
cited as an illustration, and in this connection
Captain Dahlgren takes occasion to correct
the popular error concerning the want of
wrought-iron shot on the Monitor during the
engagement in Hampton Roads. He says:
The cast-iron shot fired by the Monitor
average about one hundred and sixty-nine
pounds, and, being used with fifteen pounds
of powder, had an initial velocity of about l.
100 feet.
After the action caused ten of the Moni-
tors wrought-iron shot to be weighed; they
were found to be 1S6 to 1877 pounds; therefore
with charge of Is pounds,) their initial We
locity would have been about 1,050 feet.
So that, by using the wrought-iron shot, the
projectile velocity would have been reduced ;
and though in no great degree, yet to that ex-
tent, whatever it was, would have increased
the very cause of insufficient power.
ARMAMENT OF IRoN-cLADs.
Capt. Dahlgren, then discusses the proper
mode of arming iron-cads, comparing the re-
spectiye advantages of rifled and smooth-bore
ordnance. He says:
II, In battering an iron-clad, penetration on
ly shall be the paramount consideration and
other effects merely Incidental, the rifle can
non must be selected.
But if the conclusion and shattering of the
plate and its backing be preferred, with such
penetration as might be consequent thereon,
then the heavy, swift, round projectile will
supply the blow best adapted to such work.
So long as the present mode of plating con-
tinues there can be little doubt that it will be
most effectively attacked by cracking and
bending the iron, starting the bolts, stripping
off the armor, and breaking away large por-
tions of the wooden structure within.
And to this mode of action feel more in
clined, after Witnessing its effects upon a num-
Der of targets plated with solid iron, or with
thin plates bolted into one, the direction of
the fire being perpendicular or oblique.
The iron-clad Galena suffered most in this
way. The fire was so well directed distance
o00 yards1, that most of the shot were
clustered about the middle of the side ex-
posed, as II the funnel had served for mark /;
several remained where they had lodged in
the iron plating, which, by measurement
proved TO be 65-pounders: others had only
dinted the armor and fallen Off; while few
had passed entirely through.
Seen from the outside the damage did not
appear considerable, but within it was evident
ly irreparable, for the entire structure of the
vessel was so shattered that there was little
power of resistance left.
The number of guns being very much re-
duced, Of necessity, in iron-clads, particularly