The Sun.
London, England, 1861-09-27 00:00:00

TO THE EDITOR OF THE TIMES.

Sir,—We here have another instance of high
authority, acting on the best motives, and yet mis-
led towards adopting serious error by trusting to
conclusions drawn from those specious but unprac-
tical experiments with which the iron-cased ques-
tion has been so rife, and to which it owes so much
of its perplexity. A number of small detached
pnleastslacifdiroonn,
tvhaerysainngds,fwrolinth theirl inchheadainrecthliineekd-
to various angles with the horizon, and then fired
at with guns of the Armstrong description, varying
in " power" from the minimum service fieldpiece
down to a diminutive nondescript, purposely built
exactly to suit the scale of Lilliputian targets—
such were these, in reality, Shoebury playthings, a
series of amusements with which furnished the
" results" announced in the above quotation. In
size, substance, weight, connection, position, sup-
port, and every other known requisite for resistance
there is traceable throughout the means employed
on these trials no single practical condition, either
in plates or guns, having more than the remotest
approach to the circumstances of an ironcased ship
under fire, and proportionately incapable must they
therefore be of affording any sound conclusion as
to those best modes of constructing sueh vessels
which by such means we are fondly supposed to be
seeking for. Nevertheless, we see that " results"
thus derived can be openly taken to determine that
question of "form" which is second only, if second
in importance at all, to that which is requisite for
giving to these costly fabrics the highest speed.
These experiments, moreover, were expressly made
for the purpose they were thus applied to so soon as
completed—viz., that of invalidating those previous
experiments made at Portsmouth in 1860 by private
enterprise, and which proved—what it is difficult to
believe should ever have been doubted—that the
same natural laws by which the billiard ball is re-
pelled from the cushion and the cricket ball from
the bat would equally apply to the sides of iron-
cased ships having an appropriate form for the pur-
pose—i.e., that the "sloping sides" of the quotation
would evade a large portion of the force of heavy-
shot striking them ; this principle of shot-deflec-
tion, as totally distinct from shot-resistance, being
therefore capable of enabling lighter armour, with
less injury to itself, to effect equal protection against
equal artillery, as compared with heavier vertical
masses when opposing a direct resistance.
The able reports of your Portsmouth correspon-
dent, and your own leaders on the subject at the
time, ;make it superfluous to repeat the details of the
four days' trial, in which Mr. Jones fully established
the valuable principle he advocates ; but of his tar-
get itself it may not be so generally known that in
the -a inch thickness of skin, and the 1 inch thick-
ness of frames, of the iron ship proper which it re-
presents, the structure of the "Warrior was followed,
with the exception that the frames are 18 inches
deep and 18 inches apart, whereas the Warrioi's are
only 10 inches deep and 22 inches apart. The back-
ing outside the skin was then 14 inches of ordinary
pine—it is now 12 inches—the -Warrior's being 18
inches of teak, and the particular armour plate out-
side the backing, which was then specially fired at,
was, like the Warrior's, 41 inches thick. The target,
of 13 feet by 9, although in size only fragmentary,
yet being strongly secured upon the deck of au old
gun-brig, became part of a floating mass of proba-
bly 100 tons, and was fired at from a range of 200
yards by the solid shot 68-pounder gun with its full
charge of 161 b., the heaviest smooth-bored artillery
in use; so that every practical condition requisite
to constitute a true experiment was here present,
so far as the size admitted, the severity of proof
being equally unexceptionable. Out of the 33 shots,
in all, sustained by the four covering plates, 17 fell
on the particular one specified, within a space of
51 by 21 feet, four of them striking one over the
other before any part of the plate was removed,
and even then without being actually penetrated,
or even the soft woodwork beneath it seriously hurt.
It was against these remarkable results that the
remarkable Shoebury trials I have described were
opposed, and the Extract taken for my text, its re-
ference to the Armstrong gun in particular, was the
special provocation, so to speak, which led Mr.
Jones to urge that repetition of his last year's proof
which took place on the 21st ult., and which again
led to that further trial of the 18th inst., so truly
noted, as wall as ably reported, by your correspon-
dent. On these two occasions the same target, at
the same range of 200 yards, opposed its 43 and 5
inch plates respectively to the fire of the same Arm-
strong 100-pounder—this time the heaviest piece of
rifled ordnance yet pretending to be practical—the
thinner ones sloped at the same angle of 50 deg. as
last year, but the thicker ones vertical, by which
means Mr. Jones has placed before us the proof of
his principle comparatively as well as positively,
and has shown us that thinner plates angled will,
with less injury to themselves, afford not only equal,
but even superior protection against equal impacts,
than will plates of equal merit nearly one-fourth
thicker when placed vertical. Besides furnishing
us also, in several important particulars, with a
practical measure of the difference of force which
plates in the two cases• are required to withstand,
and of the actual effects of this difference. Thus—
In firing at the thinner plates angled the shot
invariably broke to pieces, and the pieces as inva-
riably flew an estimated distance of 1,000 or 1,200
yards. The force required to project 1101bs of ir-
regular fragments the above distance is, therefore,
the true measure of that which the plate by deflec-
tion had been enabled to evade.

In firing at the thicker plates vertical, your cor-
respondent in his last report unintentionally calls
them bin. instead of 5. No portion of the force
of impact was evaded, all had to be resisted, and
with these differences of effect :

1. The shot broke up as before, but all fragments
fell around the target, except those smaller ones
which fell back into and around the gunboat.
2. All indents were of the full 7 inch diameter of
the shot; on the thinner plates they were nearly
semicircular only-6 inches from horn to Ilona.

3. The depth of indents meaned 1-1-- inch through-
out their 7 inch diameter ; the minimum being 1Z
inch ; on the thinner plates it varied at the deepest
point only of the semicircles, from -a to 4 inch, the
general mean being also 4. The greatest depth of
indent made by the only shot which struck the
thicker plates when angled was of an inch.
4. The thicker plates were much buckled by the
shot; the thinner ones very little.
5. The backs of the thicker plates were more
seriously injured even than their fronts, being
bulged out to a considerable diameter around each
impact, with the centre of the bulge much fractured.
This was, so far as could be examined at the time,
behind the plates:where buckled off their backing.
The thinner plate detached by the third shot of the
18th inst. showed on its back only one slight trace of
the ten shot received on the 21st ult., this trace being
also of one of those six which on that occasion fell
within a space of 12 inches by 21.
6. Every shot resisted by the thicker plates would
have necessitated the eventual shifting of the plate.
No shot deflected by the thinner plates would have
occasioned any such necessity, the damage being
limited to a mere external scar. This does not refer
of course to the injury done by the six shots on the
very limited space aforesaid, when sufficient plate
was removed to have allowed a seventh shot to enter,
if striking the exact spot, with but little resistance.
These facts will be a sufficient reply to the letter
of your correspondent " C. W. G.," of the 27th ult.,
who, in his otherwise perfectly correct views, evi-
dently shares the error still entertained in very
high places, that Mr. Jones's experiments were
meant to show the greater resistance opposed by
angled plates over vertical ones, whereas his true
object was the reverse one, of 'proving how much less
resistance was required to be opposed by angled
plates in order to do the same, or even more work,
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