The Liverpool Standard, and General Advertiser.
Liverpool, Merseyside, England, 1854-10-03 00:00:00

DEVIATION 01

F COMPASSES ON B
IRON SHIPS.

)ARD

YESTRADAY afternoon, the Rev. Dr. Scoresby attended
at the Underwriters'-rooms, for the purpose of offering
some further elucidatson of his views upon this important
subject. Amongst the gentlemen present we observed
T. B. Horsfall, Esq., M.P., W. Brown, Esq., M.P., T.
Thornely, Esq., M.P., Captain Henderson, Captain Lott
(of the sia), Captain Schomberg (Government Emigra-
tion Agent), Lieutenant Lord, Mr. Maury (brother of
Lieutenant Maury), and Messrs. H. C. Chapman, Wm.
Stuart, T. B. Barclay, R. Shiel, J. Hubback, W. Fisher,
C. Palmer, C. S. Parker, S. Bright, W. T. Naylor, Chas.
Turner (Chairman of the Dock Committee), J. W. Towson,
Wm. Potter (Chairman of the Liverpool Underwriters'
Association), Rawson (Deputy-chairman of the Ship-
masters' Association), George Grant, John Torr, J. G. C.
Arbuthnot, Hugh Hornby, W. Jones, R. Rankin, S. R.
Graves, John Lockett, F. Hamilton, John Laird (iron
shipbuilder), James Tyrer, C. Cotesworth,
Mr. WM. BROWN, M.P., having, on the proposition of
Mr. POTTER, seconded by Mr. RAWSON, been called to the
chair, briefly stated the object of the meeting.
The Rev. Dr. SCORESBY then entered upon a lengthy
address, which was substantially the same as the one de-
livered before the British Association a few days ago,
and which was reported in the Standard of Tuesday
last. He appeared, he said, in consequence of an invi-
tation from the Underwriters' Association, in order to
give some further explanation of his views on the mag-
netic condition of iron ships, as producing, or likely to
produce, compass-disturbances, and to suggest available
remedies. He accepted the invitation with much satis-
faction, both on account of the importance of the subject,
and because of certain misapprehensions which had arisen
with respect to some of the statements he made at the
recent meeting of the British Association. He regretted
that any anxiety should have arisen in the public mind
by moving into this question ; but he was persuaded that
gentlemen in Liverpol interested, as they deeply were,
in the management and success of iron ships, would
not allow the matter to rest. Colonel Sabine, in a
discourse before the British Association, showed that
even the magnetism of this very globe was not free from
disturbance; then how much more likely was the mag-
netism of iron ships to be disturbed by magnetic causes?
In the outset he would clear the subject of all erroneous
impressions which had been attached to it ; and,
in the first place, he wished it to be most distinctly under-
stood, that any abservations he had made or should snake,
were net designed to draw invidious comparisons between
the relative efficiency or inefficiency of iron and wooden
ships, but were merely intended to draw attention to
that important element belonging to iron ships which, if
not ascertained and understood, might produce embar-
rassment and danger, but which, he believed, with due
care in the appliance of science, might ultimately be, for
all practical purposes, available for good. (Hear, hear.)
Nor did he wish to be misunderstood as implying that
deviation did not occur in wooden ships as well as in iron
ships. On the contrary, sass long ago as the year 1815, he
directed his attention to the deviations of ships built of
timber; and in 1819 he published, in the Transactions of
the Royal Society, his views on the causes of deviation of
compasses in the ships of that day. It would also be in
the recollection of gentlemenjwhom he saw in that room,
that, on the 23rd of January, 1822, he gave a lecture at
the Royal Institution, Liverpool, on the same subject, on
which occasion he showed the danger arising, not so
much from the fact of that deviation, but from ignorance
and inattention to that important fact. (Hear, hear.)
He showed in that lecture that, in the winter of 1810-11,
three or four ships of the royal navy were wrecked, and
that the disasters should be ascribed, not so much to the
deviation of the compasses—although doubtless that was
the first cause—as to the fact that the officers of the royal
navy had at that time very little knowledge of the fact of
the deviation of compasses. On the occasion of wreck
of the ships of the navy, to which he had alluded, a man,
named White, of little or no education, but possessing
remarkable intelligence, had observed that there was a
tendency to draw his ship towards the port when descending
the Channel. The commander of the man-of-war, on that
occasion, signalled to steer S.S.W. ; but the merchantman,
by the acuteness of his intelligence, directed that his ship
should be steered W.S.W., observing that, if the men-of-
war kept in the same course they were pursuing, they
would sleep in their shoes the same morning. His pro-
phecy proved correct, for, while he safely entered the
Downs, the ships of the Royal Navy were stranded that
night, and upwards of 2,000 persons lost themselves, in
conseqtence of the deviation of the ships' compasses.
(Hear, hear.) It was absurd, therefore, to assume that, if
the comparatively small quantity of magnetic material in
wooden ships would produce disturbance, that ships built
entirely of iron would not be liable to the same effect.
Consequently, the great question affecting the navigation
of our ships amounted to this—namely, that it was not
that they were not capable of compass guidance, but that
the compasses, being liable to certain changes and altera-
tions, derived from the changes in the magnetic condi-
tion of ships, became dangerous, if not understood. If
this were understood by the intelligent captains of our
ships, the danger, if not utterly abolished, would at all
events be vastly decreased. (Hear, hear.) Hence the real
question resolved itself into these two propositions—first,
whether the compasses in our ships were liable, under

certain circumstances, to sudden disturbance, R; hich, if

unknown and disregarded, might be dangerous ; and,
secondly, what might be done to diminish the liability of
this disturbance of the compasses ; and, thirdly, when it
did occur, what might be done to render it less danger-
ous ; and, lastly, what must be done to render the naviga-
tion of ships liable to this disturbance more safe. He
proposed to show the principles by which magnetism on
iron ships was developed; the changes to which that mag-
netism was liable ; and to suggest the measures which
might be available for diminishing these evil effects, and
so improving the advantages derivable from compass-gui.
dance. The reverend doctor then proceeded to make a series
of interesting experiments, which we have previously de-
escribed, being the same as those exhibited before the Bri-
tish Association, to prove that iron, though highly suscepti-
ble of magnetism, was not in its nature spontaneously mag-
netic in any degree, but that there were circumstances under
which a high degree of magnetic intensity was developed.
It wasamatter well known notonlythat ironbecamemagne-
tic, by virtue of the inductive influence of the earth, butthat
magnetism might be controlled, altered, or destroyed by
mechanical action. An iron bar, entirely neutral as to
its molecular magnetism, as shown by its-being devoid of
influence when placed horizontally, in an east and west
line, near a compass, became strongly magnetic, when
placed.upright, or proximately so 2 • had its polarity re-
versed, by turning it with the ,contrary end downwards ;
and again became neutral when laid on the horizontal
east and west line. If the same bar, while held in an
upright position, or inclined in the axial direction of the
earth's magnetism, were subjected to percussion or other
mechanical violence, not only did its magnetism become
much more powerful than that of simple induction, but
it strongly exhibited its augmented polarity, when placed
in the east and west neutral, or equatoral position ; and,
however it might be moved about and swung around, its
polarity remained the same. Having proved these two
propositions by experiment, Dr. Scoresby went on to
apply them to the case of iron -ships, and to point out
that, in consequence of the percussive action to which
the material was exposed, while the ships were in course
of construction, it became as intensely magnetic as it was
possible for malleable iron to be. He explained also that
if a •ship was built to the north for instance, she
would have a certain magnetic distribution, which would
be liable to great change ; when in the course of her
voyages she steamed with her head to the south, the
natural effect would be to alter the compasses which had
been adjusted by fixed magnets. To obviate this evil he
had been led to suggest, some years ago, from the expe-
rience 'he had obtained from deductive science, that if an
iron ship had been built with her head to the north,"
when launched she should be vibrated with her head in
the opposite direction, or if possible, that her engines be
fixed in a different position to which she was built; the
effect of which would be to shake down the extreme mag-
netic influence of the ship, and to render her less liable
to changes when she felt the action of the sea. (Hear,
hear.) In the course of an interview with Mr. John
Laird Birkenhead (iron shipbuilder), that theory had
been 751 End available in practice ; for he (Mr. Laird) had
stated that, after launching an iron ship, it had been his
practice to have her vibrated in the dock, which had the
effect of reducing the subsequent deviation of the com-
passes, and to enable them to get a better adjustment.
(Cheers.) Having been charged with naming only two
instances in which the compasses of iron ships had de-
viated—the Birkenhead and Tayleur—he now adduced the
cases of the Bosphorous, Propontis, Three Bells, Pasha,
Madrid, Iron Queen, Gypsy, Great Britain, and a num-
ber of others in support of his proposition, that the
magnetic properties of iron ships caused deviations of the
compasses under certain circumstances. He wished it to
be especially understood that he did not bring this as a
general charge against all iron ships ; because, probably,
the majority of such ,vessels made their passages without
being subject to these risks. What he did desire
to be particularly borne in mind was, that there
was a liability to this compass deviation, and
inattention to, or ignorance of this fact, on
the part of the commander, placed the ship in great
danger. Amongst the remedies for this evil the one in
which he had most confidence was, the placing the com-
passes in positions where they would be least liable to
these disturbing influences, namely, at the mast-head.
In his arctic explorations—which, he observed, he had
been enabled to prosecute owing to the liberality and
enterprising spirit of the merchants of Liverpool, the
compass upon which he had most depended, and by the
means of which he made his most accurate observations
was one placed at the mast-head ; affording a most satis-
factory answer to a gentleman well-known in Liverpool,
who had stated upon paper that no .compass could act in
that position, either in wood or iron ships. (Cheers.)
After some further observations, the Rev. Dr. Scoresby
resumed his seat amidst general applause.
Mr. W. COURT, the Secretary of the Underwriters'
Association, produced the following letters which had been
received from Mr. Grantham, C.E.

"L!verpool,!ept. 30, 1854

" Dear Sir,—l have been requested to *attend, .and, if neces-
sary, to reply to the proposed lecture of Dr. Scoresby, on the
compasses of iron ships, at Lloyd's Rooms, but am prevented
from doing either by urgent business, and from having io
leave town for London in the afternoon.
"I regret that a sense of public duty urged me, on a late
occasion, to call in question the correctness of the theory
framed by Dr. Scoresby on the basis of certain well-known
experiments on the change in the polarity of wrought iron,
and from which he assumed that the compasses of iron ships
were not to be trusted, I contended that the cases he men-
tioned were not analogous, nor were his arguments supported
by satisfactory proof. The only cases adduced were those of
the Tayleur and the Birkenhead, doubtful cases at the best
No evidence was given of the numberless iron vessas steering
with perfect safely into every port in Great Britain, nor of the
causes which lead to the destruction of hundreds of our
timber-built vessels every year. Dr. Scoresby described the
vibration which hehad felt in the cabins of iron steam vessels,
which, he said, must have the effect of changing the polarity
of the ship. I now ask him to prove it. Such an assertion is
far too serious to be allowed to pass without direct proof—not
by a bar of iron struck by a hammer or by a plate of iron
bent before an audience in a lecture-room, but derived from
established and well-attested facts on board the ships them-
selves. The idea, also, that the deviation in new ships is
greater than in vessels which have been twisted and shaken
at sea, and thus arrived at a kind of mean deviation, may be
correct theory, but, it is assumed, not proved. The injury to
the pivot of the compass card, caused by vibration, must 'not
be mixed up with this question ; all stean2-vessels are subject
$p this defect. •
" CO/, Chesney gave to Dr. F.coretsby sad myself some im