The Sun.
London, England, 1854-09-26 00:00:00

MLE7ING OP THE BRITISH ASSOCIATIO

LIVERPOOL, Monday Evening.—The general
mittee (Sir Philip Egerton in the chair) met this a
noon for the purpose of deciding, among other mat,
upon the question of the next place of meeting
Applications had been received from Glasgow,
Manchester, Dublin. Brighton, Cheltenham College,
Gloucester, Ryde (Isle of Wight), and Nottingham.
After hearing the claims put forward by the delegates of
the various towns charged to support the invitations,
and maturely considering the subject, the committee
decided that their next meeting, for the year 1855, should
be held in Glasgow, On the motion of Sir R. Murchiton,
seconded by Mr. Smith, his Grace the Duke of Argyll
was elected president of the association for the next
meeting. The vice-presidents appointed were the Rev.
Duncan McFarlane, president of the University College ;
Sir W. Jardine, Sir C. Lyell, Mr. James Smith, Mr.
Walter Crombie, Professor Graham, and Professor Thomp-
son.
The business of the various sections was resumed this
morning at eleven o'clock.
SECTION A.—MATHEMATICS AND PHYSICS.

THE LOBS OF THE TATLEUR AND THE ACTION OF COI-

PASSES IN IRON SHIPS.

The Rev. Dr. SCORESBY read an exceedingly interest-
ing paper on the above subject, the object of which was
twofold; first, to develop the principles upon which
the magnetism in iron ships was distributed ; and,
secondly, to show the principles upon which, and the
circumstances under which, changes of that distri-
bution must of necessity take place. The melancholy
case of the Tayleur was an example of the most impres-
sive kind, illustrating the general bearings of this most
important subject. The Tayleur was a new vessel, which
left Liverpool for Australia, on her first voyage, on
Thursday, the 19th of January, 1854, having on board
about 458 passengers, in addition to her officers and
crew, making a total of 528 persons. She was con-
structed of iron, and her registered tonnage was 1,979
tons. Her compasses (3 adapted
.for guidance) were-011
" adjusted" by large and powerful magnets, on the
principle suggested by the Astronomer Royal ;
Grey, who had charge of the adjustment, reported that
they were quite correct. She left the Mersey-at noon,
and was left by . the pilot about seven or eight
p.m., between Point Lvnas and the Skerides. The
weather was then tolerably fine; but a gale soon after-
wards commenced, which continued on Friday, mode-
rating, however, at intervals. The ship during this
time was traversing mainly south of the Isle of Man,
northwards of the Welsh coast and Holyhead. About
four o'clock on Saturday morning she was near where
the pilot had left her, and at eight o'clock, when the
wind was again blowing a gale, it was ascertained, for

the first time, that there was a material difference be-
tween the compasses. One of the compasses was near
the helmsman, by which she was steered, the other was
near the mizenmast. Judging from the former of these,
the captain was under the impression that he sas railing
down almost mid-channel, that at all events, he wasjn,a
good position for navigating the Irish Channel ; while tte
other showed a difference of almost two points. Not know-
im.; which of these wise correct, the captain assumed, from
etre:tin indications which he had before noted, that the
wheel compass was accurate, rather than the other. The
result shorted that neither was correct; that they had
not only changed in their relations to each other during

the short time the ship bad been at sea, but that they were
both largely in error as to the true direction of vessel.
It was a matter well known not only that iron became
magnetic by 'virtue of the inductive influence of the
earth, but that magnetism might be controlled, altered,
or destroyed by mechanical action. Applying this
knowledge to the case of iron ships, he pointed but tliatL,
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. This augmented mag-
netism' however, was not permanent or fixed ; but,
under different circumstances, as to the relative devia-
tions of the ship's magnetism and that of the earth was
easily changeable, and liable necessarily to be changed.
The magnetism developed by mechanical violence could
readily be neutralised, orchanged, under a proper change'
of conditions, by other processes of mechanidal violence.
If a bar of iron magnetised by hammering were held in
the reverse direction from that in wfiich the magnetism
had been developed, and again hammered, the polarity
would not only be altered but reversed. The result of
another experiment which he had made with eiongated
plates of iron, to elucidate the phenomena of mechanical
vibrations or violence, had been still more remarkable.
If a couple of iron plates were laid together, it was
found, when their condition was neutral, that held within ,
two or three inches of a compass, horizontally. east and
west, there was no action whatever on the needle, but
holding the plates upright and bending them, or; merely
giving them a vibratory shake, and then presenting
them as before to the compass, the iron was found to
have become very strongly magnetic, the end which.
was downward repelling the north pole of,the needle.
Reversing the position of the plates, while held upright,
if the vibratory action were repeated, the end formerly
repelling would now be found to:attract the north end'
of the pole. Repeating the vibratory action, while the
plates were held horizontally, in an east and west line,
the magnetism would be found, on bringing the plates
to the test, to have disappeared, all, action of the
compass having gone. To meet, probable, Abieetions
.he had made. experiments in .rolled iron pliLtei, of
the same kind es those of which. - ships ,ntere
ge-
nerally built ; and had ascertained that• the magnetisns
in those also was changeable and cOntrollablelike
in bar iron, under the requisite change of position, by
vibratory or percussive action. Ho had also made expe-
riments on a portion of a plate cut out of the side of a
ship recently built, and the result of his observations was
to establish the fact that besides the two denominations
of magnetism ordinarily received, that of simple terres-
trial induction, and that of permanent independent mag-
netism, there was another denomination corresponding
with neither ; not being absolutely controllable, like the
former, by terrestrial influences, nor capable, like the
latter, of resisting all kinds and modes of mechanical
violence. To this third denomination he gaVe the name
of retentive magnetism. The vibration of a Ship in a
heavy sea was sufficient to change the original magne-
tism developed and augmented in the course of her con-
struction. A great deal depended on the position in
which the ship had been built. In the case of the Tay-
leur, when he first heard of the catastrophe, and read
the evidence, he had stated to some friends at Torquay
that he would venture to predict that she had been built
with her head to the north. He had found, on inquiry,
she had been built with her head nearlycnorth-east.
Here, then, were the precise circumstances for expecting
a change in the ship's magnetic distribution. Having
been built with her head to the north-east, she had a
certain magnetic distribution, and when she began to
strain, with her head to the south-west, that distribution
was necessarily changed, and the first effect of it.had been
to alter the two compasses adjusted by fixed magnets-
If the captain had been aware of the changes which might,
and most probably would, take place when the ship—be—
gan to strain in a different position from that in which
she had been built—if he bad known that the compasses
miebt vary as much as two, or three, or even four points,
he would have known, of course, that he must, place no
reliance upon them. It did not follow, however, that com-
passes were of no use because, under circumstances, they
were liable to change. They ought to be, and were, of
great use for all that. But what he wished to impress upon
t he section was, that by attempting to adjust a transient by
a permanent influence, they were only aggravating error;
that captains ought always to bear in mind this liability
of their compasses to mislead them two or three points ;
that they should be always looking after their correctors
and verifications whenever the sun or a star .was in
sight ; and that., by keeping a compass aloft as far as
possible from the iron of the ship, they would always
have a standard to which they would be able`to refer,
and which he, in his Arctic voyages, had alWays found
to be correct.

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