The New York herald. [volume] (New York [N.Y.]) 1840-1920, 1854-11-19
AFFAIRS IN EUROPE.
Oorveetsor OF the Compass In Iron Ships.
IRON the London Athensum.l

CORRECTION 0OWp08o
sIips 81 the late meeting OF the British Association
and regret much that 1t was out Of my power TO
- percent and TO take part In the discussion. Per
hsps may be allowed 10 remedy this omission by
Ne assertion OF remarks in the columns Of the
AtAenGum. am the moro ANXIOUS to do this, be-
cause the circumstance that distinguished philoso
pier, Of indisputable competency and impartial
character, has nos fairly o0nsidere the question,
places In position totally different from any
which il has occupied before. have deep sstisfAc
60A N remarking that the greas principles upon
which founded the method of correcting the com
s minor ps
pSos (Which, "a viii appear In the remarks below,
had anticipated ~ probable), have now been estab
Ahed by Dr. 6coresby's beautiful experiments. Ia
Ne estimation Of the actual extent and rspdity Of
the changes produced by these notifications, may
perhaps differ in some measure from Dr. Scoresby;
md may be disposed to recommend practical
eOurse slightly different from that which he would
propose. Still am happy to ind that upon the
fundamental points OF the theory we are in complste
accordance.
/. Il may perhaps be advantageous to give few
steps of the history Of this subject. The Law tina.
DE greater part OF the disturbance Of the compass
produced by an iron ship, depends upon its polar
end not upon its induced magnetism (,n the 0rdi
me- II paper printed in the Philosophical Trans
actions" for 1889. The experiments themselves h I'd
been made in 1888. 10 page 2l2 l observe" The
most remarkable result, In scientific view, from
the experiments detailed above, IL the great inten
sity Of the permanent magns tism Of the malleaole
ron Of which the ship Is composed. IL appears,
however that almost every plate OF rolled iron Is
intensely magnetic" I' Is to be noted that used
the term permanent magnetism equivalent to po.
lar msgnetism) / then aauie to experiments on
the netsm OF plates OF wrought iron; and these
experiments were the last win which had any &C
quaiDtat ce until saw some of Dr.. Scoresbys beau.
fifu jlustI Of the change of magnetism Of iron
plates IL page 2l3 remark, at seems sufficiently
probsble that the Independent (polar) magnetism CT
the ship will change with time. This consideration
enforces strongly the necessity of periodical exami
ration IS suggested above" This is all that
was printed by me in reference to the
change Of the polar magnetism of ships and
Their occasional examinations bus it is not the
only instance in which enceavored 70 bring them
before the mott &c of the proper authorities. In 1885,
July 20, submitted memorial to the bard OF Ad
government Of the correction of the npsss in iron
ships in which occur the folio wing rsmarks:-
There Is ne reason for presumng tina. the mag
netic state of the ship Especially in the case OF
steamships) will remain invariable for many yea q;
and there is for EupposDg that 1t win vary
-"Experiments Of various kinds and in varloI
localities should be made on the same ship, for as
certain ing whether there is sensible hange in diff
ferent parts of the EARTH" And with regard to the
magnets" The important results lately arrived at
by Mr. Scoresby, and wholly unkn0wa to the per-
sons CONNIE cally engaged in tho fabri cation of
magnets, show that attention to those points on
which the permsr ency Of the magnetism depends,
cannot be expected from clmmon tIadesman The
Admiralty Il believe in accordance vita precedent
undertake the supervision for commercial ships;
and, DO other ir shios then existed, this deci
sion amounted practically to a refusal to enter on
the matter. Had the subject beel then tax an no
by the government, 1t might perhaps have been ad.
vanced several years. DID myself endeavor to col.
lect information, and took notes of the position il
which one ship WIS built; but the occupation of q
laborious Office compelled me to desist. may men.
ton, that in almost every instance reported TO me,
N which the correction failed after time, had
reason to think that the failure arose from change
~ h,.<s kInn
this consideration, combined with the feeling of
want of leisure, prevented the extension Of my in
quiries
2. am deeply stru,k with the beauty and the i'm
portance Of DR.. ScoresbY's experiments !; and il |
bring to notice the circumstance that the polar
magnetism of iron plates and the possibility Of
change in the mague ism, were 6rst strongly insist
cd ON by myself, trust it will not be understood
that mean to say that those experiments are unes
sen,ial to onr present knowledge of the subje
STU, as the frs who examined into an oecula.ed
the pane which d.. Scoresby has proposed I; and !
express M opinion that 9 Yetentive' {" retained
wtnld be better 10 grammatical sense) does not ex.
ac.ly represent the characteristics of the magnetism
of wrought iron plates. The latter appears to me
70 differ very little from the magnetism OF hard STEEL
bars. steel bar is msgDstised By induction Gas is
no iron pate)-a steel bar may have its magnetism
weakened or reversed if immersed in the sea water
II would probably lose its magnetism than an
iron ship would. But in practice the magnetism
Of iron ship is sgat more liable % change than
that OF steel magnet very carefully preserved 1t
nay be desirable that name expressive of that idea
should be given to it. ! would propose to call it,
the subpermanent polar magnetism of wrought
iron.n
Dr.. Scorsby's experiments produces an impression
of the extent Of their applicability to iron ships far
greater than is warranted by careful consideration
We may speak POLITICALLY Of the shocks which ship
receives from TIE waves; but In reAlt the plates Of
iron Of which q ship is composed sustain no such
shocks. TIE direct effect Of III most violen. see
upon them is this-that in thu course OF two or
tarse seconds of time, the plate IL plunged five o.
six feet deeper in the water, and sustAins the cor
responding by drostatc pressure. This Is very di
Irent indeed from the raps slsps in Dr. S,oresby
be Of the nature Of impact, occupying q very sinai
fr6ction Of second OF time. PROBABLY the strain
axSension to which the plates are subj 0cted mas
produce greater eject; on this, however, expen
the state Of extension Is not sudden, but gradual.
The tfemor produced by steam power is more likely
20 affect the plates in some parts of the ship. II is
svdns that there are causes IL .csOn tending
experiments ard it Is equally evident that the sctio,
~ those causes must be exceedingly SLOW. On one
poiAt, however, trust that confederation Of DR..
Scoreebys experiments will disabuse many persons
Who have not been well acquainted with the nature
- induction and subpermanent magnetism. Toe
change TO be expected In ships subpermsnent Tag
Hope, does not essentially depend on her passi az
into another magnetic hemisphere. IL does depend
mainly on this circumstance-that, supposing he,
~ have been built with her head to the NORTH or In
she line of boreal magnetism, abe IL then turned
with her head to the SOUTH ia the line Of ~ tral
magnetism, and IL SO kept exposed to slgt ire
n0sf for one or two months. II she had been moored
on the coast Of Portugal for the same time, Ia the
same position, and exposed TO the same tremors, /
apprehend that her magnetism would have under
gone nearly the same change las regards honzonts
deviation Of the com ass) as in the voyage to the
Cape Of Coed Hope.
4. think the selection Of the loss Of the Taveur
- the text for the principal dscnssi iron alps
With oil its attendant horrors (hsviug no applica
ton whatever to the matter under discussioo) Vas
unfortunate, When the feelings are ex tied, tn.
Judgment Of the speaker, well a. Of the hearers
n very liable to be perverted. The question at issue
Il the very abstract one:-B it likely thai 10 tvs
days the magnetism Of ship could be no changed
that the compass would be disturbed through an
gle Of two points? unhesitatngly suswe,:--It is
not likely; and, speaking with our present kaov