Weekly national intelligencer., 1854-11-18
NATIONAL INTELLIGENCER.
FROM OUR LONDON CORRESPONDENT
LONDON. ocronER 81, 1854.

present by the discussion of the question of the
danger of navigating iron ships owing to variation
of the compass occasioned by the attraction Of the
iron. The question received good deal Of atten-
ton at the recent meeting of the British Scientific
Association at Liverpool The rates Of insurance
on iron ships rose in consequence of statements
made at the meeting, and the merchants of Liver
pool became so anxious about the matter that Dr.
ScoREsBY, whose observations had in considerable
degree caused the ALARM requested to repeat his
observations which he did, and then anxiousy ap
piled to for remedy He Of course found it easier to
declare the danger than provide security against iii
and the effect of the discussion has been to leave inn
preston unavorable the safety Of iron ships in long
voyages. The influence Of large Of iron the
compass had however, been often previously alluded to-
but the danger attending that influence and its extent
had never before been 50 prominently stated.
Numerous attempts have been made to correct the
ratons Of the compass caused by local attraction but
the most successful have hitherto proved far from salts
factory.
The important question whether iron can be safely
used for shpbuding is involved in the variation Of the
compass by local attraction and it ia pressed into
notice particularly not only by the discussions at
Liverpool and the loss Of the Philadelphia, but also by
the circumstance that ships much larger than any before
built being constructed Of that material for the
purpose OF establishing steam communication with Aus
tralia. 1t is not merely question whether ships shall
be built Of iron, but whether such large ships shall be
built at ALL for it is mprassable to obtain panks and
beams Of wood Of sufficient size for the purpose and
they cannot be joined together without danger of
ing. The Of steam navigation TO India and Aus
trais depends on having ships largo enough to carry
supply Of fuel for the voyage there and back therefore
the question whether is possible to variation
Of the compass in iron ships also includes the solution Of
the problem whether it will be possible to establish rapid
economical steam communcation between England and
Australia.
The deviation Of the compass by shifting local atrac
ons occasioned by chain cables and other of iron
that usually found in wooden ships has for some
years engaged the attention Of scientific The greater
deviaons that when the hull is made Of that metal
have not yet think received sufficient consideration
The English admiralty has been zeaous in attending to
the perfection Of ships compasses, but the difficult
ties arising from the construction Of iron ships
quire particular attention. and do not admit of longer
delay.
Another Of danger indicated by Dr. SCORES
BY. he contends that the iron plates become mag
netc by strains and blows and that the magnetism Of
iron ships is consequently liable to change of position
and intensity This state of the case If correct
to present unconquerable difficulty. continuous
steady attraction might be compensated guarded
against, but 1t be liable to change by strains in
heavy its influences beyond the power of cacna-
ion II it the attraction of the Of iron
in the ship that had to be guarded against there would
not be much difficulty in adjusting the compass act in
dependently Of it, but the is very different when
any portion Of the ship becomes magnetic. The facility
with which low degree Of magnetism is impaired is
great that merely beating iron will render it magnetic,
much the processes of rivetng and hammerng in
tho construction Of iron ship But this magnetic
action is net told by DR.. Scoresby, permanent
and regular one since IS liable be changed by acoi
dental strains This Last Of will fear
tax in vain the ingenuity Of scientific to
Several suggestions made by Dr. Scoresby for di-
minishing the danger, but none for removing it, His
most feasible proposition to place compass for refer
ence at the masthead so as to be far possible
from the influence Of the magnetism of the ship The
efficacy of such an arrangement however, would be di-
minshed with every increase in the length Of the ship
and the monster vessel building for the Australian
trade is to be upwards of GOO feet long, the height to
which the mast elevate the compass will have, we
fear not much effect in placing it beyond the influence Of
local attraction.
The Of iron in the construction Of ships is SUBJ
ect which the entire commercial world and
country than the United States and it is most i'm
portan if there be any special danger arising from the
Ssraon Of magnetism in such ships, such is pointed
cut by Dr. Scoresby that it should be positively
tanned and eectually provided against 1t is subject
worthy the attention Of scientific of all countries
The fashionable world is good deal excited by the
newed rumors that the Emperor and Empress of the
French will visit the British Court in December The
Imperial vsters will in the first instance be received at
Osborne from whence the QUERs and Prince ALBERT will
accompany them to Windsor where series Of banquets,
balls concerts &c. will be given scale of magnif-
cence unequaed in the present reign The stay of the
Emperor and Empress win continue six eight days.
during which the Emperor viii be installed Knight Of
the Garter, with all the pomp and ceremonies incidental
on the admission Of foreign potenate into this most
ancient and honorable fraternity. Queen Verona and
Prince Albert will, it is said, return the visit in May
next when the French Exhibition will be open, and the
Royal guests will Paris in all its glory with the i'm
nense improvements going in state Of compile
ton This exchange Of visits is Of great Importance 1t
must not be looked upon simply exchange Of royal
cvilites 1t viii be great political event. and viii do
much to cement the alliance which has already been 90
cordially entered into between the people Of both
tries which alliance is, think, great triumph Of
sivizaton striking proof Of the progress Of correct
principles and feelings, and Of the most important
events Of the period.
We have little to say about the war in which France
and England now, for the FIRST time for several
turies acting allies Tho great point of interest
Sebastopo the siege Of which commenced the 18th,
when the French feet bombardsd the great fort Of the
Quarantine and Fort Alexander and the British chips
attacked Fort Constantine and the Telegraph Fort Later
rn0v To that az