The Liverpool Standard and General Commercial Advertiser.
Liverpool, Merseyside, England, 1839-05-31 00:00:00

adoption of his " principles." The radicals support
the whigs, despite the promptings of their " pnnci-
ples," because they hope yet to stand towards the whigs
in a similar relation to that now occupied by O'Con-
nell.

This foul conspiracy to which these men of " prin-
ciple" have, for four -years, been parties, has nearly
tvorn itself out,. The majorities, by which that con-
spiracy was rendered effective, at first, have gradually
dwindled away. Already these majorities—however
effective still for the ends of faction—are found to be
insufficient to enable Lord Melbourne and his col-
leagues to administer the affairs of the country. The
first serious difficulty--and Heaven knows that the
business of the nation presents difficulties innumera-
ble—with which ministers shall be compelled to grap-
ple, must destroy them. A dissolution of parliament—
let the Queen's name be abused as it may by her pre-
sent unworthy advisers—will return to parliament an
overwhelming conservative majority.
Mr. Shaw Lefevre's tenure of the Speakership does
not promise to be of an enduring character.

LIVERPOOL MECHANICS' INSTITUTION.

LECTURES ON ELECTRICITY.

On Saturday evening Professor Addams continued,
Those natural magnets called loadstones, as well as the
artificial magnets composed of steel bars, circulate around
themselves electric currents, according to definite laws, and
are able to attract certain bodies with considerable force,
such as iron, steel, nickel, and cobalt, which are the only
ones acted upon by them. Even iron, when in the state of
red rust, is not subject to magnetic influence, but in the state
of black rust it is so. The horse shoe magnet is the most
powerful kind of art ficial magnet, and next to that, the flat
bar. Although magnets will attract at either end, they will
not in the centre. The middle part of a bar is what is called
neutral, and possesses no peculiar powers of attraction. If
we, however, fracture it in the middle, the ends of the frac-
tured portions will be magnetized, but with a feebler inten-
sity, and so on to whatever extent we repeat the fracture.
All magnetic bars, if allowed to move freely upon a pivot,
will turn one of their ends towards the north : and it is this
property of the magnet which has rendered it so extremely
useful in navigation. The Chinese were acquainted with
this remarkable fact more than a thousand years ago. It two
bar magnets be suspended near each other we shall find that
they will not rest quiet unless the north pole of the one mag-
net and the south pole of the other be towards each other, as
two similar poles always repel, and two opposite poles attract
one another. A peweratl magnet will attract within twenty
or thirty feet, and even through a stone wall, by which means
many deceptive tricks may be performed. The magnetic
needle does not point directly towards the north, but taking
London as the place of observation, 23deg. 58min. to the
west. This variation of the needle from the true north is
subject to yearly change ; it is found to be different as we
alter our position upon the earth's surface. Thus in 1576
the needle pointed eastward of north ; in 1657 it pointed due
north. Since that period until 1818 it gradually pointed
more westward, when it commenced a retrogade motion ;
and in a certain number of years it will again point to the
true north, its variation being about 2min. a year. We find
that if a magnetic needle be allowed to play freely upwards
and downwards it will turn itself towards the centre of the
earth, instead of assuming an horizontal position. The pre-
sent dip of the needle at London' is 69deg. below the horizon,
in round numbers, but, like the variation of the needle, is
subject to perpetual change, as we change our situation on
the earth's surface. The needle will dip perpendicularly down
before we get to the poles, and, when we get there, will turn
backwards again. This may be easily shown by placing a
dipping needle over a powerful bar magnet, and moving it to
either end. Professor Barlow has calculated that the incli-
nation of the dip at London will never be less than 56deg.,
or more than 77 43-100 deg. Mathematicians have ascertained
that the tangent of the dip of the needle is always double the
length of the tangent of the latitude cf the place to which the
tangent is applied. Iron cannot be made to hold permanent
magnetism by induction, but steel can. Iron can, however,
for a short time be caused to become a magnet : thus it' a
piece of iron be placed at the end of a magnet, it will take
up small nails, and magnetism may in this manner be com-
municated through a number of iron nails,,even though we
place a piece of card board between the magnet and the iron.
The peculiar currents which magnetic electricity causes may
be beautifully shown by sprinkling some iron filings upon a
card board placed upon a powerful bar magnet, when by
gently tapping the board, the filings will arrange themselves
in the direction of the currents. If a bar of unmagnetized
steel be held in the direction of the dip of the needle, it will
become a magnet, as can be proved by holding to it a mag-
netic needle, for whilst unmagnetized steel will attract either
pole of the magnetic needle and repel neither, it will be found
that the bar of steel whilst held in the manner described,
will have acquired such a polarity, as to possess repulsive as
well as attractive powers. The same bar upon being held
horizontally, will ins' antly lose its previous magnetic in-
fluence. Time iron employed on shipboard, in whatever shape
it may be, is ingularly affected, and much danger may arise
where large masses are collected, or the vessel itself is built
of iron, unless proper care be taken in applying correcting
plates to the magnetic needle. These, however, have been
so ingeniously and successfully contrived by Professor Airey,
as exemplified in the " ironsicle," an iron vessel, which has
made a voyage from this port round Cape Horn, that no ap-
prehension need be entertained if his suggestions be adopted.
As percussion produces magnetism in iron and steel, there is
a danger incurred of altering the direction of the magnetic
needle by the blows given in repairing an iron vessel ; there-
fore it will be always well to ascertain by an ajunorth com-
pass, whether the local attraction on shipboard 'is prOperly
compensated for, prior to the commencement of every
voyage. By holding bars of steel in the direction of the dip
of the needle, and striking them upon one end we can per-
manently induce magnetic electricity in them.
To-morrow evening Mr. Addams will exhibit the magnetic
electric telegraph.