1824] 
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SPIRIT OF PHILOSOPHICAL DISCOVERY, AND.OF. THE 
VARIOUS SCIENTIFIC JOURNALS. 
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BMHE valuable discoveries of Professor 
/ Barlow, respecting the local influence 
of iron on the magnetic needle, have opened 
a wide and very interesting field. ‘That 
very accurate. experimentalist, M. Gay 
Lussac, has recently ,determined, _.that 
the mutual action of twe magnetic. par- 
ticles depends on the matter with which 
they are incorporated. Thus, he found 
that a magnetic needle eight inches long, 
placed in the direction of the magnetic 
meridian, made ten horizontal vibrations in 
131 seconds. _ A bar of soft iron, the same 
length, three-quarters ‘of an inch wide, and 
one-sixteenth of an inch thick, being placed 
below the middle about two inches, and 
parallel with the meridian, the rapidity of 
the oscillations were doubled, or about ten 
in sixty-five seconds. A similar bar of pure 
nickel was substituted for the iron bar; 
when the needle required seventy-eight se- 
conds to make ten yibrations. On the bar 
of nickel being remoyed, the needle again 
returned to its original intensity, making 
ten vibrations in about 130 seconds. These 
experiments were made by M. Lussac at the 
suggestion of M. Poisson, who has recently 
drawn up a most elaborate memoir on the 
Theory of Magnetic Action. ‘The present 
paper of M. Poisson is rather confined to the 
natural state of the magnetic property in 
bodies, than to the artificial or acquired 
state, as in the magnetic needle. In a se- 
¢ond memoir he proposes to apply the 
principles here demonstrated in solution of 
the phenomena attendant on artificial mag 
netism. According to the theory of M. 
Poisson, a small cylindrical needle of soft 
iron contains the boreal and austral fluids 
in equal quantity throughout its whole 
length; so that their action becomes neu- 
tralized; and the bar exhibits no indication 
whatever of magnetism. But if a magnet 
be placed near the centre of the needle, and 
in the direction of the meridian, the two 
fitiids ‘of the iron needle will become decom- 
posed, ‘or separated from each other; and 
each particle of north or south polarity will 
be in a slight degree displaced from its pre- 
vious station in the bar, or drawn towards 
the ends. “From this doctririe of magnetic’ 
‘equilibrium, M. Poisson infers that, not- 
withstanding the boreal and austral fluids 
are ‘disseminated throughout the whole 
jass of a magnetised body, yet the attrac- 
tion, and repulsion which it exercises are the 
same as if its surface were only covered by 
a thin straftum of the two fliids. He atso 
sheet, tat a small magnetic necdle, placed 
in the centre of a hollow sphere, will nothe 
subject to any magnetic action from offier 
magnets, nor even from that of the earth’s 
magnetism. ‘The application of a ring or 
plate of soft iron, of any thickness, but of 
Monruty Mac. No. 402. 
some: considerable: extent, will,’ therefore, 
neutralize the’ local action ef other bodies ; 
as was shewn previously by the profound 
researches of Mr. Barlow, of the Woolwich 
Academy. Indeed, the inductions of M. 
Poisson, though somewhat different from 
those of Mr. Barlow,. serve. to establish 
more fully the theory suggested by that 
gentleman, ‘and which he has’ already re- ~ 
duced to practice ina manner no less eredi- 
table to-his ingenuity'as an artist, than to 
his profound mathematical knowledge. ‘The 
local influence exercised by the iron of a ship 
on her compasses have been known to be 
the immediate cause of many a valuable 
ship and crew being consigned to the deep : 
but it is not known, nor ever can be known, 
how many melancholy instances of the kind 
have arisen from this: source. The devia- 
tion even of half a point in a ship’s course 
is a serious matter, especially when in the 
Vicinity of land. But independent of the 
guns and the iron in a ship haying a certain - 
influence on her compass-needles, the lading 
of many of ofr outward-bound merchant 
vessels contains a large portion of iron, 
either manufactured or in bars, which must 
greatly derange the magnetic needle, though 
it is usually disregarded. 
Organic Remains. —The American natu- 
ralists are daily tracing a conformity in geo- 
logical deposition between the Old Cor:ti- 
nents and what has been improperly called 
the New, or Western Continent of America. 
We have noticed many instances in our’ pre- 
ceding numbers of the fossil remains of the 
mammoth, elephant, and other large qua- 
drupeds being found in many different parts 
of America, more particularly in the yicinity 
of the Mississippi and Ohiorivers. But the 
Philadelphia Journ. Scien. states, that two 
travellers, Messrs. Lewis and Clark, in a 
recent expedition up the Missouri river, have 
discovered some remains of amphibia, be- 
longing to the genera sauri, which seem .to 
differ in character from all the other species 
previously known. These remains were 
found in a cavern a few miles south of the 
Missour?river, near a creek ; and from the 
conformation of the dental bone, Dr. Har- 
lau proposes to give it the name of sauro- 
cephalus lanciformis., It is probable. that 
future research will reward the labours of the 
American naturalists with .a rich harvest in 
the very interesting field) of organic re- 
mains, particularly in the genus ‘/acerta : 
for as these ‘animals: are known to, abound, 
at the present day, in the great rivers of 
both ‘Amerivas, it is a fair presumption that 
fossil remains would be found to a much 
greater extent in America;;than in» any 
part of Europe, where this family of the 
animal creation must have been extinct for 
ages—their remains not being found in any 
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