New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1868-07-10
SCIENCE

TESTING IRON BY MAGNETIsM.-A paper was
read before recent meeting OF the Institution OF Naval
Arehite cts, London. by s NJ SaXby h M on the mode
Of testing iron both as 20 condition and quality by
means of magnetism the main feature OF winch Is that
articles made of iron can rapidly tested without da
age 20 them DETACHMENT TIC author ana Aot liu's9
OF iron or stcel hut hollow I0Hwork with the exception
Of guns and sma-am barrels had not as yet been care
fuliy examined lie assumed that the "lure iron Of
commerce that which il best adapted for mauuacnr
ing purposes generally, and that test OF It's goodness is
oold INTO compact knot Yet the tensile strength now
ever useful for some purposes, IS an insufficient
OF the goodness OF ron, lnasmdch az u shows Seht
In direction, and is not Incompatible with behe.
OF iron is an aggregate OF dsu"ct PARTICLES t',
ductiyely 1t the iron is pure aud soft and peIah'
IL IN q state OF steel OF cast lron Tie oa Hou'
proved by expcI ment TO he erroneous we
with that favorable condition when rs lHT ''C' Va
strength I'm iron viz north pole to south poe ana 80 on
we cause weakness ln the metal We dtine nClJo "n
axiom that Continuous polarity ID ron n,'U NV, cO
stues strength while It's disruption OF sol H Is Wt"
ness; and flaws aud fault are examples OF s"ch weak
~ tbe nT6at ana pcculiari,ies OF polar condition
An piece OF ir0u measurable; therefore II strength
IN IRON magnetism. so J.; strength IN non me'NuIaoe'
and as any common compass is 2 magnetic mrt'f' 80
ought 10y the OF the compass TO be able to measure
she strength OF IRON, ana To detect MS Nc"Ne5S ny u"iV
ing the changes IN the position OF the needle on bN
passed along Its sides. lHe author Ge'GHDtH
position Of u piece OF steel which had been
secretly ncosed by smith IN bar OF IRON "a hches ong
aud in diameter lie carefully li sue coAp+' up ,,U
down the side Of the har, which was placed an tue ln,
rdian. ont of the MERIDIAN M thc me Oh tAc mp "3
until cOrrOhOr2ouo i compass disturbance IL, "I ~ ~
advised hin of evident local interference WIN OF 1,u
ton OF, that alternate polar continuity M!lS ",l ia "a
been found lu hdF ui SOFA non nc l' 80 a.
by The ncrd,o that end Of the steel pm was thor
oughly combined with ihe ron WINE ,e o,y JU,"
have been properly Wci0.d -Whci, o. |,' wa"
proved To be tuc fact Various other experiments were
nioe iuporrant deductions Of TIC author. To uag-
nec test chrctuily fair knowledge OK the main pOihts
tho present day the master smith or ms assistants
who equal to q cohlfe"cLs.Oh Vl A. IT,. A.
testing room, and officer for the examination Oh an I'M
portant i0rgngs or castings OF IRON Inc want Oh popsI
siug has been the Of much weakness and con
scnueuty of waste, in iron castings customary 4"c-
occurring al particular parts Of an aits.e nan
metal whereas mr. SaNby believed thdJ ~ many cases
smrb ,yca,upss arises from the imperfect manner ~
rb ti motion metal lis run into the mold; for unless
the functions of the surfaces Of the hot metal occur a he
same temperature the molecular conditions II the metal
Is defective. II not uncommon Tor hm 10 hau opPo
site pOlares occurring iu castings within tue space OF
small portions OF an inch No" tht1e are eP "
flaws in wrought irUu they absolute W'ihuosscsaud
IN most remediaOlc. lrreguaIty ~ coohng CAUSES
molecular descriptions There Is ont little dimuiy ia 'he
testing Of many articles such shafts spiucles STqt
braces knees, railway wheels, ara So on ana especy
such articles as reyove IN lath9 CHfiHs m'n"' yu,
IL remarkable THAT, m general we EhO% Ie'a o. uo
condition of iron than OF It's q@A{ me 'e5I Oh iot
when in bad condition is virtually DdH non S tu'mC
illustrated 10y samples OF Bowling lIo' Gnu
IRON both of which costly and bear the highest char
aeter; several specimens had Deen proven "y 0 @
70 be detective and on cutting the bars tAey were IouAu
TO be partly crystallz,d and partly hbrons. ,
few noteworthy defects in the common mode OF
forging iron have been detected by the magnetic test
always he done mi as near welding heat as possible II
otherwise done, 10 causes flaws percepuble by the
magnet: and it may be remarked here that many IauLs
IN condition might be Iemeded by al4e3lllE. IN Wclus
Ing iron is bad TO the ends beveled laying pieces on
augup iron across them. This crossing Of hncrs even
alter a sound weld, is an element Of weakness and u
has been proved by the magnet test 10 be very objection
able. . . -,
In conclusion samples shown 10 Illustrate the
position that irOu forged IN one direction or the
other with reference to the magnetic mcNd1u so VIII
it, strength vary. Hence it may be reasonable inquiry
whether all testing machines should Lot be placed IA
direction east and west and for cham cables especially,
In the iron Of which wish to avoid the destruction OF
elasticity.