The Roanoke times. [volume] (Roanoke, Va.) 1890-1895, 1891-01-03
FEATURES OF MAGNETISM.

Remarkable Behavior OF Some Mesals In
Certain Conditions.
1t Is now pretty widely known that
iron suddenly ceasos to DO magnetic
whom heated to tho critical point of its
.'rocalescenco" or "aftor-glow," and
that if alleged with somo IL per cont.
of manganese, as in magaaeso, steel it
becomes almost completely non-mag-
,netio Theso facts show us that iron is
not necessarily magnetic undor all con-
ditions for admixturo with small
quantity of another metal, and even
moro change Of temperature. render it
non-magnotic. Stranger still, some OBJ
sorvors report that iron again becomes
magnetic whom tho temperature reaches
wilderness, but this lacks confirm ation.
The behavior Of nickcl-stcel is worry
remarkable. AS usually received from
The maker. nicI1ol-stcel with % per
cent OF nickel is non -magactic; and
yet 1t is Il mixture OF two magnetic
metals, iron and nickel. IT. now, VIC
cool this nicl1ol-stoel TO 80 deg. C
a deg. Fairy it becomes worry do
cidcdly magnetic. and remains so when
1T again returns to tho normal Temporal
lure. If. finally. wo heat it, it remains
magnetic till it reaches its critical
temperature of $50 deg. c (i,076 deg.
Fahr), when it again becomes non
magnetic, and remains so until again
cooled to 20 deg. C. In short, this
nickel-stecl may at the common tom
Perature DO either permanently mag
netic or permanently non-magnetic as
we please. We can at will make ii per-
nm L.
mentarily to $50 deg. C. and again cooling
it; or permanently magnetic. by cooling
1T temporily to so deg. c. Niclzel-stocl
has been recommended for ship build
ing becauso non-magneto. But il tho
nickel-steel ship is to become magnetic
suddenly, and without word of warn
ing, on cooling to a deg. Fair, sending
its compasses spinning, its sphore OF
usefulness would DO limited. For.
though this Temperature is not reached
during common ocean trips. yet vessels
in port at New York. Boston or Halifax,
on the great lakes and elsewhere, arc
occasionally exposed to it, Relocating
the vessel to 10T6 deg. Fair. to unmagnc-
tho 1T seems al first to present technical
difficulties. Finally pull n bar OF nom
magnetic % per cent. uickel-stccl apart
tensilely, and, presto! its broken frag.
ments are magnetic!
This, be it understood, is tho behavior
OF 90 per cont nicilic-steel 1t does not
at all follow that. with other propor-
tions of nicl1lc. tho Same strange con.
duct will be found. Thus with five per
cent of nickic. stool becomes non-mac-
netic when heated to about 500 der. C,
Like 3b per cont. nicklo-stcel, it re-
mains non-magnetic whom cooled some
what below this temperature. regainins
ats magnetism st decidedly lowor
temperature at which it ag ain becomes
magnetic, instead of boing below zero.
is somewhat about ESQ dog C.
Again. it has become pretty VOL
known that tungsten, itsolf unmagnotic.
greatly increases tho magnetism Of
steol; and now il torns out that it plays
tho Same part with nickel, per cent. of
tungsten making nickel moro strongly
magnetic than tho steel of which
magnets wcro formerly made. Thus
Mr.. Preece states that whilo tungsten
raises the magnetic induction OF steoi
from 700 to 5000, 1t raises that Of nickel
from 100 to l.o3S. -Enginccring and
Building.