M A G N 
name of eloffe de pons, Is the next in goodnefs to Engli(h 
fteel; its power being only one feventh lefs than that of 
Englifh fteel. Thirdly, That caft fteel ought never to be 
tifed for making artificial magnets; becaufe it is capable 
of receiving but little magnetic power, in comparifon with 
the others.” 
A bar of iron may eafily be diftinguilhed from one of 
fteel by prefenting it to the magnetic needle. If the bar 
which is tried initantly acquires polarity by being placed 
vertically, which is feen by the attractions and repulfions 
obferved in the courfe of the experiment; and if it lofe 
that polarity when held horizontally, which is eafily dif- 
Covered, becaufe in this latter pofition whatever end is 
prefented, and whichever pole of the magnetic needle is 
approached, the phenomenon of attraction will always be 
obferved ; if, finally, upon turning it, the pole be changed, 
and that as often as the bar is reverfed ;—it may confi¬ 
dently be pronounced a bar of iron. If, on the contrary, 
the bar fubmitted to the fame experiments (how no fign 
of polarity, and attract indifferently the two extremities 
of the needle, in whatever manner and fituation it be pre¬ 
fented, then it may be concluded that the bar which is 
tried is of fteel. If this fame bar fhow figns of polarity, 
and, in whatever fituation it be prefented, the phenomena 
of the attraction of the oppofite poles of the needle and 
the bar, and the repulfion of the fame poles, invariably 
qnd uniformly take place, it may thence likewife be con¬ 
cluded that the bar is of fteel; for lteel alone poffeffes the 
property of acquiring and preierving, for a very long pe¬ 
riod, even when not tempered, the fmalleft degrees of 
magnetifm. Journal des Mines. 
A German author, in a work lately publiftied, Hates the 
following curious faff: A perfon having an artificial 
magnet fufpended from the wall of his ftudy, with a piece 
of iron adhering to it, remarked, for feveral years, that 
the flies in the room, though they frequently alighted on 
other iron articles, never fettled on the artificial magnet; 
and even that, if any of thofe infects approached it, they 
again in a moment removed to forrfe diftance. “ It is 
worth the trouble,” fays profeffor Voigt, who repeats this 
circumltance in his journal, “ to make further observations 
on this phenomenon ; and, were it confirmed, magnetifed 
iron might be employed to preferve it from being foiled 
by flies, and perhaps alfo for other purpofes.” 
5. Even the.rubbing of one piece of iron over another 
is not necefiary to produce the magnetic virtue. It has 
been obferved that a bar of iron, kept for a long time in 
the direCfion of the meridian, or in a fituation nearly ap¬ 
proaching to it, acquires the magnetic virtue. The itee- 
ple of Notre Dame de Chartres having been confiderably 
damaged by a great (form in 1690, fome bars of iron taken 
from it were found to be magnetic ; but, what is ttill 
more remarkable, pieces of thefie bars, which were almoft 
deltroyed by rult, formed excellent magnets. The abbe 
de Vallemont wrote at that time an account of them, which 
was puhlifhed in 169a. 
Dr. Gilbert, an Englifti phyfician and philofopher, who 
wrote on the magnet in 1640, had then obferved that the 
finall bars of an iron window-frame, placed north and fouth, 
which had remained many years in the fame pofition, were 
become magnetic. He relates alfo, that the wind having 
bent an iron bar which fupported an ornament on the 
church of St. Augultine, at Rimini, when the monks be¬ 
longing ro it were detirous, ten years after, to ftraighten 
this bar, they were much lurprifed to find that it poli'efled 
all the properties of a good magnet. Mufchenbroek (peaks 
of a iimiiar circumftance, in regard to fome pieces of iron 
taken from the tower of Delft. We read alfo in the Me¬ 
moirs of the Academy of Sciences, for the year 1731, that 
there was at Marfeilles a bell which moved on an iron 
axis, ftanding in an eaft and weft direction, and reliing 
with its two ends on (tone; that the rult of thefe ends 
mixing with the dull: rubbed from the (tone, and with the 
oil ufed to facilitate its motion, formed together a hard 
and heavy mats, which when 4§tached was tyund to pof- 
£ T I S Ms 123 
fefs all the properties of the magnet. It is believed that 
this bell had exifted in that fituation 400 years. In Scot¬ 
land, and in other northern parts of Europe, old vanes of 
turrets, window-bars, and even pokers that have ftood long 
inclined in the chimney-corner, are often very fenfibly 
magnetic, their lower extremity becoming a north, and 
the upper a fouth, pole. In the higheft part of the (teeple 
of St. Giles's church in Edinburgh, on the north fide, the 
upper bar of a hand-rail leading to a (fair is very magne- 
tical. > 
A bar of fteel long hammered or expofed to violent 
fridion, while lying in the magnetic meridian, becomes 
magnetic. This faCt was well known to Dr. Gilbert, who 
in a plate reprefents a blackfmith hammering a bar of fteel 
in the magnetic pofition. Many fmiths’ tools, fuch as 
long drills, that receive great preffure while in motion, 
broaches that are worked with a long lever, fo as to ate 
very faft, become very fenfibly magnetical; the lower end, 
iu thefe latitudes, being always a north pole. When a 
fteel punch is driven hard into a piece of iron, the punch 
has fometimes been rendered magnetical by a (ingle blow. 
There is fcarcely a cutting or boring tool in a fmith’s (hop 
that does not poffefs fome degree of magnetic power. 
Even foft fteel and iron will acquire it by being violently 
twifted or expofed to great friction ; and the magnetifm 
thus acquired is commonly permanent. From this cir- 
cumltance it is difficult to procure for nice experiments 
pieces of iron that do not poffefs fome degree of magne¬ 
tifm; and hence thefe experiments do not always fucceed. 
The fteel balances of watches are often magnetic, fome¬ 
times even (flowing evident polarity; a circumftance which 
is found to have fome effect in difturbing the proper going 
of fuch watches or time-pieces. Hence it is recommended 
to make the balances of brafs. See the article Horology, 
vol. x. p. 315. 
Magnetifm may be induced on fubftances that are fuf- 
ceptible of it, by heat. Dr. Gilbert remarks that fuch 
ores of iron as are in that particular metallic (late, which 
he confiders as moll fufceptible of magnetifm, will acquire 
this power by being kept long in a red heat, while in at 
magnetic direction ; and that their polarity correfponds 
to their pofition, that end of the tnafs which is oppofite 
the north becoming a north pole. By many experiments 
made both by Dr. Gilbert, and fince his time by Dr. Hooke, 
on iron and (ieel bars, it appears that thefe acquire perma¬ 
nent magnetifm by being expofed to a ftrong heat, and 
fluttered to cool gradually while lying in the magnetic di¬ 
rection ; but that the magnetifm thus acquired by fteel 
rods is much ltronger and more durable, if they are fud- 
denly quenched with cold water, fo as to give them a very 
hard temper. Dr. Hooke found that the end of the bar 
next the north, or the lower end of a vertical bar, always 
became its permanent north pole, and the upper end, evert 
when quenched, while the reft was (uttered ro cool gra¬ 
dually, became a very fenfible fouth pole. If thefe ope¬ 
rations were performed on bars placed in a pofition at right 
angles to the magnetic direction, no magnetifm was ac¬ 
quired. Dr. Gilbert makes a remarkable obfervation re- 
(peifting the pofition of a magnetic needle brought near art 
ignited bar of iron, which was fome years ago repeated in 
the Philofophical TranlaCtions as a new dilcovery : “ Ba- 
cillum ferreum, valide ignitum appone verforio excilo : Jlat ver~ 
forium, nec ad tale ferrum convertitur : fed flatim ut primum de 
candore aliquantuLum raniferit, confluit illtco." Ttius it ap¬ 
pears that iron is not (ufceptibfe of magnetifm when red 
hot, hut that it acquires magnetic power during its .cool- 
ing. Dr. Gilbert afeertained the degree of heat molt ta- 
vourable to the production of magnetifm; but, from his 
want of proper thermometers, he did not fucceed. Dr, 
Robilon found that, though a bright red or a white heat 
does not make iron fufceptible of magnetifm while it is 
expoied to fuch a heat, it predifpofes it for becoming mag¬ 
netical. He found that, when a bar of lteel was made tt» 
acquire magnetifm by being tempered in the magnetic di¬ 
rection, the acquired magnetifm was much ftxonger when 
* the 
