120 MAGN 
pars through the centre of the magnet in a direftioti per 
pendicular to its axis, To as to form the magnetic equator, 
a (lender piece of iron held any-where within this plane 
can acquire no fenfible magnetifm, which is demonllrated 
by its (bowing no (igns of polarity, and not being attracted 
by the magnet. Now it is well known that the greateft 
aftivjty of a magnet refides in its two poles, and that thofe 
magnets are the'beft in which this activity is Ieait diffufed. 
A certain circumference of every magnet is entirely in¬ 
active, as we lee in the experiment with the iron-filings 
defcribed at p. 112, 13. where the filings collect t'hemfel ves 
principally on two points of the furface, between which 
there is a (pace all round, to which no filings are attached. 
Many circumftances (how that the two poles of a magnet 
have contrary actions; the north pole producing a (trong 
northern polarity in the remote end of an iron bar brought 
near it, and a fouth polarity in the proximate end, while 
an oppofite effeft is produced by its fouth pole. Now, 
adopting this principle, that the aftions of the two poles 
are oppofite, it follows that if thefe actions are equal, and 
aft in a fimilar manner, each mult counteract and prevent 
the aCtion of the other, and produce what may be called 
a magnetic equilibrium. If, therefore, a (lender iron rod 
or thin plate be placed (o that every part of it lies 
within the magnetic equator, it will exhibit no magnetifm, 
will not be attracted by the magnet, and will not attraft 
iron. 
Magnetifm may be produced artificially, in a piece of 
iron or (feel, by various methods. 
1. Provide a magnet, either armed or unarmed, and 
make one of the feet of the armour, or one of the poles, 
to pafs over a plate of tempered Heel, fuch as the blade 
of a knife, but proceeding always in the fame direction, 
from the middle, for example, towards the point. After 
performing this operation a certain number of times, the 
plate of iron will be found to be magnetifed, and, like 
the magnet itfelf, it will attraft iron, if placed within the 
fphere of its attraction. 
2. The cafe will be the fame, if a long (lender bit of 
<teel be left a long time attached to a magnet : the fteel, 
by remaining in that fituation, will acquire the magnetic 
property ; it will have poles like the magnet, fo that the 
north pole will be at the end which was near the fouth 
pole of the (tone, and the end which touched the north 
pole will become the fouth pole. 
3. Provide twelve bars of tempered (feel, about fix inches 
in length, fix lines in breadth, and two in thicknefs. Care 
mull be taken, before they are tempered, to make a mark 
with a punch, or in any other manner, at one of their 
extremities. Arrange fix of thefe bars in a (traight line, 
but fo as to be in contaft, and that the marked ends (hall 
be direfted towards the north ; take an armed magnet, 
and place it on one of thefe bars, with its north pole to¬ 
wards • the marked end, and the fouth pole towards the 
other end ; then move the (tone over the whole line, be¬ 
ginning at the unmarked end of the firft, and repeat this 
operation three or four times. When this is done, re¬ 
move the two bars in the middle, and fubflitnte them for 
thofe at the two extremities, which mud be placed in the 
middle; then move the Itone in the fame direftion over 
the four bars in the middle only; for it is needlefs to 
comprehend thofe at the extremities ; and invert the 
whole line, that is to fay, turn up the face which was 
turned downwards, and magnetife the bars again in the 
fame manner, taking care to tranfpofe the bars at the ex¬ 
tremities into the place of the middle ones. 
By thefe means, you will have fix magnetifed bars, 
which mull be formed into two parcels, each containing 
three. In thefe parcels, the northern extremities mult 
be towards the fame fide ; but, when the one parcel is 
placed upon the other, care mull betaken that the north¬ 
ern extremities of the bars of the one may reft upon the 
fouth extremities of thofe of the other. Thefe two par¬ 
cels muft touch at their upper part, and be feparated on 
the other fide : this feparation may be effefted by means 
ETIS M. 
of a bit of wood placed between them. Then place the 
fix bars which were not touched in the fame manner aa 
the preceding fix, and magnetife them as above defcribed, 
by means of the double parcel of the former ; that is to 
fay, by drawing the two extremities north and Couth of 
this double parcel over the new feries of bars: you will 
thus have fix bars much-more ftrongly magnetifed than 
the former. Then make a line of the fix former, and 
magnetife them in the fame manner with the double par¬ 
cel formed of the fecond, according to the fame method, 
and you will obtain bars of fteel capable of fupporting 16 
times their weight, and more. This is the procefs of 
Mr. Michell, of the Royal Society. Mr. Canton has 
given a method of effefting the fame thing; and M. Du- 
hamel, of the Academy of Sciences at Paris, another, 
which may be feen in a fmall treatife on Artificial Mag¬ 
nets, printed in 1775. By thefe precedes, the weakeft 
commencement of magnetifm is (ufficient to produce 
magnetic bars of the greateft force. 
4. To propofe communicating the magnetic virtue with¬ 
out the ufe of the magnet is, no doubt, a fort of paradox. 
This however has been effefted in conl'equence of fonie 
theoretic confiderations in regard to the nature of the 
magnet, and the manner in which the magnetic fluid afts 
on iron. A magnet therefore is not necelfary to produce 
tile commencement of magnetifm, which may be after¬ 
wards increafed to a confiderable degree by the procefs 
before explained. Canton, Michell, and Antheaume, 
have given different methods for tnagnetifing without a 
magnet. Mr. Canton was able, in about half an hour’s 
time, to communicate to fix bars of hardened iteel, at firft 
entirely deftitnte of any magnetic virtue, the utrnoft vir¬ 
tue they were capable of receiving; and that without the 
mediation or affiftance of any natural loadftone, or of any 
artificial magnet. Mr. Canton has publifhed the defcrip* 
tion of his procefs, with fuch direftions that any perfon 
may readily perform the fame. For this purpofe procure 
a dozen bars; fix of foft fteel, each three inches long, 3 
quarter of an inch broad, and ^j-th of an inch thick, with 
two pieces of iron, each halt the length of one of the- 
bars, but of the fame breadth and thicknefs ; and fix of 
hard fteel, each 5-J- inches long, half an inch broad, 
and -jSgths of an inch thick, with two pieces of iron of 
half tlie length, but the whole breadth and thicknefs of 
one of the hard bars ; and let all the bars be marked with 
a line quite round them at one end. Then take two bars 
of iron, or an iron poker and tongs, fig. 15. the larger 
they are, and the longer they have been ufed, the betterj 
and, fixing the poker upright between the knees, hold ro 
it near the top one of the loft bars, having its marked end 
downward, by a piece of fewing filk, which muft be pulled 
tight with the left hand, that the bar may not Aide; then 
grafping the tongs with the right hand a little below the 
middle, and laying them nearly in a vertical polition, let 
the bar be Hroked by the lower end, from the bottom to 
the top, about ten times on each fide, which will give it a 
magnetic power fufficient to lift a fmall key at the marked 
end; which end, if the bar was fufpended on a point, would 
turn towards the north, and is, therefore, called the north 
pole ; and the unmarked end is, for the fame reafon, called 
the fouth pole of the bar. Four of the foft bars being 
impregnated after this manner, lay the other two, fig. 16, 
parallel to each other, at the diftance of about one-fourth 
of an inch between the two pieces of iron belonging to 
them, with a north and a fouth pole againft each piece of 
iron; then take two of the four bars already made mag- 
netical, and place them together, fo as to make a double 
bar in thicknefs, the north pole of one being even with the 
fouth pole of the other; and, the remaining two being pm 
to thefe, one on each fide, fo as to have two north and 
two fouth poles together, leparate the north from the fouth 
poles at one end by a large pin, and place them perpen¬ 
dicularly with that end downward, on the middle of one 
of the parallel bars, the two north poles towards its fouth, 
and the two fout)i pole* towards its north end; Aide them 
■' backward 
