C 35 ] 
£aeh five inches and an half long, half an inch broad, 
and three-twentieths of an inch thick, with two pieces 
of iron of half the length, but the whole breadth and 
thicknels of one of the hard bars : and let all the 
bars be marked with a line quite round them at one 
end. 
Then take an iron poker and tongs * (Tab. II. 
Fig. i.) the larger they are, and the longer they have 
been ufed, the better ; and fixing the poker upright 
between the knees, hold to it near the top one of 
the foft 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 Hide : then 
grafping the tongs with the right hand a little be- 
low the middle, and holding them nearly in a verti- 
cal pofition, let the bar be flroked by the lower 
end, from the bottom to the top, about ten times 
on each fide, which will give it a magnetic powar 
fufficient to lift a fmall key at the marked end : which 
end, if the bar was fufpended on a point, would turn 
toward 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. 2.) parallel to each 
other, at the diftance of about one-fourth of an inch, 
between the two pieces of iron belonging to them, 
a north and a fouth pole againfi: each piece of iron : 
then take two of the four bars already made mag- 
netical, and place them together, fo as to make a 
E 2 double 
* Or two bars of iron. 
