366 On the best Kind of Steel and Form 
less force, and that the magnetism of the needle would suffer a 
diminution. 
The method I had employed in magnetising the needles, was 
that of Du Hamel, by joining the opposite poles of the magnets, 
and placing them on the centre of the needle, so inclined that 
each formed an angle, as I afterwards ascertained, of about 30 
degrees with the horizon. ‘The magnets were then slid from 
the centre to the extremities of the needle, and their poles being 
again joined at a distance from the needle, the operation was 
repeated. 
As I could in no way account for the diminution of directive 
force which I have remarked, except by supposing that I had 
inadvertently changed the inclination at which the magnets were 
held, I resolved to try whether a variation of this angle produced 
any considerable difference in the degree of magnetism commu- 
nicated. For this purpose I re-magnetised the needles, by lay- 
ing the magnets, with their opposite poles joined, flat upon the 
needle, the junction of the magnets being upon the centre. They 
were then separated and drawn to the extremities of the needle, 
the surface of the needle and that of the magnets being in con- 
tact the whole time. The poles were then joined and the ope- 
ration repeated, using but little pressure. 
Experiment 13. 
Magnets moved flat upon the needle with Directive 
~ little pressure. ; force. 
Parallelogram A cael aceite rer ype 
Rhombus SE A vee, Yaris cian eae 
Piercedwhoumbos oe ee 
This manner of magnetising, therefore, ‘Appears much supe- 
rior to that before employed. 
The needles were again magnetised in the same manner as in 
the last experiment, except that the ends of the magnets were 
pressed pretty strongly against the needle. 
Experiment 14. 
Magnets moved as before, but with Directive 
strong pressure. force. 
Parallelogram Wiph Piape aig 0) te) Le sean 
Rhombus Sedo itets je tele, "aan ite ee 
Piercedthombus .. .. «.. oe «- IIdl ] 
No advantage appears to have resulted from the increased 
pressure, but the arrow-shaped needle has suffered a diminution 
of power. 
The magnets were now slid from the middle to the extremities 
of the needle at an inclination of only two or three degrees, and 
the following were the results : 
Experi- 
