for a Compass-Needle. 369 
I next proceeded to try, in a more regular manner, the effect of 
different methods of magnetising, and at the same time to ascer- 
tain whether the directive force was influenced by extent of sur- 
face, independent of mass. Two needles were made of the same 
kind of steel, in the form of right angled parallelograms, five 
inches long, the one 0°7 inch wide, and the other half this width. 
The widest was reduced in thickness until it was of the same 
weight as the other, viz. 142 grains. They were in the same 
state of softness as was necessary to work them. The magnets 
were placed together perpendicularly on the centre of the needle, 
their opposite poles being joined; their lower extremities were 
then separated and kept asunder, by placing a piece of wood,-a 
quarter of an inch thick, between them, their upper extremities 
remaining in contact. The magnets were then slid along the 
needle, backwards and forwards, from end to end: this was re- 
peated on both sides, till it was conceived the needle must be sa- 
turated. ee 
Experiment 24. Directive force. 
Small parallelogram ..  .. 2 655 
Large parallelogram .. .. «. 674 
The needles were again magnetised in the same manner as he- 
fore, excepting that the magnets were sepirated at the top by a 
piece of wood of the same thickness as that at the bottom, 
Experiment 25. Directive force. 
Small parallelogram .. «2. «2 595 
Large parallelogram .. .. 4. 580 
The magnets were placed perpendicularly together on the 
centre of the needle, and then their lower extremities separated 
by a piece of wood, to the distance of half the length of the 
needle, the upper extremities remaining in contact. They were 
then slid on the needle backwards and forwards, from end to 
end, as before. 
Experiment 26. Directive force. 
Small parallelogram ..  .. «2. 760 
Large parallelogram .. «.. «2 780 
The magnets joined, placed perpendicularly on the centre of 
the needle, as before, then moved in opposite directions from the 
centre to the extremities, keeping each magnet perpendicular to 
the needle; afterwards joined at a distance from the seedle, 
placed again on its centre, and the operation thus continued, 
Experiment 27. Directive force. 
Small parallelogram... ..  .. 998 
Large parallelogram ,, bod 4 hlbd 
Remarking that the surface of the small parallelogiam was 
Vol. 59, No. 289, May 1822, 3A unequal, 
