for a Compass- Needle. 367 
Experiment 15. 
Magnets inclined in an angle of two or Directive 
three degrees. force. 
Parallelogram AS Pesce tage 
Rhombus BS SOEE ihe AYP aba ke dt oh), oa A 
Pierced rhombus 2. «2 =. o ee 1150 5 
This method appears to be preferable to any I have yet tried, 
and was therefore employed in the subsequent experiments of 
the present series. ‘The rhombus of 63 grains, which in Ex- 
periment 10 was left with a directive force of 577, on being 
magnetised in this manner had its power increased to 600. 
The ends of the needles were now hardened at a red-heat, the 
middle remaining soft, as before. 
Experiment 16. 
Needles hardened at the ends at a red-heat. Directive force. 
Parallelogram we e,es ven, eneDrte tele 
Rhombus fo Citas ik anges: vor, UU 
Pierced rhombus «. .. ‘s., e+ ‘%. 1185 
Experiment \7. 
Ends hardened at a bright red. Directive force. 
Parallelogram pinta es ree OPEL al ES 
Rhombds) awe Jecaisge 970 
Pierced rhombus ., «1 «+ «- «2 1085 
The ends hardened at a red-heat as near to that employed in 
Experiment 16, as possible. 
Experiment 18. 
Ends hardened at a red-heat. Directive force. 
Parallelogram aeiin ale Mek Lee, vant pede 
Rhombus ce. Spies hae chces mavien LL ae 
Prarred BROWNING. « va706 oc0.ck aide oe 82 afte 
Here it should seem that an increase of power has been ob- 
- “tained by the ends of the needles having been first hardened at 
a higher temperature, and then at a lower. 
The needles were now hardened throughout at a bright-red 
heat. ck 
Experiment 19. 
Hardened throughout at a bright red, Directive force. 
Parallelogram ; AR LIN FER D EY 
Rhombus path Cate ian >. [0e os Sarasa 
Pierced rhombus. .. «- «- ++ + 1080 
The needles softened by laying them on a red-hot poker till 
they passed beyond the blue to a greyish white. This was car- 
ried to within an inch of their extremities, which remained hard. 
Experi- 
