(B) Keeping the part, C, in contact with the N pole of H M, and using the N pole of H M as a pivot, turn the needle end for end so that its head will be in contact with the S pole of H M.

(C) Pull the needle straight from H M, being careful not to slide it in either direction.

(D) Test the polarity of the ends with O C ([Fig. 5]), and save it for the next experiment.

Fig. 7.

Fig. 8.

EXPERIMENT 16. To study the bar magnet with two N poles.

Apparatus. The strange magnet just made ([Exp. 15]); iron filings; compass, O C (No. 18).

38. Directions. (A) Sprinkle filings over the whole length of the needle and then raise it ([Fig. 8]).