VOL. XLIV.] PHILOSOPHICAL TRANSACTIONS. SQl 



between the first 2 mentioned bars, with its thin end close to the north pole of 

 one of them, and its thick end close to the south pole of the other. After it 

 had lain in this position a few moments, it was taken out, and on presenting it to 

 the magnetic needle of a smair compass-box, it was observed that its thinner end, 

 the same which had been just contiguous to the north pole of one of the bars, 

 attracted the north end of the needle , and that the thicker end, the same which 

 had been contiguous to the south pole of the other bar, attracted the south end 

 of the same needle. 



This same piece of stone was then again put in between the bars, but in a 

 contrary position ; the thicker end now lying next to the north pole of one of 

 the bars, and the thinner end next to the south pole of the other. After a few 

 moments it was again taken out, and presented as before to the compass-box : 

 when it was found that the thin end now attracted the south end of the mag- 

 netic needle, and that the thicker end attracted the north end of the same. 



The piece of stone was then again placed between the bars as at the first, and 

 being again taken out and presented to the compass-box ; the thin end was again 

 found as at the first to draw the north end, and the thick end to draw the south 

 end of the needle. 



This same piece of magnet was then again placed between the bars, but in a 

 position at right angles to both the former, one of its sides being now contigu- 

 ous to the north pole of one of the bars, and its other side to the south pole of 

 the other. After which being again in a few moments taken out, and presented 

 to the compass-box as before ; it was found that the side which had been in con- 

 tact with the north pole of one of the bars, attracted the north end of the 

 needle, and that the other side which had been in contact with the south pole of 

 the other bar, attracted the south end of the same needle : while the two ends, 

 of the stone in which the polarity was before observed, were now found to be in- 

 different to either end of the needle ; so that the line of direction of the poles in 

 the stone now lay at right angles to the position in which it was situated in the 

 former experiments. 



Mr. Knight then produced two steel needles, of the same sort as those which 

 are usually fixed to the cards of sea-compasses. These needles were of the length 

 of S-i^j- inches, and weighed severally with their caps 7 dwt. 8 gr., and 7 dwt. 

 9 gr. ; one of these was tempered and of a blue colour, and the other was quite 

 hard. He also produced two iron weights, severally weighing 14 dwt. 22 gr., 

 and 15 dwt. 7 gr., both nearly of a cylindrical form, but with one of the ends 

 rounded off. 



The 1 large bars were then placed in a line, as in the former experiments, 

 but with their ends so near together, as only to admit of the cap of one of the 

 needles between them. 



