-.823*] Dr, Traill on some Thermomapietic Experiments, 451 



south end was heated, the effects were reversed. When the 

 apparatus was laid horizontally with the antimony on the mag- 

 netic meridian, and the lamp apphed to the N end, the compass 

 placed on the upper surface of the antimony deviated to the W ; 

 and when placed on the copper of the opposite limb to the E ; 

 whether the copper was to the W or the E of the antimony. 

 Heating the S end reversed the effects. 



From the care with which my friend Prof. Oersted appears to 

 have placed one side of his compound apparatus in the magnetic 

 meridian, and the notice of this arrangement by other philoso- 

 phers, I was led to beheve that it was essential to the success 

 of these experiments that one of the bars should be in that line ; 

 and my first experiments, with a smaller apparatus, induced me 

 to beheve that there is no deviation of the needle when the appa- 

 ratus is placed at right angles to the meridian ; but on repolish- 

 ing the surfaces of the metals, where in contact, and applying 

 the spirit lamp for a longer time, I found that idea to be erro- 

 neous. The apparatus acts most powerfully when placed at right 

 angles to the magnetic meridian. 



When so placed, and the copper connecting wire uppermost, 

 I applied the lamp to the W end of the apparatus ; and tliough 

 the needle within the rectangle appeared quite stationary, for 

 considerably longer than in the former experiments, it soon 

 began to deviate, and at length had its poles inverted ; making 

 short oscillations, showing a strong magnetic intensity. 



When the lamp was applied to the E end of the apparatus, 

 the needle within the rectangle did not move ; but when dis- 

 turbed, it made short oscillations, indicating that it was acted 

 on by magnetism independently of the influence of the earth. 



On inverting the apparatus, so as to have the antimony upper- 

 most, and continuing the heat to the E end, the needle placed in 

 the rectangle had its poles speedily inverted ; and it was after- 

 wards found, that when the apparatus remained in this inverted 

 position, and the lamp was applied to the W end, no deviation 

 was produced, though the needle vibrated more quickly than 

 usual. 



That the apparatus was most powerful, when at right angles 

 to the magnetic meridian, was well shown by another form of 

 the apparatus. 



I 



B 



A B C is a bar of antimony, with a right angle at B. To its 

 extremities was soldered a slip of copper, a h c, as in the figure, 

 forming a parallelogram. When A B was in the magnetic meri- 



2g2 



