448

SCIENTIFIC RESEARCHES,

(TWENTY-FOURTH MEMOIR.)

29. Explanation of the preceding phenomena upon the supposition of a motion of the

poles of the Magnet , by the Agency of Calorific Matter, as demonstrated by Experi-ments 23, 24, and 25.

It has been shown by Experiments 23, 24, and 25, that the poles of the magnetmove from the point of heat; and by applying these polar motions to all the experi-ments represented by Fgs. 1, 2, 3, and 4, we shall find that the deflections of theneedle would be such as are there represented. If, for instance, the magnet be so ad-justed in any of those figures as to permit the needle to rest in the meridian prior tohe application of heat, then a slight motion of the magnet northward in Figs. 1 and3, or southward in Figs. 2 and 4, will cause deflections such as are represented bythe dotted needles in these figures respectively. Now, instead of moving the magnetsto produce the deflections, let the lamp be applied, as shown in the figures; and themotions of the poles by the agency of heat correspond in direction with the motions ofthe magnet, and the deflections by one of these means correspond with those accom-plished by the other.

30. With respect to the phenomenon exhibited by Experiment 23, Fig. 5, when thelamp is applied to the unmarked pole of the magnet, as both poles recede from thecompass needle, their power on it necessarily abates, and the earth’s Magnetism pullsthe needle from its east and west position. But when the lamp is applied to the markedor remote pole of the magnet (Experiment 24), both poles would advance towards theneedle. Still, however, the experiment shows that the power of the magnet on theneedle has abated, which seems contrary to what one would have expected. Thephenomenon might be explained, however, by supposing that the heated pole advancedtowards the needle in a greater ratio than the cool pole, by which means it wouldpartly neutralize the effect of the latter on the needle ; or by supposing that the totalpower of the magnet was abated by the heating process ; or, which is the most proba-ble of all, by both these changes taking place in the magnet by the agency of caloric.

31. It appears upon the whole that the polar motions in the magnet are the firstgrand productions by the agency of caloric ; and that, independently of any absolutechange in the intensity, the whole of the phenomena which I have described may betraceable to these polar motions ; and, perhaps, there may be many other magneticphenomena, both natural and artificial,* which are attributable to the same secondarycause, which is itself an effect of the primitive action of caloric. But as the sun’sheat is constantly exerted between the magnetic poles of the earth, and not exterior to

* Mr. Barlow’s interesting experiments on the magnetic action of heated iron, occasionally gave very extraordinary resultswhich that gentleman could not easily account for. Barlow's Magnetic Attractions, second edition, page 142 to 149.

Mr* Christie also met with some curious anomalies in his valuable experiments on this subject. Philosophical Transactionsfor 1823, 1825, 1826. But whether the facts which I have discovered are calculated to throw any new light on the anomalieswhich attended these gentlemen’s experiments, I am not prepared to say.