6. On peculiar Physical Repulsions, by M. Saigey.
i. All bodies exert between themselves a feeble repulsive action in ordinary circumstances. The repulsion between bismuth and [p456] antimony and the poles of a magnetic needle, is a case of this general law, and is not due to magnetism. Nor is it magnetism which occasions the direction of needles formed of other substances than iron, announced lately by M. Becquerel.
ii. A very marked attraction may be observed between a cold and a heated body, or between two bodies of different temperature, whether screens be interposed or not.
iii. The metallic plates in the Cabinet de Physique de Paris, intended for the repetition of M. Arago’s experiments on magnetism by rotation, contain more or less of iron capable of attracting a very mobile magnetic needle. These plates, and those of M. Arago, were made by the same person and from the same materials.
iv. I believe that, in many cases, results obtained without the appreciable developement of magnetism or electricity, have been attributed to these powers; and from well-proved experiments I shall deduce new results relative to the diurnal variation of the needle, the direction of the plumb-line and the density, temperature and attraction of the planetary masses.—Bull. Univ. A. viii. 287.
7. On the Magnetic Effects of Metals in Motion.
| 116 | oscil- lations above a | plate of | marble | ||
| 112 | layer of | mercury | 2 | lines in thickness. | |
| 106 | plate of | bismuth | 2 | ||
| 94 | platina | 0.4 | |||
| 90 | antimony | 2.0 | |||
| 89 | lead | 0.75 | |||
| 89 | gold | 0.2 | |||
| 71 | zinc | 0.5 | |||
| 68 | tin | 1.0 | |||
| 62 | brass | 2.0 | |||
| 62 | copper | 0.3 | |||
| 55 | silver | 0.3 | |||
| 6 | iron | 0.4 |
It is also stated that he has found, from experiments, that by alloying such metals as are magnetic, like iron, nickel, and cobalt, with other metals, which like antimony diminish the magnetic force, alloys are obtained entirely neutral in their effects; thus the alloys formed by four of antimony with one of iron, three of copper with one of antimony, and two of copper with one of nickel, produce no diminution of the number of oscillations, these amounting to 116 as with the plate of marble. These three alloys are, therefore, the best for the manufacture of compasses, those of copper and nickel being the most malleable.—Annal. des Phy. 1826. Bull. Univ. A. viii. 136. [p457]
8. Duration of the Effects of Light upon the Eye.
| Flame | 0″.242 |
| Ignited Charcoal | 0″.229 |
| White | 0″.182 |
| Blue | 0″.186 |
| Yellow | 0″.173 |
| Red | 0″.184 |