Natural-Philosophical Collections. 153 
tonishing that many philosophers doubted the results of the Italian professor ; 
and it was not till 1826, that Mrs. Somerville confirmed, by the most decisive ex- 
periments, * the fact advanced by him, that the violet ray was endowed with a 
magnetising property. Nevertheless experimentalists were not yet satisfied : they 
could neither verify at will the results obtained, nor discover the causes which 
_opposed the success of their labours. ‘This state of things induced M. F. Zan- 
tedeschi, professor at Pavia, to undertake a series of experiments upon this sub- 
ject, in the same town where, in 1813, Professor Configliacchi had already made 
reniarkable observations. 
The method pursued by M. ete de etn was as follows :—He introduced into 
a dark room a solar ray by means of a heliostat, and dispersed it so that the spec- 
trum was formed horizontally. He then placed under the violet ray, in a direc- 
tion perpendicular to that of the magnetic meridian, the extremity only of the 
needles which he desired to magnetise. In this manner he obtained the follow- 
ing results :— 
1. Haying placed, in the position described, a steel wire, well polished, four 
inches long, and a quarter of a line in diameter, in five minutes he found that 
the extremity exposed to the violet ray had acquired a north pole. In eight mi- 
nutes, this wire being presented to a magnetic needle, showed well marked poles. 
2. He exposed, in the same manner, two wires of steel, similar to the pre- 
ceding, to the action of white light; in five minutes, the two extremities exposed 
had acquired a north pole; but it was feeble, and at the end of a few minutes it 
disappeared. 
In both these cases he ascertained, with much care, that the wires employed 
did not previously possess any. sensible magnetism. 
3. The violent ray reversed the well-marked poles of a wire of steel; it deve- 
loped very distinctly, in six or seven minutes, those of another wire, which 
manifested at its two extremities a very feeble repulsion for the pole of a magnet. 
4, Having placed one extremity of a magnetic needle in the red, yellow, 
orange, and green rays, and having observed the nature of its poles, and their 
energy at the end of six or seven minutes, he did not find any alteration what- 
ever; nor did he remark any effect produced by this operation upon a needle 
which had no sensible magnetism. 
5. A wire of iron covered with a film of oxide, and strongly magnetised, 
having been exposed to the violet ray, in three minutes the south pole was 
transformed to a north pole. 
6. A steel wire, well polished and magnetised, having been exposed by 
its two extremities to the violet ray, in ten minutes a north pole was formed at 
each of its extremities. 
7. Ifthe wire be oxidated, the same effect is produced in five minutes. 
The dimensions of all the wires employed were the same as those first men- 
tioned. : 
These experiments, which gave the same results in every repetition, place be- 
yond doubt the magnetising property of the violet ray. 
The causes which have prevented previous observers from arriving at the same 
facts are traced by M. Zantedeschi, to be owing to the metal coming from a 
sulphurous mine, and consequently being incapable of receiving the magnetic in- 
fluence ;—to its being too highly tempered ;—to the temperature- being too high 
or too low ;—to the diameter of the needle being too great ;—or to the violet ray 
not being made to impinge on the extremity of the needle. 
He considers that the action of the violet ray is chemical ; and he is convinced 
that, if the above causes of imperfection are attended to, its magnetising power 
may be brought into action independently of climate. The magnetism thus ob- 
tained is permanent, as he has ascertained by the examination of his wires eight 
months after the experiments, when he found them still magnetic.—Bib. Univ. 
May, 1829, p. 64. 
* Ann. de Chimie, xxxi. 393. 
VOL. I. U 
