“308 Natural-Philosophical Collections. 
-a plaster-stone naturally softer. It is in some degree the primitive molecular 
arrangement which is reproduced. We find, in the same way, that when good 
fused steel has its carbon removed by cementation with oxide of iron, it will give, 
by a new cementation with carbon, a steel much more homogeneous and perfect 
than that obtained in the same circumstances by the cementation of iron.—dn- 
niles de Chimie, xl. p. 436. 
Electricity of the Solar Rays.—(Letter.from Sig. Carlo Mattrucci of Forli, to 
Professor Gazzeri.) ‘‘ I hasten, Sir, to communicate to you some experiments 
which appear to me to deserve the attention of philosophers. Having been for a 
long time persuaded of the existence of electricity in the solar rays, I wished to 
ascertain the fact by experiment. Having for this purpose exposed to the sun’a 
delicate condensing electrometer of gold leaf, I soon perceived the leaves diverge 
and open themselves also on that side of the glass case which was directly expos- 
ed to the solar action, as if they had been attracted by it. Being induced from 
this first fact to suspect glass in this situation electrified, I was anxious to know 
if this were the case: wherefore, having left some plates of it in the sun, in a few 
moments I touched them in different places with the ball of the electrometer, 
when a very perceptible divergence ensued, which, however, was much more ap- 
parent when I touched the plates, although lightly, with a flat surface, since the 
effects of the friction and the pressure did not afiord a doubtful result. I con- 
cluded, then, that the solar rays had the power of electrifying glass, and it only 
remained for me to ascertain if this effect were owing to the real existence of elec- 
tricity in these rays, or rather to the increased temperature of the glass, which I 
could easily determine by heating a plate of glass, and trying it with the elec- 
trometer. This I did several times, but never discovered any signs of electricity. 
1 observed, also, that the glass plate exposed to the rays of the sun never became 
electric if placed beneath another glass plate, or if the face of the sun was obscur- 
ed by the intervention of a cloud. These few experiments, which I have been in- 
duced to perform, seem to me sufficient to prove electricity in the solar rays. The 
influence of such a fact on the meteorological phenomena of terrestrial magnetism, 
and on so many other phenomena of nature, will, I hope, induce yourself and 
other philosophers to pursne the subject further.” — Antologia, No. 100, (Brande’s 
Journal.) 
Crystallization of Sulphated Iron, by A. H. Van der Boon Mesch of Ley- 
den.—These crystals, which are found in the mine of Gieshiibel de Silberberg, in 
Bavaria, surpass in size, transparency, and regularity, all that it is possible to ob- 
tain by art, although M. Brongniart says, that they are rarely, if at all, found in 
nature; they are grouped round quartz flints of different sizes. Some crystals 
have the forms of oblique rhomboidal prisms, others of the Fer sulfaté basé, of 
Hauy. In general, the edges are not very angular, and the faces regular and 
united ; their specific gravity is 2.037. They are of a clear green colour, soluble 
in cold water, and their solution is blackened by gallic acid. When they are’ex- 
posed to the open air, the crystals alter ; they become brown, and decompose into 
a powder of different colours, so that this mineral must be preserved with care. 
The first change it undergoes is to pass into the state of sulphate of iron, which 
perhaps has, given rise to the opinion that this salt did not exist innature. 
When this salt is heated in a retort, sulphurous acid is disengaged, which may be 
detected by Brazil wood paper; and when it is exposed to a white flame, it be- 
comes black and magnetic. It is soluble in phosphate of ammonia, which 
transforms it into a glass sometimes red, sometimes yellow, which passes, after 
cooling, into a dull green. Melted again in this state with salt of phosphorus, it 
becomes of a very pure green. The same phenomena takes place with borax. 
The analysis which Berzelius, Bergmann, and Mitscherlich have made of this 
substance, gives 23.27 parts of oxide of iron, 28.39 parts of sulphuric acid, 38.45 
parts of water. The formation of this mineral is-attributed to the natural decom- 
ares of sulphuret of iron in calcareous stone.—Bydrag. tot. de Nat. Wet, 
N. iv. p. 2, 
