1819.] Scientific Intelligence. 71 
separates with the new scorie, and there remains an alloy of 
platinum and lead. This alloy is heated to whiteness, and 
while in this state, hammered upon an anvil with a hot hammer. 
The lead is squeezed out, and the platinum remains. 
Platinum obtained in this way is as malleable and ductile as 
the finest platinum. Its specific gravity is said to be 22-630. 
+ so, it must be alloyed with lead ; for pure platinum is not so 
eavy. 
VII. Reumic Acid. 
Some years ago a paper by Mr. Henderson, on the acid of 
rhubarb, was inserted in the Annals of Philosophy. The result 
of his experiments led him to consider it as a peculiar acid, 
which he distinguished by the name of reumic acid. The only 
characteristic property, however, by which he was able to distin- 
guish it, was that of dissolving mercury. 
A set of experiments on the juice of the rheum ponticum has 
been lately made by M. Lassaigne, with a view of verifying the 
results obtained by Mr. Henderson. The juice of this plant is 
abundant, and very acid ; but the acid possesses all the charac- 
ters of the oxalic, and has no action whatever upon metallic 
mercury. The rewmic acid, of course, does not exist as a pecu- 
har acid.—(See Ann. de Chim. et Phys. vi. 402.) 
VIII. Perchloric Acid. 
Sir Humphry Davy has verified the curious discovery made 
some years ago by Count von Stadion, of a combination of 
chlorine and oxygen, containing more oxygen than chloric acid, 
and which, therefore, may be distinguished by the name of per- 
chloric acid. A particular account of the experiments of Count 
von Stadion will be found in the Annals of Philosophy, ix. 22. 
I have likewise given an account of this curious acid in the last 
edition of my System of Chemistry. 
IX. Aurora Borealis at Sunderland. By Mr. Renney. 
(To Dr. Thomson.) 
SIR, Bishopwearmouth, Nov. 4, 1818. — 
On Saturday night, the 31st ult. between seven and eight 
o’clock in the evening, was observed, at Sunderland, that beau- 
tiful phenomenon the aurora borealis, in a more singular form 
than I have at any time before seen it. Due north appeared a 
very dark dense cloud, nearly in the form of a segment of a | 
circle ; the altitude about 15°, from behind which issued upwards 
equally fine radii, about 20° in length, and gave light equal to 
the twilight in summer, casting a sensible shadow against a wall, 
facing the north, and had a very fine appearance. The remainder 
of the hemisphere was perfectly clear. About 11, the cloud had 
the same appearance, but the radii very much altered; in some 
