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POPULAR SCIENCE REVIEW. 
nitrogen present in it as on tlie quantity of carbonaceous substances which 
possess the power of taking up nitrogen from the atmosphere. 
Trichomanes radicans in Kentucky. — The discovery of the Killarney Fern 
n Kentucky, U.S.A., is of interest, because it was not known before to 
have so northerly a range. It is now known to extend to latitude 38°. 
CHEMISTRY. 
Black Powder found in Snow ; what is it f — In a letter from M. Nor- 
denskjold on Carbonaceous Dust, with Metallic Iron, observed in Snow 
(dated from Mossel Bay, lat. 79° 53' N., received at Tromsoe July 24), the 
writer remarks that in December 1871 he found in some snow collected 
towards the end of a five or six days’ continuous fall in Stockholm a large 
quantity of dark powder like soot, and consisting of an organic substance rich 
in carbon. It was like the meteoric dust which fell with meteorites at Hessle 
near Upsal in January 1869. It contained also small particles of metallic 
iron. Suspecting the railways and houses of Stockholm might have furnished 
these matters, he got his brother, who lived in a desert district in Finland, 
to make similar experiments ; which he did, and obtained a similar powder. 
In his Arctic voyage the writer has met with like phenomena. The snow 
from floating ice has furnished on fusion a greyish residue, consisting mostly 
of diatoms (whole or injured) ; but the black specks, a quarter of a milli- 
metre in size, contained metallic iron covered with oxide of iron, and pro- 
bably also carbon. He thinks, therefore, that snow and rain convey cosmic 
dust to the earth, and invites further observation on the subject. M. 
Daubree, in presenting the letter, recalled a case of meteoric dust having 
fallen at Orgueil in 1864. He expressed the hope that M. Nordenskjold has 
obtained sufficient quantities of pulverulent matter to be able to determine 
a characteristic fact — the presence or absence of nickel. 
The Freezing of Alcoholic Liquids. — M. Melsens has made some experi- 
ments (“Naturforscher,” 1873, No. 39) on the effect of low temperatures 
on brandy and wine, and his results accord completely with those of 
Horrath, who noticed an unexpectedly slight degree of sensation of cold 
in alcohol which had been exposed to a low temperature. Melsens finds 
that when brandy is cooled to 20° and even 30° or 35° below zero, it can be 
swallowed without any discomfort, provided only it be taken from wooden 
vessels. At 30° it is viscid and opalescent, and contains about 50 per cent, 
of alcohol. At —40° or —50° the strong alcoholic liquid becomes a solid, 
and if placed in the mouth in this state the pasty mass as it melts on the 
tongue appears less cold than ordinary ice. It has to be cooled to — 60° to 
produce any impression of cold, and then is but rarely accounted very cold. 
The coldest portion prepared by Melsens had a temperature of — 71°, and 
this produced in the mouth a sensation resembling that experienced on taking 
a spoonful of hot soup. He also describes the effect of great cold on effer- 
vescing wines. 
Mr. Wanklyn and Dr. Redwood on Alum in Bread. — An important discus- 
sion on this point has been carried on in a paper called the “ Circle ” between 
