General Science. 
m 
under Captain Ross to the Arctic Regions), on the S4th of May 
1818, in north lat. 57° 52', and west long. 44° 36', was picked 
up on the Island of Bartragh, in the Bay of Killala, on the coast 
of Ireland, on the 17th of March 1819, having floated across 
the Atlantic at the rate of about four miles a day, by the in- 
fluence, no doubt, of one of the deflected branches of the Gulf 
Stream.— See Qiiarterly Review, N° xli. p. 255. 
37. Atmospherical or Meteoric Dw^^.—^Professor Rafinesque 
of New York, in a paper on atmospheric dust, maintains, that 
an imperceptible dust falls at all times from the atmosphere, 
and that he has seen it on Mount JEtna, on the Alps, on the 
Alleghany and Catskill Mountains in America, and also on the 
Ocean. This is the same dust which accumulates in our apart- 
ments, and renders itself peculiarly visible in the beams of the 
sun. He has found it to accumulate at the rate of from one- 
fourth of an inch to one inch in a year, but in such a fleecy 
state, that it could be compressed to one-third of its height. 
Hence, he takes the average of the yearly deposit at about one- 
sixth of an inch. — American Journal qf Science, N° iv. p. 397. 
38. Nicojack Cave, in which a River has its origin. — This 
singular cave, which has been only recently described by the 
Reverend E. Cornelius, is situated in the Cherokee country, at 
Nicojack, the N.W. angle in the map of Georgia. It is 20 
miles S.W. of the Look-out Mountains, and half a mile from 
the south bank of the Tenessee River. It is situated in the 
Racoon Mountain, which here fronts to the north-east. The 
mouth of the cave, which is about 160 feet wide, and 50 feet 
high, is in a precipice formed of immense layers of horizontal 
limestone. Its roof is formed by a solid and regular layer of 
limestone, having no support but the sides of the cave, and as 
level as the floor of a house. This cave is traversed by a stream 
of cool and limpid water, which is 6 feet deep and 60 feet wide 
at the mouth of the cave. A few years ago, Colonel James 
Ore followed the course of it up the cave for three miles in a 
curve, but was stopped by a fall of water. The first direction 
of the cave was S.W., then S., and then S.E. by S. Great 
quantities of nitre are found in this cave. Mr Cornelius found 
I 
