General Science. 195 
to the flame of the gas blowpipe : it became colourless and 
transparent; by continuing the heat it became white and opaque, 
and was volatilised. Blue Fluor-spar changes to a kind of red 
when heated, and when the heat is raised, it is often rendered 
colourless. 
43. Effect of Heat on Obsidian . — A specimen of obsidian 
from the Island of Ascension, with blue veins in it, when ex- 
posed to a red heat, discharged air-bubbles from the veins more 
abundantly than from other parts of the mineral. 
44. Bottle thrown out of the Isabella . — The bottle No. 2. 
thrown overboard by Captain J. Ross of his Majesty’s ship Isa- 
bella, on the 3d June 1818, lat. 65° 40' N. long. 54° 10' W. 
off Greenland, to ascertain the direction of the current in Davis’ 
Straits, was found by one of the servants of A. Macdonald, Esq. 
at Balranald, North Uist, on the 17th ?of July last, and the pa- 
per inclosed in it quite dry ; so that it was 13 months and 14 
days on its passage. The latitude of Balranald is about 57° 20' 
north. The paper has been transmitted to the Admiralty. 
45. Earthquake at Lisbon on the February 1816. — 
The earthquake which was experienced at Lisbon on the 2d 
February 1816, at 0^ 4 ' in the morning, and again at 6^ | in 
the evening, was felt by the Marquis de Angeja.) a Portuguese 
vessel bound from Bengal to Lisbon, at 0^ 46' (the time being 
reduced to that at Lisbon) and in lat. 34® 15' N. and long, 
15° 10' W. from Lisbon. The vessel w'as therefore 270 leagues 
W. S. W. ,of Lisbon. The same earthquake was experienced 
on board another vessel bound fj’om Brazil to Portugal, at 0^ 42' 
(time at Lisbon), and again at 3*" 40' in lat 36° 56' N. and 6® 52' 
W. of Lisbon. The vessel v/as therefore 120 leagues W. S. W. 
from that city. The same ship again felt the shock at 5^ 57'. 
The first shock was therefore felt at the same instant nearly at 
three places very remote from one another. The same earth- 
quake was said tobave been felt in Madeira and Holland. Ann. 
de Chim. et de Phys. tom. xi. p. 323. 
46. Expedition overland from Hudsorls Bay to the Shores 
of the Arctic Ocean . — The expedition intended to examine the 
American shores of the Arctic Ocean, reached York Fort in 
Hudson’s Bay on the 31st August, after having nearly suffer- 
