Royal Institution. 455 
quantity of alcobol contained in various wines and malt 
liquors : the highest was that of Marcella wine, which con- 
tains 26 per cent. of alcohol ; red Champagne 20, Port 
from 20 to 24, Madeira.19, claret 15, cider and perry 123 
ale 9, brown stout 8, porter 6. 
June 20.—A long paper by Dr. Herschel on Nebule 
was read: in this the Doctor retracted some of his former 
opinions respecting nebule, that they might be considered 
as clusters of stars. At present he concludes them to be 
peculiar condensed matter, supposes that they may consti- 
tute or become comets, regrets our inability to form any 
just notions of their mode of existence, presumes that they 
are much more numerous than we have hitherto been 
taught to believe, examines the general appearance of ne- 
bulosity in the heavens before space- penetrating glasses of 
various foci, and refers generally to figures of nebula given 
itt different publications by himself and others, and par- 
ticularly in the Connoissance des Tems for 1784. 
ROYAL INSTITUTION. 
is . . : ; ; 
Mr. Davy’s Lectures on Geology.—No. IV. 
Besides the natural fissures of rocks, there are deep and 
extensive chasms of frequent occurrence, the correspond - 
ing sides and angles of which intimate their formation to 
have taken place after the consolidation of the rocks in 
which they are founds’ These chasms when filled up con- 
stitute veins. 
Veins are the repositories of a great variety of substances, 
particularly of crystallized minerals and metallic ores. 
Their contents are in some measure connected with the na- 
ture of the rocks they traverse. In’the primary class of 
rocks, veins are rarely metallifereus—they generally consist 
of secondary rocks, In the secondary class, veins are 
found most abundant in metals. Tin occurs in veins in 
secondary granite ; and copper, tin, lead, iron, silver, quick - 
silver, manganese, &c. in argillaceous and siliceous schist, 
and in the traps and grey, wackes. Lead is the most plen- 
tiful ore in the secondary limestones. Veins containing 
metallic ores seldom occur in shales, sandstones, or basalts. 
Different metallic ores are pretty regularly associated in 
veins with different minerals; and the latter, when they 
appear, are said to be indications of the former: thus an 
ochrey powder, called gossan in Cornwall, denotes the 
proximity of copper, and a green earth, a species of chlo- 
rite, the proximity of tins Other circumstances, such as 
Vol. 37. No. 158, June 1811. Gg water 
