344 ] AssoiaLir 
Geology. A science which has for its object tiie investigation of the 
structure of the earth and the materials of which it is composed. 
Connected with these investigations, are deductions which may be 
derived legitimately from the known influence and effects of causes; 
these are employed as expressions of the modus operandi by which 
the earth has been brought to its present state. 
Gneiss. A stratified primary rock, composed of quartz, feldspar «iiid 
mica. 
Granite. An unstratiiied rock, composed of quartz, feldspar and mica. 
Grauioacke, groywucke. The name was origmally applied to a rock 
composed of grains and pebbles cemented together by clay. It be- 
longs to the transition series. The name is appUed also to a group 
of rocks in the same series, consisting of sandstone, slates or shales, 
alternating with limestone, sandstone, &c. The term is rather inde- 
iinite, yet very frequently used. 
Green sand. Beds of sand, sandstone, limestone and marly clays, inter- 
mixed somewhat with greenish particles, belonging to the cretaceous 
period, and situated beneath the true chalk. 
Greenstone. A variety of trap, composed of feldspar and horneblendc. 
Grit. Coarse grained sandstone. 
Gypsum. A mineral composed of sulphuric acid and lime. ^ 
Hornblende. A mineral, usually of a dark green colour. Crystallizing 
in long slender prisms, 
Hornstone. A silicious translucent mineral, resembling flint, but tough 
and more diflicult to break. 
Incandescent. White hot — a degree of heat more intense than that at 
redness. 
Icibcrg. Floating masses of ice. 
Iclithyosaunis. A fossil reptile, intermediate between the crocodile and 
fish. A fish lizard. 
Induction, A consequence, conclusion, or inference, or some general 
principle drawn from facts or phenomena. 
In-situ. Original position. 
Isothermal. "Equality of temperature. Zones, lines, &c. where an 
equality of temperature prevails are called isothermal. 
Lacvstrine^ of, or belonging to, a lake. 
Lomincr,. Plates, sometimes used as synonymous with layers. 
Landslip. Land which has slidden down an inclined plane, from its po- 
sition in a bank or terrace. It is generally produced by water, which 
either undermines the mass of earth, or insinuates itself into it, so as 
to render it semi-fluid. 
Line of Beari7)g. The point of compass to which the anticlinal ridge or 
line runs, or is directed. When the anticlinal ridge cannot be deter- 
mined, the lirie of direction m.ay be known by ascertaining the inter- 
section of the planes of the strata with the plane of the horizon, that 
will be the line of bearing. 
Liihological. Tiie character of a rock or formation considered with 
reference solely to its m/meral composition. 
Lignite. Wood partially carbonized in the earth; it usually retains the 
vegetable structure. The change does not seem to have been effected 
by heat, but is the result of some chemical process, as the action of 
pure sulphuric acid in some instances, and of water in others. 
