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[Assembly 
Outliei s. The detachment of a mass of rock from the general formation 
to which it belongs; or it is a teim applied to a mass which appears 
as if it was detached from the general formation, as its outcrop is at 
a distance from it. 
Oxide, The combination of a metal, or any substance wdth oxygen^ 
which is not acid. 
Oxygen. One of the constituent elements of the air and water; that 
portion of the air which supports life and combustion. 
Pachydermata. An order of animals with thick skins, as the hog, ele- 
phant, rhinoceros, mammoth, &c. 
Palaontology . The science which treats of fossil remains, both animal 
and vegetable. 
Pelagian. Belonging to a deep sea. 
Petroleum. Mineral pitch; a liquid approaching the consistence of tar^ 
of a bituminous odor, and which oozes out of a rock. 
PhlegrcBan fields. The burnt fields; applied by the Greeks to the region 
around Naples, from the marks of igneous action every where visible. 
Pisolite, A stone composed of rounded particles like peas, agglutinated 
together. 
Pliocene. An era or period analogous to the present, and more recent 
than the miocene. A large proportion of the animal remains of the 
pliocene strata still exist. 
Porphyry. A rock having a base whose structure is more or less com- 
pact, in which there are disseminated crystals of feldspar. 
Productus, A bivalve fossil shell, concave on one side and convex on 
the other. 
Plastic clay. One of the beds of eocene tertiary period. 
Plesiosaurus A fossil extinct reptile, having a close resemblance to s& 
lizard 
Precipitate. The fine powder which separates from solutions after stand- 
ing, or which are disengaged by the chemical action of bodies added 
to those solutions. 
Pumice, A light spongy lava. 
Puddingstme. Indurated or cemented masses of rounded pebbles, 
sand, &c. 
Pyrites. A mineral composed of sulphur and iron, or sulphur and copper. 
Quartz. The term universally applied to a simple mineral composed of 
nearly pure silex. Rock crystal is an example. 
Rock. A term applied to all mineral beds or masses. 
Sandstone. A rock composed of grains of sand. 
Saurians. Animals belonging to the tribe of lizards^ 
Sacchoroidal. Resembling loaf sugar. 
Schist, schistose. Slate and slaty. 
Septaria. Flattened balls of stone traversed by seams of calcareous spar^, 
or some other mineral. The outer surface has the appearance of a 
turtle's back; and hence they have been considered, by persons of 
little observation, as petrified turtles. 
Shale. Generally used as synonimous with slate. 
Shell Marl, The name is applied to recent fresh-water deposits, whicb 
consist of marl and numerous shells of Helices, Planorbis, &c, inter-* 
mixed. 
