LE GLOBE OÙ NOUS VIVONS

Thème.

Our globe was formerly an igneous and fhiid mass. No one knows how long that period lasted ; it probably was millions of years. Little by little, however, it cooled ; metals and minerais that were in a gaseous state became liquid and af terwards solid ; but violent perturbations often interrupted the cooling process.

When the earth's surface was cool enough for water to condense, végétation began to appear, and the inner beat of the globe gave birth to immense vegetable growths, the remains of which are now found. At the same time vaporized water disintegratecl the metallic rocks, thus forming the différent strata which are found everywhere on our globe. Geologists divide into four periods the period of formation of the globe : the primordial, that is to say, the one during which the earth was yet a luminous body ; the secondary, when océans covered the globe, and islands on which plants and trees grew, commenced to form ; the tertiary, during which climates and zones were more defmite ; and the quaternary, when the outside température ceased to decrease. It was then that man appeared, and soon took possession of ail the globe's surface.

200 Lectwes Courantes.