;

The temperate regions of the earth are those in which the changes of the seasons have the most marked effect on vegetable life. The "fall of the leaf," a phenomenon unknown to warm countries, is here the cause of a succession of beautiful and picturesque effects. The frosty nights, which mark the approach of winter, first change the aspect, and then detach from their stems the myriads of leaves the branches are left bare, and the tree stands in simple beauty of outline until the return of spring veils it anew with living green. The entire denudation of the branches indicates the life of the tree; the sap retreats to the root, and the contraction of its vessels causes the leaves to fall; were the tree dead, the withered leaves would cling to it closely, from the failure of this natural process. The trees and shrubs known as evergreens are able to resist the severity of the weather, owing to the strong tenacious viscid juices which they contain, and which are resinous and inflammable. Their stiff and glossy leaves seem especially adapted to encounter the chilling blasts of winter, and to brave its keenest frosts. The beech, though not an evergreen, has a glossy and tenacious leaf, which loses its colour, but remains long on the stem.

The mineral world is the least affected by the action of cold, yet here, also, the effect of alternate freezing and thawing is shown by the crumbling away of rocks and stone-work, in the crevices of which water has been converted into ice.

The effects of severe cold are greatly mitigated by the covering of snow which frequently protects the earth in winter. Beneath this shelter wheat will continue growing, and the temperature will remain at about 32°, while that of the air above may be below zero.

CHAPTER I.

ON ICE AND ITS PROPERTIES.

IF we collect together all that is known respecting any natural object, whether from the discoveries of scientific observers, or from the common experience of mankind, we are still very far from having found out all that is to be learned from it. It is not too much to say, that quite as much remains to be discovered respecting such an object as we know already. This is one of the great marks that distinguishes a natural from an artificial product. The one bears the impress of Infinite Wisdom; the other shows the limit of human effort. The most ingenious instrument soon informs the intelligent inquirer of all that it can do: it was made by man's device; and it can be understood, and its properties exhausted, by man's wit. How different is it with one of the Creator's works! Its properties are not only exhaustless, but there is a permanence about them, which presents a striking contrast with the shifting nature of human contrivances. The machine of one generation is altered, improved, or even set aside by the next generation. Not so with natural forms and objects, which, perfectly adapted from the first to the purposes for

which they were formed, are constant in their phenomena; and whilst the motions of some supply us with standards by which to regulate our time and to direct our voyages, the structure of others furnishes an infinite variety of examples of the exquisite skill of their Creator.

There is no substance more familiar to the inhabitants of temperate and arctic regions than ice. A few years ago it was commonly supposed that we knew all its properties; but the occasion having arisen for re-considering the phenomena of glaciers, many new properties of ice were discovered, and these of so wonderful and suggestive a nature as to give occupation to some of the highest scientific minds of Europe.

Ice is popularly known as frozen water. Its formation is accompanied by circumstances which illustrate in a most striking manner the wisdom and goodness of the Almighty, in allowing a great natural law to act with undeviating regularity up to a certain point, and then to pause and apparently to reverse its operations.

Heat is distributed by three methods:-first, by radiation, as when the sun darts its rays to the earth, or a fire its warmth to us at a distance; secondly, by conduction, as when a warm body is placed in contact with a colder one, and the heat creeps from the hotter to the colder, until the two bodies are of the same temperature; thirdly, by convection, or conveying away, which refers to the mode in which heat is distributed in liquids and