WATER is the compound of oxygen and hydrogen in the proportion of two atoms of hydrogen to one of oxygen. It is familiar to us in three states: solid, liquid, and gaseous, or ice, water, and steam. But it is only in the liquid state that water is available for carrying on the processes of life. This fact limits the temperatures at which the organic functions can be carried on, for water under terrestrial conditions is only liquid for a hundred degrees; it freezes at 0° Centigrade, it boils at 100° Centigrade. Necessarily, our experiences are mostly confined within this range, and therefore we are apt unconsciously to assume that this range is all the range that is possible, whereas it is but a very small fraction of the range conceivable, and indeed existing, in cosmical space. In its liquid state water is a general solvent, and yet pure water is neutral in its qualities, both characteristics being essential to its usefulness as a vehicle for the protoplasmic actions. Naturally, this function of water as a solvent can only exist when water is in the liquid state; solid water, that is ice, neither dissolves nor flows; and water, when heated to boiling point, passes into vapour, and so leaves the organism moistureless, and therefore dead. It is possible to grind a living organism to a pulp so that the structure of the cells is practically destroyed, and yet for some reactions which are quite peculiar to life still to show themselves for some appreciable time. But when the cell-pulp is heated to the temperature of boiling water, these chemical processes cannot be longer observed. What is left may then be considered as definitely dead. Water is, then, indispensable for the living organism; but there are two great divisions of such organisms--plants and animals. Animals are generally, but not universally, free to move, and therefore to travel to seek their food. But their food is restricted; they cannot directly convert inorganic matter to their own use; they can only assimilate organic material. The plant, on the other hand, unlike the animal, can make use of inorganic material. Plant life, therefore, requires an abundant supply of water in which the various substances necessary for its support can be dissolved; it must either be in water, or, if on land, there must be an active circulation of water both through the atmosphere and through the soil, so as to bring to it the food that it requires. Animal life presupposes plant life, for it is always dependent upon it.