One of the best preventive measures is to have a plentiful supply of pure water. We can then keep our sewers flushed—our homes clean, and so render our hearths and homes comparatively safe from the devastating pest of cholera. There is nothing in nature that possesses more interest than water. It is composed of oxygen and hydrogen. This may be easily demonstrated by throwing a piece of potassium on water, when it will instantly take fire: because of the rapid affinity of the oxygen of the water for the metal potassium the hydrogen is liberated, which burns during the decomposition which takes place. This experiment, which is equally simple and beautiful, shows the composition of water. The combinations into which water enters in the animal and vegetable kingdoms are as various and as beautiful as the magic forms of the kaleidoscope. Neither animals nor plants can live without water. It is, therefore, a necessary of life. On the purity of water, in a great measure, our health depends. Various are the sources of water, and equally various the degrees of the purity or impurity of water: for this reason—that water is the great solvent in nature. The first great source of our water supply is from the ocean, which receives the water from all the sparkling rills that murmur as they leap down the mountain side, which unite and form rivulets. These rivulets unite again, and form the mighty flowing rivers with majestic water-falls, cataracts, and cascades; and these flow on till they empty themselves into the ocean. Reader, did you ever stand on the sea beach shore and see day go out in a flood of glory—the bosom of the ocean blush as the monarch of day smiled his parting beams of light—tinging the clouds with golden hue and shedding a light on all creation and making it beautiful? These clouds were not alone created for the poet or the painter, nor to give scenic beauty to the landscape; but to supply the wants of the flowers of the valley, the beasts of the forest, and to be a source of health, power, and wealth to man. The heating rays from the sun so act upon the water as to cause a mist like a gossamer veil to arise. This is tossed about in the atmosphere by the various currents of winds which set in from the Equator to the Arctic and Antarctic regions. Thus is it that rain-bearing clouds are distributed over the land. The vapour contained in these clouds is condensed by the various degrees of temperature through which they are wafted, and form either snow or rain. This sinks down into the earth, and forms springs; or the snow, melting on the mountains, runs down and forms rivulets: and hence our chief water supply.