Among the most interesting phenomena produced are those of polarized light, and many important deductions in medicine and chemistry are derived therefrom.
WATER AS A FARMER.
Solids are not the only substances which water is capable of taking to itself. Gases are also absorbed by it. A pint of water under one pressure of the atmosphere will absorb one pint of carbonic acid. It will take seven hundred pints of ammonia gas. This power of absorption belonging to water is of the greatest importance to agriculture. As the rain descends it frees the air from noxious gases, and carries them to the earth, where they are distributed to the rootlets of the plants; in this instance that which is death to the animal is life to the plant; it also rises in all vegetation, from cell to cell, by what is known as endosmosis. It moves freely through the porous earth by capillary attraction, the interstices of the earth really constituting a system of tubing through which the liquids freely circulate. When the earth becomes compact and hard the water can not so freely move through it; if the weather is dry, then follows another important result—the air, which always bears with it more or less moisture, especially in hot weather, can not pass through the soil and bring to the roots its gift of nutrition. Any one can perform the following experiment: Walk into the garden some morning when the season is dry and hot. You will often notice that the garden walk looks damp, while the spot that you hoed the day before, perhaps, seems dry, but if you will dig down a little way into each you will find that the loosened earth where you had worked, is moist, while the former is, below the surface, quite dry. Hence a practical inference of much value—the importance of frequently hoeing and loosening the earth, to facilitate the growth of plants, especially when the season is dry. The philosophy of this is, that the air freely passing through the loosened earth becomes cooled, and the moisture it contains is condensed, and remains to nourish the plant. A curious illustration of this fact is found in the prolific growth of watermelons, which are raised with the greatest success in dry sand, which is often so hot on the surface as to be painful to the hand; and yet a hundred pounds of watermelon contain ninety-eight pounds of water. The agricultural value of a country depends as much upon its water supply as upon the excellence of its soil. Here again we find one of the grandest endowments of “our heritage.” This is a land of sweet and abundant waters. Even those portions once considered worthless have been made of immense value by irrigation. Through our pastures flow crystal streams for the advantage of the dairy, as the production of good butter depends as much upon pure water as it does upon sweet grasses.
MANY FORMS OF SIPHONS.
Glance over one of the broad corn-fields of the West. What a wonderful contrivance is each stalk for gathering sunlight and moisture! Water constitutes eighty per cent. of that vast growth! The forces of the sunbeam, which are locked up in it, will be surrendered during the coming winter, to sustain and invigorate man and beast. Take two large goblets, one of which is nearly filled with water. Place on it a piece of card-board, through which a hole has been made, pass through the opening the roots of any growing plant, like a spray of bergamot. Cover the plant with the other goblet; in a few moments the inner surface of the upper goblet will be covered with moisture, showing that the roots have absorbed and the stomata or pores of the leaves have exhaled the moisture. In every land drouth is synonymous with want and famine. With glad festivals the Egyptians greet the rising of the Nile. The seven lean years of Joseph’s time were years of drouth. If M. De Lesseps should carry out his mighty project of overflowing the Sahara with the waters of the Mediterranean, that desert may yet bud and blossom like the rose. Growth is intimately connected with climate, and the latter depends not a little upon proximity to water. The beautiful lake region of the United States would be almost uninhabitable were it not for the gentle influence of these inland seas. They cool the air in summer and warm it in winter, thus forming a great equalizing influence and preventing extremes of temperature.
WATER AS PHILANTHROPIST.
Few things are more interesting and suggestive of a kind Providence than the plan by which water is supplied to the human family by underground currents, where it is kept cool in summer, and prevented from freezing in the winter. Natural pipeage is found almost everywhere in the earth, consisting of a layer of sand or gravel found between layers of clay or rock, which are practically impervious to water.
Where the upper layer is wanting springs appear. They often gush from the foot of the hills, but not unfrequently we find them on lofty summits. Human skill has sought for these hidden streams at great depths by means of Artesian wells, some of which are two thousand feet deep. It is claimed that the Chinese used them two thousand years ago for procuring gas and salt water. There is a famous Artesian well at Grenelle, Paris, which yields six hundred and fifty-six gallons of water per minute, while two of these wells in Chicago discharge four hundred and thirty-two thousand gallons a day. As Chicago is situated on a level prairie, this water must come from the high hills of Rock River, a hundred miles away. The water coming from these great depths is warm, one proof of the heated condition of the interior of the earth.