Page:Popular Science Monthly Volume 14.djvu/566

550 opened for the admission of air, the French employ the vertical division, and open the windows inwardly on hinges as we open doors. The window apertures are also large, or rather high, descending to within eighteen inches of the floor, and ascending to within four inches of the ceiling. Outside these are latticed shutters. When the windows are open and the shutters closed the sun is effectually kept out, and the free circulation of the air is scarcely interfered with. A light balustrade of iron, within the shutters and without the glass, serves to prevent falling through the windows."

Destruction of American Forests.—It has been for some years apparent that the United States supply of timber must fail at no distant day, unless some concerted measures are taken for growing new forests or in some way preserving the old. The present condition of the lumbering business will be understood from the following facts, published by the St. Paul "Pioneer Press," and based on the observations of Mr. James Little, a lumber-merchant of Montreal, who has long studied this subject: Of the twenty-six States comprising the New England, Middle, Western, and Northwestern, to the Rocky Mountains, only four are now able to furnish lumber-supplies beyond their own requirements; the four being Maine, Michigan, Minnesota, and Wisconsin. But Maine is almost stripped of her pine-forests, and lumberers have to go to the head-waters of the rivers in search of spruce, while mere saplings, six or seven inches in diameter, go to the mill. In a few years Maine will have neither pine nor spruce for home consumption. The northern parts of Michigan, Wisconsin, and Minnesota, are the only localities of the whole twenty-six States which can furnish supplies of white pine beyond the home demand; but they will not be able to do so, Mr. Little affirms, for more than five or six years longer. The main streams are all stripped, and the dependence of the lumbermen is now on the head-waters of the tributaries. In 1870, according to the census report, there were in the United States 173,450 industrial establishments, employing 1,093,202 hands, devoted to the manufacture of wooden articles. The impression prevails that when our supply of lumber fails, as it must inevitably within the next ten years, we can find in Canada a supply that will not be exhausted in centuries. But this is an error; at least, Mr. Little asserts that there is not from Manitoba to the Gulf of St. Lawrence as much pine, spruce, hemlock, white-wood, and other commercial timber, as would supply the United States for even three years! In the light of such facts as these, it behooves the people of this country to seriously consider the subject of reforestation and the protection of young timber-trees.

Movement of Water in the Suez Canal.—The currents of the Suez Canal and the action of the prevalent winds on the water therein have been studied by M. Lemasson, who finds that Lake Timsah and the basin of the Bitter Lakes, the former in the middle of the line of navigation, the latter nearly at the middle of the southern branch of the canal, constitute two great regulators, at which the tidal currents from the two seas respectively expire. The north and south branches of the canal are not, however, independent as regards the movement of their waters. The dominant winds in this region blow, from May to October, from the north and northwest, and raise the mean level of the waters of the Mediterranean at Port Saïd, while they depress the mean level at Suez. The difference of level, which attains almost sixteen inches in September, sets up, in summer, a current from the Mediterranean to the Red Sea, which is interrupted by the tides, but nevertheless carries a considerable volume of water from north to south. In the winter, on the contrary, the south winds blow strongly, and the mean level of the Red Sea is then higher than that of the Mediterranean, the difference attaining a maximum of nearly one foot. The general direction of the current of the canal then sets from the Red Sea to the Mediterranean. The volume of water flowing annually from sea to sea is estimated at 400,000,000 cubic metres, and this with the tidal currents annihilates the effects of evaporation at the surface of the lakes, and aids the solution of the great salt deposit in the basin of the Bitter Lakes, which, instead of increasing, is diminishing, especially in the line of transit of ships.