HYDROSPHERE is a term used by geog raphers to designate the total of the water on the earth. It, therefore, includes the oceans, all lakes and rivers, the water-vapor in the atmosphere and that which has penetrated into the substance of the globe (lithosphere). To estimate the amount of this with accuracy is manifestly impossible, as we cannot easily calculate the bulk of the vapor, and know noth ing about the amount contained in the rocks and spaces beneath the surface. It is possible to give some interesting facts as to the masses of water in the oceans and large inclosed seas and lakes on the surface of the earth. The latest calculations by physicists compute the area of the oceans and seas directly connected with them at 139,295,000 square miles, and the area of all lands, including inclosed lakes, etc., at 57,254,000 square miles. The water-area is, therefore, about three-fifths of the total super ficies of the globe. Its mass, however, requires multiplication by depth, and the greater part of the oceanic area is covered by water more than 1,000 fathoms deep. Two-thirds are oc
cupied by water exceeding 2,000 fathoms in depth, and one-fifteenth of the oceanic basins lies beneath more than 3,000 fathoms (18,000 feet) of water. The deepest place yet ered is near Guam Island in the Pacific — 5,269 fathoms. This is equal to 31,614 feet, and it exceeds the altitude of the highest mountain (Everest in the Himalayas, 29,000 feet) by 2,610 feet. This makes the greatest known dif ference between the lowest and highest points on the earth's surface about miles; but it must be remembered that where as the moun tain-tops are mere points, the in the ocean floor are often areas of hundreds of square miles. It is, therefore, evident that were all the solid surface of the earth reduced to a level, the water would cover the globe to a very considerable depth — probably two or three miles. See LITHOSPHERE.