Page:Travel letters from New Zealand, Australia and Africa (1913).djvu/173

 On most ships the clock in the companion way is set back or forward at midnight, and there is not another change for twenty-four hours.

—People living in a dry country a long way from the sea do not realize that it covers three-quarters of the surface of the earth. Ninety-six per cent of the water in the ocean is pure fresh water, yet so great is the bulk of sea-water that the total amount of salt dissolved in it, if deposited in a layer over the surface of the land, would make a bed over four hundred feet thick No one is able to say what is the source of the salt in the ocean. Probably the sea has always been salt, having become so when first the waters gathered on the surface of the globe; but all rivers that flow over the land carry salt, which they have obtained from the rocks and soil, so the sea is probably becoming saltier all the time, just as some lakes without outlet are being transformed to salt seas Off the coast of Australia for fifty or a hundred miles, the sea is two hundred to four hundred feet deep, but the depth grows greater as you leave the land, and between Australia and Africa, in places, the depth is more than five and a half miles, being greater than the elevation of the highest land above the sea-level. It has been calculated that the average depth of the ocean is more than 12,000 feet. The plains of the ocean bottom are the most extensive in the world. Here and there these plains are relieved by single peaks, like Bermuda, or groups of peaks, like