Page:The National Geographic Magazine Vol 16 1905.djvu/554

Rh river finds its way to the Indian plains, and this still remains for the future to unravel.

It is of the ocean, more than of any other physical feature of our globe, that our knowledge has increased of late years. Forty years ago we were profoundly ignorant even of its depth, with the exception of a few lines of soundings then recently taken for the first submarine telegraph cables, and consequently we knew nothing of its real vast bulk. As to the life in it and the laws which govern the distribution of such life, we were similarly ignorant, as of many other details.

The Challenger expedition changed all this, and gave an impetus to oceanographic research which has in the hands of all nations borne much fruit. Soundings have been obtained over all parts of the seas, even in the two Polar seas ; and, though much remains to be done, we can now form a very close approximation to the amount of water on our earth, while the term "unfathomable ocean" has been shown to have been based on an entire misconception. Biological research has also revealed a whole world of living forms at all depths, of the existence of which nothing was known before.

In my former address, eleven years ago, I gave many details about the sea, of which I will only repeat one — which is a fact that every one should know — and that is that the bulk of the ocean is about fourteen times as great as that of the dry land above water, and that if the whole of that land were thrown into the Atlantic Ocean it would only fill one-third of it.

Eleven years ago the greatest depth known was 4,700 fathoms, or 28,000 feet. We have since found several places in the Pacific where the depth is nearly 5,170 fathoms, or 31,000 feet, or somewhat higher than Mount Everest, which has been lately definitely shown to be the culminating point of the Himalayas. These very deep parts of the ocean are invariably near land, are apparently in the shape of troughs, and are probably due to the original crumpling of the earth's surface under slow contraction.

The enormous area of the sea has a great effect upon climate, but not so much in the direct way formerly be- lieved. While a mass of warm or cold water off a coast must to some extent modify temperature, a greater direct cause is the winds, which, however, are in many parts the effect of the distribu- tion of warm and cold water in the ocean perhaps thousands of miles away. Take the United Kingdom, notoriously warm and damp for its position in lati- tude. This is due mainly to the preva- lence of westerly winds. These winds,, again, are part of cyclonic systems prin- cipally engendered off the coasts of eastern North America and Newfoundland, where hot and cold sea currents,, impinging on one another, give rise to great variations of temperature and movements of the atmosphere which start cyclonic systems traveling eastward.

The center of the majority of these systems passes north of Great Britain. Hence the warm and damp parts of them strike the country with westerly winds which have also pushed the warm water left by the dying-out current of the Gulf Stream off Newfoundland across the Atlantic, and raises the temperature of the sea off Britain.

When the cyclonic systems pass south of England, as they occasionally do, cold northeast and north winds are the result, chilling the country despite the warm water surrounding the islands. It only requires a rearrangement o£ the direction of the main Atlantic cur-