line against which the sea is made to dash its waves in the other. Impressed with the perfection of terrestrial adaptations, he who studies the economy of the great cosmical arrangements is reminded that not only is there design in giving shore-lines their profile, the land and the water their proportions, and in placing the desert and the pool where they are, but the conviction is forced upon him also that every hill and valley, with the grass upon its sides, is a part of the wonderful mechanism, each having its offices to perform in the grand design. March is, in the southern hemisphere, the first month of autumn, as September is with us; consequently, we should expect to find in the South Atlantic as large an area of water at 80° and upwards in March, as we should find in the North Atlantic for September. But do we? By no means. The area that is covered on this side of the equator with water at 80° and upwards is nearly double that on the other. Thus we have the sea as a witness to the fact which the winds had proclaimed, viz., that summer in the northern hemisphere is hotter than summer in the southern.
731. Sudden changes in the water thermometer.—Pursuing the study of the climates of the sea, let us now turn to Plate VI, Here we see at a glance how the cold waters, as they come down from the Arctic Ocean through Davis' Straits, press upon the warm waters of the Gulf Stream, and curve their channel into a horse-shoe. Navigators have often been struck with the great and sudden changes in the temperature of the water hereabouts In the course of a single day's sail in this part of the ocean, changes of 15°, or 20°, and even of 30°, have been observed to take place in the temperature of the sea. The cause has puzzled navigators long, but how obvious is it now made to appear! This " bend " is the great receptacle of the icebergs which drift down from the north; covering frequently an area of hundreds of miles in extent, its waters differ as much as 20°, 25°, and in rare cases even as much as 30° of temperature from those about it. Its shape and place are variable. Sometimes it is like a peninsula, or tongue of cold water projected far down into the waters of the Gulf Stream. Sometimes the meridian upon which it is inserted into these is to the east of 40°, sometimes to the west of 60°. On my passage to England November, 1800, I passed over this horse-shoe; the water in it was 16° colder than the water at its side. It looked as though we might have been on soundings.
