DR. CARPENTER ON OCEANIC CURRENTS.

New Zealand Times, Volume XXX, Issue 4444, 17 June 1875, Page 3

DR. CARPENTER ON OCEANIC CURRENTS.

On the night of Friday, February sth, in the Watt Institute, Dr. W. B. Carpenter delivered the Watt anniversary lecture, at Greenock, the subject of which was “ Oceanic Currents.” The lecture embodied the result of the investigations made in the course of the Lightning and Challenger expeditions. Dr. Carpenter explained that some of the mid Atlantic currents were caused by the motion of the earth. It would he apparent to anyone that at the equator the currents of the ocean would move with much greater velocity than in the temperate zones, while at the poles there were absolutely no currents. The current which crossed the South Atlantic from west to east impinged on the Coast of Guinea. There was a north and south current in the same vicinity, and the stream returned across the Atlantic, entering the Caribbean Sea, and coming out to ocean again through the Florida channel. The spread of the current through the Sound of Florida had been somewhat overstated by those who said that it flowed at the rate of four miles an hour. There were occasions when it did flow at that speed, but there were others when it did not exceed one mile an hour. He believed that the banks of Newfoundland were being formed at a regularly defined rate. The banks of Newfoundland lie in the track of the great polar current, which, year after year, brings down the icebergs from the northern regions ; and these masses of ice melted and deposited rocks and stones as they floated onward. The difference in temperature in some parts of the ocean was extremely local —sometimes the bow of a vessel was in warm water and the stern in water of a much lower temperature. There were regular strata of warm and cold water, and the depth of the ocean was not of itself a cause of change in the temperature. It was the polar currents which to a great extent caused the difference in the Mediterranean Sea, which is a sort of self-contained basin. He showed why it happened that to the north and south of the equator they could find warmer weather than could be found at the equator itself. Dr. Carpenter showed that he had discovered that the old theory (which thirty years ago was in advance of the time, and was not generally accepted at the time), with reference to the action of the sun’s rays on the water, was a correct theory. The sun’s rays would penetrate to any depth, and impart almost uniform warmth ; but there was also at work another law. The heat of the sun caused rapid evaporation, and the surface of the water thus contained an abnormal quantity of salt, which, having attained a high temperature, sank to the bottom because of its greater specific gravity, and wanned the surrounding water in its descent. The lecture was frequently applauded, and at the close Dr. Carpenter was awarded a vote of thanks.