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Temperature's Nadir
626
CURRENT TOPICS.
[J. F. I.
depth would be over 7~/4 tons per square inch. This great deep was discovered in I929 by the new German Cruiser " E m d e n . " In the South Pacific the greatest depth is the Aldrich Deep, north of New Zealand, 3o,93o feet. The deepest sounding known in the North Atlantic is Nares Deep, approximately 27,972 feet, in West Indian Waters. The deepest spot in the South Atlantic is a sounding of 26,575 feet made in 1926 by the German survey ship " Meteor." This is far out at sea, the nearest land being the forsaken island of South Georgia, east of the southern tip of South America. The other oceans show lesser depths than this. The Indian Ocean has the Wharton Deep, about 22,968 feet, south of Java and east of Cocos island. A sounding of 17,85o feet was made in the Arctic Ocean by Sir Hubert Wilkins in 1927, and a depth of I4,274 in the Antarctic is shown by a British Admiralty chart. It is interesting to learn the ocean is not so deep at the poles, but if the earth's rotation is considered, such relative shallowness in the vicinity of the polar axes seems logical. C.
Temperature's N a d i r . - - S c i e n c e N e w s Service reports that scientific workers, with the consumption of much time and labor, have approached one-tenth degree nearer the point of absolute temperature. Prof. W. H. Keesom of Leiden University has succeeded in producing a temperature of minus 272. 3 degrees Centigrade which is within seven or eight-tenths of zero temperature absolute depending upon whether such a point is accepted as corresponding to 273 or 273.1 degrees Centigrade below the freezing point of water (o° C.). It seems very improbable that absolute zero shall ever be attained. The secret of such low temperatures lies in removing heat from the system at a faster rate than it can be absorbed from its surroundings. The rate of heat removal depends upon the velocity of the molecules of the substance being cooled and since this velocity decreases with the temperature, theoretically at least, the molecules should be motionless at absolute zero. If such be true the rate of attainment of this ultimate cold point should finally become infinitely small corresponding to the infinitely slow rate of molecular movement.--Prof. Keesom obtained his low temperature by keeping a small quantity of liquid helium constantly stirred while he produced a high vacuum over it by means of a pair of powerful mercury pumps. Effect of Acids Upon Paper.--The U. S. Dept. of Agriculture has found that acids, even in minute quantities, cause papers to
CURRENT TOPICS.
[J. F. I.
depth would be over 7~/4 tons per square inch. This great deep was discovered in I929 by the new German Cruiser " E m d e n . " In the South Pacific the greatest depth is the Aldrich Deep, north of New Zealand, 3o,93o feet. The deepest sounding known in the North Atlantic is Nares Deep, approximately 27,972 feet, in West Indian Waters. The deepest spot in the South Atlantic is a sounding of 26,575 feet made in 1926 by the German survey ship " Meteor." This is far out at sea, the nearest land being the forsaken island of South Georgia, east of the southern tip of South America. The other oceans show lesser depths than this. The Indian Ocean has the Wharton Deep, about 22,968 feet, south of Java and east of Cocos island. A sounding of 17,85o feet was made in the Arctic Ocean by Sir Hubert Wilkins in 1927, and a depth of I4,274 in the Antarctic is shown by a British Admiralty chart. It is interesting to learn the ocean is not so deep at the poles, but if the earth's rotation is considered, such relative shallowness in the vicinity of the polar axes seems logical. C.
Temperature's N a d i r . - - S c i e n c e N e w s Service reports that scientific workers, with the consumption of much time and labor, have approached one-tenth degree nearer the point of absolute temperature. Prof. W. H. Keesom of Leiden University has succeeded in producing a temperature of minus 272. 3 degrees Centigrade which is within seven or eight-tenths of zero temperature absolute depending upon whether such a point is accepted as corresponding to 273 or 273.1 degrees Centigrade below the freezing point of water (o° C.). It seems very improbable that absolute zero shall ever be attained. The secret of such low temperatures lies in removing heat from the system at a faster rate than it can be absorbed from its surroundings. The rate of heat removal depends upon the velocity of the molecules of the substance being cooled and since this velocity decreases with the temperature, theoretically at least, the molecules should be motionless at absolute zero. If such be true the rate of attainment of this ultimate cold point should finally become infinitely small corresponding to the infinitely slow rate of molecular movement.--Prof. Keesom obtained his low temperature by keeping a small quantity of liquid helium constantly stirred while he produced a high vacuum over it by means of a pair of powerful mercury pumps. Effect of Acids Upon Paper.--The U. S. Dept. of Agriculture has found that acids, even in minute quantities, cause papers to