NATURAL PHILOSOPHY, 127 



AIR CARRIED BY FALLING BODIES. 



M. Melsens, at a recent meeting of the French Academy, re- 

 ported upon the fact that when a ball is allowed to fall into water 

 from some height it carries with it into the water a volume of air 

 twenty times the size of the ball; this air accompanies the ball in 

 its descent, no matter to what depth, and is only set free when the 

 ball strikes the bottom. Mariotte, who had made the same ob- 

 servation, had remarked that every drop of rain, as it falls, draws 

 along with it a volume of air two or three times its own size, by 

 which he accounts for the light wind felt near where a shower is 

 foiling. Melsens fired a pistol-ball into water, and found that the 

 volume of air then carried into the water was a hundred times 

 that of the projectile. When with an ordinary charge of powder 

 he fired into a block of porcelain paste, the hole made in the paste 

 was exactly the diameter of the ball ; but when a very strong 

 charge was used, the hole made was large enough to pass the arm 

 through. It is well known that when a smooth pebble is thrown 

 against a pane of glass, a clean circular cut is made without a 

 crack ; this, it has always been supposed, was due to the high 

 velocity of the projectile, but Melsens' experiments contradict 

 this. He found that when he fired a ball with a strong charge of 



<^ ^j 



powder, the glass was always broken into a great number of 

 pieces ; that a ball with a very low velocity cut a hole more or 

 less clean ; and that with a medium velocity a hole without any 

 cracks might be produced. 



TEMPERATURE OF MAXIMUM DENSITY OF WATER. 



The determination of this question has occupied the attention 

 of physicists for the last half century ; their results differ from 

 1.76 C. to 4.44 C. The conclusions of Despretz, which give 4 

 C., are generally received, and are said to be confirmed by the 

 most recent experiments of Professor Rosetti, of Padua; these 

 show that at 4.07 C. pure distilled water has a density of 

 1.000134, which was the maximum obtained. The experiments 

 made on the dilatation of saline solutions may lead to important 

 results bearing on the interpretation of some natural phenomena. 



OCEAN CURRENTS. 



At a recent meeting of the American Institute, of New York, 

 Professor Grimes made the following remarks on the subject of 

 ocean currents. Since the discovery of the great Gulf Stream, 

 similar currents have been traced both in the Pacific and Indian 

 Oceans ; and now physicists recognize five, one each in the North 

 and South Atlantic and Pacific, and the fifth in the Indian Ocean. 

 The six continents of the earth being arranged in pairs, from this 

 and other points of similarity, it is evident that whatever force 

 caused the one, repeated itself in forming the others. At the time 

 when the entire earth was covered with water, six elliptical cur- 

 rents were formed. Five now exist; the sixth was formed in the 

 North Indian, an ocean no longer existing, owing to the elevation 



