PHYSICS OF THE GLOBE. 115 



CURRENTS. 



In the Canadian Naturalist, H. Y. Hind publishes a thought- 

 ful article on the Mechanical Effect of Arctic Ice in producing 

 Ocean Currents. 



The Labrador and Gulf Stream Currents and their Effects 

 on American Fisheries are treated of in two memoirs by H. 

 Y. Hind, published by the Fishery Commission at Halifax. 



Dr. O. Krummel, in his Inaugural Dissertation at Gotten- 

 gen, gives an analysis of our knowledge of the equatorial 

 currents of the Atlantic Ocean, and an examination into the 

 fundamental causes of the general oceanic circulation. In a 

 note he calls attention to Aime's Submarine Current Indica- 

 tor, described in Ann. de Chen tie, III., xiii., 1845, p. 461. His 

 criticisms of most modern writers are very fair, although his 

 conclusions seem to fall short of that which we are, perhaps, 

 able to maintain with some certainty. He says: "The exist- 

 ence of a vertical circulation is undeniable, but the ascend- 

 ing current cannot alone account for the strong westerly 

 equatorial current. Temperature differences do not suffice to 

 explain the vertical circulation without taking account of 

 the terrestrial centrifugal force. Two ascending currents, 

 with the compensating Guinea current between them, suffice 

 to explain the three equatorial currents of the Atlantic." 

 This work is evidently well worthy of study by those spe- 

 cially devoted to this subject. 



Zoppritz contributes to the Anncden and to the Philosoph- 

 ical Magazine a very important memoir on Hydrodynamic 

 Problems in reference to the Theory of Ocean Currents. He 

 has, namely, attempted to solve the analytical equation for the 

 motion of a liquid ocean whose particles move over each other 

 with appreciable friction that is to say, if the wind blows 

 steadily over the ocean, and the surface layer of water fol- 

 lows the lowest layer of air, what will be the resulting move- 

 ments in the lower strata of water? The influence of the 

 steady trade-wind must, he finds, extend to the bottom of the 

 sea. By introducing Meyer's known value of the coefficient 

 of friction for sea-water, he finds, for instance, that if the par- 

 ticles of the surface of the ocean begin to move forward witli 

 a constant velocity, in 239 years the stratum at a depth of 

 100 meters will be found moving with one half the surface 



