No. 557] NOTES AND LITERATURE 



317 



the currents ever attained at Gibraltar and found that there is 

 a surface current passing inward from the Atlantic to the 

 Mediterranean, while at the same time a strong bottom-current 

 of dense water passes outward into the Atlantic. The boundary 

 between these two currents is usually at a depth of about 150 

 fathoms but this is greatly affected by the tidal conditions, for 

 during one hour the current flowed outward toward the Atlantic 

 even at the surface. 



Other studies in the open Atlantic far from land enabled them 

 to distinguish currents due to tidal action at the surprising depth 

 of more than 1,000 fathoms. Indeed, a most interesting part of 

 the book is devoted to the discussion of the physics of oceanic 

 and tidal currents, and the expedition has achieved a hopeful 

 purpose if it has done little more than point out the possibilities 

 of research in the complex subject of the relation between tidal 

 waves and tidal currents. The right-handed deviation of mov- 

 ing masses of water in the northern hemisphere due to the earth's 

 rotation is clearly shown as a result of titration to determine the 

 densities of sea water at various depths. Thus it is shown that 

 the dense, relatively warm water of the Mediterranean spreads 

 out in a great wedge in the intermediate depths of the Atlantic, 

 and that most of this water moves northward off the coast of 

 Portugal. 



Through studies in density it is shown that the so-called 

 "Gulf Stream" water overlies the cold water of Arctic origin. 



But it is impossible to do more than merely indicate a few of 

 the more important facts and laws presented in this remarkable 

 book. In fact it is impossible to review a work which is itself a 

 review of all previous studies as well as a medium for the presen- 

 tation of newly discovered facts. 



An appreciated feature of the book is the numerous charts, 

 maps and hydrographic sections showing density and tempera- 

 ture gradients, the distribution of oxygen in the ocean, and the 

 most recent results of exploration in soundings. 



For example, it is shown that in 1910 the temperature at 400 

 fathoms in a certain place was 5° C. colder than in 1873 when 

 the Challenger worked in the same region. 



The area of the ocean is stated to be 139,295.000 square miles, 

 of which 58.42 per cent, has a depth of between 2,000-3,000 

 fathoms, and about one sixth is less than 1,000 fathoms deep. 



The hydrographic sections from the Sargasso Sea to New- 

 foundland, and from Newfoundland to Ireland, as well as the 

 more intensive studies of the Spanish Bay and Gibraltar, and of 



