NATURE 



[October 24, 191 2 



Sir John Murray's principal contribution, wliich 

 is on the depths and deposits of the ocean, con- 

 stitutes chapter iv. The chapter is mainly de- 



voted to a general account of these subjects. 

 Written as it is by the greatest living authority, 

 in a style as interesting as it is scientifically 

 accurate, it cannot fail to be 

 welcome to all who wish to 

 learn the present position of 

 our knowledge of the con- 

 figuration of the ocean 

 basins and the nature of the 

 deposits which lie upon their 

 Hoors. The section dealing 

 with the mineral collections 

 obtained during the cruise 

 of the Michel Sa.rs is by 

 Urs. Peach and Home, who 

 examined the specimens. 

 The most interesting fact 

 recorded by them is the 

 discovery of glaciated 

 stones, some of which are 

 illustrated, at a depth of a 

 little more than a mile, at 

 a point 230 miles south-west 

 of Mlzen Head, Ireland. 



Dr. Helland-H a n s e n ' s 

 chapter on physical oceano- 

 graphy is certainly the best 

 summary of the modern 

 aspects of this subject which 

 has yet appeared in English. 

 Of the work of the expedi- 

 tion itself the striking 

 features are the direct 



measurements of the currents entering and leaving 

 tlie Mediterranean through the Straits of Gibraltar, 

 Ihe determination of the depths to which an 

 NO. 2243, VOL. 90] 



amount of light penetrated sufficient to produce 

 an effect on photographic plates, and the very 

 close agreement which was found in the deep- 

 water temperatures taken by the 

 best modern instruments with 

 those taken at the same 

 stations by the Challenger ex- 

 pedition more than thirty years 

 before. 



Dr. Helland-Hansen is fol- 

 lowed by Prof. Gran, with an 

 account of the pelagic plant life, 

 one of the most interesting 

 chapters of the whole book. 

 The general subject is treated in 

 a masterly way, and the import- 

 ance of these minute vegetalsle 

 organisms, forming as they do 

 the fundamental food supply of 

 the ocean, cannot be overrated. 

 The special contribution of the 

 expedition to the advancement of 

 this subject is the discovery, by 

 means of a large centrifuge 

 worked by the steam-winch of the 

 vessel, of the extraordinary abun- 

 dance of the most minute plank- 

 ton forms, especially in the 

 warmer seas. These forms are 

 so small that they pass through the meshes 

 of the finest silk nets, yet they occur in such 

 vast quantities that they constitute in these waters 



d-Hansen's photometer. On the left, 

 1 the right, closed and ready for haulin^i 



The Depths 



perhaps the most important part of the pelagic 

 plant life. 



Sections dealin<>- with the bottom fauna are con- 



