should not, include the study of the mode of formation and the structure of the 

 muds and hard rocks forming the floor of the oceans and the seas. This exclusion 

 is no longer possible, and we have included in these volumes geological and 

 geophysical ideas and observations concerning the earth beneath the seas. In 

 the great oceanographical (or oceanological) establishments of the world the 

 earth sciences relating to the oceanic environment are pursued alongside one 

 another without discrimination as to whether the air over the sea, the water, or 

 the solids beneath the sea could claim prior imjjortance. We have adopted the 

 same breadth of outlook in these volumes. 



With a composite work such as we have tried to produce, it has proved diffi- 

 cult to ensure a precise balance in the emphasis given to our wide variety of 

 topics. Sometimes, maybe, there will be too much written about a narrow field ; 

 sometimes we shall perhaps be criticized for the converse, too little written 

 about a broad field. At least, however, we hope we have covered most of the 

 topics suitable for a work on the new developments in our subject. 



When we drew up the first list of contents of this work we had supposed that 

 we should be producing one volume. We soon found, however, that we had 

 omitted a number of topics, and the contents list consequently increased. We 

 also found that our contributors could not possibly have provided, within the 

 limits we originally proposed, adequate discourses on their various topics. It 

 was apparent that we should have to subdivide The Sea into three volumes. The 

 first consists of new thoughts and ideas on Physical Oceanography ; the second 

 on the Composition of Sea Water and Comparative and Descriptive Oceano- 

 graphy ; and the third on the Earth Beneath the Sea and History. The three 

 volumes, therefore, are divided from one another by major divisions of 

 oceanography, and we believe for this reason that our readers will not be 

 inconvenienced by constant cross-referencing from one volume to another. 

 This clear division has also allowed us to index the volumes separately ; it 

 should be possible to select the volume containing information on any 

 particular topic without difficulty. We have no overall index, since for a work 

 of this magnitude it would be cumbersome. 



We considered that for ease of production we should start a new numbering 

 sequence at the beginning of each chapter for figures, equations and tables. In 

 order to avoid confusion in referring back, we have printed the chapter number 

 and section number on alternate pages. 



In collecting the material for these volumes we have had most helpful 

 cooperation from our contributors. In some topics, however, we have failed to 

 find authors, or potential authors have withdrawn. We must admit, therefore, 

 to omissions, some of which are conspicuous and important. By further effort 

 we could doubtlessly have repaired these gaps in subject matter, but this would 

 have delayed publication, and we believe the contributions we already have 

 make a valuable collection. It is possible that in the future a fourth volume 

 might be produced to deal with topics omitted or new since we first started 

 collecting material for The Sea. 



We are greatly indebted to the secretarial assistance provided by Mrs. Joyce 



