vi PREFACE 



in the form of foot-notes, but a small bibliography of the more 

 important publications in the English language is printed as 

 an Appendix. 



Two criticisms will probably occur to many readers, so it 

 may be worth while to attempt to meet them here. In the first 

 place there is no uniformity in reference to depths, tempera- 

 tures, etc. ; the metric system is sometimes used, at other times 

 the depths are given in fathoms. Theoretically it would have 

 been better to have used the metric system only. Actually the 

 British or American seafarers' concept of a fathom is more 

 vivid than that of a metre. Until the metre is universally 

 adopted e.g., in the British Admiralty charts it is inex- 

 pedient to ignore the fathom. The difficulty is, however, more 

 apparent than real, since the table for conversion (p. 198) is 

 available. 



Objection may secondly be taken to the didactic style. 

 This style is inevitable if the information is to be compressed 

 within reasonable compass. 



My best thanks are due to Mr. Wade for friendly assistance 

 in the preparation of the text figures ; to Dr. E. J. Allen, of the 

 Marine Biological Laboratory at Plymouth, for the loan of 

 process blocks illustrating the hydrographicalwork of the Inter- 

 national Council; and to Messrs. J. Engelhorn's Nachfolger 

 of Stuttgart for permission to use certain illustrations taken 

 from Krummel's " Handbuch der Ozeanographie." 



