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Full text of "The depths of the ocean : a general account of the modern science of oceanography based largely on the scientific researches of the Norwegian steamer Michael Sars in the North Atlantic"

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Frontispiece. 



THE DEPTHS OF THE OCEAN 



MACMILLAN AND CO., Limited 

LONDON . BOMBAY • CALCUTTA 
MELBOURNE 

THE MACMILLAN COMPANY 

NEW YORK • BOSTON • CHICAGO 
DALLAS . SAN FRANCISCO 



THE MACMILLAxN CO. OF CANADA, 

TORONTO 



THE "^'"' 

DEPTHS OF THE OCEAN 

A GENERAL ACCOUNT 
OF THE MODERN SCIENCE OF OCEANOGRAPHY 
BASED LARGELY ON THE SCIENTIFIC RESEARCHES 

OF THE NORWEGIAN STEAMER 

MICHAEL SARS 

IN THE NORTH ATLANTIC 

BY 

Sir JOHN MURRAY, K.C.B., F.R.S., etc. 

OF THE 'challenger' EXPEDITION 
AND 

Dr. JOHAN HJORT 

DIRECTOR OF NORWEGIAN FISHERIES 

WITH CONTRIBUTIONS FROM 

Professor A. APPELLOF, Professor H. H. GRAN 
AND Dr. B. HELLAND-HANSEN 



MACMILLAN AND CO., LIMITED 
ST. MARTIN'S STREET, LONDON 

1912 



COPYRIGHT 




PREFACE 



At the International Congress for the Exploration of the Sea 
held on the invitation of the Swedish Government in Stockholm 
in 1899, Sir John Murray was the chief British delegate, and 
acted as president of the physical and chemical section, which 
drew up a programme of work for the proposed investigations 
in the North Sea and in the Norwegian Sea. Although his 
official connection with these marine researches came to an end 
with the close of the first Congress, it is well known that he 
has followed with great interest all the proceedings of the 
International Council during the past ten or twelve years. 

In the year 1909 he chanced to visit Copenhagen at a time 
when one of the annual meetings of the Council was going on, 
and was invited by the members to take part in some of their 
deliberations. In the course of the conversations which 
followed he expressed the opinion that systematic observations 
in the Atlantic might throw much light on some of the problems 
then being studied in our more northern seas. 

Subsequently Sir John Murray wrote to me that if the 
Norwegian Government would lend the "Michael Sars " and 
her scientific staff for a four months' summer cruise in the 
North Atlantic, he would pay all the other expenses. 

When this proposal was laid before the Norwegian Govern- 
ment it was favourably received, and within a few weeks a 
satisfactory financial agreement was drawn up and adopted. 
My scientific colleagues. Professor Gran, Dr. Helland- Hansen, 
Mr. E. Koefoed, and Captain Thor Iversen, who had long been 



vi DEPTHS OF THE OCEAN 

associated with me in oceanographical investigations in the 
Norwegian Sea, likewise received the proposal with enthusiasm. 
A large part of the winter of 1909-10 was spent in making the 
necessary rearrangements on board the ship, in the selection 
and installation of new apparatus and instruments, and in 
choosing the routes where we might expect to get the most 
interesting results. 

By the ist of April 19 10 the ship was fully equipped and 
ready for sea. The first port of call was Plymouth, where 
Sir John Murray embarked, and the last piece of apparatus — 
a large centrifuge — was installed on board. After being 
hospitably entertained by scientific men in London and 
Plymouth, we sailed on the 7th of April for the south-west of 
Ireland, where it was arranged that we should occupy our first 
observing station. The ship worked down the western coasts 
of Europe as far as the Canaries, then proceeded across the 
Atlantic, by way of the Azores, to Newfoundland, afterwards 
re-crossing from Newfoundland to the coast of Ireland, and 
returned to Bergen by way of the Faroe Channel. About 
1 20 observing stations were established, and the expedition was 
in all respects successful. 

It was agreed that the zoological and all other collections 
and observations made during the cruise should be sent to 
Bergen, Sir John Murray generously agreeing to provide ^500 
to enable the collections to be sorted out and arranged for 
study by specialists. 

It was further arranged that a general account of the cruise 
and of the results of the observations should be published as 
soon as possible after the return of the expedition, and this 
volume has accordingly been prepared. Its main object is to 
indicate the most important results of the voyage in so far as 
these can be stated at the present time, although the biological 
collections and the physical observations have as yet only been 
examined in a preliminary way. In preparing the various 



DEPTHS OF THE OCEAN vii 

chapters the previous investigations of the " Michael Sars " in 
the North Sea and in the Norwegian Sea generally have been 
taken into consideration, in order to compare the physical and 
biological conditions prevailing in northern waters with those in 
the Atlantic. In this way it is hoped that the book as a whole 
will present the student with a fairly complete epitome of recent 
advances in the modern science of oceanography, even though 
it has proved impossible to give a complete review of the 
literature of the subject. 

The historical chapter and the chapter on the Depths and 
Deposits of the Ocean have been prepared by Sir John Murray ; 
that on Physical Oceanography by Dr. Helland- Hansen ; that 
on Phytoplankton by Professor Gran ; and that on the Bottom 
Fauna by Professor Appellof, while the chapters dealing with 
the equipment of the ship, the working of the gear, the narra- 
tive of the cruise, the fishes from the sea-bottom, the pelagic 
animals, and general biology have been written by myself 

In the examination of the zoological collections I have 
received most valuable assistance from Mr. James Grieg, 
Mr. Einar Koefoed (who took part in the expedition and also 
in the special examination of the fishes), Mr. Einar Lea, 
and Mr. Oscar Sund. All the original drawings have been 
made by Mr. Thorolv Rasmussen, who also took part in the 
cruise, and was continually engaged in making drawings and 
sketches on board ship. To all these gentlemen I acknowledge 
my indebtedness. 

The biological collections have been distributed to 
specialists in different parts of the world, and the following 
have sent me preliminary reports on their results, which I 
have been able to use in this book : — 

Mr. Paul Bjerkan, Bergen ; 

Dr. Kristine Bonnevie, Christiania ; 

Dr. August Brinkmann, Bergen ; 

Dr. Hjalmar Broch, Trondhjem ; 



viii DEPTHS OF THE OCEAN 

Professor Carl Chun, Leipzig ; 
Mr. C. Dons, Tromso ; 
Dr. P. P. C. Hoek, Haarlem ; 
Dr. O. Nordgaard, Trondhjem ; 
Professor G. O. Sars, Christiania ; 
Professor R. Woltereck, Leipzig. 

Sir John Murray's secretary, Mr. James Chumley, has 
given us most valuable assistance by correcting the English 
manuscript and taking care of all printing arrangements. Sir 
John Murray wishes also to acknowledge the co-operation of 
Dr. Caspari and the other assistants in the " Challenger " office 
in correcting proofs and preparing the indexes of this book. 

The authorities of the Bergen Museum have undertaken to 
publish a detailed account of the voyage and of the physical and 
biological observations, in a series of quarto volumes which 
will be issued from the press at intervals during the next few 
years. These more detailed reports will undoubtedly form 
valuable contributions to the science of oceanography. I 
hope also that this general account will be of use to those 
engaged in the study of oceanography, and that it may lead to 
further investigations in the North Atlantic — that wonderful 
ocean bordered by nearly all the seafaring countries. As will be 
seen from several of the following chapters. Sir John Murray's 
well-known scientific views and his original ideas have been of 
great value to this expedition. I wish therefore to express my 
indebtedness to Sir John Murray, not only for the opportunity 
of engaging in this interesting Atlantic cruise, but also for 
his kindness in giving the benefit of his great experience to 
the advancement of the undertaking. 

JOHAN HJORT. 

Bergen, February 19 12. 



^1HABDM.74-T0ill, 



CONTENTS 



Table I. for converting Metres into Fathoms . . . xiii 
„ II. for converting Degrees Fahrenheit into Degrees 

Centigrade ...... xiv 

,, III. showing Mean Temperature at Various Depths for 

THE Whole Ocean ..... xvi 

„ IV. showing Positions of " Michael vSars " Stations , xvii 



CHAPTER I 

A Brief Historical Review of Oceanographical Investigations 



CHAPTER II 

The Ship and its Equipment 



CHAPTER III 

The Work and Cruises of the " Michael Sars 



52 



CHAPTER IV 

The Depths and Deposits of the Ocean . 



129 



CHAPTER V 



Physical Oceanography 



39637 



X DEPTHS OF THE OCEAN 

CHAPTER \T 

I'AGE 

Pelagic Plant Life ....... 307 

CHAPTER Vn 

Fishes from the Sea-Bottom . . . . -387 

CHAPTER Vni 

Invertebrate Bottom Fauna of the Norwegian Sea and North 

Atlantic . . . . . . .457 

CHAPTER IX 
Pelagic Animal Life ....... 561 

CHAPTER X 
General Biology ....... 660 

INDEXES 

Index of Proper Names ...... 787 

Index of Genera and Species . . . . .791 

General Index ....... S09 




MAPS AND PLATES 



Map I. Reproduction of Lieut. Maury's Map of the North Atlantic, 
1854 

„ II. Bathymetrical Chart of the Oceans showing the " Deeps,' 
according to Sir John Murray 

,, III. Depths of the North Atlantic compiled from the latest 
sources, 191 1 . 

,, IV. Deposits of the North Atlantic, after Sir John Murray 

Plate I. Cyclothone . 

,, II. Argyropelecus and Gonostoma 

,, III. Red-coloured Shrimps 

„ IV. Flying-Fish and Pilot-Fish . 

„ V. Sargasso Fish 

„ VI. Sargasso Crabs 

„ VII. Coast Fishes from the bottom 

,, VIII. Deep-Sea Fishes from the bottom 

,, IX. Bathytroctes 



DEPTHS OF THE OCEAN 



I. Table for Converting Metres into Fathoms 



Metres. 


Fathoms. 


Metres. 


Fathoms. 


I 


0-55 


200 


109.36 


~ 


1.09 


300 


164.04 


3 


1.64 


400 


218.73 


4 


2.19 


SCO 


273-41 


5 


2-73 


600 


328.09 


' 


3-28 


700 


382.77 


7 


3.83 


800 


437-45 


8 


4-37 


900 


492.13 


9 


4.92 


1,000 


546.82 


lO 


5-47 


2,000 


1,093.63 


20 


10.94 


3,000 


1,640.45 


3° 


16.40 


4,000 


2,187.27 


40 


21.87 


5,000 


2,734.08 


50 


27-34 


6,000 


3,280.90 


60 


32.S1 


7,000 


3,827.72 


70 


3S.2S 


8,000 


4>374-53 


So 


43-75 


9,000 


4,921.35 


•90 


49-21 


10,000 


5,468.16 


100 


54.68 







DEPTHS OF THE OCEAN 

II. Table for Converting Degrees of Fahrenheit into 
Degrees of Centigrade 



°F. 


°c. 


°F. 


°c. 


"¥. 


°C. 


°F. 


"C. 


°F. 


°C. 


1 
80.0 


26.67 


75-5 


24.17 


71.0 


21.67 


66.5 


19.17 


62.0 \ 


16.67 


79-9 


26.61 


75-4 


24.'! r 


70.9 


21.61 


66.4 


19. II 


61.9 


16.61 


79.8 


26.56 


75-3 


24.05 


70.8 


21.56 


66.3 


19.05 


61.8 


16.56 


79-7 


26.50 


75-2 : 


24.00 


70.7 ! 


21.50 


66.2 


19.00 


61.7 


16.50 


79.6 


26.44 


■ 75-1 


23-95 


70.6 1 


21.44 


66.1 


18.95 


61.6 


16.44 


79-5 i 


26.39 


75-0 i 


23-S9 


70.5 1 


21.39 


66.0 1 


18.89 


61.5 


16.39 


79-4 


26.33 


74-9 


23-83 


70.4 


21.33 


65-9 


18.83 


61.4 


16.33 


79-3 


26.28 


74-8 


23.78 


70.3 


21.28 


65.8 


18.78 


61.3 


16.28 


79.2 j 


26.22 


74-7 


23.72 


70.2 


21.22 


65-7 


18.72 


61.2 


16.22 


79-1 


26.17 


74-6 


23.67 


70.1 


21.17 


65.6 


18.67 


61. 1 


16.17 


79-0 


26.11 


74.5 


23.61 


70.0 


21. II 


65.5 


18.61 


61.0 


16. II 


78.9 


26.05 


74-4 


23-56 


69.9 


21.05 


65-4 


18.56 


60.9 


16.05 


78.8 


26.00 


74-3 


23-50 


69.8 


21.00 


65-3 


18.50 


60.8 


16.00 


78.7 


25-95 


74.2 


23-44 


69-7 


20.95 


65.2 


18.44 


60.7 


15-95 


78.6 


25.89 


74-1 


23-39 


69.6 


20.89 


65.1 


18.39 


60.6 


15.89 


.78.5 


25-83 


74.0 


23-33 


69-5 


20.83 


65.0 


18.33 


60.5 


15-83 


78.4 


25.78 


73-9 


23.28 


69.4 


20.78 


64.9 


18.28 


60.4 


15-78 


78.3 


25-72 


73-8 


23.22 


69-3 


20.72 


64.8 


18.22 


60.3 


15-72 


78.2 


25.67 


73-7 


23-17 


69.2 


20.67 


64.7 


18.17 


60.2 


15-67 


78.1 


25.61 


73-6 


23.11 


69.1 


20.61 


64.6 


18.11 


60.1 


15.61 


78.0 


25-56 


73-5 


23-05 


69.0 


20.56 


64.5 


18.05 


60.0 


15-56 


77-9 


25-50 


73-4 


23.00 


68.9 


20.50 


64.4 


18.00 


59-9 


15-50 


77.8 


25-44 


73-3 


22.95 


68.8 


20.44 


64.3 


17-95 


59-8 


15-44 


77-7 


25-39 


73-2 


22.89 


68.7 


20.39 


64.2 


17.89 


59-7 


15-39 


77.6 


25-33 


73-1 


22.83 


68.6 


20.33 


64.1 


17-83 


59-6 


15-33 


77-5 


25.28 


73-0 


22.78 


68.5 


20.28 


64.0 


17.78 


59-5 


15.28 


77-4 


25.22 


72.9 


22.72 


68.4 


20.22 


63-9 


17.72 


59-4 


15.22 


77-3 


25-17 


72.8 


22.67 


68.3 


20.17 


63.8 


17.67 


59-3 


15-17 


77.2 


25.11 


72.7 


22.61 


68.2 


20.11 


63-7 


17.61 


59-2 


15.11 


77.1 


25-05 


72.6 


22.56 


68.1 


20.05 


63.6 


17-56 


59-1 


15-05 


77.0 


25.00 


72.5 


22.50 


68.0 


20.00 


63-5 


17-50 


59-0 


15.00 


76.9 


24-95 


72.4 


22.44 


67.9 


19.95 


63.4 


17.44 


58.9 


14-95 


76.8 


24.89 


72.3 


22.39 


67.8 


19.89 


63-3 


17-39 


58.8 


14.89 


76.7 


24.83 


72.2 


22.33 


67.7 


19.83 


63.2 


17-33 


58.7 


14.83 


76.6 


24.78 


72.1 


22.28 


67.6 


19.78 


63.1 


17.28 


58.6 


14.78 


76.5 


24.72 


72.0 


22.22 


67.5 


19.72 


63.0 


17.22 


58.5 


14.72 


76.4 


24.67 


71.9 


22.17 


67.4 


19.67 


62.9 


17.17 


58.4 


14.67 


76.3 


24.61 


71.8 


22.1 1 


67-3 


19.61 


62.8 


17.11 


58.3 


14.61 


76.2 


24.56 


71.7 


22.05 


67.2 


19.56 


62.7 


17.05 


58.2 


14.56 


76.1 


24.50 


71.6 


22.00 


67.1 


19.50 


62.6 


17.00 


58.1 


14.50 


76.0 


24.44 


71-5 


21.95 


67.0 


19.44 


62.5 


16.95 


58.0 


14.44 


75-9 


24-39 


71.4 


21.89 


66.9 


19-39 


62.4 


16.89 


57.9 


14.39 


75.8 


24-33 


71-3 


21.83 


66.8 


19-33 


62.3 


16.83 


57-8 


14.33 


75-7 


24.28 


71.2 


21.78 


66.7 


19.28 


62.2 


16.78 


57.7 


14.28 


75-6 


24.22 


71. 1 


''■'' 


66.6 


19.22 


62.1 


16.72 


57.6 


14.22 



DEPTHS OF THE OCEAN ^ 

II. Table for Converting Degrees of Fahrenheit into Degrees of 
C^^TlG^Mi-E— Continued 



°F. 


°C. 


"F. 


°C. 


°F. 


°C. 


°F. 


°C. 


°F. 


°C. 


57-5 


14.17 


52-9 


II. 61 


48.3 


9-05 


43-7 


6.50 


39-1 


3-95 


57-4 


14.11 


52.8 


11.56 


48.2 


9.00 


43-6 


6.44 


39-0 


3-89 


57-3 


14.05 


52-7 


11.50 


48.1 


8-95 


43-5 


6-39 


38-9 


3-83 


57-2 


14.00 


52.6 


11.44 


48.0 


8.89 


43-4 


6.33 


38.8 


3-78 


57-1 


13-95 


52-5 i 


11-39 


47-9 


8.83 


43-3 


6.28 


38.7 


3-72 


57-0 


13.89 


52.4 


11-33 


47-8 


8.78 


43-2 


6.22 


38.6 


3-67 


56.9 


13-83 


52-3 


11.28 


47-7 


8.72 


43-1 


6.17 


38.5 


3.61 


56.8 


13-78 


52.2 


11.22 


47-6 


8.67 


43-0 


6.11 


38.4 


3-56 


56.7 


13.72 


52.1 


11.17 


47-5 


8.61 


42.9 


6.05 


38.3 


3-50 


56.6 


13.67 


52.0 


II. II 


47-4 


8.56 


42.8 


6.00 


38.2 


3-44 


56.5 


13.61 


51-9 


11.05 


47-3 


8.50 


42.7 


5-95 


38.1 


3-39 


56-4 


13-56 


51-8 


11.00 


47-2 


8.44 


42.6 


5-89 


38.0 


3-33 


56.3 


13-50 


51-7 


10.95 


47-1 


8-39 


42.5 


5-83 


37-9 


3-28 


56.2 


13-44 


51.6 


10.89 


47-0 


8.33 


42.4 


5-78 


37-8 


3.22 


56.1 


13-39 


51-5 


10.83 


46.9 


8.28 


42.3 


5-72 


37-7 


3-17 


56.0 


13-33 


51-4 


10.78 


46.8 


8.22 


42.2 


5-67 


37-6 


3-11 


55-9 


13.28 


51-3 


10.72 


46.7 


8.17 


42.1 


5.61 


37-5 


3-05 


55-8 


13.22 


51.2 


10.67 


46.6 


8.11 


42.0 


5-56 


37-4 


3.00 


55-7 


13-17 


51. 1 


10.61 


46.5 


8.05 


41.9 


5-50 


37-3 


2-95 


55-6 


13.11 


51.0 


10.56 


46.4 


8.00 


41.8 


5-44 


37-2 


2.89 


55-5 


13-05 


50-9 


10.50 


46.3 


7-95 


41.7 


5-39 


37-1 


2.83 


55-4 


13.00 


50.8 


10.44 


46.2 


7.89 


41.6 


5-33 


37-0 


2.78 


55-3 


12.95 


50.7 


10.39 


46.1 


7-83 


41-5 


5.28 


36-9 


2.72 


55-2 


12.89 


50.6 


10.33 


46.0 


7-78 


41.4 


5.22 


36.8 


2.67 


55-1 


12.83 


50-5 


10.28 


45-9 


7.72 


41-3 


5-17 


36-7 


2.61 


55-0 


12.78 


50-4 


10.22 


45-8 


7.67 


41.2 


5-11 


36.6 


2.56 


54-9 


12.72 


50-3 


10.17 


45-7 


7.61 


41. 1 


5-05 


36.5 


2-50 


54.8 


12.67 


50.2 


10. II 


45-6 


7-56 


41.0 


5.00 


36.4 


2.44 


54-7 


12.61 


50.1 


10.05 


45-5 


7-50 


40.9 


4-95 


36.3 


2-39 


54.6 


12.56 


50.0 


10.00 


45-4 


7-44 


40.8 


4-89 


36.2 


2-33 


54-5 


12.50 


49-9 


9-95 


45-3 


7-39 


40.7 


4-83 


36.1 


2.28 


54-4 


12.44 


49-8 


9.89 


45-2 


7-33 


40.6 


4-78 


36.0 


2.22 


54-3 


12.39 


49-7 


9-83 


45-1 


7.28 


40.5 


4-72 


35-9 


2.17 


54-2 


12.33 


49.6 


9-78 


45-0 


7.22 


40.4 


4-67 


35-8 


2. II 


54-1 


12.28 


49-5 


9.72 


44-9 


7.17 


40.3 


4-61 


35-7 


2.05 


54-0 


12.22 


49-4 


9.67 


44-8 


7.11 


40.2 


4-56 


35-6 


2.00 


53-9 


12.17 


49-3 


9.61 


44-7 


7-05 


40.1 


4-50 


35-5 


1-95 


53-8 


i 12. II 


49-2 


9-56 


44.6 


7.00 


40.0 


4-44 


35-4 


1.89 


53-7 


12.05 


49.1 


9-50 


44-5 


6.95 


39-9 


j 4-39 


35-3 


1.83 


53.6 


12.00 


49.0 


9-44 


44.4 


6.89 


39-8 


1 4-33 


35-2 


1.78 


53-5 


11-95 


48.9 


9-39 


44-3 


i 6.83 


39-7 


' 4-28 


35-1 


1.72 


53-4 


11.89 


48.8 


9-33 


44.2 


6.78 


39-6 


1 4.22 


35-0 


1.67 


53-3 


11.83 


48.7 


9.2S 


44.1 


6.72 


39-5 


4-17 


34-9 


1.61 


53-2 


11.78 


48.6 


9.22 


44.0 


6.67 


39-4 


4-II 


34-8 


1.56 


53-1 


11.72 


48.5 


9.17 


43-9 


6.61 


39-3 


4-05 


34-7 


1.50 


53-0 


11.67 


48.4 


9.11 


43-8 


6.56 . 


39-2 


4.00 


34-6 


1-44 



DEPTHS OF THE OCEAN 



II. Table for Converting Degrees of Fahrenheit into Degrees of 
Centigrade — Continued 



°F. 


.°c. 


°F. 


°C. 


°F. 


°C. 


°Y. 


°C. 


°F. 


°C. 


34-5 


1-39 


33-1 


0.61 


31.8 


- 0.1 1 


30-5 


-0.83 


29.2 


-1.56 


34-4 


^■Zl 


2,Z-'' 


0.56 


31-7 


-0.17 


30-4 


-0.89 


29.1 


- 1. 61 


34-3 


1.28 


32-9 


0.50 


31.6 


- 0.22 


Z^-Z 


-0-95 


29.0 


-1.67 


34-2 


1.22 


32.8 


0.44 


31-5 


-0.28 


30.2 


- 1. 00 


28.9 


- 1.72 


34-1 


1. 17 


32.7 


0-39 


31-4 


-o-ZZ 


30.1 


- 1-05 


28.8 


-1.78 


34-0 


I. II 


32.6 


0.33 


31-3 


-0-39 


30.0 


- I. II 


28.7 


-1-83 1 


33-9 


1.05 


32-5 


0.28 


31.2 


-0.44 


29.9 


- i-U 


28.6 


-1.89 


33-8 


1. 00 


32.4 


0.22 


3I-I 


- 0.50 


29.8 


- 1.22 


28.5 


-1-95 1 


33-7 


0.95 


32.3 


0.17 


31.0 


-0.56 


29.7 


-1.28 


28.4 


- 2.00 


33-6 


0.89 


32.2 


0. II 


30-9 


- 0.61 


29.6 


- 1-33 


28.3 


-2.05 I 


33-5 


0.83 


32.1 


0.05 


30.8 


- 0.67 


29-5 


-1-39 


28.2 


- 3. II 


33-4 
33-3 


0.78 
0.72 


32.0 


0.00 


30-7 
30.6 


-0.72 
-0.78 


29.4 
29-3 


- 1-44 
-1.50 


28.1 
28.0 


-2.17 
- 2.22 


31-9 


- 0.05 


33-2 


0.67 



















III. Table showing Decrease of Mean Temperature with 
Increase of Depth for the whole Ocean 

Calculated from the " Challenger " and all other observations available up to the year 1S95. 



Depth. 


Temperature. 


Fathoms. 


Metres. 


°F. 


°C. 


100 


183 


60°. 7 


i5'-95 


200 


366 


50°. I 1 10^05 


300 


549 


44'-7 ' 7 -05 


400 


732 


4i°.8 i 5 .44 


500 


914 


40 .1 4 .50 


600 


1097 


39.0 3°.89 


700 


1280 


38°-i 3-39 


800 


1463 


37°-3 2°.95 


900 


1646 


36°.8 , 2°.67 


1000 


1829 


36^5 . 2^.50 


1 100 


2012 


36°. I 1 2°. 28 


1200 


2195 


35°-8 


2 .11 - 


1300 


2377 


35°-6 


2 .00 


1400 


2560 


35 -4 


i°.89 


1500 


2743 


35 -3 


i°.83 


2200 


4023 


35 -2 


i\78 



Except in the Norwegian Sea and in the North-West Atlantic to the south-east of Greenland, 
the temperatures in the North Atlantic at all depths down to the bottom are above the means 
for the whole ocean as given in this table. On the other hand, the temperatures in the North 
Pacific in the same latitudes and depths are, for the most part, below these means. 



DEPTHS OF THE OCEAN 



IV. Table showing the Positions of the " Michael Sars " 
Observing Stations, 1910 



Night Stations where the nets were towed between midnight and dawn are distinguished 
by asterisks. 



Station. 



Date. 



Depth in 
Metres. 



Depth in 
Fathoms. 



From Plymouth to Gibraltar. 



April 



9 


N. 

49' 27' 


10 


49 30 


10 


49 32 


lo-n 


49^ 38' 


16 


51 24 


16-17 


50 33 


17 


49 54 


18 


48° 53' 


18 


47° 49' 


19-21 


45° 26' 


21 


44 25 


21 


43 II 


22 


41 32 


22 


41 15 


22-23 


40° 56 


23 


40° 15 


23 


38° 20' 


29-30 


35° 56' 



w. 
8° 36 




9° 42 




10 49 




II' 35 

9° 27 




10 42 




12 10 




11^ 31 

10° 52 




9 20 
9° 18 
9° 26 




9° 05 
8° 54 
9° 28 




9^ 23 




9 43 




5 43 





146 

149 
184 
923 

68 
168 
[813 



4700 

166 
78 
69 

154 

i860 

About 400 



80 
82 

lOI 

504 
37 
92 

991 



2570 

91 

42 

38 

"84 

1017 

219 



From Gibraltar to Gran Canaria. 



19 
20 
21 
22 
^23 
'24 

25 A 
'25 B 
26 
27 
28 
29 
30 
31 
32 

33 

'34 



May 



2-3 

5 

5 

5 

5-6 

6-7 



9 

9 

9-10 
10 
10 
10 
II 
13-14 



36° 


5' 


35 


25 


35 


31 


35 


42 


35 


32 


35 


34 


35 


36' 


35 


46' 


36" 


53' 


36^ 


31' 


36^ 





35 


10 


34 


38' 


33 


47' 


33 


27' 


31' 


17 


28° 


52' 



4 42 




6° 25 




6° 35 




6^51 




7 7 




7 35 




8"2.s 




8° 16 




6° 48 




7° I 




7 19 




7" 55 




8° 22 




8° 27 




8" 32 




10° 6 




14° 16' 



141 

535 

835 

1215 

1615 
2300 

2055 
50 



77 
292 

456 

664 

883 

1258 

1124 

27 



184 


lOI 


105 


57 


100 


55 


170 


1187 



DEPTHS OF THE OCEAN 



IV. Table showing the Positions of the "Michael Sars" 
Observing Stations, \()\o— Continued 



Station. 



Date. 



Position. 



Depth in Depth in 
Metres. i Fathoms. 
I 



Between Gran Canaria and Cape Bojador (Africa). 



35 
36 
37 
38 
39 A 

'39 B 

40 
41 

^42 



May 18-19 


27° 27' 


14° 52' 


2603 


1424 


„ 19-20 


26° 12' 


14° 26' 


10 


5 


„ 20 


26° 6' 


14° 33' 


39 


21 


„ 20 


26° 3' 


14° 36' 


77 


42 


„ 20-21 


26° 3' 


15° 0' 


214 


116 


„ 21 


26° 3' 


15° °' 


267-280 


146-15 


„ 22-23 


28° 15' 


13° 29' 


1197 


655 


M 23 


28° 8' 


13 35 


1365 


747 


„ 23-24 


28° 2' 


14° 17' 







From Gran Canaria to Fayal (the Azores). 



43 
44 

*45 
46 

47 
48 

49 A 

49 B 
*49C 

50 
*5i 

52 
*53 

54 

55 
*56 

57 



*S8 



May 2 7 
28 



June I 



26-29 
29 



1-2 

4 

5-6 

6-7 

8-9 

10 

10 

lO-II 

II 



11-13 



28° 


2' 


28" 


37' 


28" 


42 


28" 


56' 


29" 


2 


28" 


54 


29 


6' 


29" 


8' 


29 


7 


30 


8' 


31 


20 


31 


24 


34 


59 


35 


37 


36" 


24 


36" 


53' 


37 


20 


37 


11 


37 


33 


37 


33 


37 


37 


37 


38 


37 


42 



17 
19° 

20° 

21° 

22° 

24° 

25° 

25° 
25° 
31° 

35° 

34° 

ZZ 

30° 

29° 

29° 

29° 

29° 
29° 

29° 
29° 
29° 
29° 



5160 



3886 

2615-2865 
• 3185 

3239 

3239 

1700 
1510 
1735 
1235 

948 

990 



2822 



2124 

1430-1567 
1742 
1770 
1770 

930 

825 

949 
675 
518 
541 



DEPTHS OF THE OCEAN 



IV. Table showing the Positions of the "Michael Sars' 
Observing Stations, igio—Co/ituu/ed 



Station. 



Date. 



Position. 



Depth in Depth in 

Metres. Fathoms. 



From the Azores to Newfoundland. 







N. 


w. 






59 


June 17 


38° 30' 


28^ 37' 


225 


123 


60 


„ 20 


37° 9' 


38° 5' 






61 


„ 20 


37° 7' 


38° 34' 




... 


62 


„ 20-21 


36° 52' 


39° 55' 






63 


„ 22 


36° 5' 


43° 58' 


5°35 


2753 


64 


„ 24 


34° 44' 


47 52' 






65 


„ 25 


37° 12' 


48^ 30' 






66 


„ 26 


39° 30' 


49° 42' 






67 


„ 27 


40° 17' 


50° 39' 


... 




68 


„ 28 


39° 20' 


50° 50' 






69 


„ 29 


41° 39' 


51° 4' 


'.'.'. 




70 


„ 30 


42° 59' 


51° 15' 


1 100 


602 


70 a 


„ 30 






... 




71 


„ 30 


43° 18' 


51° 17' 


147-138 


80-75 


72 


July I 


44° 35' 


51° 15' 


75 


41 


73 


„ I 


45° 58' 


51° 25' 


70 


38 


74 


5) 2 


47" 25' 


52' 20' 


156 


85 



From Newfoundland to Glasgow. 



75 


July 9 


76 


9 


77 


„ 10 


78 


„ 10 


79 


„ 10 


80 


M II 


81 


„ 12 


81 A 


,, 12 


82 


V 13 


83 


„ 14 


84 


15 


*85 


" 15- 


86 


„ 16 


87 


,1 17 


88 


„ 18 


88 a 


„ 18 


88 b 


„ 19 



16 



47° 


22' 


47° 


11' 


47° 


18' 


47 


17' 


47° 


16' 


47° 


34' 


48° 


2' 


48° 


24' 


48" 


30' 


48" 


4' 


47 


58' 


47 


29 


46" 


48' 


45 


26' 



49° 16 

47° 6 

44° 54 
44° 2>2 
44° 17 

43° II 

39° 55 

36° 53 
2,2,' 35 
32° 25 
31° 41 
30° 20 

27° 46' 

25° 45' 



380 

171 

202 
271 



2157 
3120 



66 

2^ 

93 
no 

147 
1094 



1180 
1706 



DEPTHS OF THE OCEAN 



IV. Table showing the Positions of the "Michael Sars" 
Observing Stations, i<^io— Continued. 



Station. 


Date. 


Position. 


Depth in 


Depth in 










Metres. 


Fathoms. 




1 "N- 


\v. 






89 Jul: 


^ 20 


45° 55 


22° 24' 






90 


21 


46^58 


19° 6' 






91 


22 


47° 32 


16° 38' 


4922 


2691 


*92 


23-24 


48° 29 


13° 55' 






93 


25 


50° 13 


11° 23' 


1257 


687 


94 


26 


50° 13 


11° 23' 


1565 


856 


*95 


26-27 


50^ 22 


11° 44' 


1797 


983 


96 


27 


50° 57 


10° 46' 


184 


lOI 




From Qlasg 


ow to Bergen. 




97 Au^ 


^ust 4 


56° 15 


8° 28' 


139 


76 


98 


5 


56° 33 


9° 30' 


I 000- I 360 


547-744 


99 


6 


57° 45 


13° 40' 


149 


82 


100 , 


6 


57° 48 


'-° 43; 


1530 


836 


lOI , 


, 6-7 


57° 41 


11° 48' 


1853 


1013 


*I02 


, 9-10 


60° 57 


4° 38' 


1098 


600 


103 


, 10 


60° 26 


2° 34' 


159 


87 


104 


, 10 


60° 35 


3° 20' 


234 


127 


105 


, 10 


60° 45 


3° 50' 


670 


366 


106 


, lO-II 


60° 54 


4° 28' 


1 1 40 


624 


107 


5 II 


61° 4 


5° 5' 


730 


399 


108 


) II . 


61° 13 


5° 47' 


249 


136 


109 


) II 


61° 22 


6° 24' 


228 


124 


no 


, 11-12 


61° 39 


5° 57' 


170 


93 


III 


, 12 


61° 32 


5° 15' 


300 


164 


112 


, 12 


61° 24 


4° 34' 


560 


306 


TI3 


, 12 


61° 16 


3° 50' 


1080 


591 


114 


, 12-13 


61; 8 


3° 16' 


1047 


573 


"5 


, 13-14 


61° 


2° 40' . 


580 


317 


116 


> 14 


60° 52 


2° i' 


125 


69 




H.M.S. "Challenger 

Shortenins; sail to sound. 



CHAPTER I 



A BRIEF HISTORICAL REVIEW OF OCEANOGRAPHICAL 
INVESTIGATIONS 

The phenomena displayed at the surface of the ocean have Development 
been the object of observation from the earliest ages, — waves, scjenceTf^^'^'^ 
currents, winds, tides, and the temperature of the water were oceanography. 
matters of very great importance and concern to the earliest 
navigators. It was not, however, till about the time of the 
famous "Challenger" Expedition, nearly forty years ago, that 
any systematic attempts were made to examine the deeper and 
more remote regions, or to explore the physical and biological 
conditions of the ocean as a whole. 

It seems desirable to commence this book by indicating, as 
briefly as possible, the various steps by which the present 
development of the modern science of oceanography has been 
reached. This can best be accomplished by (i) pointing out 
some of the scientific observations made previous to the 
"Challenger" Expedition, (2) referring to the expeditions 
contemporaneous with and subsequent to that expedition, and 
{3) referring to the work carried out at marine biological 
laboratories, and in connection with international and other 
fishery investigations. 

B 



Early 

soundines. 



Cusanus" 
bathometer. 



Puehler's 
apparatus. 



Alberti's 
apparatus. 

Hooka's 

apparatus. 



First sound- 
ings laid down 
on maps. 



First attempt 
at deep-sea 
sounding. 



Magellan. 



2 DEPTHS OF THE OCEAN chap. 

From time immemorial soundings were taken by hand 
with a plummet, always in shallow water near land, but attempts 
have not been wanting to sound the ocean without the aid of a 
line. Thus about the middle of the fifteenth century Cardinal 
Nicolaus Cusanus invented a bathometer, consisting of a hollow 
sphere with a heavy weight attached by means of a hook ; on 
touching the bottom the weight was detached, and the sphere 
returned to the surface, the interval of time from the launching 
of the apparatus to the re-appearance of the sphere at the 
surface indicating the depth. A century later Puehler improved 
on Cusanus' bathometer by adding a piece of apparatus 
(clepsydra) to measure the time from the disappearance to the 
re-appearance of the float, using for this purpose a clay vase 
with a small orifice at the bottom, through which water was 
made to enter during the period of the experiment, the amount of 
water in the vase indicating the depth. Alberti subsequently 
replaced the sphere by a light, bent metal tube. In 1667 
Robert Hooke described in the Philosophical Transactions a 
similar apparatus, shown in the tailpiece to Chapter IV., with 
which experiments were made in the Indian Ocean, but there 
was always doubt as to the moment when the float returned 
to the surface, and to remedy this Hooke introduced first a 
clockwork odometer to register the descent, and then two 
odometers — one for the descent and the other for the ascent. 
These various forms of bathometers, though interesting historic- 
ally, proved of little practical value. 

Soundings in shallow water first appeared on a map by 
Juan de la Cosa in 1504, and soundings were laid down 
on maps by Gerard Mercator in 1585 and by Lucas Janszon 
Waghenaer in 1586. 

Probably the first attempt at oceanographical research to 
which the term " scientific " may be applied is Magellan's 
unsuccessful effort to determine the depth of the Pacific Ocean 
during the first circumnavigation of the globe. In 1521, we 
are told, Magellan tried to sound the ocean between the two 
coral islands, St. Paul and Los Tiburones in the Low Archi- 
pelago, making use of the sounding lines carried by explorers 
at that period, which were only 100 to 200 fathoms in length. 
He failed to touch bottom, and therefore concluded that he had 
reached the deepest part of the ocean. This first authentic 
attempt at deep-sea sounding ever made in the open sea is 
historically extremely interesting, though scientifically the result 
was negative. 



OCEANOGRAPHICAL INVESTIGATIONS 3 

The expedition of Edmund Halley, Astronomer-Royal, in Haiiey's 
1699, to improve our knowledge concerning longitude and the expedition. 
variation of the compass, was a purely scientific voyage, though 
it may be said that scientific voyages were really initiated at 
the time of James Cook in the second half of the eighteenth 
century. 

Cruquius introduced bathymetrical contours on a chart of the Bathymetricai 
River Merwede published in 1728. Thus contour lines were Jownonmips. 
first used on maps to show the depths of the sea and not the cruquius. 
heights of the land. 

In a map published by Philippe Buache in 1737 we find the Buache. 
bottom of the sea again represented by isobathic curves, 
intended to show that certain elevations of the sea-floor 
correspond to the orography of the neighbouring land. He 
develops these ideas in his Essay on Physical Geography, 
published in 1752, maintaining that the globe is sustained by 
chains of mountains crossing the sea as well as the land, 
forming as it were the framework of the globe — a view 
previously expressed by Father Athanasius Kircher. His Kirchei. 
conception of submarine mountains was a first step towards 
founding geography on the real form and relief of each region. 

The dredge seems to have been first used by two Italians, First use of 
Marsigli and Donati, about the year 1750, for obtaining marine ''^'^^•^^se- 
organisms from shallow water, and a modification of this form Doiiatf/^"*^ 
was introduced by O. F. Muller in 1799, which was known as o. f. Muiier. 
the naturalist's dredge. 

In the middle of the eighteenth century Dalrymple and Temperature 
Davy made observations on the temperature of the equatorial observations. 
currents during a voyage to the East Indies. anc/Da?)!^ 

In 1770 Benjamin Franklin published the first map of the Benjamin 
Gulf Stream (see figure in Chapter V.), and in 1776 Charles F'^nkiin. 
Blagden was engaged in the study of temperature distribution ^^^g^'*^"- 
on the North i^merican coasts, reporting on his results to the 
Royal Society of London in 1781. 

During Cook's voyages (1772-73), temperature observations James Cook, 
beneath the surface were taken by the Forsters, father and son. The Forsters. 
but the first use of self-registering thermometers for determining 
the temperature beneath the surface of the sea was during Lord 
Mulgraves' expedition to the Arctic in 1773 by Dr. Irvine, who Irvine. 
seems also to have constructed a water-bottle for bringing up 
water-samples from various depths, one sample giving a reading 
of 40^ Fahr., while the surface temperature was 55^ Fahr. 



I'ullcn. 



4 DEPTHS OF THE OCEAN 

During this expedition also some of the earhest attempts at 
deep-sea sounding were made by Captain Phipps, the deepest 
sounding being 683 fathoms, from which depth he brought up a 
sample of Blue mud. 

In 1780 Saussure determined the temperature of the 
Mediterranean at depths of 300 and 600 fathoms by protected 
thermometers, and in 1782 Six's maximum and minimum 
thermometer was invented, and subsequently made use of by 
Krusenstern in 1803, by Kotzebue in 18 15, by Sir John Ross 
accompanied by Sir Edward Sabine in 18 18, by Parry in 1819, 
and by Dumont d'Urville 
in 1826. Slow-conduct- 
ing water - bottles were 
used by Peron in 1800, 
by Scoresby in 181 1, who 
recorded warmer water 
beneath the colder sur- 
face layers in the Arctic 
regions, and by Kotzebue 
accompanied by Lenz in 
1823. Protected thermo- 
meters were used for 
deep - sea temperatures 
by Thouars in 1832, by 
Martins and Bravais in 
1839, and by Sir James 
Clark Ross during his 
Antarctic expedition from 
1839 to 1843, the last- 
mentioned making also 
many observations on 
the density of the water at various depths. In 1843 Aime- 
introduced reversible outflow thermometers, and about 1851 
Maury used cylinders of non-conducting material for taking 
temperatures in deep water. But it was only when thermo- 
meters with bulbs properly protected from pressure came into 
use that oceanic temperatures could be recorded with precision. 
The first thermometer of this kind seems to have been used in 
1857 by Captain Pullen of H.M.S. "Cyclops," and shortly 
thereafter improved forms of the Six pattern (Miller-Casella) 
and of Negretti and Zambra's reversing pattern were introduced, 
and have been largely used ever since, improvements and 
modifications being incorporated from time to time. 




Captain James Cook. 



OCEANOGRAPHICAL INVESTIGATIONS 5 

Scoresby in 181 1 recorded some soundings off the coast of Deep 
Greenland, and Sir John Ross during his voyage to Baffin's ^^""'^'"ss- 
Bay in 181 7-1 8 took some deep soundings by means of an /r*^!^' 
apparatus, designed by him and made on board, called " deep- 
sea clamms," in depths of 450, 650, 1000, and 1050 fathoms, 
bringing up from the last-mentioned depth several pounds of 
greenish mud. With the deposit -samples worms and other Deep-sea 
animals were brought up, and when sounding in 1000 fathoms ^n""^'^- 
a star-fish was found entangled in the line a little distance above 
the mud, thus proving that animal life was present in deep 
water. 

In 181 7 Romme published in Paris a work on winds, tides, Romme. 
and currents, and Risso in 1826, Lowe from 1843 to i860, ^^isso. 
Johnson from 1862 to 1866, and Giinther from i860 to 1870, ^°'^''- 
published important papers dealing with deep-sea and pelagic Jo^"^^"- 
fishes. In 1832 James Rennell published an investigation of ^""^^^'' 
the currents of the Atlantic Ocean, based upon the observations 
recorded by sailors up to that time. 

During the United States Exploring Expedition in 1839- wiikes and 
1842 under Captain Wilkes, accompanied by Dana, several ^^"^■ 
deep soundings were taken with the aid of a copper wire, and 
a few dredgings in shallow water were also made. 

Important sounding and dredging work was carried out by 
Sir James Clark Ross, accompanied by Hooker, during the 
British Antarctic Expedition in 1839 to 1843, the first truly British 
oceanic soundings in depths exceedino; 2000 fathoms being^ :^"''^''f5\^ 

o r^ o ^ <-> li,xpedition. 

taken. After many unsuccessful attempts to sound in deep r^^^^^ ^^^.j^ 
water, due to the want of a proper line, Ross had a line 3600 Ross and 
fathoms in length specially constructed on board. It was fitted °°^^'' 
with swivels here and there, strong enough to carry a weight of 
76 lbs., and was allowed to run out from an enormous reel in 
one of the ship's boats. With this line the first abysmal Soundings in 
sounding on record was taken in 2425 fathoms on the 3rd ^4Ter'^^^' 
January 1840, in lat. 27"" 26' S., long. 17° 29' W., and frequently 
during the cruise similar and greater depths were sounded. 
Such deep soundings could only be attempted in calm weather, introduction 
and a note was kept of the time each lOO-fathoms mark left the °i[te,"!^is j,^ 
reel, a lengthening of the time-interval indicating when the sounding. 
weight had reached the bottom. The dredge also was success- Dredgings in 
fully used during this expedition in depths down to 400 ^^'^^i^ ^'''^^'^'■• 
fathoms, abundant evidence of animal life being forthcoming, 
though unfortunately the deep-sea zoological collections were 



DEPTHS OF THE OCEAN 



Hooker on 

Antarctic 

diatoms. 



subsequently lost to science. In April 1840 the dredge came 
up full of coral from a depth of 95 fathoms, and in the following 
January dredgings in 270 and 300 fathoms gave abundance of 
marine invertebrates in great variety, the deepest dredging in 
400 fathoms in August 1841 bringing up some beautiful speci- 
mens of coral, corallines, flustrae, and a few crustaceous animals. 
Hooker made known some of Ross's results, and drew attention 
to the great role played by diatoms in the seas of the far south. 



Edward 
Forbes. 

Audouin and 
INIilne- 
Ed wards. 

Michael Sars. 




.Sir James Clark Ross. 

In 1839 the British Association appointed a Committee to 
investigate the marine zoology of Great Britain by means of 
the dredge, the ruling spirit of this Committee being Edward 
Forbes, who made many observations on the bathymetrical 
distribution of life in various seas. Before this time, it is true, 
Audouin and Milne-Edwards in 1830, and Michael Sars in 
1835, had published the results of dredgings in comparatively 
shallow waters within limited areas along the coasts of Europe. 

In 1840-41 Forbes studied the fauna of the yEgean Sea, 



OCEANOGRAPHICAL INVESTIGATIONS 



7 



taking a great majiy dredgings at different depths, and came to 
the conclusion that marine animals were distributed in zones of 
depth, each characterised by a special assemblage of species. 
He divided the area occupied by marine animals into eight 
zones, in which animal life gradually diminished with increase 
of depth, until a zero was reached at about 300 fathoms. He 
supposed that plants, like animals, disappeared at a certain 
depth, the zero of vegetable life being at a less depth than that 
of animal life. In his Report on the Investigation of British 

Marine Zoology by means 
of the Dredge (1850), Forbes 
suggested that dredgings off 
the Hebrides and the Shet- 
lands, and between the 
Shetland and Faroe Islands, 
would throw much light on 
marine zoology, thus point- 
ing to the scene of the 
subsequent important work 
carried on by Carpenter 
and Wyville Thomson, and 
Murray and Tizard. 

In 1844 Loven carried 
on researches on the distri- 
bution of marine organisms 
along the Scandinavian 
coasts, confirming and ex- 
tendine the observations 
recorded by Forbes, and m 
1845 Johannes Mliller com- 
menced to study the pelagic 
life of the sea by examining 
samples of sea-water and by 
means of the tow-net, thus giving a great impetus to the study 
of marine biology. 

In 1845 Sir John Franklin set sail on his ill-fated North 
Polar Expedition, accompanied by Harry Goodsir, who recorded 
the results of dredging in depths of 300 fathoms. 

In 1846 Spratt took dredgings in the Mediterranean down 
to a depth of 310 fathoms; he afterwards brought up shell- 
fragments from a depth of 1620 fathoms in the Mediterranean. 
In 1850 Michael Sars published the results of his dredgings 
off the coast of Norway, giving a list of 19 species living at 



Forbes' 
observations 
in ^^igean Sea. 
Marine 
animals 
distributed 
in zones of 
depth. 



Zero of life 
in the sea. 




Professor Michael Sars. 



John Franklin 
and Goodsir. 



Spratt. 



Michael Sars 
and G. O. 
Sars. 



8 



DEPTHS OF THE OCEAN 



depths greater than 300 fathoms. He was afterwards assisted 
by his son, G. O. Sars, in carrying on this work, and in 1864 
they gave a Hst of 92 species Hving in depths between 200 and 
300 fathoms, and showed a few years later that marine Hfe was 
abundant down to depths of 450 fathoms. 

In 1856 Mac Andrew pubHshed the results of his observations 
on the marine Mollusca of the Atlantic coasts of Europe and 
northern Africa, giving a list of 750 species obtained in his 
dredgings, which covered 43 degrees of latitude. 

The oceanographical researches of the United States 
Coast Survey may be said to date back to 1844, when the 
Director, Bache, issued instructions to his officers to preserve 
the deposit-samples brought up by the sounding-machine. 
J. W. Bailey studied these deposit-samples, and published the 
result of his examination in 1851, followed in 1856 by other 
papers on deposits and on the formation of greensand in 
modern seas. 

The name of M. F. Maury, of the United States Navy, was 
for a long period associated with the hydrographical work of 
the United States. He issued several editions of his Sailing 
Directions to accompany the wind and current charts published 
by the U.S. Hydrographic Office, the last edition appearing in 
1859. About this time the need was felt for an improved and 
more trustworthy method of sounding in deep water, and 
various attempts were made to devise forms of apparatus to 
replace the heavy weight attached to a line which had to be let 
down and then drawn up to the surface again, the difficulty 
being to know when the weight touched the bottom. This 
problem was finally solved by Midshipman Brooke, who 
conceived the idea of detaching the weight used to carry down 
the sounding lead upon striking the bottom, the sounding tube, 
enclosing its deposit-sample, being alone drawn to the surface. 
He used a spherical weight (a bullet), with a hole passing 
through the centre to receive the sounding tube, suspended by 
a cord to the upper part of the sounding tube ; on touching the 
bottom the cord was thrown off its support and remained at the 
bottom along with the weight. With the aid of Brooke's 
sounding apparatus, the records of deep-sea soundings rapidly 
accumulated, and enabled Maury to prepare the first bathy- 
metrical map of the North Atlantic Ocean, with contour-lines 
drawn in at 1000, 2000, 3000, and 4000 fathoms, which was 
published in 1854 and is reproduced in Map I. The deposit- 



REPRODUCTION OF LIEUT MAURY S MAP OF NORTH ATLANTIC, 1854. 




stematic 
soundings. 



Berryman. 



OCEANOGRAPHICAL INVESTIGATIONS 9 

samples procured were examined and described by Bailey and romtaies 
by Pourtales, the results being of great importance and interest. 

Systematic soundings in the North Atlantic were commenced Sy 
by Lee in the U.S.S. "Dolphin" in 1851-52, and continued in 
the same vessel by Berryman in 1852-53. In 1856 Berryman 
on the U.S.S. "Arctic" sounded across the North Atlantic 
from Newfoundland to Ireland, with the object of verifying the 
existence of a submarine ridge, along which it was proposed to 
lay a telegraph cable ; his deposit-samples were described by 
Bailey. 

In 1857 Pullen and Dayman in H.M.S. "Cyclops" ran a ruiien and 
line of soundings along the great circle from Ireland to ^^y"''^"- 
Newfoundland, a little to the north of Berryman's line. A 
modification of Brooke's sounding-machine was used, in which 
the spherical weight was replaced by a cylindrical one suspended 
by wire instead of cord, and with a different valve for 
collecting the deposit. The deposit-samples were examined 
and described by Huxley, who found in the bottles a viscous Huxley, 
substance, described by him as BatJiybms, which was subse- Bathybins. 
quently shown by the "Challenger" observers to be a chemical 
precipitate thrown down from the sea-water associated with the 
deposits by the alcohol used in their preservation. 

In 1858 Dayman in H.M.S. " Gorgon " sounded across the Dayman. 
North Atlantic from Newfoundland to the Azores, and thence 
to the south-west of England. 

In i860 Sir Leopold M'Clintock on board H.M.S. M'Ciintock 
"Bulldog" surveyed the route for the telegraph cable between ^"'^ ^^ ^iii^h. 
England and America, in the region previously sounded by 
Berryman and Dayman. He was accompanied by G. C. Wallich, 
who published in 1862 an interesting account of the very 
important observations he made during the cruise on life in 
deep water and on the deposits covering the floor of the 
North Atlantic. 

In i860 a teleo^raph cable laid alone: the bed of the Animals 
Mediterranean gave way at a depth of 1200 fathoms, and was subnmrine° 
raised for repair by Fleeming Jenkin, who brought up to the cable. 
surface portions of the cable about forty miles in length, to 
which living organisms were found attached. Corals were 
growing on the cable at the place where it broke in 1200 
fathoms, and other forms were adhering to the cable where 
it had lain in lesser depths, including molluscs, worms, bryozoa, 
alcyonarians, and hydroids, thus establishing beyond all doubt 



lO 



DEPTHS OF THE OCEAN 



the fact that members of the higher groups of animals really 
lived at great depths in the sea. 

Since 1861 Swedish and Norwegian expeditions to the 
Arctic regions and the North Atlantic have been numerous, 
and during one of these in 1864 many animals were dredged 
from depths of 1000 to 1400 fathoms by Otto Torell. In the 
same year Bocage published a paper on the occurrence of the 
glass-rope sponge {Hyalonema) at depths of 500 fathoms off the 
coast of Portugal, which was confirmed in 1868 by Perceval 
Wright, who went there for the purpose and dredged up 
specimens from 480 fathoms. 

From the year 1867 dredgings as well as soundings were 
carried out under the auspices of the United States Coast 
Survey by Pourtales and Louis 
Agassiz off the coast of Florida, and 
between Cuba and Florida. Pour- 
tales took up the examination of the 
deposit-samples after the death of 
Bailey, the number of samples 
collected up to 1870 being nine 
thousand. Louis Agassiz reported 
on the results of the dredgings, and 
compared some of the dredged 
forms with fossil types ; he con- 
cluded by stating his conviction that 
the continental areas and the oceanic 
areas have occupied from the earliest 
times much the same positions as at 
the present day. 

■' Sir C. Wvvili.e ThOxMson. 

In 1868 were commenced a series of short cruises in the 
North Atlantic and Mediterranean, under the direction of 
British naturalists, which may be regarded as preliminary and 
leading up to the great "Challenger" Expedition. Thus in 
1868 Wyville Thomson and W. B. Carpenter carried out 
oceanographical work on board H.M.S. "Lightning," taking 
dredgings in depths down to 650 fathoms, and showing beyond 
question that animal life is there varied and abundant, repre- 
sented by all the invertebrate groups, a large proportion of 
the forms belonging to species hitherto unknown, others being 
specifically Identical with tertiary fossils hitherto believed to 
be extinct, or illustrating extinct groups of the fauna of more 
remote periods. The temperature observations seemed to 




OCEANOGRAPHICAL INVESTIGATIONS ii 

disclose two adjacent regions in which the bottom tern- Peculiar 
peratures differed as much as 15° Fahr. (30^ Fahr. in the l-ondSonsTn 
one region and 45 Fahr. in the other), and it was con- the Faroe 
eluded that great masses of water at different temperatures ^^^""'^'• 
were moving about, each in its particular course, maintaining 
a remarkable system of oceanic circulation, and yet keeping 
so distinct from one another that one hour's sail might be 
sufficient to pass from the extreme of heat to the extreme of 
cold. 

In 1869 Gwyn Jeffreys was associated with Carpenter and h.m.s. 
Wyville Thomson in carrying on the work on board H.M.S. "i^o'cupme." 
"Porcupine," which made three cruises: (i) to the west of carp'^nter, 
Ireland, where dredgings down to 1470 fathoms were taken; and Thomson. 
(2) to the Bay of Biscay, where dredgings were taken in depths 
exceeding 2000 fathoms; and (3) to the Faroe Channel to 
confirm and extend the "Lightning" observations. In 1870 
the " Porcupine " carried on work in the Mediterranean and 
the Strait of Gibraltar, which was continued in 1871 on board 
H.M.S. "Shearwater." 

About the same time Leigh Smith made several voyages Leigh Smith. 
to the Arctic regions, and, like Scoresby, recorded warmer layers 
of water beneath the colder surface waters of the Arctic Ocean. ^ 

The researches briefly noticed in the preceding paragraphs The 
paved the way for the special investigation of the physical, E^J^gdidon^'^ 
chemical, and biological conditions of the great ocean basins 
of the world carried out on board H.M.S. "Challenger" from 
December 1872 to May 1876 by a staff of scientific observers. 
During this period she circumnavigated the world, traversed 
the great oceans in many directions, made observations in 
nearly all departments of the physical and biological sciences, 
and laid down the broad general foundations of the recent 
science of oceanography. The results of the "Challenger" 
Expedition were published by the British Government in fifty 
quarto volumes, and became the starting-point for all subsequent 
observations. 

Contemporaneous with the " Challenger " Expedition was The 
that of the U.S.S. " Tuscarora," under Belknap, in the Pacific ^^'''^^^'°'^'^' 
Ocean, which contributed greatly to our knowledge of the 

' Leigh Smith's temperature observations were pubhshed in Proc. Roy. Soc. Loud., vol. xxi. 
pp. 94 and 97, 1873, and in Natural Science, vol. xi. p. 48, 1897. In the former paper Wells 
(juotes a reading of 64° F. in 600 fathoms and a reading of 42° F. at 300 fathoms near Spitz- 
bergen, and argues that they indicate the southward flow of a vast body of warm water from the 
circumpolar region, while in the latter paper Leigh Smith refers to a warm undercurrent running 
into the Arctic basin between Greenland and Spitzbergen. 



The 

" Albatross. 



12 DEPTHS OF THE OCEAN 

distribution of temperature in that ocean and of the deep-sea 
deposits covering its floor. Piano wire was first used for 
oceanic sounding work on board the " Tuscarora," though for 
some years previously Sir WilHam Thomson (Lord Kelvin) 
had been experimenting with it on board his yacht. 

Also contemporaneous with the "Challenger" Expedition 
was the circumnavigating cruise of the German ship "Gazelle," 
during which many 
valuable oceanograph- 
ical observations were 
recorded. 

In 1876 the U.S.S. 
"Gettysburg" took a 
series of deep - sea 
soundings in the North 
Atlantic, and in the 
years 1876 to 1878 
the Norwegian North 
Atlantic Expedition on 
board the S.S. " Vorin- 
gen " made important 
physical and biological 
observations in the seas ; 
between Norway and 
Greenland, making thus 
the first survey of the 
Norwegian Sea ; the 
scientific results were 
published in English 
and Norwegian. 

From 1877 to 1880 
the United States Coast Survey steamer " Blake" explored the 
Caribbean Sea, the Gulf of Mexico, and the coasts of Florida, 
under the direction of Alexander Agassiz, who published in 
1888 a general account of the results. At the same time the 
U.S. Fish Commission steamer "Albatross" was engaged in 
making observations along the Atlantic coast of the United 
States, and later, in 1891, explored the Panamic region of the 
Pacific under the direction of Alexander Agassiz. 

During the " Challenger" Expedition the naturalists became 
convinced, as a result of their observations in different parts 
of the world, that a ridge must separate the bodies of cold 
and warm water found by the "Lightning" and "Porcupine" 




Dr. Alexander Agassiz. 



OCEANOGRAPHICAL INVESTIGATIONS 13 

Expeditions to occupy the Faroe Channel. On the representa- 
tions of Murray and Tizard, H.M.S. " Knight Errant" in 1880, i^iunayand 
and H.M.S. "Triton" in 1882, were engaged in re-examining j^^^/i^-j^i^u 
the Faroe Channel. The result was the discovery of the Errant."' " 
Wyville Thomson Ridge, which separates the warm and cold The "Triton." 
areas, and accounts for the great difference in the marine faunas Wyviiie 
in the deep water on either side of this ridge. Detailed lists of Rid^.^°" 
the animals obtained by these four expeditions were published 
in a paper by Murray,^ who shows that 216 species and varieties 
were recorded from the warm area, and 217 species and varieties 
from the cold area, while only 48 species and varieties were 
found to be common to the two areas. 

From 1880 to 1883 the French ships " Travailleur " and The 
"Talisman" investigated the eastern Atlantic, while from 1881 ;|,Travaiiieur." 
to i88s the Italian ships " Washing^ton " and " Vettor Pisani," "Talisman." 
the former in the Mediterranean and the latter during a ington." ^^ 
circumnavigating cruise, were eno-apfed in biologrical and other The"Vettor 

. ,-r ^ 1 ^ ^ ^ * Pisani." 

scientihc work. 

In 1883 J. Y. Buchanan took part in the sounding expedi- ]■ v. 
tion of the S.S. " Dacia," belonging to the India- Rubber, ^JJ^ ,^"j^"^j^„ 
Gutta-Percha, and Telegraph Works Company, of Silvertown, 
when surveying the route for a submarine cable from Cadiz to 
the Canary Islands, which resulted in the discovery of several 
oceanic shoals rising steeply from deep water ; and again in 
1885-86 he joined the same company's S.S. " Buccaneer" while The 
exploring the Gulf of Guinea, accompanied by a trained natural- "buccaneer. ' 
ist, John Rattray, when valuable observations as to the depth, john Rattray. 
temperature, density, currents, and plankton were made. 

During the years 1883 to 1886 the U.S.S. " Enterprise" The "Enter- 
brought together a most important collection of deposit-samples p"^^" 
taken throughout a cruise embracing all the great oceans. 

From 1884 to 1892 Murray investigated the sea- lochs John Murray, 
along the west coast of Scotland on board his steam-yacht, the 
" Medusa," and discovered in the deeper waters of Loch Etive ^^jg^j^i^^ - 
and Upper Loch Fyne remnants of an Arctic fauna. The 
physical results obtained were used by Mill in his Memoir on h. r. Miu. 
the Clyde Sea Area.- 

Since the year 1885 the Prince of Monaco has carried on rrince of 
oceanographical work in a systematic manner in the Mediter- 

^ "The Physical and Biological Conditions of the Seas and Estuaries about North Britain," 
Proc. Phil: Soc. Glasgow, vol. xvii. p. 306, 1886. 

- Trans. Roy. Soc. Edin., vols, xxxvi. and xxxviii., 1891, 1894. 



14 DEPTHS OF THE OCEAN 

ranean and North Atlantic on board his yachts " Hirondelle,'' 
'' Hirondelle H," " Princesse Alice," and " Princesse Alice H," 




H.S.H. The Prince of Monaco. 



and he has founded and endowed a magnificent oceanographical 
museum at Monaco and an oceanographical institute in Pans ; 
many important memoirs have been issued from the Monaco 
press. 



OCEANOGRAPHICAL INVESTIGATIONS 15 

From 1886 to 1889 the Russian steamer " Vitiaz," under 
Makaroff, made a voyage round the world, during which 
valuable observations on the temperature and specific gravity 
of the waters of the North Pacific were made, and in 1890 
Russian scientists, notably Lebedinzeff and Andrusoff, investi- 
gated the physical and biological conditions in the deep water 
of the Black Sea. 

In 1889 a German expedition on board the S.S. " National" 

was despatched to the 



The "Vitiaz.'" 
Makarofi'. 



Lebedinzeff 
and Andrusoff 



Observations 
in Black Sea. 



The 

'• National. 




Plankton 
Expedition. 



Professor Victor Hensen. 



North Atlantic, with the 
special object of study- 
ing the plankton (hence 
called the Plankton Ex- 
pedition) by improved 
methods, under the 
direction of Victor 
Hensen, who was ac- 
companied by several 
other scientific men. 

From 1 890 till 1898 
the Austrian steamer 
" Pola " made observa- 
tions in the Mediter- 
ranean and the Red 
Sea, the chemical work 
being in the hands of 
Natterer, whopublished Natterer, 
someinterestingresults. 

In 1890 systematic 
observations in the 
North Sea and adjacent 
waters were commenced 
by Swedish investiga- 
tors under Otto Petters- 



The " Pc 



son and Gustav Ekman, important results as to temperature, 
salinity, alkalinity, currents, gases, and plankton being achieved, 
a summary of which was published by Pettersson in English.^ 

During the years 1893 to 1896 Nansen made his remarkable 
drift on board the " Fram " across the North Polar Sea, during 
which valuable oceanographical observations were taken, his 
soundings tending to prove that the position of the North Pole 
is occupied not by land but by a deep sea, as Murray had 

1 Scott. Geogr. Mag., vol. x., 1S94. 



O. Pettersson 

and 

G. Ekman. 



Nansen's drift 
in the 
" Fram.'" 



i6 



DEPTHS OF THE OCEAN 



The 

•' Valdi/ia/ 



Chun. 



previously indicated. His scientific results were published in 
the English language in six handsome volumes. 

During 1895 and 1896 the Danish ship " Ingolf " was 
engaged in the investigation of the northerly portions of the 
Atlantic, the physical and biological results being published in 
English. 

From 1897 to 1909 Sir John Murray, associated at first 
with F, P. Pullar and afterwards with Laurence Pullar, carried 
out a bathymetrical survey of the Scottish fresh-water lochs, 
including detailed physical and biological observations, and the 
report on the scientific results was published in six volumes in 
1 9 10. During these investigations very careful observations 
were made by Chrystal on seiches, as a result of which our 
knowledge of these oscillations and their causes was widely 
extended. Another kind of oscillation was also discovered, 
which has been called the temperature seiche. This occurs at 
the discontinuity layer, where there is a rapid fall of temperature. 
This temperature oscillation in Loch Ness had a period of 
about three days, and a maximum rise and fall of about 200 
feet. The period of these oscillations is dependent on the 
difference in density between the upper warm layer and the 
lower cold layer : the smaller the difference in density, i.e. the 
smaller the temperature differences in a lake, the longer does the 
period of the oscillation become. These observations in the 
Scottish lakes have recently been extended by further systematic 
work in Loch Earn under E. M. Wedderburn, and have already 
suggested explanations of phenomena in the ocean, where long- 
period oscillations are observed in various depths, and the 
explanation is probably the same as that given for the lakes. 

In the years 1897 to 1899 the Belgian Antarctic Expedition 
on board the " Belgica " carried on important work. This was 
the first vessel to winter in the Antarctic regions, and the 
scientific results are necessarily of great interest and value. 

In 1898-99 the German Deep-Sea Expedition on board the 
" Valdivia" investigated the physical and biological conditions 
of the Atlantic and Indian Oceans, penetrating into the 
Antarctic as far as the ice would permit. The extremely 
valuable scientific results are being issued in a series of 
magnificent memoirs under the editorship of Chun, the leader 
of the expedition. 

In 1899 the U.S.S. "Nero" surveyed the route for a 
telegraph cable between the Sandwich and Philippine Islands 
by way of Midway and Ladrone Islands, many of the soundings 



OCEANOGRAPHICAL INVESTIGATIONS 17 

being in very deep water, including the deepest cast hitherto 
recorded, viz. 5269 fathoms, in the vicinity of Guam Island in 
the Ladrone group. The deposit-samples brought home were 
examined by Flint, ^ who records many distinct patches of 
Diatom ooze within the tropics, but Murray has examined these 
samples, and declares them to be identical with what he has 
called Radiolarian ooze ; the frustules of the large Coscinodiscus 
rex are, however, very numerous in these deposits. 

In 1899-1900 the 
U.S.S. "Albatross" 
carried on oceano- 
graphical observations 
throughout the tropical 
portions of the Pacific, 
under the personal 
direction of Alexander 
Agassiz,who issued the 
scientific results in a 
series of profusely illus- 
trated memoirs, under 
the auspices of the 
Museum of Compara- 
tive Zoology, Cam- 
bridge, Mass. 

In 1 899-1 900 the 
Dutch steamer " Sib- 
oga " investigated the 
oceanographical condi- 
tions in the seas of 
the Dutch East Indies. 
Though limited to such 
a circumscribed area 
the observations are of great value, and the results are being 
issued in English, German, or French, under the editorship of 
the leader of the expedition. Max Weber of Amsterdam. 




Flint. 



The 

"Albatross, 
I 899- I 900. 



Alexander 
Agassiz. 



The 

" Siboga.' 



Professor Carl Chun. 



Max Weber. 



During the years 1901 to 1903 the British National The 
Antarctic Expedition on board the " Discovery " under Scott, Scott'''"''^'^'' 
the German South Polar Expedition on board the " Gauss " xhT'' Gauss.' 
under von Drygalski, and the Swedish South Polar Expedition 
on board the "Antarctic" under Otto Nordenskjold, were The 

" Antarctic." 
^ "A Contribution to the Oceanography of the Pacific," Bull. U.S. Nat. Mus., No. 55, 
Washington, 1905. 



DEPTHS OF THE OCEAN 



The "Scotia.' 
Bruce. 



The "Edi." 

The 

" Stephan." 

The 

"Planet." 



The 

"Albatross, 

1904. 



Alexander 
Agassiz. 



The 

" Nimrod." 

Shackleton. 



James Murray. 



The 

" Fran9ais." 

The 

" Pourquoi 

pas ? " 

The 

" Deutsch- 

land." 



simultaneously engaged in the exploration of different portions 
of the Antarctic regions, and in 1 902-1 904 the Scottish 
National Antarctic Expedition on board the "Scotia" under 
Bruce was likewise busy in the far south. The results of all 
these expeditions have added very largely to our knowledge of 
the oceanography of the Antarctic. 

Between 1903 and 191 1 the German ships "Edi," 
"Stephan," and "Planet" took many soundings throughout 
the different ocean 
basins, the last -men- 
tioned recording the 
greatest known depth 
in the Indian Ocean. 

In 1904 we find 
the U.S.S. "Albatross" 
again carrying on 
oceanographical work 
in the eastern Pacific 
under the personal 
direction of Alexander 
Agassiz, the published 
results constituting a 
great advance in our 
knowledge of the Pacific 
Ocean. 

In 1907-1909 an- 
other British Antarctic 
Expedition on board 
the " Nimrod," under 
Shackleton, was en- 
gaged in making scien- 
tific observations and 
pushing south beyond 

anything previously attained. The biological work was under 
the direction of James Murray, formerly of the Scottish Lake 
Survey, and the results issued under his editorship are excellent 
in quality. 

Mention may also be made of the two French Antarctic 
Expeditions under Charcot, the first from 1903 to 1905 on board 
the " Francais," and the second from 1908 to 1910 on board 




Dr. Anton Dohrx, 



the " Pourquoi pas 



Still more recently the German 



Antarctic Expedition of 191 1 on board the " Deutschland " 
has, during the outward voyage, taken valuable serial 



OCEANOGRAPHICAL INVESTIGATIONS 



19 



temperatures and salinities off the Atlantic coast of South 
America. 

In addition to the specific expeditions referred to in the 
foregoing paragraphs, many British surveying and cable ships 
have been busily engaged during the past thirty years amassing 
valuable information regarding the depth of the ocean in various 
parts of the world. Temperature observations were also in- 
cluded in the work carried on by H.M. surveying ships, and British 
by some of the cable ships when accompanied by scientific ships.^^"^ 
men like J. Y. Buchanan and R. E. Peake. The principal 
ships and the oceans investigated by them may be here briefly 
enumerated : — 



H.M.S. 


" Egeria " 


Atlantic, Indian, and Pacific 


1887 to 1899 


H.M.S. 


" Waterwitch '' 


)) )) 


1894 ,, 1901 


H.M.S. 


" Rambler" 


?5 !5 


1888 „ 1904 


H.M.S. 


" Penguin " 


Indian and Pacific 


1890 „ 1906 


H.M.S. 


"Stork" 


Indian and Atlantic 


1888 „ 1897 


H.M.S. 


" Investigator " 


Indian Ocean 


From 1886 to the 
present time 


H.M.S. 


" Dart " 


Pacific Ocean 


1888 to 1902 



Other ships were engaged in one or other of the great 
oceans for shorter periods, including H.M.Ss. " Myrmidon," 
" Marathon," " Flying Fish," "Goldfinch," "Sealark," "Sylvia," 
" Fantome," and " Mutine." 

Of British cable ships mention may be made of the British cable 
following :— '^'P'- 



s.s. 


" Britannia " 


Atlantic, Indian, and Pacific 


1888 to 


1907 


s.s. 


" Great Northern " 


Atlantic and Indian 


1882 „ 


1897 


s.s. 


" Chiltern " 


)» 


1886 „ 


1897 


s.s. 


" Amber " 


)) )) 


1888 „ 


1906 


s.s. 


" Scotia " 




1883 „ 


1898 


s.s. 


" Seine " 


,, ,, 


1885 „ 


1899 


s.s. 


" Electra " 


)) -)) 


1887 „ 


1903 


s.s. 


" John Pender " 




1878 „ 


1901 


s.s. 


" Duplex " 


M )) 


1906 ,, 


1907 


s.s. 


" Silvertown " 


Atlantic and Pacific 


1889 „ 


1900 


s.s. 


" Retriever " 


M 


1880 „ 


1907 


s.s. 


" Sherard Osborn " 


Indian and Pacific 


1888 „ 


1907 


s.s. 


" Recorder " 


„ ,, 


r888 „ 


1907 


s.s. 


" Dacia " 


Atlantic 


1883 „ 


1905 


s.s. 


" Minia " 


)) 


1885 „ 


1907 


s.s. 


" Norseman " 


,, 


1893 „ 


1907 


s.s. 


" Buccaneer " 


„ 


1886 „ 


1906 



Many other ships were engaged for shorter periods, including 



20 DEPTHS OF THE OCEAN 

S.Ss. "Westmeath," " Roddam," "Volta," " Mirror," " Viking," 
" Grappler," " Faraday," " Anglia," " Newington," " Henry 
Holmes," "Cambria," "International," "Clan McNeil," 
"Patrick Stewart," "Cruiser," " Colonia," "Magnet," etc. 

It is quite impossible in this brief review even to mention 
the names of all the investigators and authors who have 
during the past thirty years made important original contribu- 




Professor Ernst Haeckel 



tions to the science of oceanography. Among those who have 
not taken an active part in extensive explorations and ex- 
peditions, but whose influence on the development of the 
Ernst science has been very great, the names of Ernst Haeckel 
Haeckel. ^^^ Anton Dohm should be mentioned. Through his 
voluminous publications on the radiolaria and on other marine 
groups in ^the "Challenger" Reports, through his charming 
Plankton-Studien, and through his more popular writings, 
Haeckel has created a widespread interest in all marine 



OCEANOGRAPHICAL INVESTIGATIONS 21 



The work of 
marine bio- 
logical labora- 
tories and of 
international 
and other 
fishery investi- 
gations. 

Anton Dohrn. 



investigations among the intelligent reading public of the 
whole world. 

Although small and more or less permanent marine labora- 
tories had been established on various parts of the European 
and American coasts previous to 1880, it must be acknowledged 
that the foundation of the Zoological Station at Naples in that 
year by Anton Dohrn marks an era in all that concerns the 
histology and embryology of marine organisms, and these studies 
have in turn given a great impetus to the systematic investiga- 
tion of many purely oceanic problems. 

Similar marine laboratories have since been founded in many 
parts of the world, some for researches of purely scientific 

interest and others for the 
investigation of economic 
questions connected with the 
study of the habits and 
development of the food 
fishes. 

By far the most import- 
ant of these organisations 
was that resulting from an 
International Hydrographic 
Congress held in Stockholm 
in 1899, which was largely 
brought about by the exer- 
tions of Otto PetterSSOn. Pettersson 

An International Commis- 
sion for the Scientific In- 
vestigation of the North Sea 
was established, the partici- 
pating countries being Great 
Britain, Germany, Holland, 
Belgium, Russia, Denmark, 
Sweden, and Norway. Many important researches have been 
undertaken, and many elaborate reports have been issued by the 
scientific staffs of each of the countries concerned. This inter- 
national work, which has been carried on for over ten years, 
and is still in operation, has given a great impulse to nearly all 
departments of oceanic science, one result among the many The -Michael 
others being the organisation of the " Michael Sars " Expedition i^Jantic eI!^ 
in the North Atlantic in 19 10, to an account of which this pedition, 1910. 
volume is chiefly devoted. J. M. 




Hydrographic 
Congress, 



International 

North Sea 
Council. 



Professor Otto Pettersson. 




Michael Sak- 



CHAPTER II 



THE SHIP AND ITS EQUIPMENT 



Importance of 
development 
of mechanical 
aids in deep- 
sea work. 



It has often been said that studying the depths of the sea is Hke 
hovering in a balloon high above an unknown land which is 
hidden by clouds, for it is a peculiarity of oceanic research that 
direct observations of the abyss are impracticable. Instead of 
the complete picture which vision gives, we have to rely upon a 
patiently put together mosaic representation of the discoveries 
made from time to time by sinking instruments and appliances 
into the deep, and bringing to the surface material for examina- 
tion and study. Our difficulties are greatly increased by the 
fact that it is impossible to watch our apparatus at work. A 
trawl, for instance, is lowered to a great depth, and a few . 
fathoms below the surface it disappears from view ; later on it 
is brought on board and found to be empty. Is this because 
there was nothing to catch where it was operating, or has it 
somehow or other got out of order, or failed to reach the bottom, 
or met with some similar mishap, and so been prevented from 
catching anything.'* These questions can only be answered by 
examining the trawl when once more on deck, and drawing one's 
conclusions accordingly. 

Obviously, therefore, the progress of oceanography depends 
to a great extent upon the development of mechanical aids, by 
which we mean not only the scientific instruments employed, 
but also the whole arrangements of the ship itself. To be able 



THE 




9 




Fig. I. — Deck Arrange- 
ment ON BOARD THE 

" Chai-lenger." 



SHIP AND ITS EQUIPMENT 23 

to haul in some thousands of fathoms of 
line within reasonable time would be quite 
out of the question without a steam-winch, 
and it is precisely because the use of steam 
first made it possible to examine properly 
the vast marine areas of the world that 
oceanic research is such a comparatively 
new science. The cruise of the " Chal- 
lenger," the first great expedition specially 
fitted out to investigate the ocean, took 
place during the years 1872-76. Since 
then oceanography has made giant strides, 
and we have now many appliances at our 
disposal that were unknown to the pioneers 
of those days. 

It is interesting to compare our modern 
methods with those of the "Challenger" 
Expedition, for we can then see what great 
advances have been made, and realise to 
what extent we have availed ourselves of 
the scientific inventions of our times. A 
critical examination of the mode of work- 
ing adopted by the " Michael Sars " will be 
of use in this connection. 



The "Challenger" was a spar - deck The ; 
corvette of 2306 tons displacement, with Ej^'^dulon^'^ 
an auxiliary engine of 1234 indicated horse- 
power. The length of her deck was 226 j 
feet, and her greatest breadth was 36 feet. 

Almost amidships on her main deck, 
and just before the main mast, was a big 
steam-winch of 18 horse-power, with a long 
axle that extended right across the ship 
and carried large end-drums (see Fig. i, 8). 
Hemp lines were used, which were hauled 
in by being passed round the end-drums. 

The sounding-line was operated by two 
large reels on the forecastle, 5 feet long 
and 2^ feet in diameter (4 and 5), 3000 
fathoms of line, one inch in circumference, Methods 
to each reel. The breaking strain was ^^p.^^^'^^ °^ 
about 700 kilos (14 cwt.), and the weight 



24 ' DEPTHS OF THE OCEAN 

of 3000 fathoms of line in water was roughly 108 kilos. When 
heaving the lead the weight used was sometimes 150 and 
sometimes 200 kilos. During the whole of the voyage of the 
"Challenger" only two temperature lines with eight ther- 
mometers, and nine sounding-lines with thirteen thermometers, 
were lost ; eleven thermometers collapsed under high pressure 
at great depths. 

For dredging and trawling they employed hemp lines 2, 2^, 
and 3 inches in circumference, with a breaking strain from 1600 
to 2550 kilos, spliced together to form a length of 4000 fathoms, 
which was coiled on the forecastle (1,2, and 3). An attempt 
was made to use swivels to keep the line from twisting, but 
this had to be abandoned owing to their being damaged in the 
blocks. 

It is evident that in the arrangement and working of all the 
apparatus account had to be taken of these immense lengths of 
line. In the first place, they were extremely bulky, and required 
a large amount of deck space for coiling and handling, as the 
line had first to be led from the forecastle to the winch, and 
frequently from the end-drum on one side of the axle to its 
fellow on the other side, when the strain on the dredging rope 
was so great that the friction of the revolving drum was not 
sufficient to make it bite. This happened sometimes even when 
ten or twelve men were holding on abaft the winch. A second 
important consideration was the severe strain on the line every 
time the big heavy ship lurched, or when the lead or the dredge 
stuck fast on the bottom. 

The weight of 3000 fathoms of sounding-line in water was, 
as already stated, over 100 kilos, and the weights amounted to 
200 kilos, so that there was not much margin left for friction in 
the water and accidental jerks, when we remember that the 
breaking strain was only 700 kilos. Accordingly, when sound- 
ing or trawling great care had to be taken to provide against 
such contingencies, and large accumulators were used, consisting 
of rubber bands 3 feet long and J-inch thick, which could be 
extended to 17 feet, and thus counteracted sudden jerks on the 
line. For sounding, forty of these were employed, while for 
trawling there were as many as eighty, which together could 
support 2J tons, or the breaking strain of the line. 

Fig. 2 shows the two accumulators, one for sounding 
and the other for trawling, attached to blocks high up on a 
yard, thus enabling them to expand and contract freely. 

Before sounding all sail was taken in, and the ship was 



THE SHIP AND ITS EQUIPMENT 



25 



brought head to wind by means of her engine to keep her from Method of 
drifting off too much. With three or four heavy weio-hts of ^°""''^"§- 




Fig. 2.— Sounding and Trawling on board the "Challenger." 

50 kilos each attached, the sounding-lead was heaved, and the 
apparatus was so constructed that the weights slipped off upon 
reaching the bottom, thus doing away with the necessity of 
hauling the entire mass up again. The Baillie sounding 



DEPTHS OF THE OCEAN 



Method of 
dredging and 
trawling. 



r" 



machine (Fig. 3) was the one in general use on board the 

" Challenger." 
Time required From the Narrative of the Cruise we get the following 
Sje^^v^ale"^'" particulars regarding the time - 

required for sounding in deep 

water : — 

Station 81. Began sounding 5 
P.M. ; found bottom at 2675 fathoms ; 
finished hauling in at 6.20 P.M. 

Station 225. Began sounding 
12.30 P.M. ; found bottom at 4475 
fathoms ; finished sounding at 3 P.M. 

We see, therefore, that sound- 
ing in about 3000 fathoms took 
nearly an hour and a half, where- 
as for about 4500 fathoms two 
and a half hours were required, 
which must be considered very 
quick work. On the same line 
and with the same arrangement 
as for sounding, series of tem- 
peratures were taken and deep- 
water samples obtained. 

Heavy lines and strong 
accumulators were, however, 
necessary for the dredge and 
trawl, which were each fastened 
to a stout 2-inch line, paid out 
through a block attached to the 
big accumulator (see Fig. 2). 
From 300 to 500 fathoms first 
ran out, then a weight of about 
80 kilos ' was allowed to slide 
down the line till it was stopped 
just a little in front of the appli- 
ance. The weight consequently reached the bottom before 
the appliance, with the result that this latter merely skimmed 
the ocean floor. 

All this time the ship lay with her head to the wind to 
enable the appliance to reach the bottom, for which operation 
about three hours were required. When all was in readiness 
the ship was allowed to drift with the wind abeam, and thus 
towed the dredge or trawl along. 



Fig. 



Baillie Sounding Machine. 
The tube (/) was generally made to project 
18 inches below the weights {e}. 



THE SHIP AND ITS EQUIPMENT 27 

Hauling in was done rapidly, as will be seen from the 
following extracts : — 

Station 79, depth 2025 fathoms. The dredge was lowered at 11 A.M., Time required 
and 2800 fathoms of Hne paid out ; at 4 p.m. commenced hauling in, and for dredging 

c ' ^ o ' jj^j} trawling. 

the dredge came up at 5.45 p.m. 

Station 244, depth 2900 fathoms. The trawl was lowered at 4 A.M., 
and 3500 fathoms of line paid out ; commenced hauling in at noon, and 
the trawl came up at 3.50 P.M. 

Thus in the course of twelve hours it was possible to carry out 
a successful trawling at a depth of about 3000 fathoms. 

With such means as they had then at their disposal — a 
sailing ship with auxiliary engine and hemp lines — it was 
scarcely possible to devise a more thorough system of working. 
During the whole three and a half years, when trawlings and 
dredgings were made at 354 stations, there were only eleven 
cases of the parting of the dredge or trawl line. But gear of 
this kind necessitated lavish space and a large number of hands, 
both of which were generally to be had on the old sailing ships. 
It entailed ample space on deck for the coils of line and high 
masts for the accumulators, while numbers of men were needed 
to coil the lines and to hold on abaft the end-drums of the 
winch. A sailing ship, however, required much less coal than ( 
a steamer, which is a great advantage on a voyage round the • 
world. 

In the Narrative of the "Challenger" Expedition it is Recent 
mentioned that at the time the vessel was being got ready for "methods. 
her cruise, Sir William Thomson (Lord Kelvin) was engaged Lord Kelvins 
in trying once more to solve the problem of taking soundings on^s^ouSg 
with wire instead of with a hemp line, and that a sounding with wire. 
apparatus constructed by him was placed on board just before 
the ship sailed ; the drum, however, collapsed when first used. 
Notwithstanding this Sir William Thomson continued with the 
utmost energy, and eventually with complete success, to develop 
his method, and it was employed by the American sounding 
vessels "Tuscarora" (Captain Belknap) and "Blake" (Captain 
Sigsbee). Wire has great advantages over a hemp line, firstly, 
because it enables soundings to be taken more quickly, since 
the steel wire meets with far less friction in the water ; and 
secondly, because it requires much less space. 

Fig. 4, which is taken from Sigsbee's excellent book,^ Advantages of 
represents sections of the hemp lines used by the "Challenger," hemp Une. 

^ Sigsbee, Deep-Sea Soundiiio and Dredging, Washington, 1880. 



28 



DEPTHS OF THE OCEAN 



and of the steel line (piano wire) afterwards adopted for 
sounding. It will be obvious at once what a saving of space 
is obtained by the use of a steel line. This 
will be clear, too, if we look at Sir William 
Thomson's sounding machine, the principle 
of which is clearly illustrated by the follow- 
ing instructive figure from Sigsbee's book 

(P'g- 5)- , . , , 

The wire is wound m by a large wheel 

consisting of a drum 2 feet 6 inches in cir- 
cumference between two thin galvanised iron plates 6 feet in 
circumference, the object of making this wheel of such a size 
being to enable the line to be paid out and hauled in quickly. 

In taking soundings the art consists in getting the wheel 
and line to stop the moment the plummet touches the bottom. 



00 



Fig. 4. — Sounding-Line 
AND Wire. 
a and l>, Circumference of 
the hemp sounding-line of 
the "Challenger" ; c, piano 
wire. (From Sigsbee.) 




The line drifts when free of the lead, as it is, of course, relieved 
of the weight as soon as the bottom is reached, but there still 
remains the weight of the line itself, while the momentum of 
the wheel will cause it to continue revolving for a little while. 
The wheel must consequently be made as light as possible, and 
a resistance of some sort must be provided, rather stronger at 



THE SHIP AND ITS EQUIPMENT 



29 



/4 



any moment than what is necessary to counteract the weight of 
the length of line paid out. Thomson obtained this by means 
of a brake, a hemp line running in a separate groove at the side 
of the big wheel, and passing from there to a block, through 
which the brake could be tightened by means of weights. 

Sir William Thomson used a plummet weigh- 
ing 34 lbs., and commenced his sounding with 
a counter-weight of 10 lbs, on it. This was 
sufficient to run out the line at the rapid rate of 
2000-3000 fathoms in thirty to fifty minutes. 
Gradually, as more line was paid out, the 
counter-weight was increased proportionately to 
the length of wire in the water (12 lbs. for each 
1000 fathoms of wire), and this caused the wheel 
to stop almost instantaneously when the bottom 
was reached. The depth could be ascertained 
from the number of revolutions on the register. 
1^ If the wheel did not stop instantaneously, an 

SL ^ error would result in the determination of the 
^K^^K depth, and if the steel line came into contact 
SBHb with the bottom, it easily kinked, and the 
^^HpF plummet was likely to be lost. To obviate this 
^^■^ a few fathoms of hemp rope were inserted be- 

^H tween the plummet and the steel line. 

^B Obviously this sounding machine is a great 

■ advance on the old hemp lines. ^ Economy of 

space, smaller weights, greater speed, less fric- 
tion in the water (and consequently a more 
perpendicular line, resulting in greater accuracy), 
are some of the advantages. For this reason 
attempts have continually been made to improve 
Thomson's machine, and in the course of time 
a number of very good sounding machines have 
been constructed, amongst others those of Le 
Blanc, Sigsbee, and Lucas. Sigsbee's sounding- 
tube is shown in Fig. 6. All of them are based 
on Thomson's model ; thus Sigsbee says of his own admirable 
machine : " The modification or improvement made by me on 
the original Thomson sounding- machine lies chiefly in the 
employment of a peculiar kind of accumulator, and its adap- 

^ It is interesting here to observe that the " Challenger" hemp line could be used for sound- 
ing in depths down to 26,000 fathoms before reaching its breaking strain, whereas the wire could 
only be used down to a depth of 16,700 fathoms. Depths beyond 26,000 fathoms, should such 
depths exist, could not be explored by either method. 



Fig. 6.— Sigsbee's 
Sounding -Tube. 
(From Brennecke.) 



Recent 

sounding 

machines. 



30 DEPTHS OF THE OCEAN 

tation to the various uses of accumulators, dynamometer, brake, 
correct register, and governor." 

On board the " Michael Sars " we employed the sounding 
machine constructed by Lucas. It was selected originally 
because it had been extensively used by the telegraph cable 
ships, and because it was the smallest and the cheapest. Weights 
used as brakes in Thomson's machine are replaced by spiral 
springs, which can be tightened or slackened with a screw, 
and can at the same time be relied upon in a high sea as 
accumulators (see Fig. 7, which explains the construction). 



During the winter of 1877-78 the United States Coast 
Survey steamer "Blake" undertook a cruise in the Gulf of 




Fig. 7.— Lucas Sounding Machine. 

Mexico, under the command of Captain Sigsbee and under the 
Wire rope for pcrsonal supcrvision of the late Alexander Agassiz. As it 
dredging. ^^g proposed to Carry out investigations with the dredge and 
trawl along the bottom, Agassiz suggested the use of a wire 
rope instead of hemp ropes. Thanks to Sigsbee's inventive 
genius and practical methods, this plan was successfully adopted, 
and has since been adhered to by every expedition of any 
importance. 

Fig. 8 shows sections of the "Challenger" hemp lines, 
3 inches, 2^ inches, and 2 inches in circumference (a, d, c), and 
of the wire rope, i|- inch in circumference, used by the 
" Blake " (d). 



THE SHIP AND ITS EQUIPMENT 31 

The wire rope consisted of six strands, each made up of 
seven wires (like piano wires about 1 mm. in 
diameter), or altogether forty-two wires, with 
a tarred hemp line in the middle. The 
breaking strain of the whole was about 4 
tons. Its weight per fathom was 1.12 lbs. 

0000 

a h c d 

Fig. 8. 
a, b, c, Circumference of hemp lines used for trawling on board 
the "Challenger," and d, of wire rope used for trawling on board 
the "Blake." (From Sigsbee. ) 




n 




in the air, and i lb. in the water. We thus 
get a breaking strain of about 4000 kilos ; 
weight in water of 5000 fathoms 2300 kilos ; 
so that with 5000 fathoms out, there were 
about 1 700 kilos over for resistance (friction) 
in the water, and for strains due to heavy 
seas or sticking fast on the bottom. The 
great strength of this line made it less 
necessary to use accumulators, and they 
were only employed occasionally during the 
" Blake " expedition. 

Fig. 9 shows how Sigsbee worked the Method of 
wire rope on board the "Blake.;' It was ^Jf ""^ 
wound round a big drum (i), driven by a 
small steam-winch, and led from the drum 
over blocks of considerable diameter (2) to 
the large steam-winch (3), which had a large 
end-drum 55 centimetres (22.6 inches) in 
smallest diameter. From here the line went 
to a big boom (4) on the foremast (5). 

When dredging or trawling the appliance 
was first lowered to near the bottom, while 
the ship was stationary, and afterwards the 
_ vessel went astern during the process of 

Fig. 9.-d^ck Arrange- paying out and dredging. This manner of 
MENT OF THE "Blake." working was so successful, and conduced to 

(From Sigsbee.) '^ 



32 DEPTHS OF THE OCEAN 

such precision, that it may be considered quite the equal of any 
system adopted by subsequent expeditions. Sigsbee relates 
that he made one day, off Havana, between 7 a.m. and 5 p.m., 
as many as ten hauls with the dredge at depths varymg from 





Fig. 10. — Dredges. 
a, Previous model ; fi, Sigsbee's dredge. (From Sigsbee ) 

SO to 400 fathoms. Although the bottom was unsatisfactory 
and the dredge stuck fast every time, he managed to avoid an 
accident and made very successful catches. He allowed from 
three to five minutes for lowering or for hauling in a line ot a 
hundred fathoms, and from ten to thirty minutes for the actual 



THE SHIP AND ITS EQUIPMENT ^3 

dredging, the time required for dredging depending, of course, 
upon the nature of the bottom. 

The joint labours of Agassiz and Sigsbee led to a great 




Fig. II.— The "Challenger" Trawl. Fig. 12.— Sigsbee's Trawl. (From Sigsbee.) 

improvement in the appliances. Previously the dredges had 
ploughed into the ocean floor (Fig. 10, a), but the one employed 
by Sigsbee (Fig. 10, d) was believed to have skimmed over it, 
and so collected the animals which lived upon the surface, 
sweeping them up from a wide extent of ground. Both kinds 

D 



" Challenger 
trawl. 



34 



DEPTHS OF THE OCEAN 



of dredge have, however, their advantages, according to the 
animals it is desired to procure. 

The "Challenger" used a trawl (Fig. 1 1) constructed like 
the ordinary beam-trawl, which was employed particularly by 




Fig. 13. — Tow-Net fixed at End of Line ("Challenger"). 

the fishermen in the shallow waters off the flat English coasts. 
The beams were of different lengths, 17, 13, and 10 feet, 
but the lo-feet length was found to be the best 
for deep water. It was, however, difficult to 
tell, when the depth was at all great, whether 
the trawl had reached the bottom right side up, 
and whether it was open while being towed. 
Sigsbee solved this difficulty by having tripping 
lines on both sides (Fig. 12) ; otherwise the size 
of his trawl was identical with that of the 
" Challenger," viz. 10 feet between the runners. 
Sigsbee's appliances and methods of work- 
ing were adopted by the " Valdivia" and other 
recent expeditions. 



Pelagic During the cruise of the " Challenger" the 

of?he"^^^ appliances used for making pelagic captures 
"Challenger." cousisted of Small nets resembling long night- 
caps, of fine muslin or calico, and 10 to 16 inches 
in diameter at the mouth. They were towed 
at various depths, even as far down as 800 
fathoms, with a weight attached a little in front 
of the opening (Fig. 13), or they were some- 
times made fast to the line (Fig. 14) and lowered 
to a depth of about 2 miles (over 3600 metres), 
the object being to ascertain whether or not fi 
organisms lived in the deeper layers of water 
different from those captured in the surface layers. 

Since the time when the "Challenger" conclusively proved 
that life was present everywhere in the ocean, not only over 
the bottom at the profoundest depths, but also in the inter- 
mediate layers of water, much labour has been expended upon 



14. — Tow-Net 
fixed on the Line 
(" Challenger"). 



THE SHIP AND ITS EQUIPMENT 



35 



the investigation of the animal Hfe of the sea. The appHances Closing nets 
for capturing animals at the bottom have undergone only slight aJewSrr'^' 
alterations, whereas many different kinds of contrivances for 
capturing the pelagic animals have been tried from time to 
time, some of them being of real practical value. 

Chun has done more perhaps than any other naturalist in Chun and 
the way of studying the vertical distribution of organisms. Jios^ngnet. 
Together with Petersen he constructed a vertical net that could 




Fig. 15. — Nansen's Closing Net. 



16. — Chun's Net. (From Chun.) 



be let down closed, then opened, and finally closed again, so 
as to catch the smaller organisms existing in a specified layer 
of water, say between 400 and 200 metres beneath the surface. 
Subsequently other closing nets were constructed on the 
principle of this invention. Fig. 15 shows Nansen's closing Nansen 
net open (a), and shut (d), the construction of the net itself ^^i^^^^g 
and the closing mechanism being easily understood from the 
illustrations. It is extremely simple and reliable, and we have 
tested it in various ways during the cruises of the " Michael 



Chun large 
net. 



Prince of 
Monaco's 
pelagic 
trawl. 



36 DEPTHS OF THE OCEAN 

Sars." We have found that if the appliance is sent down open 
to a considerable depth, immediately closed and hauled in again, 
it fails to capture anything, thus proving that vertical appliances 
need not be closed while being lowered. 

For studying the vertical distribution of larger organisms 
Chun used during the " Valdivia " Expedition a large silk net, 
4 metres in length (Fig. 16). By lowering it to different depths 




Fig. 17.— Monaco's Pelagic Trawl, (From Steuer.) 

and comparing the catches so obtained, he could determine 
at what particular depths the animals lived, and he succeeded 
in collecting by this means valuable data as to pelagic deep- 
water forms. 

The Prince of Monaco has also added largely to our 
knowledge of the habitats of the larger pelagic organisms by 
means of his pelagic trawl (Fig. 17), which is designed for 



Petersen 

young-fish 

trawl. 




Fig. 18. — C. G. Joh. Petersen's Pelagic Young-Fish Trawl. (From .Schmidt.) 



being towed horizontally through the water. In addition he, 
made some remarkable captures of large pelagic animals, chiefly 
cuttle-fish, by shooting whales and examining their stomach con- 
tents, for the whale is still far more capable of catching living 
marine creatures than any scientific appliance hitherto invented. 
The young-fish trawl designed by C. G. Joh. Peterser 
(Fig. 18) is a considerable improvement on the Prince 01 
Monaco's pelagic trawl. It is very easy to construct, and 
may be of any size or mesh. For catching young fish, etc., J 



THE SHIP AND ITS EQUIPMENT 



Zl 



he generally uses sackcloth, but a better fine-meshed material 
would undoubtedly be more desirable. 

Hensen evolved various forms of apparatus for a quantitative 
study of the pelagic organisms, that is to say, for estimating 
the relative amounts of plankton organisms present in a given 
volume of water. He recommends vertical nets of the finest 
silk cloth, such as is used in the milling 
industry (see Chapter VI.). 

In actual practice, however, it has 
been found impossible to capture pelagic 
organisms of every sort with the same 
net ; for the larger forms may escape the 
net altogether, while the smallest forms 
may pass through the meshes of even 
the finest silk. There are other objec- 
tions to the method, for it is an almost 
impossible task to ascertain the total 
quantity of floating organisms in deep 
and shallow water where there are 
strong currents ; and it is hardly likely 
that the larger organisms at any rate, 
even though the nets succeed in cap- 
turing them, are uniformly distributed 
throughout the water- masses over large 
areas, so that an estimation of their 
total number could not be arrived at 
with our present appliances. Still, 
Hensen's theoretical analysis of plank- 
ton problems has been of great service 
to oceanic research, and so, too, has 
his plankton net (Fig. 19), whose co- 
efficient of capture naturalists have 
attempted to calculate. It has been of 
the utmost value, for instance, in investigating certain uni- 
formly distributed minute species in less extensive areas. The 
apparatus consists of a filtration net of miller-silk, with a brass 
cylinder at the lower end of the net, and a large conical part 
made of canvas, the object of which is to control the amount of 
water entering and so enable the silk net to filter it. 




Hensen 
plankton net. 



Fig. 19. — He.nskn's Large 
Plankton Net. (From Chun.) 



The steamer "Michael Sars " was built in 1900 by the The "Michael 
Norwegian Government to undertake researches in connection Sai^." 
with the Norwegian fisheries, and to study the natural con- 



3^ 



DEPTHS OF THE OCEAN 



Methods 
employed 
on board. 



©" 



ditions on which they depend. It was therefore necessary to 
have a vessel capable of making investiga- 
tions similar to those carried on by oceanic 
expeditions, and at the same time suitable 
for practical fishery experiments, which are 
every year becoming of more and more 
importance in the work of scientific re- 
search. A ship of this kind, however, had 
to be small, otherwise it was impossible to 
reckon on sufficient means for its upkeep. 
Accordingly the size we selected was that 
of a first-class fishing trawler. Her length 
is 125 feet between perpendiculars, and 
she is of 226 tons burden ; her engines 
indicate 300 horse-power, and can give her 
a uniform speed of 10 knots; her coal 
consumption is small, being about 5 tons 
per twenty-four hours when going at the 
rate of 9 knots, and she can carry in her 
bunkers about 80 tons. As will be seen 

from Fig. 20 there is plenty of space on ftUy 

deck forward of the engines. The big 
winch is placed here just abaft the hatch 
of the storeroom, in which there is 
cold storage for 10 tons of fish, and 
stowage for appliances, instruments, cases 
of glass bottles, etc. Forward of this 
storeroom are the cabins of the engineers 
and mates and the quarters of the crew. 
Abaft the engines there is a labora- 
tory on deck, and below there are cabins 
and a messroom for the scientists. The 
deck is perfectly clear on either side 
of the deck-house, so that there is ample 
room for working with appliances and 
instruments. 

If we compare Figs. 20 and 21 we 
shall get a good idea of the appearance of V^ \Z} 
the deck of the " Michael Sars." On the 
starboard side there are two small winches, 
the forward one of 3 horse-power and the 
aft one of i horse-power. The forward fig. 20.— Deck arrange- 
winch (2), by means of a long axle (see >.'-,',„- .^^S ™=^ 



THE SHIP AND ITS EQUIPMENT 39 

also Fig. 22), drives a big reel with 6000 metres of wire, 3.5 
mm. in diameter, for the hydrographical instruments and the 
Lucas sounding machine (6 and 5), and it can also be used 
to drive the big centrifuge (10) by means of a hemp line. By 
a similar arrangement the aft winch drives two drums with 
2000 metres of wire, 3 and 4 mm. in diameter, for the vertical 
nets and hydrographical work in moderate depths. 

In calm weather and when the currents are slight all the 
appliances may be operated simultaneously, provided care be 




Fig. 21.— Side View of Arrangement of Gear on board the "Michael Sars." 

taken that one appliance, let us say, is lowered while others 
are being hauled in. But when there are strong currents there 
is always a danger of the appliances colliding, and it is best 
in that case to work one at a time from each winch. 

For the larger nets and the trawl we use the big winch (i), 
which takes tl>e long steel line, 9000 metres in length, increas- 
ing from 34 mm. to 44 mm. in diameter. When trawling the 
line passes round the big reel {9), on which there is a register, 
and from there it is led to the gallows (12 and 13) and paid 
out astern. When operating the big vertical nets, the line 
is passed round a block in the accumulator, which hangs from 



40 DEPTHS OF THE OCEAN 

the boom on the foremast, and is then led to the forward 
gallows (i i). 

Pelagic appliances, to be towed horizontally, are either 
fastened to the trawl wire like the trawl itself, or else the wire 
is led round a smaller winch (4), situated abaft the deck-house, 
and then paid out over the stern. 

The vessel may thus tow both steel lines at the same time, 




Fig. 22. — The Forward Starboard Winch. 

and a number of appliances may be operated simultaneously. 
This mode of working differs in many ways from the system 
adopted in former expeditions. 

Fig. 22 shows the forward starboard winch. The little Lucas 
sounding machine may also be seen, fastened quite simply to 
the rail of the ship, taking up very little space and requiring 
the attention of only one man. The large Pettersson-Nansen 
water-bottle, used for hydrographical observations at great 
depths, is also in a handy position. What simplifies matters 



THE SHIP AND ITS EQUIPMENT 



41 



very much, and enables us to dispense with the big projecting 
structures, or sounding platforms, that were formerly necessary, 
is the fact that in our little ship we are so near the surface of 
the sea that the 
person taking ob- 
servations stands 
only a few feet 
above the water, 
and it is conse- 
quently much 
easier to get the 
appliances on 
board as soon as 
they come up. 
It is much easier 
also to manoeuvre 
with a little 
steamer, so as to 
humour the appli- 
ances and keep 
the lines perpen- 
dicular whilst be- 
ing lowered or 
hauled in. Obvi- 
ously these are 
great advantages, 
not merely at the 
moment of taking 
observations, but 
also in our whole 
system of work- 
ing ; being able to 
operate a number 
of appliances sim- 
ultaneously, for 
instance, means a 
great saving of 
men and time. 

In the case of 
both sounding machine and hydrographical apparatus we 
are able to haul in the line at the rate of 120 metres per 
minute, or 6000 metres in fifty minutes. But the forward 
starboard winch was unfortunately too weak to keep up this 




-The Otter Trawl. 



42 



DEPTHS OF THE OCEAN 

was much line out and the weight was 



speed when there 
considerable. 

Trawling. For trawHng, former expeditions employed the model designed 

by Sigsbee, lo feet in breadth. This appliance, notwithstanding 
all its good points, is too small for catching large animals. 
Modern fishing steamers, which are quite small compared with 
the expedition ships of former days, mostly operate trawls 120 
feet in length, having a span of about 60 to 80 feet, with a 
height at the entrance many times greater than that of the 
trawls employed for scientific purposes. Seeing then that a 
great many trials have been made in all oceans with the dredge 
and with Sigsbee's trawl, it was advisable to try whether a 
larger appliance would not yield different species and bigger 
catches, and it was natural to select as a model the appliance 
supposed to be best adapted for catching fish, namely, the 

Otter trawl. Otter trawl in use among fishermen. 




Fig. 24.— The Otter Board. 

The difference between the otter trawl (Fig. 23) and the 
beam trawl (see the "Challenger" trawl, Fig. 11) is that in the 
case of the former the appliance is kept distended by means of 
otter boards, working on the principle of an otter for trout 
fishing or a kite in the air. The otter boards (Fig. 24) are 
attached to the line by bridles, and thus have a tendency to 
spread when towed along through the water. The regular 
trawlers use two steel lines of colossal dimensions, up to 3 
inches in circumference and with a breaking strain of 20 tons ; 
these are wound round two large drums that are keyed on to 
the slow axle of the trawl-winch (see Fig. 25), from which each 
line passes to its gallows and then astern, being carefully 
fastened with chains during the time that the vessel goes ahead 
towing the trawl after it. Sigsbee, it will be remembered, went 
astern when trawling, and he had one winch for winding the 
wire round the drum and another for the actual hauling in. 

It is quite evident that the system adopted by the regular 
trawlers economises labour, for it is simple, and space is saved 
by using only one winch. The otter trawl, again, has to be 



THE SHIP AND ITS EQUIPMENT 



43 




towed at a good speed to keep the boards in position, and the 

vessel skilfully steered, so that the lines 

must necessarily be towed from the stern. 

It was found very difficult, however, to 

adopt this plan to our requirements, the 

chief drawback being that everything must 

be of the very strongest materials. Sir 

William Thomson long ago, when working 

at his sounding machine, discovered that 

the drums were easily burst, and the 

trawlers too have had similar experiences, 

in spite of their using drums of cast metal 

several inches thick. 

The " Michael Sars " could not, of 
course, use such large appliances, for if in 
addition to overcoming the resistance of 
two ponderous otter boards, 6 feet by lo 
feet, she had to tow a pair of wires each 
many thousands of metres long, she could 
obviously not have got over much ground ; 
and besides, it would have been next to 
impossible to prevent such long lines from 
fouling one another. We were compelled 
therefore to trust to a smaller size of trawl, 
and to substitute a single warp, from the 
end of which we led a connecting line, 50 
fathoms in length, to either otter board 
(see Fig. 26, line and bridle). A similar 
arrangement for small otter trawls had 
been already successfully tried by C. G. 
Joh. Petersen. During previous cruises of 
the " Michael Sars " we had operated a 
trawl with 50 feet of headrope at a depth 
of 1830 metres, and during our Atlantic 
expedition we succeeded in working the 
same appliance at a depth of 5160 metres. 
Our success must be ascribed to the solid 
construction of our gear. The drum of 
the winch which took the 9000 metres of 
wire was of the best cast steel, and the 
blocks were made as substantial as pos- 
sible, though even then they had to be 
changed during the cruise, because 




Fig. 25. — Deck Arrange- 

the MENTS OF A TRAWLER. 



44 



DEPTHS OF THE OCEAN 



steel wire soon wore deep grooves in them. Our trawlings, too, 
took a long time, for the 20 horse-power winch that wound in 




Fig. 26.— The "Michael Sars" trawlinc; wi 
AND Otter Trawl. 



>M-: Wire Rope 



the wire directly on to the drum was unable to maintain its full 
speed when the load was unduly heavy. 

On 31st May, at Station 48, the trawl was shot at a depth of 




Fig. 27. — Hauling in Long Lines by means of Line Winch. 

5160 metres with 8750 metres of wire ; we commenced lowering 
at 5.45 A.M. and started trawling at 11.20 a.m.; hauling in 
began at 2.50 p.m., and the trawl was once more on board at 



THE SHIP AND ITS EQUIPMENT 



45 



9 P.M. Hauling in took, therefore, six hours ten minutes, and the 
average rate was 24 metres per minute, or about a third of the 
speed at which Sigsbee hauled in his little trawl. 

In addition to the trawl the "Michael Sars " can use lines Lines and 
and drift nets, in which respect she is equipped like an ordinary '^"'"^'^• 
fishing steamer. The lines are passed out over the stern and 
hauled in amidships by means of the little after starboard winch, 
which is really the same as the little winch used for the hydro- 
graphical instruments. This is moved forward on the deck, 
and the lines are hauled in as in Fig. 27. Herring drift nets are 




Fig. 28.— Hauling in Drift Nets. 

set from the stern ; when all the nets are out the vessel swings 
round on the warp. This warp is hauled in by means of the 
large end-drum on the big winch and over the reel in the bows, 
and the nets are hauled over the side on to the fore part of the 
deck (Fig. 28). 

As regards the net constructed by Victor Hensen (Fig. 19), 
a great deal of work has been devoted to studying its 
"coefficient of capture"; it is suitable for making quantitative 
studies of the occurrence of such plankton organisms as copepods, 
peridinii, etc., but for other purposes it has little practical value. 
Its upper part is furnished with a canvas cone, which allows no 
water to filter through, and therefore offers an effectual resist- 



Pelagic 
appliances. 



46 



ance to the water, both 
hauled in. It is, 
besides, quite use- 
less for towing, for 
which purpose it 
was never intended. 
In the construction , 
of our nets on the 
"Michael Sars" our 
idea was to make 
the fore part in such 
a way that as much 
water as possible 
might percolate 
through. As a rule 
they are i metre in 
diameter at the 
entrance and 4.5 
metres long (see 
Fig. 29). The fore 
part is cylindrical 
for a length of ij 
metres and of the 
same size as the 
entrance. There is 
first half a metre of 
shrimp net, then i 
metre of coarse silk 
with a mesh of 12.5 
mm., and the after 
part, consisting of a 
cone, 3 metres long, 
of finer silk with a 
mesh of 0.8 mm. 
These filter the 
water admirably. 
We can tow them 
at a great speed and 
haul them on board 
rapidly, even with 
the little after star- 
board winch ; and 
they capture young 



DEPTHS OF THE OCEAN 

while being lowered and while being 




'-^'^fdj 




Fig 29 -The "Michael Sars" Tow-Net. 
A, net ; B, coarse silk ; C, finer silk ; D, lead. 



THE SHIP AND ITS EQUIPMENT 



47 



fish almost as well as the trawl itself. The cylindrical fore part 
is largely responsible for this, as it retains within its walls the 
animals that do not pass immediately into the after part, which, 
owing to its great length, lets the water filter easily through. 
One great advantage of these tow-nets is that they can be 
lowered very rapidly when used as vertical nets. They then 




Fig. 30. — Large Vertical Closing Net. 

assume the shape depicted on the left in Fig. 29. The net in 
the foremost portion of the cylinder is the only part that offers 
any resistance, and it too is wide meshed, so that the water 
easily passes through it ; the rest descends like a thick rope. 
They can also be used as closing nets, and we have actually 
employed in that capacity nets J, f , and i metre in diameter at 
the entrance. 

We further constructed two large closing nets, 3 metres in 



48 



DEPTHS OF THE OCEAN 



Large closing diameter at the mouth and 9 metres long, one of silk and the 

"^*^' other of net ; one of these is depicted open on the right and 

shut on the left in Fig. 30. They proved to be our most 

successful pelagic appliances. We used them sometimes as 

vertical nets and sometimes for towing. The closing mechanism 

(Fig. 31) was constructed 
on Nansen's principle. A 
slip-weight sets free the 
cords that support the 
ring, which falls down 
and leaves the whole 
hanging by a noose. This 
noose draws the net to- 
gether so that nothing 
more can enter it. Two 
sizes of mesh are used in 
the construction of these 
nets ; in the fore part a 
mesh of about i centi- 
metre and in the after 
part one of almost J centi- 
metre from knot to knot. 
In deep waters, how- 
ever, and especially out 
in the open ocean, even 
these large appliances, if 
merely used as vertical 
closing nets, fail to furnish 
a representative picture 
of the animal life. The 
animals can only be cap- 
tured by long horizontal 
hauls, and therefore to 
ascertain what exists at the 
different depths we must 
tow a large number of 
appliances simultaneously. 




Fig. 31. — Closing Mechanism. 



Method of 
using tow- 
nets. 



Fh 



> shows the plan we generally adopted during the 
Atlantic cruise of the " Michael Sars." Two lines were used : 
a long line from the big winch for the deep-water appliances, 
and a shorter one from the after winch for lesser depths. 
Silk tow-nets either i metre or f metre in diameter, and 
Petersen's young-fish trawls were alternately attached, and to 



THE SHIP AND ITS EQUIPMENT 



49 



the end of the longest line we fastened the large tow-net just 
described. 




Fig. 32. — The "Michael Sars" towing Ten Nets and Pelagic Trawls. 
(Surface net not shown. ) 

A difficulty which arose when organising this system was 
that the cord by which a tow-net or trawl is attached to the 
wire becomes easily entangled, in which 
case the appliance is rolled round the wire 
or else torn off. To avoid this we screwed 
a brass knob (Fig. t,^,) on the wire and 




Fig. 33.— Brass Knob for Tow-Nets. 

fastened the tow-net to a brass ring, which 
could be threaded on above the knob (Fig. 
34), The appliance is thus kept from 
sliding down the wire, and is free to move 
in any direction (see also Fig. 32). This 
method of working enables one to operate as many appliances as 

E 




Fig. 34.— Brass Ring 

for Tow-Nets. 



50 



DEPTHS OF THE OCEAN 



Centrifuge. 



the vessel is able to tow through the water, and by comparing 
the catches in the manner described in Chapter IX. one can 
ascertain the depths at which the animals lived. It is really a 
development of the plan adopted by the "Challenger," which 
towed its small nets along at different depths, or else attached 
them to the sounding-line (see above, p. 34). 

The pelagic investigations of recent years have shown 
that a great many marine organisms are so small that they pass 
through the meshes of all nets — even the finest silk nets (see 




Fig. 35. — Centrifuge dri\e.\ by Electric Motor. (From a catalogue.) 

Chapter VI., where these organisms and their occurrence are 
described). To catch them in greater quantities we employed 
a large centrifuge (Fig. 35) as used by physiologists, which 
could centrifuge 1200 cubic centimetres at a time. The centri- 
fuge was driven by one of the small steam-winches usually 
for a period of seven minutes and at a speed of 500 to 700 
revolutions per minute. 

This short description of the outfit of the "Michael Sars " 
does not claim to be exhaustive. During past years probably 
most kinds of fishing gear and scientific instruments available 
for the investigation of the sea have been made use of by us. 
When undertaking a definite limited cruise, however, a pro- 
gramme of the researches contemplated must necessarily be 
drawn up in advance and the gear selected accordingly. 

Our Atlantic cruise proved that a greater number of 
appliances could hardly have been employed during a cruise 



THE SHIP AND ITS EQUIPMENT 51 

of a few months' duration. But on the other hand a number 
of problems arose during the cruise, which we would fain have 
had the opportunity of investigating further. 

It is especially our knowledge regarding the physical and 
biological conditions in the waters of the abyssal regions, and 
regarding the large pelagic organisms, that may still be con- 
sidered as very imperfect. In order to study these problems 
more effectively, still more powerful winches, longer lengths of 
wire, and larger and better pelagic fishing gear are the principal 
things wanted. Future expeditions will thus have to face a 
serious task, not free from technical difficulties. 

J. H. 




Group of Appliances used on board the "Challenger. 




S.S. "Michael Sars" in Plymouth Harbour. 



CHAPTER III 



THE WORK AND CRUISES OF THE " MICHAEL SARS 



In this chapter it is proposed to point out briefly the nature and 
extent of the oceanographical work and fishery problems in 
which the S.S. "Michael Sars" has been engaged in the 
Norwegian Sea during the past ten years. Thereafter we will 
turn to the special cruise in the North Atlantic from April to 
August 1 910, and will recount the operations of the ship and 
the proceedings on board at the observing stations along the 
coasts of Europe, Africa, and Newfoundland, and during the 
voyages across the whole extent of the Atlantic. 

Since the summer of 1900 the " Michael Sars " has made a 
great number of cruises in the Norwegian Sea. Fig. 36 shows 
the location of the stations occupied during the years 1900- 
1904, and a good deal more work has been done there sub- 
sequently. In the winter our task has been a particularly 
arduous one. We have found that stormy weather nearly 
always prevails at that season, and it is light for only a few 
hours each day. The temperature of the air is so low that all 
the water that falls on the deck and rigging freezes, and the 



CRUISES OF THE "MICHAEL SARS " 



53 




quantity of ice thus formed is sometimes sufficient to weigh 
down the ship. 

Captain Iversen has given an account of one of the cruises, iversen's 

account of a 
winter cruise. 
















Fit,. 36.^The "Michael Sars" Observing Stations during the Years 1900-1904. 

that to Jan Mayen in February 1903, and his description 
presents such a vivid picture of the difficulties to be encountered 
when studying the Norwegian Sea and its fisheries, that it may 
well be printed here : — 

We came in here {i.e. Lofoten) yesterday with all well on board. 



54 DEPTHS OF THE OCEAN 

We could not quite keep the course proposed, as the weather took 
charge of us a bit sometimes and no mistake. I will endeavour to give 
a few particulars of the trip. 

We were pretty deep in the water when we left Bergen on the after- 
noon of the 9th February, every available hole and corner being crammed 
full of coal ; consequently we got a bit of a washing that night. We 
had a hard gale dead ahead, but managed all the same to take up three 
stations before she refused to look at it about midnight of the loth. 
All the nth we lay hove-to, though we were able to take up one station ; 
and on the I2th we stopped the engines to save coal, and got sail on 
her. Not till the afternoon of the 13th did the sea and wind go down 
enough for us to continue our course. During this storm we had 
frequent spits of snow and shipped a lot of water. To enable us to take 
up our stations we stretched a rope from davit to davit along the whole 
of the starboard side where we had to work. We did this to have 
something to hold on to, and so save us from being washed overboard. 
Koefoed was given a rope to tie round him, which fastened him like a 
dog to the davit where he worked. Otherwise everything was all right, 
except that the sheet of the mainsail parted so that the sail was damaged 
and a couple of thermometers were smashed. An interesting sight was 
a school of bottle-nose whales which we observed in lat. 63° 3' N., long. 
2° 44' E. They were seven in number, most of them being males, 
" barrel hoops." 

On the 14th and 15th we had good weather with little snow, so we 
made excellent progress northwards and took up a few stations. On 
the morning of the i6th we had clear weather and could see the ice- 
blink, the water at the same time becoming cold. After taking up a 
station during the night just clear of the ice we steamed through ice- 
floes all the next morning. We saw Jan Mayen in the distance, but the 
ice lay thick all round it. About midday we had to look sharp and get 
out again, as the wind increased to a gale, accompanied by severe frost 
and remarkable shrouds of mist, which assumed the most fantastic 
shapes and were constantly in motion. I have never seen anything like 
them before. We shaped our course for Vesteraalen, and got sail on 
her to steady her a bit. The whole of the afternoon we were pretty 
well cased with ice— hull, spars, and standing rigging — and on running 
suddenly into the middle of an ice-floe about nine o'clock that evening 
we had a hard job to get the ship round against the wind, her sails 
being so stiff with ice that it was impossible to take them in. However, 
we managed gradually to get her bows up against a large cake of ice 
and brought her round with the help of the engines. There was just 
room to turn her and that was all. We then set our course back the 
way we had come, and so got clear. 

The stations we took up during the severe frost were the reverse of 
easy, as the metre-wheels froze up, and we had to keep them warm 
with thick, red-hot iron bars that were brought from the engine-room 
and held close to the wheel-axles. 

On the night of the 17th we ran into another storm, which lasted 
till we arrived in port. 

On the 19th, at midday, we saw land, but were unable to make it 



CRUISES OF THE "MICHAEL SARS " 55 

out, as the fog hid everything except a strip along the shore. All that 
day we tried to establish our whereabouts, but were compelled to lie to 
for the night in a hard south-westerly gale. Next day we found that 
we were off Gaukvaer Island and stood in for the land. After burning a 
little coal our vessel behaved splendidly, and after we had used up most 
of our coal and water, and so were very light, we could run before the 
sea in any direction without even having to keep the laboratory door 
closed. We wanted all our electricity this journey, for it w^as practically 
night the whole time. 

The " Michael Sars" has carried out a great many different investigations 
kinds of investigations in the Norwegian Sea, viz. : observa- !^4ndiaei 
tions on the salinities, temperatures, and movements of the Sars." 
water-layers ; observations on the floating organisms of various 
sizes and kinds ; observations on the bottom fauna, especially 
bottom fishes. We have also made practical fishing experiments 
to discover what kinds of fish may be caught in the different 
areas of the sea. 

To describe all the cruises that have been made would take 
too long and lead to much repetition. In the subsequent 
chapters of this book the most important results are summarised. 

In order to study the movements of the water-layers and the 
distribution of floating organisms, cruises were undertaken at 
different seasons, as opportunity offered, from the coasts of 
Norway to Iceland, Jan Mayen, and Spitsbergen. To ascer- 
tain the fluctuations in the water-layers we have run a line of 
observations, nearly every year since 1900, and always in the 
month of May, from the Sognefjord to the north of Iceland. 
This route lies exactly across the axis of the Atlantic water that 
streams through the Faroe-Shetland Channel into the Norwegian 
Sea, and we have consequently been able to obtain a section of 
this layer every year, and to compare its volume in different 
years. Besides a great many special studies, measurements of 
the velocity of the currents have been made out in the open sea 
and in the fjords. 

At the time the " Michael Sars" commenced working there investigations 
were hundreds of square miles of coast banks where no fishing fi°h1n7^°^ ^^^ 
had ever taken place, and there was therefore a real fascination industry. 
in experimenting in these virgin areas with the appliances in 
common use along the coast, more particularly with long lines. 
Expeditions were made for several years along the whole coast 
for capturing spawning cod on all the banks where the depth was 
30-100 fathoms, and for halibut, tusk, and ling on the continental 
slope ; drift-net fishing was also undertaken for herring. 

In these investigations we have chiefly aimed at ascertaining 



56 DEPTHS OF THE OCEAN chap. 

the geographical distribution, horizontal as well as vertical, of 
the most important species of fish, especially during the spawn- 
ing period, when many of them are most sought after, and when 
each species may be supposed to congregate at localities where 
the natural conditions, such as depth, salinity, and temperature, 
acre especially favourable and characteristic. These breeding 
places have been discovered partly by searching for the spawn- 
ing fish, and partly by charting the distribution of the newly- 
spawned eggs, which float immediately above the shoals of 
spawning fish. 

The development and growth of the fish, and the geographical 
distribution of the different stages, formed another important 
subject for our scientific studies. By various means it is now 
possible to ascertain the age of the different individuals in a 
shoal of fish, and we are in consequence able to study the growth 
of fishes in different areas. 

Some of our fishing experiments have had an immediate 
influence on the development of the fishing industry, and have 
led to fish being found on hitherto unutilised banks, which have 
since turned out to be profitable fishing grounds. The study of 
the natural history of fishes may be said to have as its main 
object the widening of our knowledge regarding all the physical 
and biological phenomena on which depend the life of the fishes 
and the fishing industry. 

During the winter of 1909-10 a great deal of time was spent 
in preparing the " Michael Sars " for an extended cruise in the 
North Atlantic, in selecting the route to be followed, and in 
preparing instruments and apparatus of the latest and most 
approved patterns. 

A glance at the depth map is sufficient to make it clear that 
the greater part of the North Atlantic is deeper than 2000 
fathoms. The coast plateaus off Africa, Spain, and the United 
States are very limited, and the continental slope is, as in the 
Norwegian Sea, very steep. The bathymetrical curves for 500 
and 1000 fathoms lie in close proximity to one another. Only 
off Newfoundland and from the Bay of Biscay northwards along 
the western shores of Ireland and Great Britain do we find the 
continental shelf or coast banks widening out into tolerably 
broad plateaus. From the coast banks round Iceland a low 
ridge extends in a south-westerly direction, known as the 
Reykjanes Ridge. This is continued southwards as the Dolphin 
Rise, with deeper water on either side. From this low ridge 



CRUISES OF THE "MICHAEL SARS 



rise the Azores and St. 



57 

Paul's Rocks, and other volcanic cones 
and islands of small extent 
rise from the deeper water, 
like the Bermuda, Madeira, 
and Canary Islands, and the 
Dacia, Josephine, and other 
banks. 

The route of the " Michael 
Sars " from Plymouth to Gib- 
raltar (Fig. 37) was selected in 
order to find the most favour- 
able localities for using the 
fishing gear, that is to say, 
where the continental slope is 
less steep than usual, and 
where accordingly the gear 
would be working on com- 
paratively level ground. We 
expected to find the best 
ground where the coast banks 
are broadest ; for instance, off 
Ireland, in the Spanish Bay 
(Gulf of Cadiz), south of the 
Canaries, and off the New- 
foundland Banks. In our 
crossings of the ocean we 
had particularly to take into 
consideration the distance be- 
tween the coaling harbours. 

All preparations being 
complete, the " Michael Sars " 
sailed from Bergen on the ist 
April, the first port made 
being Plymouth, where Sir John 
Murray joined the expedition. 
While at anchor at Plymouth 
the captains of trawlers in- 
formed us that the bottom on 
the coast banks and on the 
continental slope was very 
rough in some places, but that 
if we took a westerly direction 
we should have a good opportunity of using the trawl down to 




Route of the 
" Michael 
Sars." 



From 

Plymouth to 
Gibraltar. 



Fig. 37. — The "Michael Sars" Observing 
Stations from Plymouth to Gibraltar. 



58 



DEPTHS OF THE OCEAN 



great depths. Our previous cruises had taught us what damage 
a rough bottom, especially coral, may do to the fishing tackle. 
Fig. 38 shows a piece of such coral brought up by the " Michael 
Sars " when fishing on the slope between the North Sea and 

the deep water of 
the Norwegian Sea. 
To avoid the corals 
we followed the 
advice given us and 
took a westerly 
course when we left 
Plymouth on the 9th 
of April, and from 
the outermost west- 
erly skerry, Bishop's 
Rock, we steered 
out over the coast 
banks to the conti- 
nental slope. Every- 
thingwas meanwhile 
got ready for trawl- 
ing and for the 
hydrographical and 
plankton observa- 
tions. 

Before leaving 
the coast bank we 
made observations 
at our first three 
stations in depths of 
T46, 149, and 184 
metres, partly to test 
the winches and in- 
struments and partly 
to get a section of 
the waters on the 
bank. All our 
arrangements for 
hydrographical and pelagic work were found satisfacftory. 
We secured a number of samples, and thoroughly tested the 
appliances. It was particularly important to see if the closing 
nets were to be relied on, so we lowered them to a depth of 
50 metres, and closed them immediately. They came up empty. 




38. — Piece of Coral {Lophohelia). 
About \ nat. size. 



CRUISES OF THE "MICHAEL SARS " 



59 



showing that they do not catch anything when sent down open. 
Successful trawlings at Stations i and 3 resulted in both cases 
in catches of over 300 fishes belonging to the ordinary coast- 




feN >.>>»"> 




Fig. 39.— Three Deep-Sea Fishes from Staiion 4, 923 metres (ahout 500 fathoms). 
a, Macrm-us cequalis, Gthr. Nat. size, 23 cm. 
h, ChimcBra mirabilis, Collett. Nat. size, 71 cm. 
c. Mora mora, Risso. Nat. size, 45 cm. 

bank species. Even these first hauls, however, made it evident 
that the big winch did not run smoothly when paying out line. 

On the morning of Monday, nth April, a sounding at Station 
4 gave us 923 metres. The big trawl was shot with 2360 metres 
of wire. At x p.m. we assumed that it was on the bottom, and 



6o 



DEPTHS OF THE OCEAN 



towed it for three hours till 6 p.m., when hauling in began. It 
came up at 7 p.m. with a catch of 330 large fishes [Macrurus, 
Mora, Lepidion, CJimicsra, etc. ; see Fig. 39). This haul was 
a thorough success. Perhaps never before had so large a 
draught of fish been made at such a depth. The trawl itself 
worked most satisfactorily, and considering its size hauling in 
was done rapidly (about 40 metres per minute). During the 
process of lowering, however, the big drum got jammed on the 
axle, and in spite of all our efforts we could not move it. There 
was nothing to be done, therefore, but to make for the nearest 
port to repair it, so we steamed into Cork and had it put right 
at the workshop on Wednesday morning (the 13th). We found 
after finally getting the drum off the axle that a lot of sand from 
the foundry had been left in by mistake, which accounted for its 
not working properly. By Friday (15th) the sand had all been 
scraped off, and the drum was once more in its place. But in 
the meantime a strong north-easterly gale had set in, and it was 
not till Saturday (i6th) that we were able to steam westwards 
under the lee of the Irish coast. The wind continued strong 
and northerly, but for all that we steamed back to Station 4, 
occupying a couple of small stations (5 and 6) on our way, and 
recommencing our interrupted section, proceeded out to still 
greater depths. 

On Sunday, 17th April, a sounding at Station 7 gave 
us 1 81 3 metres. The trawl was shot with 4000 metres of 
wire and towed for two hours. It came up all twisted and 
tangled, due to the fact that the swivels for keeping the wire 
and bridle from twisting had failed to act. The small steel 
balls in the bearings of the swivels had been crushed by the 
severe strain or the bend in the blocks. The trawl was got 
ready for a fresh attempt, but in the meantime the wind and 
sea rose to such an extent that we decided to give up further 
work in the deep water. To wait for good weather would have 
delayed us too long, so we set our course for the north-west 
point of Spain. 

The pelagic life of the upper 150 metres was extremely 
uniform. Several series of hauls with fine-meshed closing nets 
revealed the fact that quantities of the same diatoms extended 
down to a depth of over 150 metres. This was particularly 
interesting evidence as to the depth at which plant life can 
exist, even as far north as about lat. 49' 30' N., under special 
conditions. From this and other experiments made later Gran 
is of opinion that the same vertical circulation which produces 



CRUISES OF THE "MICHAEL SARS 



6i 



a uniform temperature throughout the deep layer also intro- 
duces materials, particularly nitrogenous matter from the 
surface — that is to say, indirectly from the coasts — which 
are favourable to the development of plant life. The plants 
were in consequence extraordinarily abundant. At Station 3 
we found great quantities of diatoms, even in a haul with the 
closing net from 160 metres up to 100 metres. 

On our way southwards from Station 7 we were prevented 
by the high sea from attempting any fishery experiments, so 
we had to content ourselves with making hydrographical 

observations (at Stations 8 and 
9), and it was not till we were 
well down in the Bay of Biscay 
at Station 10 that the sea be- 
came calmer and the weather 
moderated. We sounded here 
and got 4700 metres, so that 
we now had an opportunity of 
trying our appliances in really 
deep water (see Fig. 40). 

We commenced at this Vertical hauls. 
station, while the ship was still 
hove to, by taking a series of 
twelve water- samples as far 
down as 4500 metres, and 
made a number of vertical 
hauls with the closing nets 
down to 1000 metres. Every- 
thing was found to work 
splendidly, and all these opera- 
tions took only about three 
hours. 

Temperatures were recorded by means of the best kinds 
of reversible thermometers, which give readings exact to 
within a few hundredths of a degree even at the greatest 
depths. At this station we found the temperature at 3000 Temperatures 
metres to be 2.40° C. and at 4500 metres 2.56^ C. It was thus ^n deep water. 
apparently warmer near the bottom than 1700 metres (or 
nearly 1000 fathoms) above the bottom. It has often been 
thought that the water might derive a certain amount of heat 
from the sea-bottom, and this may have been the case here, 
but there is also another possibility, namely, that the water 
at 4500 metres had sunk from the upper layers and had been 




Fig. 40. 



-The Captain sounding in 4700 

Metres. 



62 



DEPTHS OF THE OCEAN 



Trawling in 
deep water. 



slightly warmed while sinking, just as happens with air that 
suddenly sinks from a great height towards the earth. This 
rise of temperature has also been attributed to decomposing 
organic matter and to radio-active matter in the deposits at the 
bottom. Whatever may have been the cause, we certainly 
found a similar slight rise in the temperature of the deepest 
layer on several subsequent occasions during our cruise. 

We next resolved to try the big trawl, and to reach the 
bottom at 4700 metres we estimated that it would be necessary 
to allow 8000 metres of wire, that is to say, 8 kilometres (Fig. 




Fig. 41.— The large Winch. 

41). We were engaged in paying out line from 5.30 p.m. to 
7.15 P.M., and at midnight we commenced hauling in, which 
lasted for about six hours. The trawl contained only two fishes 
[Macrzcrus) and a number of lower forms of animals : holo- 
thurians, a few worms, a gasteropod, a chalk-coloured crab, some 
ascidians, and one or two other things (see Chapter VH.). 

This seemed to us such a poor catch that we came to the 
conclusion that something had gone wrong. The trawl was 
therefore dropped again, and could be seen sinking down in 
perfect order. After being towed for three and a half hours, 
it suddenly stuck fast and stopped the ship. Hauling in took 



CRUISES OF THE ''MICHAEL SARS " 63 

eight hours, and the trawl came up (Fig. 42) in perfect order, 
containing an enormous mass of perhaps a ton of clay-like 
Globigerina ooze, that was as stiff as dough, and looked as if 
it might have been dug out of a chalk pit. We carefully sifted 
and washed it all with the hose, and found only the following 
animals : four actlnians, of which two were growing on hermit 
crabs, two cirripeds, a holothurian, some gasteropods, and a 
few worms. The question now presented itself — was animal 
life really so sparse down at those depths, or did our catch fail 
to represent it properly ? Had the trawl perhaps, when dragged 
through the ooze, been rendered 
incapable of doing its work of 
capture? If so, how had we 
been able to go on towing for 
such a length of time ? This 
was a problem that could only 
be solved by further experi- 
ment. A number of glass 
floats, about 3 inches in dia- 
meter, were sent down with 
the trawl, and were found to 
have been reduced to the finest 
powder by implosion through 
the immense pressure at this 
great depth. 

One thing at any rate we 
had learned. The enormous 
weight of 8000 metres of wire, 
with a huge trawl at the end, 
had worn deep grooves in our 
blocks and rollers in a very 
short space of time. It was necessary, therefore, to have 
rollers in reserve if much of this work was to be attempted. 

After a few successful pelagic hauls we resumed our course 
on the morning of the 21st April in the direction of Spain, 
our intention being to do some trawling at different depths on 
the continental slope, where the trawlers had told us the bottom 
was good. But when we made the coast of Spain at Cape 
Sisargas, an easterly gale sprang up and put a stop to all work, 
so after a few hydrographical observations (Stations 11 and 12) 
we steered southwards along the coast of Portugal. On the 
22nd the weather cleared up, and off the town of Vianna we 
saw the first line-buoys, and shortly afterwards the picturesque 




Fig. 42.— Otter Trawl coming up. 



64 



DEPTHS OF THE OCEAN 

vith their red lateen-sails came into 



Portuguese 

fishing 

industry. 



fishing-boats witn their red lateen-sails came mto view on 
the horizon. 

One of these came close to us, and we had an opportunity 
of learning something of their industry. Their boats were flat- 
bottomed, with a deep rudder that acted as a sort of keel. 
They were working with nets on a hard bottom, and, as a rule, 
in 30-40 fathoms of water. Their catches consisted of the 
lobster - like " languste " [Palinurzis vzilgaris), large crabs 
{Cancer, Liikodes), skates (Raia clavata, R. circularis), sharks 
iyCentrina and Miistelus), and breams {Pagellus centrodontus) , 

They also earned some money 
by going on board the trawlers 
and getting the small fish (small 
whitings, hake, etc.), which are 
generally thrown away. We 
came across the trawlers them- 
selves not long afterwards, and 
boarded a boat belonging to 
Boston, England. They were 
irawling for soles {Soiea V2il- 
garis) and large hake ; other- 
wise they got, as a rule, only 
skates and whitings. We shot 
our own trawl to see what 
there was on the bank, and 
captured the same fishes that 
the trawlers had spoken about 
(Station 14). 

The fine weather tempted 
us to try to make a series of 
hauls at different depths along the edge of the coast banks. 
We accordingly lowered the following appliances in the 
evening : a tow-net at the surface and two more at 50 metres 
and 100 metres respectively, a young-fish trawl at 150 metres, 
tow-nets at 300 metres and 500 metres, and another young-fish 
trawl at 750 metres. 

We had, however, scarcely begun towing our nets before a 
northerly gale sprang up. Hauling in had therefore to be done 
in the dark, and the sea became high and broke over the stern, 
where the gear was being got in. The result was that the 
violent pitching of the ship tore the silk cloth of the nets and 
did considerable damage. We lost the tow-nets sent to 100 
metres and 500 metres, as well as the young-fish trawl at 750 




Portuguese Fishing-Boat. 



CRUISES OF THE "MICHAEL SARS 



65 



metres, and a good deal of harm was also done to the others. 
All the same we managed to get some samples of interesting 
deep-sea forms, though such catches were of a more or less 
fortuitous nature. 

Off Lisbon the sea became calm, and we took hydrographical 
observations at Station 17, obtaining water-samples from many 
depths. Here, 
out on the edge 
of the continental 
slope, and in the 
Spanish Bay, the 
weather was 
beautifully warm, 
and the sun shone 
brightly. We 
now met with 
some extremely 
interesting forms 
of animal life. 
Numerous dol- 
phins swam 
round our bows, 
and when stand- 
ing in the fore 
part of the ship 
we saw thousands 
of small pelagic 
crabs {Poly bins ; 
see Fig. 4$), 
sometimes as 
many as fifty of 
them in three 
minutes. We 
also sighted a 
turde. 

While steam- 
ing along Gran studied the plankton filtered from water dan's inves- 
obtained by a pump, and found in every sample more than [IfJ'pfank^on. 
forty species of diatoms and peridinii, whereas to the west of 
Ireland we had come across a diatom-plankton, rich in indi- 
viduals but very poor in species, consisting of the ordinary 
North European coast diatoms. This showed that we had now 
reached a southern and warmer marine region, with a totally 

F 




Fig. 44. — Bargaini 



66 



DEPTHS OF THE OCEAN 



distinct assemblage of animal and plant life in the upper 
water-layers. 

On the morning of 
Monday 25th April 
we anchored off Gib- 
raltar, where we had 
our boilers overhauled, 
and procured reserve 
rollers and blocks, as 
well as new swivels 
for the trawl line. 



Currents in During our stay at 

GibfSil''^ Gibraltar we made two 

short trips : one to 

the Strait to study the 

currents, and the other 

to the Mediterranean 

to test our pelagic 

appliances. The 

Strait of Gibraltar has 

for a long time past attracted the attention of hydrographers. 

Through this narrow channel the exchange of water between 




Fig. 45.— roRTUGUESE Fisherman. 




Fig. 46. — Pelagic Crab [Polyhius henslowi, Leach). Nat. size. 

the Atlantic and the Mediterranean takes place, and there are 
great fluctuations in the two streams. A knowledge of the 
laws that govern the currents of this marine thoroughfare 



CRUISES OF THE "MICHAEL SARS " 67 

is accordingly of the utmost importance, not merely because 
of the light it throws on the question of ocean circulation, but 
also because of its value to navigation. As early as 1871 Nares 
and Carpenter made a study of these currents, and important 
investigations have been made in later days by the Danish 
research vessel "Thor" under the direction of Joh. Schmidt. 
No direct measurements of the actual velocities of the currents 
at different depths and their direction had previously been 
undertaken, but current-meters, especially the excellent one 
constructed by V. W. Ekman, put it in our power to make the 
attempt. 

The " Michael Sars " had previously measured currents off 
the coast of Norway by anchoring a life-boat fore and aft with 
grapnels and a stout hemp line. We endeavoured to work on 
the same principle in the Strait of Gibraltar (Station 18), but 
were unsuccessful at first ; one line after the other parted, owing 
to the velocity of the current. Finally we had to anchor the 
ship itself with i|^-inch steel line and a warp anchor, in 400 
metres of water on a hard bottom. This held, and she lay at 
anchor from 1.30 a.m. till 5 p.m. on the 30th April. During 
this time Helland-Hansen worked unceasingly. One current- 
meter was used continuously at a depth of 10 metres, and 
another was lowered to different depths right down to the 
bottom. In addition he took a series of water-samples and 
temperatures at different depths. 

He found that there were two strong currents in the Strait, 
one going east from the Atlantic into the Mediterranean in the 
upper layers, and one going west at the greater depths. The 
limit between them was for the most part at a depth of about 
150 metres, but it varied so much that in the afternoon between 
2 and 2.30 P.M. it was at a depth of 50 metres, while between 
4 and 5 A.M. even at the very surface the current went westwards. 
These variations practically coincided with the tidal movements. 

There were high velocities in the upper east-going current ; 
at 10 metres the velocity varied between i and 2^ knots, and 
at 25-30 metres between 1.7 and 3 knots. At a depth of 
100-120 metres the current was always westerly, but the 
velocity was only between half a knot and a knot, whereas at 
150-200 metres, where the current was also westerly, the 
velocity varied from 0.3 knot to as much as 5 knots; close to 
the bottom a velocity of ^ knot was measured. Helland- 
Hansen's interesting observations are the first reliable figures 
regarding the niovements at the different depths, and they are 



68 



DEPTHS OF THE OCEAN 



Pelagic inves- 
tigations in 
the Mediter- 
ranean. 



Water strata 
in the Medi- 
terranean. 



Noctihuc 



of great assistance towards a proper understanding of the 
water circulation in the Strait of Gibraltar. 

At Station 19, a few hours' steaming from the entrance to 
the Mediterranean, we experimented with different appliances, 
to ascertain the best way of arranging our subsequent pelagic 
investigations. The big silk tow-net, 3 metres in diameter, 
was lowered to a depth of 900 metres and immediately hauled 
up again. It was found to work well, and captured a number of 
pelagic fish (eight specimens of Argyi^ope/ectis, a. few scopelids, 
and some young fish), but our catch seemed to indicate that 
vertical hauls were not nearly so productive as horizontal hauls, 
and we therefore decided to make long horizontal hauls our 
principal mode of catching pelagic fish during the remainder of 
the cruise. 

At this part of the Mediterranean there was a sharply 
defined limit between an upper water-layer, where the temper- 
ature was fairly high and the salinity almost identical with that 
of the upper layer in the Spanish Bay in the Atlantic, and a lower 
water-layer with " bottom-water" of uniform temperature (a little 
below 13° C.) and salinity (over ;^S per thousand). Several 
series of temperatures and water-samples were taken, and the 
limit between the two layers was found at a depth of 150-200 
metres, though subject to considerable variation, as in the Strait 
of Gibraltar but not to such an extent. 

The surface water here was so full of phosphorescent 
Noctiluca as to be almost as thick as broth, and when the 
contents of the tow-net were emptied into a glass they formed a 
sediment a centimetre in thickness at the bottom of the glass. 
In the evening the sea resembled a star-spangled sky, and the 
wires following the vessel looked like gleaming stripes. During 
the day we now saw for the first time the beautiful surface 
organisms of the south, such as Velella and the Portuguese 
man-of-war [P/iysalia), with which zoologists and sailors in 
Mediterranean waters are so well acquainted. 



From the 
Spanish Bay 
southwards 
along the 
north- west 
coast of 
Africa. 



The region from Spain along the coast of North Africa is 
well known to zoologists from the successful labours of the 
French " Travailleur " and " Talisman " Expeditions. Series of 
trawlings at various depths were undertaken by these two ships 
with only small beam trawls, so that we had every hope of 
accomplishing something with our large trawl. We were able 
besides to turn to good account the information acquired from 
the fishermen, large numbers of whom have shot their trawls 



CRUISES OF THE "MICHAEL SARS " 



69 



along these shores in recent years. They had given us to 
understand that we could reckon on finding good trawling 
grounds as far down as 250 fathoms on many of the coast banks 
off Morocco, such as the stretch from Cape Spartel to Casa 
Blanca, from Mogador to the bay at Agadir, and south of Cape 




Fig. 47. — Depths and Stations in the Spanish Bay. 

Juby on the inner side of the Canary Islands. We? also 
learned that their catches chiefly consisted of hake {Merhiccius 
vu/gaj'is), which, as a rule, made up two-thirds of the whole ; 
soles [Solea vulgaris), and different kinds of silvery or brilliantly- 
coloured spiny-finned fish (mostly Sparidse), which they call 
"salmon." 

Our plan was to carry out two series of trawlings from the 
coast banks outwards to great depths, one in the Spanish Bay 
and one south of the Canary Islands, so as to have a general 
idea of the fauna at diff'erent depths in different latitudes. We 



70 DEPTHS OF THE OCEAN 

wished also to take a thoroughly good hydrographic section 
right across the Spanish Bay, with water-samples and tempera- 



.^•' 




Fig. 48.— Three Shore Fishes from Station 20, 141 meires (about 75 fathoms). 
a. De/itex maroccanus, Cuv. et Val. Nat. size, 25 cm. 
&. Mullns sunnuletus, L. Nat. size, 29 cm. 
c. Peristedion cataphracUim, Cuv. et Val. Nat. size, 30 cm. 



CRUISES OF THE "MICHAEL SARS 



71 



tures from all depths, and we hoped to trace the course of 
the salt-water layer that flows out from the Mediterranean to 
the Atlantic, which we felt would be interesting to all hydro- 
graphers. 

We left Gibraltar on 4th May and steamed through the Trawiings in 
Strait and past Cape Spartel in perfect weather till we came to ^p^"^^^ ^^y- 
the coast bank, where at Station 20 (see Chart, Fig. 47) we saw 
seven trawlers at work. Our trawl was dropped in 1 4 1 metres, and 
towed for two and a half hours. The resulting catch of 163 
fishes was a good sample of the ordinary species to be found 
there, namely hake, different kinds of gurnard {Trigla sp.), 




Fig. 49. — Two Deep-Sea P'ishes of the Family Ai.epocephalid^. 

a. Alepocephalus from Station 23 (1215 metres). Nat. size, 60 cm. 

b. Conocara from Station 25 (2055 metres). Nat. size, 20 cm. 

mullet [Ahtlhis sttrmuletiis), and silvery or brilliantly-coloured 
spiny-finned fishes [Capros, Pagelhcs, Dentex ; see Fig. 48). 

The next station (Station 21), in 535 metres, yielded 117 
fish, including hake, but all the beautifully-hued fish had dis- 
appeared. Instead we found the deep-sea fauna coming into 
evidence [Maa^urus, CJiinicErd), and at the three following 
trawling stations our catches were made up entirely of true 
deep-sea fish (Fig. 49), namely : — 

Station 23 at 12 15 metres, 77 fishes. 
Station 24 at 1615 metres, 32 fishes. 
Station 25 at 2055 metres, 29 fishes. 

From a technical point of view these hauls were in every 
way satisfactory, as our winch, trawl, and all connected with 
them worked perfectly smoothly. The new swivels (Fig. 50) 



DEPTHS OF THE OCEAN 



Relation 
between 
Mediter- 
ranean and 
Atlantic 
waters. 



r 







procured at Gibraltar were a thorough success, and stopped the 
twisting in the trawl-warp and bridle. The bottom was every- 
where well adapted for trawling. 

At Station 23 we towed a small young-fish trawl at 12 15 
metres. It touched the bottom and brought up a quantity of 
empty pteropod shells which had been sifted out from the 
bottom deposit. It is extraordinary to find these deposits of 
shells belonging to plankton organisms only at certain relatively 

shallow and intermediate depths, for, when 

alive, the pteropods float over all depths. 

Our trawlings further resulted in a fine 
collection of invertebrate animals ; at Station 
24, for instance, we found the trawl full of 
siliceous sponges. 

These waters offer a good field for a 
thorough study of the distribution of animal 
life, for the nature of the bottom and the gentle 
slope permit of trawling at all depths. Our 
time unfortunately was too short to permit us 
to do more than obtain a general impression. 

We next turned our attention to the hydro- 
graphical investigations, and steamed to the 
north side of the bay near Cadiz (Station 26), 
whence we ran a series of stations, at all of 
which careful hydrographical observations were 
made (Stations 26-30). 

At the conclusion of the " Challenger " 
Expedition Buchan showed that it was pos- 
sible to trace the course of the comparatively 
warm Mediterranean water out into the North 
Atlantic Ocean, In 1909 the Danish expedition in the " Thor" 
under Schmidt made some observations from the Strait of 
Gibraltar westwards, and secured extremely accurate determina- 
tions of temperature and salinity, showing that the Mediterranean 
water (in a very diluted state) makes its way out through the 
Spanish Bay, sinking down to a depth of 1000-1200 metres. 

In our investigations we aimed at studying more closely the 
relation between Atlantic water and Mediterranean water, and 
we also endeavoured to become familiar with the currents on 
both the Spanish and Moroccan sides of the bay. Unfortun- 
ately we had to abandon our current measurements, but the 
variations of salinity and temperature from our many adjoining 
stations give a fairly good idea of the conditions. It is enough 



Fig. 50. — The 
Swivel. 



CRUISES OF THE "MICHAEL SARS " 



n 



to mention here that in the neighbourhood of Spain the diluted 
Mediterranean water was found at far less depths (as near 
the surface, in fact, as 400 metres) than farther south in the 
bay. The surface current runs along the Spanish coast in an 
easterly or south-easterly direction, and off the Moroccan coast 
in a southerly or south-westerly direction (see Chapter V.). 

Hydrographical investigations were continued all the way 
southwards along the continental edge to the Canary Islands. 
We were prevented from attempting any other kind of work, as 
near Mogador we encountered a stiff north-east trade-wind, before 
which we had to run. Every now and then a heavy sea broke 
over our quar- 
ter, sweeping 
the deck clean. 
Not till we 
reached the 
Canaries did 
the wind and 
sea go down. 
At Lanzarote 
we met with 
calm weather, 
so we did some 
pelagic work, 
taking vertical 
and horizontal 
hauls. The 
latter resulted 
in the capture 
of several in- 
teresting deep-sea fish, a number of leptocephali, and the beautiful 
transparent Plagiisia. 

On Saturday, 14th May, we anchored at Porta de la Luz, 
the harbour of Grand Canary. 





\ , 






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W 



Fi.;. 51. 



A Fishing Sen 



t'O I'ORTA DE 



Luz. 



In Porta de la Luz we obtained a good deal of information 
regarding the fishing industry from a number of fishing schooners 
which work along the African coast, several being in port at 
the time of our visit. 

Most of them are well -boats, which carry live fish in 
addition to the ones they salt. They employ partly hand lines 
and partly curious large basket-traps, baited with fish and placed 
on the bottom in the position shown in Fig. 52. 



74 



DEPTHS OF THE OCEAN 



African "coast 
fisheries. 



When the boats arrive in port they transfer the live fish 
into big floating- tanks, of which we saw many. We were able 
to examine the kinds they caught, and learned from the people 
the names in current use. This was a piece of good fortune for 
us, because the local guide-books give misleading information. 
The fish caught are spiny-finned and silvery, or of brilliant 
colours. The following are the commonest species : — 

Chiacarone = Dentex vulgaris. 

Besugo = Pagrus vulgaris. 

Burr oor Chlerne = Diagranwia 7nediierrafieuf?i. 

Chopa = Canlharus lineatus. 

Saifia = Sargus rotidelettii. 

Dorado = Chrysophrys aurata. 

Most of them are at present sold alive and eaten fresh, but 
some are salted, being first split down the back and sliced. 

They are also 
occasionally dried, 
though this kind 
of stock-fish does 
not keep long. 

The harbour 
pilot was thor- 
oughly acquainted 
with the industry. 
He himself owned 
one or two 
schooners, and 
had taken part in 
the fishing round 
the islands and 
off the African 
coast. According 
to him the best 



'A 


m' mum 


■' J^jfe'- r" ^' ■ ■■ rj i- 




f'^lf**^ 




* V , - 





Fio. 52.— A Basket-Trap ox board a Fishing Schooner. 



places were on the stretch from Cape Juby and beyond Cape 
Bojador to the River Ouro, and down near Cape Blanco. The 
trawlers found it too expensive to go so far. Only hand lines 
and traps are used at present, and most of the fishing is done 
on a hard bottom in about 16-30 fathoms of water. He advised 
us to go as far as Cape Bojador, where there was a little bay 
sheltered from the trade-winds. We decided to follow his advice, 
partly because we hoped to see a little of the mode of fishing 
practised in the Canary Islands, and thus learn more about the 
animal life than we ourselves could expect to learn in the short 



CRUISES OF THE "MICHAEL SARS 



75 



time at our disposal, and partly with the idea of making a series 
of trawHngs like those we had made in the Spanish Bay. 




^iG. 53.— "Michael Sars" observing Stations off the Canary Islands and 
Coast of Africa. 

Accordingly we left Gran Canaria on i8th May, and steamed 
for Cape Bojador (see Chart, Fig. 53). On the way we 
resolved to try our trawl in deep water, as the weather was fine. 



fishinj 



76 DEPTHS OF THE OCEAN chap. 

We sounded, therefore, at Station 35 and got 2603 metres. The 
trawl was dropped with 5200 metres of wire and towed for 
about two hours till 6 p.m. At 9 p.m. it was on board again 
with an extremely interesting catch, including two baskets of 
holothurians and twenty fishes, several of which were remarkable 
bottom forms {Harriot fa, Bathysaurus, Halosanrus, Alepoce- 
phalus, and different species of Macrurus). There were also 
several pelagic fish, including the interesting Gastrostoimis 
bairdii, with its huge gullet, which had previously only been 
found on the American side of the Atlantic. 

At Bojador there were seven fishing schooners and two 
smacks at anchor. Some of the people were rowing about in 
boats setting traps, while others were jigging from the vessels 
themselves. We went on board the " Isabelita." Along the 
port-rail stood ten men with hand lines, each furnished with 
three hooks, by means of which they hauled up the big grey 
"burro" as fast as they could pull. Every now and then they 
captured " chiacarone " and smaller silvery fish with red fins and 
strong teeth. Their bait consisted of anchovies and sardines, 
Seine-net which they secured near the shore by means of a seine net. We 
were told that at daybreak next morning they were going close 
inshore to use their seine, and we obtained a promise to be 
allowed to accompany them. To our surprise we were asked 
to bring carbines and revolvers, as the fishermen were very 
much afraid of the Arabs. 

Before daybreak we rowed towards the shore along with the 
fishermen to work the seine. The view was magnificent. For 
miles we could see the coast stretching away in a straight, 
clear-cut line like a mole, a hundred feet or so above the sea ; 
up beyond the cliffs the land apparently was quite fiat, and the 
sun rose over this line as it does from the horizon at sea. 
Unfortunately the breakers prevented us from landing, and we 
had to He a short distance out from the shore. On the heights 
above we could see the dreaded Arabs, with their long, thin 
firearms ready for use ; but they sat as motionless as statues, 
and were probably only thinking of defending themselves. 

The Spanish fishermen now made several casts with their 
seine (see Fig. 54), but were unsuccessful. They had expected 
to catch large quantities of sardines for bait. We got from 
them, however, some interesting samples of the small fish that 
live in quite shallow water, which it would otherwise have 
been difficult for us to obtain. Among them were young fish 
(sardines and anchovies), and a number of small spiny-finned 



CRUISES OF THE "MICHAEL SARS " tj 

fish i^Sargus, Box, Pristipoma), besides fry of the horse-mackerel 
[Caranx trachurus), and hake. The fishermen gave us the 
whole of the catch and would take nothing for it. On parting 
from them we felt that we had made the acquaintance of capable 
energetic men, engaged in an interesting industry. 

The guide-books sold on the islands state that the fishing 
industry is undeveloped, because the island population is 
apathetic, and the Spanish Government little interested in it. 
This is hardly correct ; their African fishing seems to evince 
both enterprise and a power of adaptation to circumstances. 
It is no small matter to have to sail in the trade-winds, 
which are sometimes very violent off the coast of Africa, and 
there is besides an absence of harbours. The fish caught are 
best suited for selling alive in the local markets, and it is 




Fig. 54.— Uau 



extremely doubtful whether it would pay to start a fishery on 
a large scale, as has often been proposed, and commence 
salting and drying. The kinds of fish may possibly be unsuitable 
for curing, and the warm climate is very likely less favourable 
than that of northern lands. As long ago as the middle of the 
eighteenth century an enterprising man named George Glas 
made great efforts to establish a fishery, and maintained that 
the Spanish did not need to depend on Newfoundland for their 
fish, as they could make their African coast fishery the richest 
in the world. He did his utmost to prove the truth of his 
assertion, but failed, partly because of the natural difficulties, 
and partly owing to various tragic occurrences. Taking every- 
thing into account, the conditions under which it is carried on 
and the present state of the markets, the fishing industry of the 
Canary Islands is quite creditable, and the friendliness of the 
fishermen towards our expedition was much appreciated by all 
on board. 



78 



DEPTHS OF THE OCEAN 



Our plan after leaving Bojador was to undertake a series of 
trawlings over the coast banks and continental edge. This 





Fig. 55.— Three Coast Fishes from Station 37, 39 metres (about 20 fathoms). 

a. Serranus cabrilla, L. Nat. size, 21 cm. 

b. Corisjidis, L. Nat. size, 18 cm. 

c. ScorpcETia scrofa, L. Nat. size, 48 cm. 

proved, however, a matter of great difficulty. Both at Station 
37 (see Fig. 55) in 39 metres of water, and at Station 38 (see 
Fig. 56) in "]"] metres, the trawl stuck fast on the hard bottom. 



CRUISES OF THE "MICHAEL SARS " 79 

Still, we succeeded in making some small catches of the animals 
that live on the bank, including soles and megrims [Solea and 
Arnoglossus lophotes), gurnard, weevers, monkfish, a large 






'm 



Mt^ 





Fig. 56. 
a. Pagrus vulgaris, Cuv. et Val. Nat. size, 50 cm. 
h. MurcBna helena, L. Nat. size, 102 cm. 

[a and b from Station 38, tj metres — about 40 fathoms.) 
c. Centrisciis scolopax, L. Station 39, 267-280 metres. 

beautifully-coloured muraena i^Murcsna helena), and a number 
of skates. At Station 39 (see Fig, 56, c) in 267-280 metres of 
water, we were more successful, catching a quantity of spiny- 
finned fish (Dentex, Pag^'its, Scorpcrna, Trigla), hake and 
skates, and quite a number of deep-water fish. A pelagic haul 



8o 



DEPTHS OF THE OCEAN 



CHAP. 



on the edge of the continental slope yielded some interesting 
captures, especially several spotted eel larvae (leptocephali). 




*(l 



Fig. 57. — Two Deep-sea Fishes from Station 41. 

a. Sy?iaphobranchus pinnatus, Gron. Nat. size, 31 cm. 

b. Bathypterois dubius, Vaill. Nat. size, 17 cm. 

Deeper trawlings were impracticable. The captain sounded 
in several places to try and find a spot where there was a chance 
of trawling along the slope at a fairly uniform depth, but the 




Fig. 5S. 
Leptocephalvs Co/ign 



■'ulgaris. 



slope was too steep, and we had to abandon the idea. The 
only place where, according to the chart, there was any prospect 
of trawling at so great a depth as 1000 metres was between the 



CRUISES OF THE "MICHAEL SARS " 8i 

coast of Africa and the island of Fuerte Ventura. Here we 




Fig. 59. 

Ceratias, n.sp. Nat. size, 13 cm. Station 42. 

sounded at Station 41 and got 1365 metres. We shot our trawl 
with 3400 metres of wire, and towed it for three and a half 

hours. Hauling in took an hour 
and fifty minutes. Our catch con- 
sisted of about fifty deep-sea fishes 
(see Fig. 57), several baskets of 
holothurians, and a number of in- 
teresting invertebrates, including 
some beautiful, large, red-coloured 
prawns, no less than 30 centimetres 
long. This catch was extremely 
interesting, as it yielded the same 
species of fish that we got in 
our hauls to the west of Ireland 
(Mo7^a^ Trachyrhyncus, Alepoce- 
phalus, Synaphobranchus). 

The trade-winds had mean- 
while freshened considerably, so 
we steamed under the lee ot 
Fuerte Ventura, and at Station 
42 used our pelagic appliances at 
„ ^^_. various depths. The captures Eel larv? 

» Ifc J were particularly interesting, in- 

«eiS ir eluding as they did nineteen larvae 

^" p0^ of eels (leptocephali). One indi- 

vidual among these (Fig. 58) be- 
longed to the ordinary conger-eel 
iyLeptocepIialus Congi'i viclgaris), but the other eighteen were all 
of another species closely resembling the conger larva, but 

G 




\i 



Fig. 60. — Spirilla. (From Chun.) 



82 DEPTHS OF THE OCEAN 

differing from it in the number of muscle segments ; some of 
them were only 4.2 cm. long. There were further some remark- 
able deep-sea fish, including a curious Ceratias (Fig. 59), and 
the little rare cuttle-fish, Spimla (Fig. 60), which is of such 
interest to zoologists. 

During the night some fiying-fish (Fig. 61) with mature eggs 
came on board, and on our way back to Gran Canaria we saw a 
quantity of flying-fish near the island. We anchored once more 
at Porta de la Luz on Tuesday, 24th May. 

From the From Plymouth to the west coast of Africa we had been 

Uie^Azores" chiefly cruising over the coast banks and continental slopes. 




Fig. 61. — Flying-Fish [Exocaiiis spilopus, Val.). Nat. size, 32 cm. 

Now we were to begin a voyage across the Atlantic from the 
Canary Islands to the Azores and thence to Newfoundland. 
Our task henceforth was therefore to investigate a deep 
ocean, the average depth of which may roughly be put at 
5000 metres. Everything accordingly had to be so arranged 
that we could lower our instruments and appliances to profound 
depths. 

The experiences of previous expeditions had made it clear 
that the larger organisms, at any rate, are sparsely scattered over 
the vast ocean depths. We therefore prepared ourselves for 
long pelagic hauls of a day's or a night's duration, during the 
course of which it would be necessary to employ simultaneously 
as many appliances as we could at different depths, partly to 



CRUISES OF THE "MICHAEL SARS " 83 

accomplish as much as possible in a limited space of time, and 
partly to discover what creatures inhabit the various water- 
strata. 

While on our way to the Azores we hoped to be able to 
reach the Sargasso Sea and study its peculiar animal life. 
Accordingly before leaving Gran Canaria we interviewed some 
Norwegian skippers, who had spent many years in the waters 
lying between the Canary Islands and the West Indies, and 
were advised by them not to steer direct for the Azores, but 
to follow a westerly course as far as the longitude of those 
islands and then turn northwards. We followed their sugges- 




■-^0^ 



ohQ 



^ 



40' 67o 



O O^Q. 






o^'^ 



68" 



d6o~ 

065 

O, 



V^.C 



6A 



53' 



a/' 



0R£5 ■. 



dO' 



Fig. 62. 



Michael Sars" Stations from Canary Islands to the Azores and 
Newfoundland and thence to Britain. 



tion, leaving Gran Canaria on 27th May, and, as will be seen 
from the chart (Fig. 62), first steered westwards, making some 
investigations at Stations 43-52, and then northwards to Fayal, 
one of the Azores, occupying Stations 53-58, and arrived at 
Fayal on 13th June. 

Hydrographical investigations were made all this time, and Uniformity 
we took as many as fourteen water-samples at different depths graphical 
at each station, from the surface down to 2000 metres, thus conditions and 
securing some excellent material from this area. Fig. 63 shows ° 
a section of the ocean on our westerly route. It is remarkable 
how uniform the hydrographical conditions proved to be. The 



84 



DEPTHS OF THE OCEAN 



curves of salinity and temperature lie exactly parallel, both 
decreasing regularly as we descend in depth. 

The animal life, too, showed everywhere great uniformity. 
While on this route we made seven long pelagic hauls, some at 
night, with a number of appliances working at different depths 
simultaneously. The weather was all that could be desired, and 
we had therefore a splendid opportunity of testing even the 
very finest of our appliances. As a result we succeeded in 
collecting a great variety of forms, a full description of which 
can only be given after thorough systematic examination. It 





5.lQt 


5 


1 S 





■^ 


e - 


6 


'^ 


± 




— 


- 




.18- 


SMOloo 


L 


1 




- 




}V 


3eoQ!i» — 1 — --miin: 




Z7Z 


.500 


-- 




1 








- 


- 




12! 


,\'5 50"„„ 1 




- — 


1000 






'i>: ^ 








— 




'"" 


31 

6°_ 











— 








5S2ilJ- . 


' j ~"~^-~.^ 


-~^ 




-- 




il- 




~"~ 


■^.^ 



Fig. 63. — Hydrographical Section showing the Temperature and Salinity at 
Stations 44 to 51. 

will suffice here to mention the main features of the catches, 
and to describe one or two particularly remarkable forms 
(especially fishes) that attracted our attention at the time, or 
during our first cursory inspection in the laboratory. In the 
following chapters the material collected will be treated in a 
more systematic manner. 

It was interesting to find that from the corresponding depths 
we always obtained catches practically identical in character. 
In the appliances towed at the surface and down to 150 metres 
there were small colourless young fish of many species, and fish- 
eggs of very different sizes, some even as small as 0.5 mm. in 
diameter, and leptocephali occurred in considerable quantities. 
A profusion of crystal -clear pelagic forms, such as the large 



CRUISES OF THE -MICHAEL SARS " 



85 



transparent amphipod (Cystosoma), Veiella, Cesttmt veneris. Animal life 
lanthina, Ptei'otrachea, Physalia, and Glazicus atlanticus, were ^g^^Js*^^"^ 
also characteristic. 

At depths of 300 metres down to 500 metres silvery fishes 
were much in evidence. The commonest of them were the flat- 



\ 




Ullf' 




Fig. 64.— Two Silvery Fishes from a depth of about 300 Metres. 

a. Chauliodus sloanei, Bl. and Schn. Nat. size, 6 cm. 

b. Argyropelecus hemigymnus, Cocco. Nat. size, 3.5 cm. 

shaped Argyropelectis (see Fig. 64, U) Stoinias, Chauliodus (Fig. 
64, a), and Seri'ivovier. The fish which we met with most 
frequently, however, was the grey-coloured Cyclothone signata, 
hundreds of which were sometimes taken in a single haul (see 
Plate I., Chapter X.). Several species of red prawns were 
also found here. 

Our hauls from 1000 metres down to 2000 metres were 



86 



DEPTHS OF THE OCEAN 



equally interesting. They invariably contained black Cyclothone 
microdon (see Plate L, Chapter X.), and different species of 
red prawns in abundance. In addition there were many of the 
rarer sorts of black-coloured fish, Photostomias, etc., mentioned 
in the following pages, and dark brown medusae. Atolla, 



Fig. 65. ^Stalk-eyed Fish-larva. 



for instance, was especially characteristic, and so were red 
chsetognaths, and at some stations red nemertines. 

Besides the commonest forms which are almost always found 




Fig. 66. — New Species of Leptocephalus. 



occurring at the same depths, we obtained something of special 
interest at nearly every station. We can best illustrate this 
perhaps by a brief description of our most noticeable finds at 




Yio, 67.— Two Black Fishes with many Phosphorescent Organs, sometimes found 

IN the Upper Layers at Night. 

a. Photosiomias gite}-nei, Coll. Nat. size, 17 cm. 

/'. Idiacanthi/s ferox, Gthr. Nat. size, 22 cm. 

the stations marked on the chart (Fig. 62), remarking only 
that in their selection we have been guided by what we consider 
the most interesting. 

At Station 45 we made a haul with seven appliances during 
the night. In the upper 150 metres there was a quantity of 
young fish (some of which were stalk- eyed ; see Fig. 65), 



CRUISES OF THE "MICHAEL SARS " 



^7 



pteropods, leptocephali (one of which displayed remarkable 
pigment ; see Fig. 66), and cuttle-fish. There were besides a 
few black fish {IdiacantJms ferox, Photostomias gtiernei\ see 
Fig. 67). 

In the deep hauls at 1000 metres and 1500 metres there 
were numerous very rare animals. For instance, we secured 
specimens of the cuttle-fish Spirnla, and of the fish Melanocetus 
krechi, the type of which had been discovered by the " Valdivia " 
Expedition in the Indian Ocean, so far removed from the scene 
of its recapture. Again, 
Aceratias macrorhimts indictts, 
a small brown fish (28 mm. 
long; see Fig. 68), and Cyema 
atrum (Fig. 69), had hitherto 
only been met with in the 
Pacific and Indian Oceans, 
and off the coast of Morocco. 
It was extremely interesting to find at one spot all these proofs 
of the wide distribution of such " rare " pelagic fishes. 

At Station 47 we sounded in 5160 metres. Trawling was 
tried, but was a failure, as the trawl got out of order and merely 
captured a sea-pen {^Umbelhda gilnthcri). During the night we 
sighted a turtle, which was thus about 250 nautical miles from 
the nearest land, the island of Palma. 

At Station 48 we made another attempt at trawling. The 
big trawl was dropped with 8750 metres of wire at 11.20 a.m. 




Fig. 68. 

Aceratias macrorhinus indiciis, A. Br. 

Nat. size, 2.8 cm. 






Fig. 69. 

Cyema atnim, Gthr. Nat. size. 

At 2.50 P.M. we commenced hauling in, and the trawl came up 
at 9 P.M. This time everything seemed to have gone right, 
for the trawl apparently went down and came up again in Trawling ii 
full working order. Strangely enough, the catch was meagre ^^^'^p '''^'^'• 
in the extreme, consisting of half a barrel of ooze, a number of 
pumice fragments, the earbone (bulla tympanica) of a whale, 
two sharks' teeth [Cai'ckarodon and Oxy rhino), a fragment of a 
nautilus shell, two holothurians, about ten pteropod shells, an 
'antipatharian, a sertularian, Umbellula, six fishes {^AlepocephahiSy 
Malacoste2ts indicus, Argyropeleciis, leptocephalus in its transition 
stage from the larval form, a new form resembling Ipnops 



S8 



DEPTHS OF THE OCEAN 



murrayi, for which Koefoed and I propose the name Bathy- 
microps regis, and an ophidiid not yet determined). All these 
fishes, if we except, perhaps, Bat/iymicrops regis, were prob- 
ably captured while the trawl was being hauled in. There were 
thus no undoubted bottom -fish in this long haul with our 
large appliance, and taking everything into consideration, 

we had caught 
extremely little. 
Chapter VII. 

deals more fully 
with the signific- 
ance of this result. 
We were interested 
to find a fragment 
of a sea-pen [Um- 
bellula gihitheri. 
Fig. 70) which con- 
tinued shining 
brightly on the 
deck, thus furnish- 
ing fresh proof of 
the well-known 
fact that some of 
the lower animals 
from the profound- 
est depths emit 
light. 

While towing 
the trawl we made 
some interesting 
observations on the 
pelagic animal life, 
as we put two tow- 
nets on the trawl 
wire, the one being 
towed at about 40 
metres, and the other at about 2000 metres, and during the 
whole of the day we took samples from the surface. 

The tow-net at 40 metres contained a mass of red copepods, 
which were not observed at the surface during the daytime, but 
suddenly appeared as soon as it grew dark, soon after 6 p.m. 
The surface plankton comprised Physalia, a great many molluscs, 
such as lanthina and Pterotrachea, one of the remarkable little 




Umbelhila giintheri (phosphorescent). 



CRUISES OF THE "MICHAEL SARS 



fishes called SQ2i-\\ovse.s, (Hippocanipiis, Fig, 71), and the beautiful 
belt of Venus {Cestum veneris) ; 
very many pelagic foraminifera 
were present in the fine nets. 

Our deep tow- net caught a 
large Alepocephalus, showing that 
this fish may be pelagic. So far 
as we know it had hitherto been 
taken only in the trawl, and this 
catch was all the more interesting, 
because our trawl at the end of 
the same wire also captured a 
specimen ; previously one would 
have taken it for granted that 
this specimen must have been 
caught at the bottom. 

At Station 49 B we towed seven 
appliances in daylight, and no 
black fish were captured in the 
upper layers. We observed a 
number of Portuguese men-of-war 
{Physalia), around which were a 
great many small fishes — prob- 
ably horse-mackerel {Caranx), 
which we caught in one of the young-fish trawls — and fry of 
Scombresox. A beautiful large transparent amphipod {Cystosovia) 




Fig. 71. — Hippotaiiipiis. 




Fig. 72. 
Opisthoproctus soleatus, Vaillant. Nat. size, 6.5 cm. 



was secured at 200 metres, and young Argyropelecus at 500 
metres. In the deeper appliances we found large ostracods 



90 



DEPTHS OF THE OCEAN 



{Gigantocypris) with eggs, Opisthoprochis soleatus (a remark- 
able little fish, with large telescopic eyes, caught once or twice 



,i'' 3 




Fig. 73. 
Opisthoprodus grimaldii, Zugmayt 



Nat. size, 2. 6 cm. 



previously ; see Fig. 72), and another species of the same genus, 
Opisthopi'ocUis grimaldii (see Fig. ']^, two specimens of which 
were taken by the Prince of Monaco off the coast of Portugal. 



P 



D 



\V 






rm'*T]7- 



^--^^> — 



Fig. 74. — Floating Long Lines. 
b. Big buoys ; c, drift anchor ; d, leather buoy. 



There were also some specimens of the little Aceratias viacro- 

rhiniis indicus. 
Drift nets We had all along intended to try drift nets and floating lines 
and lines. ^^^ j^^ ^^ occan to sce whether big fish were to be caught there, 



CRUISES OF THE "MICHAEL SARS " 



91 



so we now made the experiment. A line was set perpendicularly 
with 1300 cod hooks, a fathom and a half apart (see Fig, 74), 
and we also put out six cod nets. Only one fish was caught on 
the line, at a depth of 550 metres, namely, Omostidis loivei 
(Fig. 75), which Lowe captured at Madeira, and is recorded 
by GUnther as having been found near the Philippines by the 




Fig. 75. 
Omosiidis kncei, Gthr, Nat. size, 14.5 cm. 

" Challenger." A large ossified spine springs from its gill-cover 
and extends right along the side of its body, and it has very 
large teeth ; it has a beautiful silvery appearance. Our bait 
(sprats) was unfortunately several months old, so that this 
experiment cannot be regarded as in any way conclusive. 

In the nets there were three pilot-fish {^Naitcrates d2Lcto7% 




Fig. 76. 
Naucrates diictor, L. Nat. size, 23 cm. 



Fig. 76), and under the boat when hauling in the nets a number 
of fish were noticed, of which we saw a good many subsequently ; 
they seemed to be plentiful near the surface of the sea, and two 
species, Lirus ^naculahis (Fig. ']']^ and Lints oralis, were 
eventually secured. 

At Station 51 we fell in with larger and smaller patches of 
drifting Sargasso weed with the ordinary gulf-weed animals 
clinging to it, such as small crabs, naked molluscs, and fishes 



92 



DEPTHS OF THE OCEAN 



(Syngnatkus ; see Plates V. and VI., Chapter X.), and in the 
open water between the patches were Portuguese men-of-war, 
invariably attended by small fishes. This seems to be a 
phenomenon corresponding to the association of the cod-fry 
with jelly-fishes in the Norwegian Sea. 

At this station we made a very successful haul during the 




Fic. 77. 
Lints maci/Iafus, Gthr. Xat. size, 9.5 cm. 



night of 5th-6th June with nine appliances. In addition to the 
ordinary surface animals previously referred to, the tow-net at 
the surface secured as many as sixty-one leptocephali belonging 




Fig. 78. — New Species of Leptocephalus. 

to what we have since found to be a new species (Fig. 78), 
of which twenty-three specimens were captured at Station 52. 
There was also an interesting high leaf-shaped leptocephalus 
(Fig. 79), another specimen of which was taken at Station 56. 

In the upper appliances there were quantities of fish-eggs 
and young fish, another Cystoso7na, and Ceratias couesii, which 
had previously been taken by the " Albatross " off the east 



CRUISES OF THE "MICHAEL SARS " 93 

coast of North America, by the "Challenger" near Japan, and 
by the "Valdivia" in the Indian Ocean at the bay of Aden. 
At this night-station, too, there were black fish in the upper 
layers, such as Ash^onesthes 7iiger (Fig. 80), a dark Dacty- 
lostoinias, and some black Cyclothone at 300 metres. An 




Fig. 79. — New Spfxies of Leptocephalus. 



interesting cuttle-fish with stalk-eyes was taken at 350 metres, 
and deeper down we got Serrivoiner, Ahmichthys scoiopaceus, 
MalacosteiLS niger, M. choristodactylus. 

At this station we were able to try an apparatus for 




Fig. 80. 
Asironesthes niger. Rich. Nat. size, 3.5 cm. 

ascertaining the depth to which the rays of light penetrate. 
It was constructed by Helland-Hansen, and is likely to Heiiand 
prove useful in the study of the forms of life in deep water. ^^^"J^^^^^^j. 
The apparatus shows the intensity of the light both from above and °™^ ^^ 
and from the sides. By means of panchromatic plates and p^ 
colour filters it is possible to tell, not merely whether there is 



otometric 
experiments. 



94 DEPTHS OF THE OCEAN 

light, but also the proportion of the different prismatic colours 
at different depths. At the very first attempts the apparatus 
acted perfectly, and as far down as looo metres at any rate 
showed light in considerable quantities, whereas at a depth of 
1700 metres the plates were unaffected even after an exposure 
of two hours. We may assume accordingly that the amount of 
light at the latter depth is infinitesimal. The ultra-violet and 
blue rays are the ones that penetrate deepest. There were 
plenty of these rays at 500 metres, whereas the effect of the red 
and green rays there was imperceptible even after an exposure 
of forty minutes. At 100 metres the rays were of every colour, 
though red rays were least numerous, while there were rather 
more green rays, but even at this depth blue and ultra-violet 
rays predominated. These experiments are of great assistance 
in dealing with such problems as the growth of plants, for 
which light is essential, the colours of animals at different 
depths, and the remarkable modifications in the organs of sight 
and phosphorescent light-organs that are so characteristic of the 
higher animal groups in the ocean depths. 

Another haul by night was made at Station 52, though only 
with four appliances, the deepest of which was at about 600 
metres. The catches in the tow-nets at the surface and at 30 
metres were particularly interesting, including a quantity of 
young fish, amongst which were young fiying-fish and a number 
of young Scojubresox, many leptocephali, one of which was 
afterwards found to be a small undeveloped larva of the common 
eel ; that is to say, a transition stage from the ^gg to the fully 
developed leptocephalic larva. It was extremely interesting, 
too, to find eggs of the deep-sea fish Trachypterus at the 
surface of this deep basin. 

In our deepest appliance we found the beautiful Macrostomias 
longibarbatus, captured by us at Station 28 in the Spanish Bay, 
and previously recorded by the " Valdivia " Expedition from 
the Gulf of Guinea and the Indian Oceart. We also captured 
a specimen of Opisthoproctns soleatus, as well as a species of 
Oiieirodes resembling niegaceros (Fig. 81). The haul with the 
trawl resulted in a take of at least two litres of large red prawns. 

As we had now reached the Sargasso Sea, at Stations 5 1 
and 52, we set our course northwards towards the island of 
Fayal, where we intended to coal before crossing over to 
Newfoundland. While steaming towards the bank which 
surrounds the Azores, we frequently saw sperm whales, some- 
times swimming on the surface and easily recognisable by 



CRUISES OF THE "MICHAEL SARS " 95 

their abrupt heads, and sometimes with their flukes in the air. 
A school of other whales, probably the " caaing-whale," was 
also seen. 

At Station 53 we reached a lesser depth of water, namely 
2615 to 2865 metres, and had, accordingly, arrived at the slope 
rising from the deep basin of the Atlantic to the plateau of the 
Azores. A sample from the bottom showed much pumice, 
pteropod shells, and a large percentage of carbonate of lime, 
with siliceous spicules of sponges and radiolaria. 

We shot the big trawl with 6400 metres of wire, and towed 
it from ten in the morning till two o'clock in the afternoon. At 
5,15 P.M. it came up with a most successful catch. The greater 
abundance of organisms here as compared with profound depths 
was surprising. There were at least 500 holothurians belonging 




Fig. 81. 
Oneirodes sp. Nat. size, 2.5 cm. 

to several species, large red crustaceans, fifteen Pagurtts, a 
number of actiniae, lamellibranchiates, and sponges, as well as 
thirty-nine fishes (different species of Macrtirus, Alepocephalus, 
Halosanropsis, Bathysaurits, Benthosaurus, and Synapho- 
brancJms). This haul proved again that animal life was 
abundant at about 3000 metres (1500 fathoms). 

Our pelagic hauls were equally interesting. They were 
carried out during the night of 8th June, and nine appliances 
were towed simultaneously. The surface tow-net contained a 
quantity of the large medusa [Pelagia atlanticd), a number of 
what are sometimes called salmon-herrings (scopelids, most of 
them Mydophuni coccoi or M. pMiictatiini), and as many as 
thirteen black Astronesthes niger. This was the more remark- 
able because we had towed appliances on the trawl-wire at a 
depth of 30 metres the previous day, for at least four or five 
hours, and had not captured a single scopelid or Astronesthes. 
A better proof of the vertical wanderings of these animals seems 



96 



DEPTHS OF THE OCEAN 



hard to find. Young fish, too, were nearly absent during the 
day, if we except a few specimens taken in a tow-net at 60 
metres, but at night we got masses of them at 50 metres. 
Among these young fish in the upper layers we found again 
five little eel larvae of a size smaller than the grown larvae, 
and there were besides a number of interesting young fish 
with telescopic eyes, young flying-fish, and different species 
of leptocephali. At 150 metres we secured two remarkable 
leptocephali with long rostrums (see Fig. 82). 

In the intermediate layers, that is to say, from 300 to 500 




82. — Two New Leptocephali with Rostrums. 



metres, we found stomiatids, there being no fewer than fourteen 
specimens of Ckauliodus sloaiiei in a little tow-net half a metre 
in diameter. At 800 to 1300 metres there were plenty of 
" rare " fishes; for instance, seven specimens of the large-mouthed 
Gastrostonius bairdii, a specimen belonging to a new genus of 
the Gastrostomidai (Fig. 83), a small fish which has not yet 
been described (Fig. 84), one Cyema atrtini, three Aceratias 
macrorJiinus indicus, masses of black cyclothones, and several 
others of the more common forms. This station may well be 
called an El Dorado for collecting zoologists, and instead of a 
few days, months might profitably be spent to the south of 
the Azores, where we found so many new and interesting forms. 
At Station 56, situated about 100 nautical miles from 
Fayal, the depth was 3239 metres. Here we lowered nine 
pelagic appliances on the evening of loth June, and hauled 



CRUISES OF THE "MICHAEL SARS " 97 

them ill next morning between 2 a.m. and 4.30 a.m. Our 
catches resembled those at the preceding stations. At 50 to 
150 metres there were quantities of fish larvae and young fish, 
including two small eel larvae and also the young of Macrttrus, 
a deep-sea fish, the young stages of which thus occur in the 
upper water-layers. Many of the young fish had telescopic 




Fig. 83. — Two Gastrostomid.^. 

a. Gastros/omiis bairdii, Gill nnd Ryder. Nat. size, 47 cm. 

b. New genus. Nat. size, 20 cm. 

eyes. The fact that we obtained young flounders showed that 
we were nearing land. At greater depths we secured nothing 
of any particular note, merely the usual deep-sea forms. 

While examining the material from our tow-nets in the 
morning, we noticed numbers of small silvery fishes near the 



ot turtles. 



Fig. 84. 
A new species, not classified yet. 

surface ; and later on, when we commenced steaming towards 

Fayal, we came across one turtle after another. The boat was Great capture 

therefore lowered, and a regular turtle-hunt began. Our plan 

was to row carefully up to the animals, which lay quite still on 

the glassy surface, seize them by the hind leg with our hands, 

and heave them into the boat ; in this way we captured as 

many as fifteen turtles belonging to the species Thalassochelys 

H 



98 



DEPTHS OF THE OCEAN 



corticata. Under the turtles there were often quite a number of 
the Httle silvery fish alluded to above, and we caught some of 
them in a net and found that they were horse mackerel (Caranx 
tracJmi'its, see Fig. 86). Some larger fish too were occasionally 
seen below the turtle near the mouth, just where the neck 

leaves the carapace. 
These swam under the 
boat as soon as the 
turtle was caught, but 
we captured three, and 
found them to be wreck- 
fish i^Polyprion ameri- 
cantis). Quantities of 
blue isopods were 
seen beneath one or 
two of the animals. 
Our meeting with tur- 
tles was extremely in- 
teresting, as we found 
Michael that their stomach con- 
tents consisted entirely 
of medusse and salpae, immense quantities of which floated near 
the surface of the sea. In the transparent blue waters we 
could perceive thousands and thousands of beautifully-coloured 
and iridescent chains of salpae, sometimes as much as 6 to 7 




Fig. 85. — T. H. Murray on board the 
Sars," iith June 1910. 




Nemichthy. 



Fig. 86. 
Caranx trachurus, L. Nat. size, 10.5 cm. 

metres in length, besides siphonophores and floating aurelias, 
with little fish in attendance, — a fascinating pelagic animal life. 

We made yet one more pelagic haul at Station 58, and 
caught a splendid specimen of one of the most remarkable deep- 
sea forms \Nemichthys scolopaccus). This is a long fish, with a 
long beak like that of a bird, large eyes, quite short body, and 



CRUISES OF THE ''MICHAEL SARS" 99 

an immense tail. Our specimen was about 125 centimetres 
long, of which the beak accounted for 8 centimetres, while the 
distance from the corner of the mouth to the anus was 4 centi- 
metres, the remainder being thus over a metre long. This 
creature has been caught previously in both the Atlantic and 
Pacific. 

After sounding at Station 58 in 1235 metres, we decided to 
shoot our trawl. Hardly was it well out, however, before it 
stuck fast, and brought the ship completely to anchor. We 
availed ourselves of this circumstance to obtain some current 
measurements, hauled in on the trawl-wire, and passed it forward 
to the bow, being thus as it were riding on a warp. 

We commenced measuring the currents at midnight, and 
went on till 3 p.m. next day, when we attempted to haul in the 
trawl. Unfortunately, however, the wire parted, so that we 
lost the trawl and 1500 metres of line as well. Still we had at 
any rate succeeded in taking some measurements, our mode of 
working being to have one current-meter constantly recording 
velocities at 10 metres, while another current-meter was lowered 
to different depths. The movement of the water-masses at 
10 metres was a typically tidal one. In deep water, too, there Tidal currents 
were relatively strong currents as far down as 800 metres, and "^J^^^ °p^" 
distinct indications of tidal movements. Generally speaking, 
the currents in deep water had an opposite motion to those of 
the surface layers, but a fuller account will be found in Chapter V. 
It is sufficient to state here that our expedition succeeded 
in measuring currents out in the ocean at considerable depths, 
and that we found tidal movements even at profound depths. 
We anchored at Fayal on 13th June. 

One of the most interesting tasks of our expedition was to From the 
take a section across the western basin of the North Atlantic j^ewfoimd- 
from the Azores to North America. A section of the Gulf land. 
Stream as far south as we could manage would, we felt sure, 
be of value, and it would also be interesting to compare the 
animal life which we had found in the eastern basin between 
the Canaries and the Azores with that of the waters farther 
west. Unfortunately the accident by which we lost our trawl 
and 1500 metres of wire on the Azores plateau prevented us 
from sweeping the greatest depths, but we were still in a 
position to carry out pelagic experiments. 

It would have been desirable to set our course from the 
Azores to the Bermudas, and then on to Boston, finishing with 



lOO 



DEPTHS OF THE OCEAN 



a series of short zig-zag sections between the land and the edge 
of the coast-banks, till we reached Newfoundland. We should 
in that case have been able to study the remarkable transition 
that occurs on passing from the almost tropical conditions of 
the Sargasso Sea to those of the icy Labrador Stream, which 
creeps southwards along the Labrador coast from Baffin's Bay 
to Newfoundland, and even farther south. The short time at 
our disposal made this impossible, and we were compelled to 
cross from the Azores to the nearest coaling station, namely 
Newfoundland, and then make for home. 
The mere distance between the 
Azores and Newfoundland, between 
1 200 and 1300 nautical miles, was a 
serious consideration for our little vessel, 
for we had to count upon meeting head- 
winds and currents, especially when we 
reached the Gulf Stream off the New- 
foundland Bank ; and there was always 
the possibility of fog delaying us. We 
resolved accordingly to go westwards 
towards the eastern boundary of the 
Gulf Stream, and then turn northwards, 
which would increase the distance to 
1800 miles, but would offer better condi- 
tions of wind and current. We should 
also be enabled to visit again the Sar- 
gasso Sea, the animal life of w^hich we 
had found so interesting, and we should 
further be able to take a section right 
across the axis of the Gulf Stream. To 
prepare for all emergencies we not only 
filled our bunkers as full as they could hold with the best 
Welsh coal, but also piled our decks with as much as we could 
find room for. This done, we said farewell to Horta's little 
harbour on the afternoon of 17th June. 

During the first two or three days of our journey west we 
had wind and sea dead against us, so work was limited to 
hydrographical observations at Stations 59 and 60 (see Chart, 
Fig. 62). The weather afterwards cleared up, and at Station 61 
we met with certain fishes, hitherto regarded as extremely 
rare, swimming about on the surface of the Atlantic. On lower- 
ing a boat to examine a drifting log overgrown with barnacles 
(Fig. 87), we found it surrounded by fishes like those observed 




Fig. 87. 

Lepas anatifera. 



hi 



CRUISES OF THE -MICHAEL SARS " loi 

by us in the Sargasso Sea near Station 50, and we succeeded 
in capturing eleven specimens belonging to the species 
Pimcleptcj^iLS bos chii 2ind Lirus pei'-ciformis. 

At Station 62 we tried nine pelagic appliances at different 

depths on the night of 20th June. Our catches were very 

satisfactory at all depths, and much 

^ resembled those taken between the 



I^Sl 



Canary Islands and the Azores. 
Fir.. 88.-THE SMALLEST LARVA ^^ the Upper kycrs there were 

OF THE Common Eel caught some extremely interestmg leptoceph- 
"^.'.'™:'.o,'rKa..'tr" aH, including no fewer than eleven 

specimens of the common eel larvae Eel 
(Fig. 88), 5 to 5.7 centimetres long, showing that the little eel 
larvae are to be met with west as well as south of the Azores. 
We also found two individuals, only 4.7 and 5.1 centimetres 
long, of leptocephali belonging to the deep-sea fish Synapho- 
branchus pinnattis. This had previously only been met with 
in sizes approximating to the full-grown larva (10-13 cm.), of 
which we found several at the different stations ; but it was 
most interesting to come across 
such small (early) development 
stages of the species. 

At depths from 300 metres 
to 50 metres there were again 
the same colourless Cy clot hone 
signata as well as silvery 
Argyropelecus, Stomias, and 
Chaiiliodus. We got, too, a 
new species of Ce^'alias. In 

the deepest hauls, below 500 \ ' y' — j 

metres, the forms were the same "-- >^' A 

as in previous hauls. There Vl' 

was the little black fish, Cyclo- \ 

tJione microdon, once more, red ^^^ 89.-LARGE closing net. 
prawns (particularly Acanthe- 

phyra), red sagittae, dark - brown medusa i^Atolla), large 
ostracods {Gigantocypi'is), and the same kinds of " rare " fish: 
GastrostoTjms bairdii, Cyema atrum, Gonostoma grande, Dactylo- 
stoniias, and several others. 

These numerous horizontal hauls accorded so closely with 
each other that we now began to feel that there must be a well- 
defined conformity in the vertical distribution of the different 
forms. Still, to avoid any uncertainty, we considered it desirable 




I02 DEPTHS OF THE OCEAN 

Vertical to try at the same time some vertical hauls with our closing 
oflnimah" nets. Accordingly, at Station 63 we made two series of hauls, 
one with a silk net i metre in diameter, and the other with the 
large 3-metre silk net {Fig. 89). 

These experiments merely resulted in our capturing the 
species which occur most commonly, — a fresh proof that it is 
difficult to become acquainted with the fauna when only vertical 
hauls are made. A great many of the forms are too scarce to 
be caught by such means, and can only be taken by long- 
continued horizontal towing. In the case of the commonest 
species, however, these vertical hauls do give an indication 
of the vertical distribution as well as of the quantitative occur- 
rence at different depths. It is advisable, therefore, to supply 
a few particulars of our experiments with the large net : — 

Only 10 fishes were taken in a haul from 4500 metres up to 1500 
metres, where we closed the net. All of them belonged to the species 
Cydothone inicrodon. 

In a haul from 1350 metres up to 450 metres we got 44 fishes; 27 
specimens of Cyc/othone mzcjvdon, 3 of C. signata, and 14 young fish 
(stomiatids and others). 

In a haul from. 500 metres up to 200 metres some small specimens of 
Cydothone signata and a number of young fish were caught. From 200 
metres to the surface there were only young fish. 

This agrees with what we found when making horizontal 
hauls. The black Cyclotkone 7Jzicrodon is only to be met with 
in deep water, where the light-coloured C. signata is absent, 
and C. signata occurs nearer the surface — from about 500 
metres up to 200 metres — but has not been taken in depths less 
than 200 metres. 

It is important to note how much fewer the individuals are 
in the deepest hauls. Though we drew the net through 3000 
metres (from 4500 up to 1500 metres), we only caught 10 
fishes, while in the 900 metres of water from 1350 metres up to 
450 metres we got 44 individuals, 27 of them belonging to the 
same species as the 10 fishes from greater depths. 

Similar conditions appear to prevail in the case of the red 
prawns, for in our deepest haul we caught only 1 1 large red 
prawns, but in the haul immediately above it there were 35 
individuals. This seems to indicate that the deepest water- 
layers cannot at all compare in abundance of organisms with 
the intermediate layers. 

At this station we also recorded a very large series of 
hydrographical observations, namely, twenty water-samples and 



CRUISES OF THE "MICHAEL SARS " 103 

temperature readings down to a depth of 4850 metres. We 
were interested to discover that the bottom temperature was 
only sHghtly under 2^° C, and thus exactly agreed with what 
we had previously found in the eastern basin. 

During the night several flying-fish came on board, and in 
the morning we again saw small patches of the Sargasso weed. Sargasso 
Gran came to the conclusion that these patches must be much ^^^^' 
younger, or, rather, that they have drifted for a shorter 
time, than the ones found farther east. They had long 
vigorous shoots, which reached higher up above the water 
than the older growths, and it was easy to tell the top in every 
patch. In the older growths, which had been drifting about for 
a long time, the shoots in every direction were more stunted, 
and the patches became mere tangled masses of weed and lay 
deeper in the water. We found on them the ordinary small 
crabs {Planes mijiutus), needle-fish {Syngnatktcs pelagicus), frog- 
fish [Antennarius), molluscs, compound ascidians, and hydroids 
(see Plates V. and VI., Chapter X.). 

Station 64 was one of our most successful stations. The 
pelagic appliances were lowered in the morning between 
6.30 A.M. and 9 A.M., and hauled in from 2.30 p.m. to 5 p.m., 
with excellent results. In the surface layers we secured a 
quantity of fish-eggs, including various stages of the eggs of 
scombresocids, tiny young fish with stalk-eyes, two small eel 
larvae (4.1 cm. and 4.8 cm. long), a number of remarkable 
cuttle-fish, and three small leptocephali (1.7 cm., 1.7 cm., and 
2.1 cm. in length), all differing in appearance. They cannot 
belong to the larvae of the common eel, because they have too 
many muscle segments (over 130). 

In deep water we got the same familiar forms in unusually 
large quantities. The following table shows the numbers of 
the species most commonly occurring, belonging to the genus 
Cyclotkone : — 

Light-coloured, Dark-coloured, 
Cyclothone signata. C. nncrodoii. 

Young-fish trawl at 500 metres . 1240 214 (small individuals) 

„ ,, 1000 „ . 82 448 

,, ,, 1500 ,, . 22 322 

1344 984 

Thus of the two species we were able to preserve more 
than 2000 individuals ; we endeavoured to keep all that were 
brought on board, but a good many were damaged by the 
apparatus, and had to be thrown away. 



I04 DEPTHS OF THE OCEAN chap. 

These results served to confirm the opinion we had formed 
at the previous station (63) that the Hght- coloured species 
lives nearer the surface, while the dark-coloured species inhabits 
greater depths. Red prawns, sagittse, and other creatures were 
found in large numbers in deep water, and we continued to 
meet with such forms as G astro sto77ius and Opisthoproctus, and 
a new Oneirodes (Fig. 90). 

We also discovered a curious little young fish, 4 cm. long, 

which we can only suppose to be a transition stage from a 

Larval leptocephalus to a Gastrostoimis (probably G. bairdii, which we 

so often met with). Its head shows clear indications of the 




Fig. 90. 
Oneirodes, n.sp. Nat. size, 1.4 cm. 

remarkable gullet, the tiny eyes far forward near the snout, and 
the small ventral fin. Posteriorly the body much resembles a 
leptocephalus, but here, too, there seems to be a commencement 
of the strange organ which is situated at the end of the long 
tail of Gastrostonuis. What is chiefly interesting about this 
find is that it affords fresh proof of the relationship between the 
saccopharyngidae and eels. When search is made, as it prob- 
ably will be soon, for still younger stages of the common eel 
larvae than the ones we found, it will probably be of zoological 
interest to seek in these teeming waters for transition stages 
between this strange form and the earlier leptocephalid stages. 

Another deep-sea fish at this station that deserves mention 
was a form, as yet apparently undescribed, which resembles the 
undoubtedly blind fish {Cetomimus) found at Station 35 ; the 
eyes appear very much reduced, just as in the case of its 
relative. Both of them were taken in deep water, at 1000 
metres. 



CRUISES OF THE "MICHAEL SARS " 



105 



In addition to the silk nets Gran now commenced using 
his big steam centrifuge (Fig. 91) for centrifuging the water 




Fig. gi. — The Large Centrifu 

samples from difterent depths. Several successful experiments useofthe 

had already been made centrifuge. 
with it, but it was at this 
station that he started to 
employ it systematically, 
and he continued to avail 
liimself of its help until 
the end of the cruise. By 
means of it he was able 
to collect in a little drop 
below the microscope all 
the most minute organ- 
isms, and in spite of the 
movements of the little 
ship and the vibration 
from the propeller, he 
was able with his micro- 
scope to study the many 
hitherto unknown forms 
in their living state, to 
draw them, and to count the number of the different species 
(Fig. 92). A full description of these investigations will be 



pp/ 




p, 




i 



Fig. 92. 



-Gran counting the smallest 
Microscopic Plants. 



io6 DEPTHS OF THE OCEAN 

found in Chapter VI. A few particulars may, however, be 
given here. 

Among the exceedingly diminutive plants found in the 

open sea, calcareous flagellates or coccolithophoridse are the 

most important, especially in the w^armer waters. During the 

"Challenger" Expedition, Murray discovered that they were 

distributed everywhere over the surface of all warm seas, and 

he stated that they were plants. These small organisms occur 

in far greater abundance, both of species and individuals, than 

had hitherto been supposed. In reality they, together with 

Great diatoms and other algse, constitute the fundamental source of 

cocc"omho-°^ food for all animals in tropical and sub-tropical waters. In the 

phorida; in the Sargasso Sea there were in every litre 12 or 15 species and 

. argabso -ea. ^qoo to 3000 individuals. In colder masses of water they 

decrease very greatly in quantity, yet even on the edge of the 

Newfoundland Bank, with a temperature of 2^^ C, we still met 

with one or two species numbering 50 individuals to the litre. 

In the Arctic and Antarctic Oceans, on the other hand, they 

are not found at all. 

After occupying Station 64 we were compelled to turn 
northwards and steer for our next coaling station, St. John's, 
Newfoundland. We had to abandon any idea of following up 
in a southerly direction the remarkable finds we had made, and 
probably thus lost the chance of making the most interesting 
discovery of all, namely, the earliest stages of eels, Gastrostomiis, 
and other forms. Still there was the possibility of learning 
something about the currents off the coast of North America, 
as well as the connection between the different water-layers and 
the plants and animal forms existing in them. 

Fig. 93 shows a temperature and salinity section from the 
Sargasso Sea to Newfoundland. At Stations 64 and 65 we see 
the vast layer, with a salinity of over 35 per thousand and high 
temperature down to considerable depths, the same as found 
by us over the whole distance from away beyond the Canary 
Islands. 

On our way north from Station 64 on 28th June we saw 
patches of Sargasso weed all the morning, and numbers of flying 
fish, about 10 centimetres long, started up in front of our bows. 
This led us to believe that we should capture the same forms as 
before, when we lowered our pelagic appliances in the evening 
at Station 66. Great was our astonishment, therefore, to discover 
next morning on hauling in our appliances that the catches 



CRUISES OF THE "MICHAEL SARS 



107 



mainly consisted of true "boreal" plankton, that is to say, 
animal forms which we were accustomed to get in the so-called 
extension of the Gulf Stream in the Norwegian Sea right up 
to the very shores of Spitsbergen. There was the amphipod 
Etitheinisto, the copepod Eiichceta, and " whale's food " (the 
pteropod Clione Iwiacina), large quantities of which are met with 
from time to time in the waters between Spitsbergen and the 
north of Norway. This last is not an "arctic" form, that is, it 
is not associated with polar water in the Norwegian Sea, but 
on the contrary is found in Atlantic water to the south of Iceland, 



C9 .,, C7 66 








see-s-i 96 



Fig. 93.— Hydrographical Section from the Sargasso Sea to the 

NEWFOrNDI.AM) BAXK. 

according to Danish observations. It seems, however, to be 
associated with the northern portion of the Adantic and the 
Atlantic water that enters the Norwegian Sea. These animal 
forms were entirely absent during the whole of our cruise from 
the Canary Islands to Station 64, so that their occurrence at 
Station 66, where lower temperatures were recorded at no great 
depth beneath the surface, is very significant. 

We fancied now that we had said farewell to the Sargasso 
Sea and its interesting animal life, but at Stations 67 and 69, in 
close accordance with the hydrographical conditions depicted in 
F^g- 93. we came once more across more southerly forms. 



io8 DEPTHS OF THE OCEAN 

In the upper layers there were the same young fish, many of 
them with stalk-eyes, and leptocephali, while flying fish, Sar- 
gasso weed, and the familiar Sargasso animals were all once 
more in evidence. 

We found a large cluster of eggs, weighing approximately 
a kilo, drifting about at Station 69, belonging to the common 
angler-fish [Lopkius piscatoritts), the development of which was 
studied by Alexander Agassiz ; we hatched out the eggs and 
obtained the stages depicted by him. Angler-fish only inhabit 
the coast banks, so that our find of slightly developed eggs, that 
could not have been drifting many days, indicated that we were 
now in the neighbourhood of the American coast bank. 

In deep water we found once more at Stations 67 and 69 
the deep-sea animals of the Sargasso Sea, that is to say, all 
the black fishes and red crustaceans which we have so often 
mentioned already. There were not merely the commonest 
kinds of small fish, but also large ones (such as three examples 
of Gastrosto7}ms), and fishes which are caught in other oceans 
(Aceratias, Serrivomer). 

While we were hauling in our appliances at Station 67, a 
storm got up, which gradually increased to a hurricane, worse 
than anything hitherto encountered by the " Michael Sars." It 
lasted for twenty-four hours, during which the ship was smothered 
in spray. Our engines were kept going full steam ahead, yet 
the vessel was driven a whole degree (60 nautical miles) astern. 
vStill her buoyancy stood her in good stead, and she did not ship 
a single sea. 

At Station 70, on the edge of the coast bank, where the 
depth was iioo metres, we discovered that we had for the 
second time left purely oceanic conditions behind, and once 
more the true boreal plankton appeared in the surface layers. 
There was the little copepod Cala^ius finmarchicus, the commonest 
crustacean in the Norwegian Sea, and we also now met with 
EiUhemisto, NyctipJianes, Krohnia hamata, Limacina helicina,^ 
and Clione limacina, all species that are regarded as specially 
characteristic of the Norwegian Sea. Still in the deep water 
from 350 metres down to iioo metres we continued to get the 
familiar pelagic deep-sea fish Cyclothoiie signata and C. microdon, 
as well as the medusa Atolla and other forms ; so that the area 
of distribution of these animals extends from Africa to North 
America, that is to say, in all the water from the one continental 
slope to the other. 

^ Limacina was taken in numbers by Ilaeckel and Murray off Scourie in Scotland. 



CRUISES OF THE "MICHAEL SARS " 



109 



Our deepest young-fish trawl was unintentionally towed along 
the bottom, and came up full of most beautiful bottom-living 
organisms (0///?>/rrt;, asterids, Phormosoma, pennatulids, crinoids, 
pycnogonids, lycods, and Macrurtis, as well as many other forms 
which need not be detailed here). 

We had thus reached the Great Bank of Newfoundland, and 
had accomplished our task of taking a section right across the 
Atlantic from the shores of Africa. During the transit we had 
occupied twenty-nine hydrographical stations, and twenty stations 




75 



/ 



fLEHlSH CAP 



RE A T 



^ 



Fig. 94.— "Michael Sars" Stations 69 to 80. 

where we towed pelagic appliances, and had besides carried out 
many other investigations, so that we had every reason to be 
satisfied with the results of our venture. 

The coasi batik itself (Fig. 94) offered us a totally different Newfoundland 
field for study, which no doubt would have proved very interest- ^'''"^'' 
ing, but unfortunately our time was too short to attempt system- 
atic researches ; we had to steam for our coaling station, content- 
ing ourselves with one or two shallow stations on the way. 

Fig. 95 shows the hydrographical conditions from our last 
true oceanic station (69) to a station (74) just off St. John's. It 
is extraordinary what a sudden change there is from the warm 
salt oceanic water to the cold coast water. The curves of 



no DEPTHS OF THE OCEAN 

temperature and salinity between Stations 69 and 70 go down 
straight like a wall — the well-known "cold wall" of oceano- 
graphers. Over the bank there is a surface layer, about 40 
metres in depth, with a temperature of over 6° C, similar to 
what we get in the boreal portion of the Norwegian Sea along 
the coast of Norway. Below that, however, the temperatures 
are under 2° C, and even as low as — 1.5° C, that is to say, the 
water may be as cold as what Nansen found near the North 
Pole. Probably at no other part of the globe are there such 
peculiar temperature conditions — conditions comparable with 
those in the Arctic regions, though the latitude is the same as 
that of Paris. It would have been an agreeable task to trace 
these conditions by following up the currents and animal life 




Fig. 95. — Hydrographical Section 'across jthe^Great Newfoundland Bank. 

both northwards and southwards. Still even our random in- 
vestigations furnished interesting results. Thus we discovered 
that from Station 70 to St. John's there was the same northerly 
plankton already mentioned, and an examination of the young 
fish showed that they accorded with what had previously been 
found by Norwegian naturalists off the coast of Norway, and 
by the Danes south of Iceland. 

On the outer side of the coast bank, at Station 71, we met 
with larvse of red-fish {Sebastes). At Station 72 there were cod- 
eggs and numbers of little cod-fry, besides fully developed eggs of 
haddock (Gadus csglefinus) and haddock larvai, 3^ millimetres 
in length and upwards, and also young fish of the boreal long 
rough dab [Drepauopsettd). At Station ']2i we came across 
eggs of this dab (besides a number of eggs that we have not 
yet determined), and the shallow-water form Animodytes. At 
Station 74 there were neither eggs nor young fish. 



CRUISES OF THE "MICHAEL SARS 



1 1 1 



Similar catches are taken off the coasts of Norway and 
Iceland ; near and just beyond the continental edge there are 
larvae of red-fish, and on the bank in 30 or 40 fathoms of water 
there are larvae and eggs of cod and haddock. It was interest- 
ing to find the eggs and larvae of these fish at Station 72, where 
the bottom-temperature was between 2' C. and 4.6° C, whereas 
nearer land, where the bottom-temperature was o' C, or even 
less, they were absent. 









'*9f3TE»_-^:-^- 



Fig. 96. — French Fishing Schooner. 

At Station 72 we sighted the first fishing-boats (Fig. 96). Fishing 
They belonged to Frenchmen from the Island of Miquelon, ;j;f^^^"'f°",,d- 
south of Newfoundland, and as the weather was good, we paid land Bank. 
them a visit, spending a very pleasant time with these hos- 
pitable fishermen, who willingly gave us information about their 
industry (Fig. 97). They sail from Brittany and Normandy in 
April, and reach the Newfoundland Bank in May, at which time 
of the year there is ice over the whole northerly portion of the 
bank. They commence fishing in the south-eastern portion, 
which is probably the only part having warm bottom-water, and 
collect their bait by lowering nets with cod-heads in them. 



112 DEPTHS OF THE OCEAN 

Quantities of gasteropods (most likely a species of Biiccinuni) 
creep into the nets, and form a very serviceable bait, just as on 
the eastern side of the Atlantic. Afterwards they remove to 
the southern portion of the bank, where they were when we met 
them. This was, according to the captain, lat. 44° 30' N., and 
long. 53° 34' W. The cod spawn here in July, and were just 
on the point of doing so. They were from 60 centimetres to 
over a metre long, and upon inspecting the catches of several 
dories (flat-bottomed boats used for cod-fishing in Norway 
also) we found the roes to be quite mature. The fishermen 
also catch squid {Gonahis fabricii \ see Fig. 98) with a grapnel 




Fig. 97. — -Hand-line Fishing. 

— a red piece of metal with hooks all round it — exactly in the 
same way as they are caught on the north and west coasts of 
Norway. 

After July the fishermen work their way northwards, 
probably because the cod move northwards along the bank 
as the cold water recedes during the course of the summer. 
According to their statements, which would justify a thorough 
investigation, there are for the most part only small-sized cod 
farther south and west on the banks off Nova Scotia and Cape 
Breton Island, or on what they call the " Banquereau." Is it 
perhaps the case here too, as in Norway and Iceland, that the 
larvse and young fish drift with the current and grow into cod 
far away from the place where they were spawned } 

On the Norwegian coast the cod chiefly spawn between 



CRUISES OF THE "MICHAEL SARS 



1 1 



Romsdal and Tromsoe, but 
greatest quantity off Fin- 
marken, that is to say, along 
the northernmost portion of 
the coast, to which they are 
carried by the current. Simi- 
larly in Iceland they spawn 
on the south and west coasts, 
but the young fish are chiefly 
found on the north and east 
coasts. The current there 
goes from the south to the 
west, and thence round the 
north and east coasts, making 
a circuit round the island. 

The current off New- 
foundland runs along the 
coast in a south - westerly 
direction, towards Nova 
Scotia and the United States. 
It is possible, therefore, that 
it is mosdy young fish that 
are found down south, de- 
rived to some extent at any 
rate from eggs spawned on 
the Great Newfoundland 
Bank. 

Cod spawn on the Nor- 
wegian coast banks as far 
north as lat. 70° N., and 
chiefly during March and 
April. Here on the New- 
foundland Bank, a little north 
of lat. 50^ N., and in the 
vicinity of the warm oceanic 
water their spawning season 
was in July. 

The bottom-temperature 
on the bank was, as we have 
seen, very low — lower indeed 
than in the north of Norway 
during March — and it was 
interesting, therefore, to note 



the young fish are found 



m 




, — Bait ( Goiiatus fahricii). 
Nat. size, 27 cm. 



foundland to 
Glasgow 



114 DEPTHS OF THE OCEAN 

the summer growth periods and winter stagnation periods in 
the scales of cod which we procured from the French fishermen. 
Scales (see Chapter X.) illustrate the growth of the cod by 
means of " summer-belts " and " winter-rings," Those which we 
examined had extremely distinct winter-rings, and although it 
was already July, the summer-belt for the year had not yet 
commenced. It must therefore have been the winter season 
still down in the deep water where the cod were taken — and this 
though we were in the latitude of Paris and the month was July. 

On 3rd July the "Michael Sars " anchored in the harbour 
of St. John's. 
From New- It was our Original intention to go from Newfoundland to 

Reykjavik in Iceland, as this was the nearest coaling station 
on our way back to Europe, and we hardly expected when 
starting on our expedition that the little ship would be able 
to steam right across the Atlantic without having to put in 
anywhere for coal. We had now, however, formed such a 
favourable opinion of her seaworthiness, and her coal-con- 
sumption had been so small, especially on the voyage from 
the Azores to St. John's, that we decided to venture across the 
ocean without a stop. The distance from Fayal to St. John's 
by the way we had come was about 1800 nautical miles, and 
from St. John's to Ireland was roughly 2000 miles, so that the 
difference was not so very formidable. 

As far as our scientific work was concerned, the direct route 
to Ireland was bound to be the more interesting. It is true 
that very little is known about the sea leading to Baffin's Bay, 
but the physical conditions, and therefore also the animal life, 
are presumably very uniform and not likely to differ much from 
the conditions prevailing to the eastward of the Newfoundland 
Bank. The direct route to Ireland, on the other hand, would 
give us a fresh section across the Atlantic, and enable us to 
study the varying conditions in the northerly portion of that 
ocean. Another reason for selecting this route was the possi- 
bility of again studying the remarkable conditions in the Gulf 
Stream observed on our southern section between Stations 64 
and 70 (see Fig. 93). We therefore filled up our bunkers once 
more and piled the deck with the best coal we could procure, 
prepared ourselves for as long a cruise as the ship was able to 
accomplish, and left St. John's on the 8th July. 

The water-masses of the North Atlantic may be roughly 



CRUISES OF THE 



divided into four principal groups 
water, or Gulf , 
Stream water, | 
(2) Mediterranean 
water, (3) Arctic 
polar water, and 
(4) the so - called 
bottom -water, all 
of which we were 
able to study on 
our voyage across 
to Ireland. Fig. 
99 shows the posi- 
tions of Stations 
79-93, and the 
vertical distribu- 
tionof the different 
water -masses in 
their relation to 
one another on 
our route from 
the Newfoundland 
Bank to Ireland. 
Near America, on 
the actual coast 
bank and just out- 
side the edge of 
the bank (Stations 
75-79), we found 
only the cold 
Labrador Current, 
which descends 
from Baffin's Bay, 
follows the coast 
of Labrador, and 
sweeps south-west 
past Newfound- 
land. Immediately 
outside St. John's : 
we met several ice- ; 
bergsofthekind so ^ 
familiar to all who \ 
cross the North 



MICHAEL SARS" 115 
(i) true Atlantic oceanic 




ii6 



DEPTHS OF THE OCEAN 



Atlantic (Figs, loo and loi), and we had thus an ocular demon- 
stration of the origin of the cold water on the Great Bank, as 



Jifl^^ 



Fi<;. loo. — Icebergs outside the Harbour of St. John's. 

well as of the dangers which the bank-fishers have to face. 
Icebergs, fog, and the great ocean-steamers are the chief perils 




Fig. ioi.— Iceberg outside St. John's. 

these men have to reckon with, and it was an unpleasant 
sensation for us also to have to steam for three whole days over 
the bank in fog. 



CRUISES OF THE "MICHAEL SARS " 117 

At Station 80 we became aware of the influence of Atlantic 
water, and at the same time we got clear weather, but, as the 
figure will show, it was at Station 81 that we first met with the 
real Atlantic or Gulf Stream water with a salinity of about 35.5 
per thousand, which extended in a layer 100-200 metres deep 
right across to near the coast bank outside Ireland. Below 
this layer the salinity and temperature decrease till we come 
down to bottom-water, with a salinity of less than 35 per 
thousand ; the temperature was the same as what we had found 
in bottom-water to the south of the Azores, namely, a little 
under 2^° C. Our investigations made it apparent that this 
bottom-water is in continuity with the surface water in the 
north-west corner of the Atlantic. 

Our investigation of the plants of the sea was continued Plants. 
during this cruise ; we made collections with silk nets, and 
centrifuged water - samples with the big steam centrifuge, 
with the result that, in spite of high seas and heavy rolling of 
the vessel on the eastern side of the ocean, Gran was able to 
proceed with his classification and enumeration of the minute 
living organisms that had hitherto eluded observation. 

At almost every station he determined the number of 
extremely small organisms, chiefly coccolithophoridse, per litre 
of sea-water, and ascertained that here, too, on our northerly 
route they constituted the greater portion of the plant plankton. 
An exception must, however, be made in the case of the coast 
banks of Newfoundland and Ireland, where there was also a 
very abundant plankton of larger organisms, large enough to 
be retained by the tow-nets. One single species (a calcareous 
flagellate) at a station just outside the European coast bank 
numbered 200,000 per litre, and actually affected the transparency 
of the sea. 

Gran succeeded in collecting abundant material for the 
study of these little-known forms (many of them new to science), 
and for a proper understanding of their significance in the total 
plant life of the sea. In Chapter VI. he has set down the 
chief results of his observations. 

We found again a complete accordance between the distri- 
bution of the different water-masses and the occurrence of 
characteristic "societies" of pelagic animal life. At Stations Pelagic life of 
75-79 on the Newfoundland Bank (see Fig. 94) the boreal l^^^;^^ 
organisms were mixed with arctic forms. Thus there were : 



ii8 DEPTHS OF THE OCEAN 

Calamis jinmarchicMS and C. hyperboi^eus, Euchcsta, Euthemisto, 
Lmiacma, Aglantha, Beroe, Pleurobrachia, Mertensta, Sagitta 
arctica, and Krohnia haniata — forms that in the Norwegian 
Sea are met with in " Gulf Stream water" or in " Polar water." 
At Station 80 — just beyond the continental slope — this 
animal life was still typically represented at all depths examined, 
but in deep water we found co-existing with it our black fish 
and red crustaceans of the southern section. We made a few 
hauls here with the closing net, and obtained the following : — 

In a haul from 525 metres to 235 metres we got calanids co-existing 
with Cyclothom signata. 

In a haul from 950 metres to 525 metres w^iowwd^ EucJiceta norvegica, 
Calanus Jinjnarchicus, Calanus Jiyperboreus and Clione limacina, together 
with Cyclotho7ie inicrodon and the medusa Atolla. 

Besides this, our horizontal hauls gave us Gastrostomus bairdii and 
large red prawns {Acanthephyrd). 

All the arctic forms had disappeared, however, at Station 
81, and they did not occur again in our hauls during the rest of 
Boreal our section to Ireland. In their place we found the boreal 
pelagic h e. ^j^j^iais^ s\\Q}[i as we are familiar with in the Gulf Stream water 
of the Norwegian Sea right up to Spitsbergen, strongly repre- 
sented, everywhere mingled with true oceanic Atlantic forms, 
like those that predominated in the southern section. At Station 
81 we secured at the surface a quantity of eggs and young of 
scopelids, as well as radiolaria, salpae, small Pelagia, and different 
kinds of leptocephali ; of pteropods we got Clio pyraniidata. 
In deep water there was the abundant oceanic fauna observed 
in the Sargasso Sea previously referred to. If we consider this 
short account of the animal life, together with the hydrographical 
section (Fig. 99), the accordance will become apparent. It is at 
Station 81 that the real oceanic "Atlantic water" or "Gulf 
Stream water " occurs, whereas at Station 80 the cold Labrador 
Current is still the controlling influence. 

Generally speaking, the same pelagic fauna was noted from 
here across the Atlantic, though no doubt a closer investigation 
may reveal various differences in the different areas traversed. 
There is one feature that deserves particular mention, notwith- 
standing the incompleteness of our material, namely, the 
extraordinary abundance of forms met with from Stations 86 to 
8S. These stations lie exactly over the longitudinal ridge that 
stretches northivards fro77i the Azores. Just as was the case on 
the plateau south of the Azores, so here too we made exception- 
ally big catches at all depths, and the surface contained millions 



CRUISES OF THE "MICHAEL SARS 



119 



of chains of salpse the one day and of medusae [Pelagia) the 
next. 

We caught a large moonfish (Mola rotunda. Fig. 102), Moonfish. 
which was moving along near the surface with its dorsal fin 
above water ; we harpooned it from a boat, and got it on board 
with block and tackle and the steam winch. The length was 
2,11 metres, and the height of the body 1.2 metres. A huge 




Fig. \02.—Mola rottinda, Cuv. Nat. size, 211 cm. 



cuttle-fish, too, was found drifting about. Do these creatures, 
like the turtles farther south, feed on the abundant salpee and 
medusae, and was that the reason why we found them here ? 
Is a richer pelagic life generally to be found just over the ridge, 
in the same way that we always find a richer plankton over the 
slope of the coast banks ? These problems must be left for 
future solution. 

On the eastern side of our section, towards the Irish coast 
bank, the conditions were again peculiar, especially at the 
surface. We found here increasing quantities of young of the 



Trawling on 
the Mid- 
Atlantic rid<r< 



I20 DEPTHS OF THE OCEAN 

needle-fish Nerophis, Fierasfer, Arachnactis and Lepas fascicu- 
laris, as well as young stages of coast -bank forms, stray 
specimens of which were also met with just off the slope 
(Stations 92 and 94). 

It will be an interesting task to compare the western and 
eastern portions of this section, as well as the whole of this 
northerly section, with the section farther south from the Canary 
Islands past the Azores to the Gulf Stream. One thing which 
did strike us particularly was that the boreal plankton — the 
Gulf Stream forms of the Norwegian Sea — were entirely absent 
from the southern section (Stations 45-64), but were everywhere 
present in the northern section. It must be remembered, 
however, that our pelagic hauls did not reach the very deepest 
water-layers, which may have the same plankton in both 
sections, including the boreal species known from the Norwegian 
Sea. We further noticed in the southern section more of the 
remarkable "rare" deep-sea fish that have been found in other 
oceans (the Indian Ocean, for instance) than in the northern 
section. 

The distribution according to size of individuals belonging 
to the different larval forms was noteworthy. As previously 
mentioned, we came across very small larvae — from 4 cm. to 6 cm. 
long — of the common eel to the south and west of the Azores ; 
on the northern section also we found larvse of the eel, but 
they were all full-grown leptocephali. This distribution does not 
seem to be specially characteristic of the eel, for on the southern 
section we came across many small larvse and eggs belonging 
to other forms, none of which were met with farther north. 
Future investigations will doubtless make all this clear, and 
may lead to valuable discoveries. 

The accident to our trawl on the Azores bank, already 
mentioned, prevented us from trawling in very deep water, but 
for all that we were able to carry out two successful trawlings at 
considerable depths. The first was at Station 88, on the longi- 
tudinal ridge north of the Azores, where we shot our trawl in 
3120 metres of water. There were numbers of echinoderms of 
all kinds (starfish, sand-stars, sea-urchins, and holothurians), as 
well as a score of bottom-fish (Macrurits, Synaphobrancktis, 
Bathysaurus). The haul was extremely interesting, as it gave 
a fresh proof of the abundance of animal life as far down as 
3000 metres — not in this case on a continental slope, but out on 
a ridge in the middle of the ocean. Off the coast of Ireland we 
succeeded in trawling at 1000 fathoms (1797 metres, Station 95), 



CRUISES OF THE "MICHAEL SARS " 121 

which we had attempted in vain after leaving Plymouth, and we 
towed the big trawl for two and a half hours with very satis- 
factory results. There were quantities of echinoderms (300 Trawling off 
holothurians, 800 ophiuroidse), molluscs, corals, crustaceans, and Jrek^c/ 
82 fishes [Maci'urus, Antimora viola, A/epocep/tahis, Bathy- 
saurns (Fig, 103 a), Notacanthus, Halosauropsis (Fig. 103 b), 







i 



Fig. 103. — Two Deep-Sea Fishes from Station 95, 1797 metres (about 1000 fathoms). 

a. Bathysaiirus ferox, Gthr. Xat. size, 42 cm. 

b. Halosauropsis macrochir, Gthr. Nat. size, 60 cm. 

and Synaphobranchi). We also found in the trawl a basketful 
of stones, coal, and cinders. 

The " Michael Sars " anchored at Glasgow on the 29th 
July after a passage from Newfoundland lasting three weeks. 
Duringthis time we had worked at twenty-two stations, and had 
made investigations all the way across the Atlantic. In spite of 
having steamed about 2000 miles, and having been three weeks 
at sea, we had still nearly ■}^'] tons of coal left, or enough for 
another week's work. We had thus proved that a little vessel 
may carry out investigations formerly attempted only with large 
ships, and this fact is certain to be taken into account when 
future expeditions are planned. Taking everything into 
consideration, we had made very satisfactory hydrographical 



122 DEPTHS OF THE OCEAN 

and biological observations over a large part of the North 
Atlantic. As previously stated, one of the principal objects 
of the expedition was to carry out researches in the North 
Atlantic likely to increase our knowledge of the marine area 
explored by the " Michael Sars " during the past few years, 
namely, the Norwegian Sea lying between Norway, Greenland, 
Iceland, and the North Sea. It was important, therefore, to 




Fig. 104.- 



Michael Sars" Stations from Glasgow to Bergen. 



examine the adjoining portion of the Atlantic and to investigate 
the inflow of the Atlantic water. 

After leaving the vicinity of the Newfoundland Bank, the 
Gulf Stream bends sharply eastwards and forms the surface 
layer examined by us between Stations 81 and 92 (see Fig. 99). 
Off the edge of the Irish coast bank a portion turns northwards 
towards the Norwegian Sea. The sea-bottom is here very 
complicated, for the deep basins of the Atlantic and Norwegian 
Sea are separated by a submarine ridge (see Fig. 104). To the 
north-west of Ireland the wide Atlantic plain narrows to a kind 



CRUISES OF THE "MICHAEL SARS " 123 

of valley, which is bounded on the west by the Rockall bank, 
and on the east by the coast bank of Scotland. Farther north 
this valley shallows towards the extensive ridge that stretches 
from Iceland past the Faroe Islands to Shetland, and separates 
the Atlantic Ocean from the Norwegian Sea at all depths 
beyond 400 to 500 metres. The part of this ridge between the 
Faroe Islands and Shetland is known as the Wyville Thomson 
Ridge, which has frequently been examined, first by British, 
afterwards by Danish, naturalists ; in fact, it may be regarded 
as a classical field for oceanic research (see Chapter I.). The 



'tm 



■^^^iifeMfcwNi-^ 



Fig. 105.— Rockall. 



" Michael Sars " had made investigations there previously, both 
on the Atlantic side south of the ridge and in the Norwegian 
Sea to the north of it. In Fig. 104 our former research-stations 
are marked with a cross. 

It was desirable, however, to re-investigate this area, em- 
ploying there the same methods of working as we had adopted 
in the North Atlantic, and we felt it necessary to have a 
section south of the Wyville Thomson Ridge and another 
one to the north of it. The valley between Britain on the one 
side and Rockall and the Faroes on the other is really the only 
connection between the two deep basins, for it is only through 



Glasgow 
to Bergen. 



124 



DEPTHS OF THE OCEAN 



this channel that the water of the Atlantic streams into the 
Norwegian Sea ; to the west of the Faroes, over the long ridge 
that extends to Iceland, the Atlantic water is checked by the 
East Iceland Polar current. 

Our southern section was from Glasgow to Rockall, with 
stations on the British coast bank, on its seaward slope, and on 
the Rockall Bank. We had beautiful weather in which to make 





tot 

li- 


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-ZZZZZZ-- "_- - z z r - -_-_------- 


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J 

f500 — 








/ 




2000 . 


>5?55%r*'^=i«Lyr 





Fig. 106. — Section across the Wvvili.e Thomson Ridge. 



investigations, and approached close to the rocky little islet, 
which we photographed (Fig. 105). This rock is well known, 
Rockall. owing to many a sad disaster (only recently the transatlantic 
steamer " Norge " was wrecked there), and shows distinct 
traces of the power of the waves. All its brown granite-like 
sides are clad with small algse (green-spored algae), kept moist 
by the spray, and the top is covered with a thin layer of guano ; 
the rock and its surroundings swarm with auks and gulls. 



CRUISES OF THE "MICHAEL SARS " 125 
After completing this section, we proceeded towards the Wyviik 

homs 
Lidge. 



Wyville Thomson Ridge, and occupied a station (loi) at a Thomson 



depth of 1000 fathoms, where we employed the trawl as well as 
a number of pelagic appliances, and then concluded our work 
by taking two sections on the northern side of the ridge (see 
stations in Fig. 104). 

The Jiydrographical conditions here have often been de- 
scribed. Fig. 106 gives a general idea of what we found at 
Station loi south of the Wyville Thomson Ridge, and at 
Station 106 to the north of it. South of the ridge salinities 
and temperatures are rather lower than what we found in our 
northern Atlantic section, but the differences are not very 
considerable either in deep water or in the upper layers. The 
upper layers extend with little variation down to the level of the 
ridge in 500 metres, but the difference in the deep water on the 
two sides of the ridge is unmistakable, as the ice-cold bottom- 
water of the Norwegian Sea comes close to the northern 
margin of the ridge. 

These conditions, however, are generally known, and our 
attention was chiefly turned in another direction. During our 
previous investigations in the Norwegian Sea we discovered 
that the hydrographical conditions often varied very consider- 
ably within a short distance or in the course of a short period 
of time. The variations were not always of the same character. 
A number of eddies, both large and small, occurred apparently 
during the movements of the water-layers, and there were up 
and down movements in the boundary-layers^ — possibly big 
submarine waves or something of that sort — as well as distinct 
pulsations in certain currents. We resolved, therefore, on our 
way over to Bergen to make a careful study of these phenomena 
in the Faroe-Shetland channel. To be able to do so, it was 
necessary to have our stations very close together and to occupy 
them in rapid succession, and also to lie stationary for at least 
twenty-four hours at one of them. 

Altogether we had fourteen stations north of the ridge in the investigations 
Faroe-Shetland channel (Nos. 103-116; see Fig. 104) along two cVan*nrL'°^ 
nearly parallel sections, the distance from one station to another 
being about 20 nautical miles, and the distance between the 
sections a little over 25 miles. We found that the hydro- 
graphical conditions varied greatly in the different localities, 
and that there was an extraordinary difference between the two 
sections. At Station 115, on the continental edge to the west 
of Shetland, we anchored a buoy, and remained stationary there 



126 DEPTHS OF THE OCEAN 

for twenty-four hours, taking continuous observations of tempera- 
ture and salinity at different depths. It was quite evident that 
there were considerable vertical fluctuations, the intermediate 
layers showing up and down movements with an amplitude 
of as much as 35 metres during a period that corresponded 
practically with the tidal period. 
Pelagic hauls. After leaving Glasgow we made pelagic hauls with our 

silk nets and young-fish trawls on the coast bank, on the slope, 
out in the deep channel, near the southern flank of the Wyville 
Thomson Ridge (Station loi), and to the north of it (Station 102), 
At every depth our catches to the south of the ridge closely 
resembled those we made in our northern Atlantic section 
between Newfoundland and Ireland, and particularly the catches 
made in the eastern portion of that section. 

In the upper layers there were all the boreal animals 
characteristic of Atlantic water in the Norwegian Sea, as, for 
instance, Eiithemisto and Clione liniacina. But there was also a 
mass of Atlantic forms that do not occur all the year round in 
the Norwegian Sea, though they are known to wander in at 
certain seasons of the year, as at the end of the summer or 
during autumn. The tow-nets gave a mixture of ^r«^/^;2«^/2i", 
Salpa fusiformis, numbers of scopelids, leptocephali (full- 
grown larvse of the common eel), the young of Macriirus, and 
Nerophis csquorezis. 

At a depth of 300 metres we captured the silvery Argyro- 

pelecus, and in deep water, from 500 metres downwards, there 
was the characteristic fauna of black Cyclothone microdon, 
red crustaceans [Acantkephyra), and other forms, which thus 
occur right tip to the southern slope of the Wyville Tho^nson 
Ridge. 

On the northern side of the ridge we towed our appliances 
at 50, 100, 150, 200, 300, 500, 700, and 750 metres (Station 102) 
without catching a single specimefi of these Atlantic deep-sea 

forms ; but in the upper layers there were not merely boreal 
forms, but also salpae, the area of distribution of which is 
mainly Atlantic. 

These results quite accord with our previous observations 
during the cruises of the " Michael Sars." Hauls in the deepest 
waters of the Norwegian Sea have not yielded any pelagic fish 
other than the black Paraliparis bathybii (Fig. 107), which 
used to be considered a bottom-fish ; it is interesting to note 
that it is black. There was a complete absence of Cyclothone 
and the red Atlantic crustaceans belonging to the genus Acan- 



CRUISES OF THE "MICHAEL SARS " 127 

thephyra, the only pelagic crustaceans found by us north of the 
ridge being Hyinenodora glacialis and species of Pasiphcea. 

In the upper layers, however, different scopelids have been 
found both by us and by others, and on the Norwegian coast 
the silvery species of Argyropeleats, which inhabit depths of 
about 300 metres in the Atlantic, have occasionally been met 
with. It seems tolerably certain, therefore, that the Wyville 
Thomson Ridge shuts out the whole of the Atlantic pelagic deep- 
sea fauna from the Norwegian Sea, and that it is only in the 
superficial layers from the surface down to 400 or 500 metres 
that pelagic forms are able to wander in from the Atlantic. 

That the bottom -fauna is different on either side of the Benthos of 
ridge is well known. Our trawlings, both on this occasion and ch^^ner 
previously, have merely helped to confirm the fact ; still we 
secured a very large amount of material, which in itself is of 




107. 

Paraliparis bathybii, Coll. Nat. size, 23 cm. 
(Taken in pelagic haul in Norwegian Sea, May 1911.) 

considerable interest. At Station loi (south of the ridge), in 
1000 fathoms (1853 metres) of water, a haul of two hours' 
duration yielded a barrel-full of lower animals, most of which were 
echinoderms, and ninety fishes (Alacrurus, Antimo7'a, Alepo- 
cephalus, Harriotta, and Synaphobranchi), representing a fauna 
that may be said to characterise the north-east Atlantic from 
the Wyville Thomson Ridge southwards, far along the coast of 
Africa. The remarkable fish, Hari'iotta raleighana, which we 
captured at Station loi, a few miles from the deep water of the 
Norwegian Sea, had been previously taken by us at Station 35, 
to the south of the Canary Islands. On the other hand, fish 
that exist only a few miles farther north, on the northern side 
of the ridge, never enter the Atlantic, though in the deep water 
of the Norwegian Sea they may be met with as far north as 
Spitsbergen, and perhaps even still farther north. 

The "Michael Sars " anchored at Bergen on 15th August. E.xtent of 
During her four and a half months' cruise she had traversed 1 1 , 500 ^^^ '^™'^^' 



128 DEPTHS OF THE OCEAN chap. n. 

miles, and occupied 1 16 research stations; on a rough estimate we 
had lowered and hauled in about 1500 kilometres of wire with 
our four winches. Only the greatest attention and energy on 
the part of the crew could have made this possible. Thanks to 
them we have probably opened up a new way for ocean research, 
by showing what a little vessel can accomplish, which is by no 
means the least valuable result of our expedition. The follow- 
ing chapters aim at giving the results of our scientific observa- 
tions from a more general and systematic point of view than 
was possible in this brief account of the actual cruise. 

J. H. 




^4^ 



S.S. "Michael Sars " towinc. Otter Trawl. 



m 



("." 



^Ni 



BATHYMETRICAL CHART Of 

THE ©CEAiXS 

SHOWING THE DEEPS 
According to Sir John Murray 




V 




SiF"nxG Deposit: 



CHAPTER IV 



THE DEPTHS AND DEPOSITS OF THE OCEAN 



I. The Depths of the Ocean 

In the opinion of astronomers the earth is the only planet of The earth as 
our solar system which has oceans on its surface. If Mars and ^ p'^"^'- 
the moon once had oceans, these have apparently disappeared 
within their rocky crusts. Our earth is in what is called the 
terraqueous stage of a planet's development. The ocean is less 
than the hydrosphere, which is regarded as including all lakes 
and rivers, the water-vapour in the atmosphere, and the water 
which has penetrated deep into the lithosphere. 

If the whole globe were covered with an ocean of uniform 
depth, and if there were no differences of density in the shells of 
the rocky crust, the surface of the ocean would be a perfect 
spheroid of revolution. But, as every one knows, the surface of 
the earth is made up of land and water, and at all events the 
superficial layers of the lithosphere are heterogeneous. The Figure of 
figure of the earth departs from a true spheroid of revolution, ^^^ '^'^'''^' 
and is called a geoid. The surface of the ocean is, therefore, 
farther removed from the centre of the earth at some points 

129 K 



I30 



DEPTHS OF THE OCEAN 



Attraction 
of the 
land-masses. 



Measurements 
of depth. 



Hand line. 



Brooke's 
sounding 



machine 



than at others ; the gravitational attraction of emerged land 
causes a heaping-up of the sea around continental and other 
coasts. The extent of this heaping-up near elevated continents, 
and consequent lowering of the sea-surface far from land, appear 
to have been much exaggerated. The difference of level due to 
this cause has sometimes been estimated at thousands of feet. 
Recent researches indicate that the differences of level at 
different points of the sea-surface do not depart more than 300 
or 400 feet from a true spheroid of revolution. 

The other causes which, in addition to the tides, may affect 
the level of the ocean are meteorologic, such as barometric 
pressure, temperature, the action of wind, evaporation, precipita- 
tion, the inflow of rivers, but in no cases do these affect the 
level of the ocean more than a few inches or a few feet. 

All depths recorded by the sounding-line in the open sea are 
referred to the surface of the ocean, and near coasts to mean sea- 
level. The first method of ascertaining the depth of the ocean 
was by means of the hand line and lead, armed with tallow, used 
by ordinary sailors. A great advance was made when Lieutenant 
Brooke, of the United States Navy, devised the apparatus for 
detaching the weight or sinker when it struck the bottom, the 
line bringing up only a small tube with a sample of the bottom- 
deposit. During the "Challenger" Expedition the line used 
was a fine hempen rope, and the time when each loo-fathoms 
mark passed over the ship's side was carefully noted. When 
a great change of the rate was observed, the lead was known to 
have reached the bottom. It is believed that even the deepest 
soundings taken in this way are correct to within 100 feet. 

Another advance was made when fine wire was used for the 
soundings, and the machine recorded automatically the moment 
when the sinker struck the bottom. There are many types of 
wire deep-sea sounding machines now in use, but the most 
compact and practical of these is the Lucas sounding machine. 
Sounding instruments are referred to in greater detail in another 
chapter (see p. 30). 

To give the total number of deep soundings recorded by 
British and other ships up to the present day, even in depths 
exceeding 1000 fathoms, would be difficult. An approximation 
has been made by counting the number of soundings in depths 
exceeding 1000 fathoms laid down on the latest charts. It 
must be remembered that not all the recorded soundings can be 
laid down on small scale charts where they are at all numerous. 

In 1886 Sir John Murray had three hemispheres drawn on 



IV DEPTHS AND DEPOSITS OF THE OCEAN 131 

Lambert's equal-surface projection, one to show the Atlantic Equai-smface 
Ocean, one the Pacific, and one the Indian Ocean, on which all hemShSes. 
the soundings recorded up to that time, in depths exceeding 
1000 fathoms, were laid down in position, and contour-lines of 
depth drawn in. Since then these hemispheres have been kept 
up to date by Dr. Bartholomew by the inclusion from time to 
time of new soundings recorded in depths greater than 1000 
fathoms, and the contour-lines have been redrawn. The North 
Atlantic from one of these hemispheres is shown on Map III., 
where practically all soundings recorded in depths greater than 
1000 fathoms are placed in position, the two last figures being 
omitted. 

The total number of soundings laid down on these charts Number of 
is 5969, of which 2500 are in the Atlantic (1873 in the North l^^'^t^l^eater 
Atlantic and 627 in the South Atlantic), 2466 in the Pacific than 1000 
(1266 in the North Pacific and 1200 in the South Pacific), and f^^^"'^'- 
1003 in the Indian Ocean. These figures show that pro- 
portionately a great many more soundings have been taken 
in the Atlantic than in the Pacific, which covers an area so 
much larger. Of these 5969 soundings, 2516 were taken in 
depths between 1000 and 2000 fathoms, 2962 in depths between 
2000 and 3000 fathoms, and only 491 are laid down in depths 
exceeding 3000 fathoms, of which 46 exceed 4000 fathoms, and 
only 4 exceed 5000 fathoms. It may be added that though only 
four soundings over 5000 fathoms have been laid down on the 
charts, in reality seven have been recorded, three in the South 
Pacific in the Aldrich Deep, and the other four taken by the 
U.S.S. "Nero" in the Challenger Deep in the North Pacific, 
near the island of Guam, but in such close proximity to one 
another that only the deepest, 5269 fathoms, could be laid down 
on the map. 

The deepest sounding hitherto recorded is that of 5269 Deepest 
fathoms just mentioned. • This is equal to 9636 metres, or ^oundini. 
31,614 feet, or 66 feet less than six English miles, and it exceeds 
the greatest known height above the level of the sea (Mount 
Everest in the Himalaya Mountains, 29,002 feet) by 2612 feet. 
The known range of variation in the level of the earth's crust, Range of 
from the greatest height above sea-level to the greatest depth i^'evd of'the^ 
below sea-level, is thus 60,616 feet, or about ii|- English miles, earth's cmst. 
but this range is very small when we remember that the 
diameter of the earth is nearly 8000 miles ; in fact, on a six-feet 
globe a mere scratch one-tenth of an inch deep would represent 
the extreme variation in the irregularities of the earth's surface. 



Deepest 
soundings in 
the Atlantic 
and Indian 
Oceans. 



132 DEPTHS OF THE OCEAN 

The second deepest sounding on the ocean -floor is 5155 
fathoms in the Aldrich Deep in the South Pacific, depths 
exceeding 5000 fathoms being Hmited to the Pacific Ocean. 
The deepest sounding recorded in the Atlantic is 4662 fathoms 
in the Nares Deep to the north of the West Indies, and the 
deepest in the Indian Ocean 3828 fathoms in the Wharton 
Deep to the south of the East Indies. 



Superficial 
area of the 
earth. 



Area of 

Antarctic 

continent. 



Area of land 
on the globe. 

Area of 
water on 
the globe. 



Areas of the 
ocean-floor 
at different 
depths. 



In 1886 Professor Chrystal calculated for Sir John Murray 
the supLprficial area of the earth, regarded as a spheroid of 
revolution, as equal to 196,940,700 square English miles, of 
which the land - surface was estimated at 55,697,000 square 
miles, and the water-surface at 141,243,000 square miles.^ At 
that time the area of land surrounding the south pole was 
estimated at 3,565,000 square miles, but the results of all the 
recent south polar expeditions seem to indicate that the 
Antarctic continent covers a larger extent than was supposed. 
The latest measurements by Sir John Murray give a probable 
area of about 5,122,000 square miles for Antarctica, so that 
the total land-surface of the globe may now be estimated at 
57,254,000 square miles, which may be supposed to include 
all lakes and rivers, leaving about 139,686,000 square miles 
for the waters of the ocean and seas directly connected 
therewith. 

Planimeter measurements of the most recent depth hemi- 
spheres gave 139,295,000 square English miles for the area 
of the whole ocean, and this figure will be adopted throughout 
this publication. 

The approximate areas between the consecutive contour- 
lines drawn in at equal intervals of 1000 fathoms worked out 
as follows for the whole ocean : — 



Fathoms. | Square English Miles. 


Percentage. 


0-1000 21,725,000 
1000—2000 26,915,000 
2000-3000 81,381,000 
3000-4000 9,058,000 
Over 4000 , 216,000 


15-59 
19-34 
58.42 1 

6.50 , 

0.15 


' i39j295>ooo 


100.00 



Scottish Geographical Magazine, vol. ii. p. 550, l< 



IV DEPTHS AND DEPOSITS OF THE OCEAN 133 

This table shows at a glance that the greater portion of 
the ocean-floor is covered by deep water, i.e. by water exceed- 
ing 1000 fathoms in depth, equal to more than four- fifths of 
the entire superficies of the ocean, two-thirds being occupied by 
water exceeding 2000 fathoms in depth, while only one-fifteenth 
of the entire sea-floor is covered by water exceeding 3000 
fathoms in depth. 

Those parts of the ocean in which depths greater than 3000 
fathoms have been recorded are called "deeps," and have had "Deeps." 
distinctive names conferred upon them, just as mountain ranges 
and peaks on the dry land (Mount Everest, for example) are 
distinguished by names. These deeps are shown on Map H., 
and will presently be dealt with in some detail. 

The table also shows that a comparatively large area, about Areas of the 
one-sixth of the ocean-floor, is covered by water less than 1000 SanT^ 
fathoms in depth, of which by far the greater proportion is continental 
covered by still shallower water. Thus if we divide this area ^°p^* 
into two portions by the 500-fathoms line, we find that the 
area within that line is about 17 million square miles (or 
over 12 per cent of the entire ocean) compared with only 
4|- million square miles (or 3 per cent of the entire ocean) 
beyond that line, i.e. having depths between 500 and 1000 
fathoms. Again, of the area covered by less than 500 fathoms 
of water, more than one-half is occupied by the continental 
shelf or continental plateau lying between the shore-line and 
the loo-fathoms line, which has elsewhere^ been estimated at 7 
per cent of the whole ocean. The relatively large area covered 
by the gentle slopes of the continental shelf in depths less than 
100 fathoms, as compared with the relatively small area covered 
by the steeper gradients of the continental slope in depths 
greater than 100 fathoms, is strikingly shown by these figures, 
for while about 7 per cent of the ocean-floor lies within the 
lOO-fathoms line, only about 5 per cent occurs within the next 
succeeding 400 fathoms (between the 100- and 500-fathoms 
lines), and only about 3 per cent within the next succeeding 
500 fathoms (between the 500- and looo-fathoms lines). 

The position occupied by the junction of the continental Continental 
shelf with the continental slope, as indicated by the change nSSne 
of gradient, has been called the continental edge (see Fig. 144, 
p. 198), and varies in depth according to circumstances, but on 
the average all over the world is not far from the lOO-fathoms 

1 Sir John Murray, Presidential Address to the Geographical Section of the British Associa- 
tion, Dover, 1899. 



134 



lud-li 



DEPTHS OF THE OCEAN 

inciding generally with what we have designated the 



Area of the 
Atlantic 
sea-floor at 
different 
depths. 



Continental 
shelf and 
slope in the 
Atlantic. 



Let us now consider the distribution of depth in the three 
great oceans (the Atlantic, the Pacific, and the Indian Oceans), 
regarding them as extending in each case as far south as 
the shores of the Antarctic continent. 

Atlantic Ocean. — The Atlantic may be looked upon as 
including the Arctic Ocean and Norwegian Sea, the 
Mediterranean, Caribbean, and Gulf of Mexico, and as being 
separated from the Pacific in the south at the meridian of Cape 
Horn (long. 70° W.) and from the Indian Ocean at the meridian 
of the Cape of Good Hope (long. 20' E.). As thus defined 
the Atlantic Ocean covers an area of about 41,321,000 square 
English miles, the distribution of depth being shown in the 
following table : — 



Fathoms. 


Square English Miles. 


Percentage. 


o-iooo 
1000-2000 
2000-3000 
3000-4000 
Over 4000 


11,388,000 
7,531.000 

19.539,000 

2,848,000 

15,000 


27.56 

18.22 

47.29 

6.89 

0.04 


41,321,000 


100.00 



These figures show that nearly three-fourths of the Atlantic 
sea -floor are covered by water exceeding 1000 fathoms in 
depth, and over one-half by water exceeding 2000 fathoms in 
depth, but the most characteristic feature of this ocean when 
compared with the Pacific and Indian Oceans is the large 
proportion covered by water less than 1000 fathoms in depth. 
The table shows that this shallowest zone (from o-iooo fathoms, 
which includes both the continental shelf and the continental 
slope) covers about i\\ million square miles, while the succeed- 
ing zone (1000-2000 fathoms) covers only 7^ million square 
miles. If again we divide the shallowest zone into two portions 
by the 500-fathoms line, the predominance of the area covered 
by shallow water is still more pronounced, the area less than 
500 fathoms being nearly 10 million square miles as compared 

1 Murray and Renard, Deep-Sea Deposits Chall. Exp. p. 1S5, 1891 ; Murray, Summary 
of Results Chall. Exp. p. 1433, 1895. 



IS.C. 



IV DEPTHS AND DEPOSITS OF THE OCEAN 135 

with i|- million square miles between 500 and 1000 fathoms. 
This is due to the large expanses of shallow water in the Arctic 
regions and Hudson Bay, on the Banks of Newfoundland, off 
the east coasts of North and South America, between Green- 
land and the British Isles, around the British Isles, and in 
the Baltic. 

The most striking feature of the Atlantic Ocean is certainly Mid-Atiamic 
the low central ridge (dividing the ocean into eastern and '^''^ 
western deep basins), which was until recently supposed to be 
continuous from Iceland through both the North and South 
Atlantic as far as lat. 40° S., but is now known to be discon- 
tinuous in the neighbourhood of the equator ; on the other hand, 
it has been extended farther south by the soundings taken on 
board the "Scotia" in 1904 by Dr. W. S. Bruce, so that the 
southern limit of the ridge now extends as far south as lat. 
53" S. At the position of the break in the ridge on the equator 
the floor of the ocean seems to be more than usually irregular, 
for depths less than 2000 fathoms alternate with depths exceed- 
ing 3000 and even 4000 fathoms. On this ridge, with the 
exception of the Azores group, the only islands are St. Paul's 
Rocks, Ascension, Tristan da Cunha, and Gough Island. The 
northern extremity of the ridge between lat. 50° and 60° N. is 
peculiar because of the number of isolated soundings exceeding 
2000 fathoms apparently surrounded by shallower water. 

Another point that strikes one in the Atlantic is the gentle Shoie-siopes 
slope off the American coasts and off the coasts of the British of the Atlantic. 
Isles, as compared with the slopes off Africa and off Spain and 
Portugal. This is still more remarkable when compared with 
the slopes off the Pacific coasts of America. The wide shore 
platform off the coast of the southern half of South America is 
especially noteworthy, as well as that off the coasts of the United 
States and Newfoundland. The shallow area surrounding 
Rockall Bank also attracts attention. The series of banks made Submarine 
known as a result of the work of telegraph ships, off the north- A^JlI^nti? ''^^ 
west coast of Africa to the north of the Canary Islands, is another 
striking instance of the irregularity of the floor of the Atlantic. 
In the same neighbourhood the area with depths less than 2000 
fathoms surrounding Madeira and extending northwards towards 
the coast of Portugal is remarkable. In the South Atlantic, 
besides the central ridge, three smaller shallow areas should 
be noted, two neighbouring ones to the east of the South 
American coast in lat. 30° S., and the third midway between 
the ridge and the Cape of Good Hope. 



136 DEPTHS OF THE OCEAN 

The principal area exceeding 2000 fathoms in depth is 
continuous throughout the Atlantic, although much broken up 
by areas of shallower water ; there are besides in places isolated 
areas in which the depth exceeds 2000 fathoms, as in the Gulf 
of Guinea, near the Canary Islands, at the northern extremity 
of the Mid-Atlantic ridge (as already mentioned), as well as in 
the Norwegian Sea, the Mediterranean Sea, the Carribbean 
Sea, and the Gulf of Mexico. 

The areas exceeding 3000 fathoms in depth (" deeps ") will 
be referred to under a later heading. 



Pacific Ocean. — The Pacific may be looked upon as extend- 
ing southwards from the Arctic circle in Behring Strait to the 
Antarctic continent, including the fringe of partially enclosed 
seas along its western border, and as being separated from 
the Atlantic in the south at the meridian of Cape Horn (long. 
70' W.), and from the Indian Ocean at the meridian of Tasmania 
(long. 147° E.). As thus defined the Pacific Ocean covers an 
area of about 68,634,000 square English miles, the distribution 
of depth being shown in the following table : — 



Fathoms. 


Square English Miles. 


Percentage. 


O-TOOO 
1000-2000 
2000-3000 
3000-4000 
Over 4000 


7,174,000 
12,214,000 
44,633,000 

4,412,000 
201,000 


10.45 

17.80 

65-03 

6.43 

0.29 


I 
68,634,000 100.00 



These figures show that nearly nine- tenths of the Pacific 
sea- floor are covered by water exceeding 1000 fathoms in depth, 
and nearly three- fourths by water exceeding 2000 fathoms in 
Continental depth. Unlike the Atlantic, the shallowest zone in the Pacific 
hrihe^PactfiT (o- 1 000 fathoms) is smaller than the succeeding zone (1000-2000 
fathoms), indicating that the Pacific land -slopes are on the 
average steeper than those of the Atlantic, and this is strikingly 
shown by the near approach to the land of the deep contours 
in certain regions, as off the coasts of South America, North 
America, Japan, the Philippine Islands, and South-East Australia. 
The ratio between the two areas on either side of the 500-fathoms 
line is not so strikino- as in the case of the Atlantic, the area 



rv DEPTHS AND DEPOSITS OF THE OCEAN 137 

less than 500 fathoms in the Pacific being about 5 million 
square miles, as compared with 2 million square miles for the 
area between 500 and 1000 fathoms. 

The Pacific Ocean differs from the Atlantic in having much shore-siopes 
more steeply sloping shores both on the east and west sides, of the Pacific, 
greater depths, and very many small islands, chiefly of volcanic 
and coral formation. This gives a very irregular appearance to 
the depth-map of the Pacific, and shows sharper contrasts in rises 
and depressions of the ocean-floor than are found in either of the 
other great ocean basins. Along the west coasts of both North 
and South America the steep slopes are most remarkable, the 
land descending from the great heights of the Rocky Mountains 
and the Andes to depths of 2000 fathoms and more in a 
comparatively very short horizontal distance. This is par- 
ticularly striking off the coast of South America between the 
latitudes of 10° and 35° S., where depths of over 3000 fathoms 
(in three cases over 4000 fathoms) are found within a very short 
distance from the shore-line. It is noteworthy that all the very deep 
soundings recorded in depths of over 4000 fathoms are taken com'^arSvei- 
comparatively near land, viz. off South America (as just near land. 
mentioned), off the Aleutian Islands, the Kurile Islands and 
Japan, the Philippines, the Ladrone Islands, the Pelew Islands, 
between the Solomon Islands and New Pommerania, and to the 
north of New Zealand, east of the Kermadec and Friendly 
Islands. 

The greater part of the area with depths less than 1000 
fathoms lies in the western Pacific, in the fringe of partially 
enclosed seas which lie between the continents of Asia and 
Australia and the islands fringing their eastern shores, such as 
the Behring Sea, the Sea of Japan, the Yellow Sea, China Sea, 
Java and Arafura Seas, and around the New Zealand plateau. 

The area covered by depths between 1000 and 2000 fathoms Pacific area 
lies mostly south of the equator, that part north of the equator beJ^^gtTiooo 
consisting of detached areas in the Behring Sea, Sea of Okotsk, and 2000 
Sea of Japan, and China Sea, narrow bands round the various ^' °^^^' 
island groups and along the western shores of North America, 
widening greatly off the coast of Central America, and nine small 
areas where the floor of the ocean rises from surrounding depths 
of over 2000 fathoms. The area in the South Pacific with depths 
between looo and 2000 fathoms was formerly supposed to extend 
from the Southern Ocean between Auckland Islands and the 
Antarctic continent in a wide band north-eastv/ards towards the 
coasts of Central America without a break, but recent investiga- 



138 DEPTHS OF THE OCEAN 

tions by the late Alexander Agassiz on board the U.S.S. 
" Albatross " showed that this rise from the general depth of 
over 2000 fathoms was not continuous. This has led to a great 
decrease in the figures given for the area with depths between 
looo and 2000 fathoms, and a corresponding increase in the 
area with depths between 2000 and 3000 fathoms. 
Pacific area The area exceeding 2000 fathoms in depth in the Pacific is 

SocTfathoms. Connected with the corresponding area in the Atlantic by a 
comparatively narrow trench running to the south of Cape Horn 
between South Georgia and South Orkney, and is continuous 
throughout the Pacific except for detached areas in several of 
the fringing seas on the west, one in the Coral Sea, and one 
large and six small areas in the South-West Pacific, where the 
soundings are very numerous and the contour-lines of depth are 
very sinuous. 

The areas exceeding 3000 fathoms in depth will be referred 
to under a later heading. 

Area of the ludiau Oceaii. — The Indian Ocean may be looked upon as 

Indian Ocean extendincj southwards from the Bay of Bengfal and Arabian Sea 

sea-floor at i a • • • i i • i -r^ ^ c^ i t • 

different to the Antarctic contment, mcludmg the Red Sea and Persian 

depths. Gulf, and as being separated from the Atlantic in the south at the 

meridian of the Cape of Good Hope (long. 20° E.) and from the 
Pacific at the meridian of Tasmania (long. 147° E.). As thus 
defined the Indian Ocean covers an area of about 29,340,000 
square English miles, the distribution of depth being shown in 
the following table : — 



Fathoms. 


Square English Miles. 


Percentage. 


O-IOOO 
1000-2000 
2000-3000 
Over 3000 


3,163,000 

7,170,000 

17,209,000 

1,798,000 


10.78 

24-44 

58-65 

6.13 


29,340,000 


100.00 



These figures show that, like the Pacific, nearly nine-tenths 

of the Indian Ocean sea-floor are covered by water exceeding 

1000 fathoms in depth, while nearly two-thirds are covered by 

Continental more than 2000 fathoms of water. The shallowest zone in 

inthe^'indiar ^^ Indian Ocean (o-iooo fathoms) is much smaller than the 

Ocean. succecdiug zoue ( 1 000-2000 fathoms), indicating that the average 



IV DEPTHS AND DEPOSITS OF THE OCEAN 139 

land-slopes throughout the basin are, as in the Pacific, steeper 
than those of the Atlantic. The ratio between the two areas 
on either side of the 500-fathoms line is again much less than 
in the case of the Atlantic, the area less than 500 fathoms in the 
Indian Ocean being over 2 million square miles, as compared 
with less than i million square miles for the area between 500 
and 1000 fathoms. 

The Indian Ocean, unlike the other two, is completely land- 
locked to the north. The area with depths less than 1000 fathoms 
forms a zone of varying width along the main land-masses, a fairly 
wide zone round the various island groups, and extends into the 
Red Sea and Persian Gulf. The area with depths between Indian Ocean 
1000 and 2000 fathoms is made up of the greater part of the ^i^p^ti,^''^ 
Bay of Bengal and the Arabian Sea, a fairly wide belt along between 1000 
the east coast of Africa, a much narrower one along the western fathom?" 
shores of the Sunda Islands and Australia, a large expanse 
between Tasmania and the Antarctic continent which narrows 
considerably towards the west, and a large tract extending from 
lat. 30" to 55' S. and long. 35° to 94 E., forming a plateau on 
which are situated the islands of Prince Edward, Crozet, 
Kerguelen, M'Donald, Heard, St. Paul, and Amsterdam, as 
well as one or two small isolated areas. 

With the exception of a comparatively small area in the Indian Ocean 
Southern Ocean, about lat. 60° S. to the south of Australia, the 2000 feAom"^ 
area with depths between 2000 and 3000 fathoms is a continuous 
one, though interrupted by areas of deeper and shallower water ; 
it is continuous with the corresponding area of the Atlantic, but 
distinct from that of the Pacific, being separated from it by the 
rise that runs southwards from Tasmania to the Antarctic 
continent. 

The areas exceeding 3000 fathoms in depth are referred to 
under the next heading. 

Deeps. — As already indicated, those areas of the ocean-floor 
covered by more than 3000 fathoms (5486 metres) of water 
have been called Deeps, and, though occupying a relatively Deeps. 
small proportion of the ocean-floor, estimated in the aggregate 
at about 9 million square miles, they are extremely interest- 
ing from an oceanographical point of view. Map II. shows 
the distribution of these deeps throughout the great ocean 
basins, according to the present state of our knowledge, and it 
will be seen that the total number is fifty-seven, of which thirty- Number of 
two occur in the Pacific, five in the Indian Ocean, nineteen in '"°^^" ^^^^' 



140 



DEPTHS OF THE OCEAN 



Largest 
deejDS. 



Valdivia 
Deep. 



the Atlantic, and one partly in the Atlantic and partly in the 
Indian Ocean. From the point of view of depth the Challenger 
Deepest Deep in the North Pacific and the Aldrich Deep in the South 
deeps. Pacific are the most important, for only these two include 

depths exceeding 5000 fathoms, while in eight other deeps 
depths exceeding 4000 fathoms have been recorded. On the 
other hand, in some cases the deeps enclose low rises, on which 
the depth is less than 3000 fathoms. The deeps vary in form 
and size to a most extraordinary degree, and future soundings 
may show that some of them should be subdivided into two or 
more portions, or that two or more deeps as now laid down 
should be united into a single deep. 

From the point of view of superficial area, the most im- 
portant deeps are the Valdivia, Murray, Tuscarora, Wharton, 
Nares, Aldrich, and Swire Deeps, which are estimated to cover 
in each case an area exceeding 500,000 square miles. In the 
following paragraphs the principal deeps of the world are briefly 
characterised, arranged in the order of magnitude : — 

Valdivia Deep lies in the far south, partly in the Atlantic 
and partly in the Indian Ocean. It is based principally on 
soundings taken by the German Deep-Sea Expedition on board 
the "Valdivia," and has a maximum depth of 3134 fathoms. It 
is estimated to cover a total area of 1,136,000 square miles, 
nearly one-half of which (523,000 square miles) lies to the west 
of long. 20° E., i.e. within the Atlantic basin, while the remain- 
ing half (613,000 square miles) lies to the east of that meridian, 
and is therefore in the basin of the Indian Ocean. The outline 
of this deep, especially in its western portion, is largely hypo- 
thetical, and future soundings may modify the area assigned to 
it at present. 
Murray Murray Deep, situated in the Central North Pacific between 

^'^'^P- lat. 25" and 40° N., is estimated to cover an area of about 

1,033,000 square miles, and is founded on soundings taken 
partly by the "Challenger" Expedition. The maximum depth 
recorded in it is 3540 fathoms, and there is a small area within 
the deep in the vicinity of this deepest sounding where depths 
of only 2800 and 2900 fathoms are recorded. 
Tuscarora Tuscarora Deep lies in the North- Western Pacific, and is of 

Deep. elongated form, extending from the Tropic of Cancer north- 

eastwards to near the Aleutian Islands in lat. 52° N., approach- 
ing to within a comparatively short distance of the shores of 
Japan and the Kurile Islands. Its area is estimated at 908,000 
square miles, and the maximum depth is 4655 fathoms, recorded 



IV DEPTHS AND DEPOSITS OF THE OCEAN 141 

by the U.S.S. " Tuscarora" in 1874. A considerable portion of 
this deep is covered by depths exceeding 4000 fathoms, includ- 
ing one large elongate area founded on eight soundings, and 
two small areas founded each on single soundings — one towards 
the southern end of the deep and the other in the extreme 
north. 

Wha7'ton Deep lies in the eastern Indian Ocean, extending wharton 
from lat, 10 S. to the Tropic of Capricorn, and is estimated to ^^'^' 
cover an area of 883,000 square miles ; it includes the two 
deepest soundings yet recorded in the Indian Ocean, viz. 3828 
and 3703 fathoms, taken in 1906 by the German ship " Planet" 
in what is called by the Germans the " Sunda Graben " at no 
great distance from the coast of Java. 

Nares Deep is the largest deep lying wholly in the Atlantic Nares Deep. 
Ocean, and at the same time the deepest. Its outline is most 
irregular, extending from lat. 18° N. to 34° N., and in the 
neighbourhood of the West Indies the floor of the deep sinks 
to depths exceeding 4000 fathoms over a limited area, the 
maximum depth being 4662 fathoms, recorded by the U.S.S. 
"Dolphin" in 1902. This deep is estimated to cover an area 
of 697,000 square miles. 

Aldrich Deep lies in the Central South Pacific, extending Aidrich Deep, 
from lat. 15° to 47° S., and is estimated to cover an area of 
about 613,000 square miles. It includes seven small areas 
lying along its western border in which the depth exceeds 4000 
fathoms. In three of these the depth exceeds 5000 fathoms, 
viz. 5022, 5147, and 5155 fathoms, recorded by Commander 
Balfour on board H.M.S. "Penguin" in 1895. Numerous 
soundings have been taken round these* seven deepest areas, 
and seem to prove that they are all separated from one another 
by ridges covered by water between 3000 and 3700 fathoms in 
depth. The outline of this deep is remarkable, and it is 
possible that future soundings will show it to be two distinct 
deeps, for a rise, on which soundings in 2000 to 2900 fathoms 
have been recorded, interrupts the sequence of great depths. 

Swire Deep lies in the North-West Pacific in close proximity SwireDeep. 
to the Philippines, and extends from about lat. 4° N. to 
lat. 25' N., covering an area of about 550,000 square miles. It 
is broken up by several rises on the ocean-floor where depths 
of 2700, 2800, and 2900 fathoms have been recorded ; on the 
other hand, at remarkably short distances from the coasts of 
Mindanao and Samar Islands in the Philippines are two areas 
with depths exceeding 4000 fathoms, a similar depth being 



142 



DEPTHS OF THE OCEAN 



recorded also at the northern end of the deep. The maximum 
depth, which occurs off Samar Island, is 4767 fathoms. 

Tizard Deep in the South Atlantic is estimated to cover an 
area of about 468,000 square miles, extending southwards from 
the equator to lat. 22" S. on the western side of the Mid- 
Atlantic ridge. The greatest depth recorded in it is 4030 
fathoms, just south of the equator. In the southern portion of 
the deep two low rises occur, where depths rather less than 
3000 fathoms have been recorded. 

Buchanan Deep lies to the east of the Mid- Atlantic ridge in 
the South Atlantic, between lat. 6° and 22° S., and covers an 
estimated area of 298,000 square miles. This deep appears to 
be somewhat flat-bottomed, because the numerous soundings 
recorded within it do not reach 3100 fathoms though exceeding 
3000 fathoms, the maximum depth being 3063 fathoms. 

Brooke Deep lies in the North-West Pacific between the 
latitudes of 12° and 19^ N., and covers an area estimated at 
about 282,000 square miles. Its greatest depth is 3429 fathoms. 
Several elevations of the ocean-floor, rising to within 1400, 
1 1 00, and even 1000 fathoms of the surface, are situated close 
to the western and northern borders of this deep, separating it 
from the Challenger Deep on the west, and from the Bailey 
Deep on the north. 

Moseley Deep lies in the North Atlantic to the east of the 
Mid- Atlantic ridge between lat. 9° and 18^ N., and is estimated 
to cover an area of about 279,000 square miles; the deepest 
sounding recorded within it is 3309 fathoms. 

Bailey Deep lies in the North- West Pacific, between the 
Brooke and the Murray Deeps, on the Tropic of Cancer. It is 
estimated to cover an area of about 241,000 square miles, and 
the deepest sounding recorded in it is 3432 fathoms. 

Jeffrey Deep, in the eastern Indian Ocean, extends in 
a narrow band round the southern and western coasts of 
Australia, and as laid down on the map at present is estimated 
to cover an area of about 228,000 square miles. It is based on 
nine widely scattered soundings in the southern portion and 
four soundings closer together at the northern end, leaving a 
long stretch where no soundings have been taken. Further 
investigation may show that what is now regarded as one 
continuous deep is really two distinct deeps. 

Belknap Deep lies in the Central Pacific, extending from 
about lat. 12 to 17' N., and covering an area estimated at 
about 165,000 square miles. Near the centre of the deep a 



,v DEPTHS AND DEPOSITS OF THE OCEAN 143 

rise based on a sounding in 2600 fathoms occurs between two 
soundings in 3100 fathoms, and the floor of the deep sinks from 
this rise towards the east to the maximum depth of 2)ZZ7 
fathoms. 

C/mn Deep hes in the North Atlantic between lat. 20" and Chun Deep. 
29^ N., and is very pecuHar in outhne ; it is estimated to cover 
an area of about 159,000 square miles, and the greatest depth 
is 3318 fathoms. 

Challenger Deep lies to the east of the Ladrone Islands in challenger 
the western Pacific, and extends from lat. 11' to nearly 20° N., ^^'"^i"- 
covering an area estimated at about 129,000 square miles. In 
1875 the "Challenger" recorded a depth of 4575 fathoms 
between Guam and the Pelew Islands, and in 1899 the United 
States steamer " Nero" took a sounding in 5269 fathoms to the 
south-west of Guam, which is the deepest sounding hitherto Deepest 
recorded. The 4000-fathoms area extends in a narrow trench bounding. 
as far to the north-east of the "Nero" sounding as the 
"Challenger" sounding is south-west of it, and a small isolated 
area occurs still farther north, based on a single sounding in 
4204 fathoms. At a comparatively very short distance from 
this deep trench is a pronounced rise within the deep based on 
three soundings : one in 1800 fathoms and two in 1000 fathoms ; 
another slight rise is based on a sounding in 2900 fathoms. 

The remaining deeps are smaller, and need not be referred 
to in detail, their position being clearly shown on the accom- 
panying map (Map II.). Attention may be drawn, however, 
to the great depth of the Planet Deep, situated in the tropical 
Pacific between the Solomon Islands and New Pommerania, in 
which a sounding in 4998 fathoms was recorded in 19 10 by the 
German survey ship "Planet" a short distance to the west of 
Bougainville Island. 

2. Deep-Sea Deposits 

The systematic investigation of deep-sea deposits was first First 
undertaken by Sir John Murray during the "Challenger" Ex- sJudy'oV 
pedition, and the only standard work dealing with the whole ™_f^^".^^ 
subject is Murray and Renard's " Challenger''' Report on Deep- ' 
Sea Deposits, published in 1891. That Report was not based 
merely on the deposit-samples brought home by H.M.S. 
" Challenger," though the detailed descriptions were limited 
to those samples, but included the results of the examination 
of samples collected by many other ships, received at the 



144 



DEPTHS OF THE OCEAN 



Number of 
deposit- 
samples 
examined. 



Composition 
of marine 
deposits. 



" Challenger" Office from the British Admiralty and from many- 
other British and foreign sources. Since the publication of the 
" Challenger "Report, deposit-samples collected by H.M. survey- 
ing ships and by British cable ships, as well as by many ships 
belonging to other nations, have been forwarded to the 
"Challenger" Laboratory for study, so that nearly all the 
samples of deposits procured from deep water over the ocean's 
floor have passed through our hands, and are available for the 
preparation of maps showing the distribution of the different 
types of deposits, and for the determination of the various 
constituents entering into the composition of deep-sea deposits. 
How extensive this material is may be surmised from the fact 
that nearly 12,000 deposit-samples have been examined in the 
" Challenger" Office. Some of these samples were very small, 
in a few cases insufficient even to indicate the type of deposit ; 
but the great majority sufficed for the determination of the 
deposit-type, and of the percentage of calcium carbonate, while 
a very large number were available for detailed study and 
description. The samples have all been dealt with in a 
uniform manner, the methods of examination and description 
fully explained in the " Challenger " Report having been adopted 
throughout, for, notwithstanding the large amount of sounding- 
work carried on since that Report was published, the general 
results, the classification, and the nomenclature given therein 
have been fully substantiated and found quite adequate in every 
respect, no new types having been discovered. 

In this place we are dealing only with deep-sea deposits, i.e. 
those occurring in depths greater than 100 fathoms, the littoral 
and shallow- water deposits found in depths less than 100 
fathoms being excluded. It may be stated, however, that these 
shallow-water and shore deposits near land are principally made 
up of relatively gross materials directly derived from the 
adjacent coasts, and from rivers pouring their waters and 
detritus into the ocean. Coral sands prevail near coral reefs. 
Volcanic sands off volcanic islands, and continental detritus near 
the embouchures of great rivers. All these materials become 
finer in texture with increasing distance from land, and in the 
greater depths of the ocean. 



The constituents entering into the composition of deep-sea 
deposits may conveniently be divided into two classes : (A) 
those of organic origin, precipitated by organisms from the dis- 
solved constituents of sea- water, and (B) those of inorganic 



IV DEPTHS AND DEPOSITS OF THE OCEAN 145 

origin, derived from (i) the decomposition of terrestrial and 

submarine rocks, (2) extra- 
terrestrial sources, (3) pro- 
ducts synthesized at the 
bottom of the sea. 

Organic remains belong- Materials of 
ing to the vegetable kingdom "^g^™'^ ongi"- 
are on the whole compara- 
tively rare on the sea-floor, 
when compared with those 
belonging to the animal 
kingdom ; still, in the neigh- 
bourhood of land, vegetable 
matter, branches of trees, piant remains 
leaves, fruits, etc., may be 
carried into deep water 
through the agency of large 
rivers, storms, off- shore 
winds, etc., along with the 
shallow water. Similarly 




in marine 
deposits. 



Fig. 108. 
Discosphara thomsoni, Ostenfeld. 



From the surface 



remains of sea-weeds 
in coral-reef re- 
gions, the re- 
mains of algae 
which lived on 
the reefs, such 
as LithotJiani- 
niuin and Coral- 
Una, occur in 
the deposits in 
the vicinity. But 
the most con- 
stant compon- 
ents of vegetable 
origin are the 
remains of algse, 
which secreted 
either calcium 
carbonate or 
silica from the 
surface waters 
of the ocean to 
form their hard 
parts, viz. the calcareous coccospheres and rhabdospheres (see 




Fig. 109. 

Rhabdosphcera claviger, Murray and Blackman. 



From the surface ( " "/* " ). 



146 



DEPTHS OF THE OCEAN 



Figs. 108 and 109) characteristic of tropical and sub-tropical 
regions, and the siliceous diatoms characteristic of extra-tropical 
regions. While the diatom remains are so abundant in the deposits 
of the Southern Ocean and of the North Pacific as to form a 
distinct deposit-type (Diatom ooze), the remains of the pelagic 
calcareous algae are always overshadowed by the abundance of 




^^ 




Fig. no. 
Eucoronis challengeri, Haeckel. From the surface (magnified). 

the remains of pelagic foraminifera and mollusca in the deposits of 
the warmer regions of the ocean. These pelagic calcareous algae 
are so fragile in texture, that it is principally their broken-down 
parts (coccoliths and rhabdoliths) that occur in the deposits ; in 
certain favourable localities coccospheres of small size may be 
fairly numerous, but rhabdospheres are practically unknown in 
deep-sea deposits, being apparently easily dismembered, and the 
same remark seems to apply to the large-sized coccospheres. 



DEPTHS AND DEPOSITS OF THE OCEAN 147 
Traces of albuminoid orP:anic matter may be found in most Albuminoid 

'-* matter. 




Fig. III. 
Staitracanfha miirrayana, Haeckel. From the surface (magnified). 

deep-sea deposits, especially in the neighbourhood of land, and 

1 





^r^rrrrrr 





Fig. 112. 

Hexancistra qiiadricuspis , Haeckel. 

From the surface (magnified). 



Fig. 113. 
Lampro7nitra huxleyi, Haeckel. 
From the surface (magnified). 



may be either of animal or vegetable origin ; a greenish organic 
matter is generally associated with the glauconite in the Green 



148 DEPTHS OF THE OCEAN 

sands. The benthonic deep-sea animals live by eating the mud 
or ooze covering the ocean-floor, and appear to find all the 




Fig. 

Haliomma ivyvillei, Haeckel. 



From the surface (magnified). 



Animal 
remains in 
marine 
deposits. 



Siliceous 
remains. 



nourishment they require therein. The excreta of these animals 
are associated with a certain amount 
of slimy albuminoid matter, and in cer- 
tain localities these excreta become so 
numerous that the term " coprolitic 
mud " has been proposed for the 
deposits containing them. 

The animal remains found in deep- 
sea deposits are either siliceous or 
calcareous, those of a chitinous char- 
acter being extremely rare, if not 
entirely absent. The siliceous remains 
of radiolaria (see Figs, no to 117) 
and the spicules of siliceous sponges 
are widely distributed over the ocean- 
floor, the radiolarian skeletons being so abundant in certain 
regions as to make up a very large part of the deposit, which 




Fig. 115. 
Lithoptera darwinii, Haeckel. 
From the surface (magnified). 



,v DEPTHS AND DEPOSITS OF THE OCEAN 149 

is then called Radiolarian ooze ; sponge spicules, though present 
in nearly every bottom-sample examined by us from deep and 
shallow water, very seldom take any considerable part in the 
formation of the deposits. 

The calcareous remains of foraminifera, corals, alcyonaria, Calcareous 
annelids, Crustacea, echinoderms, bryozoa, molluscs, tunicates, '■'^"^^'"^• 
and fishes seem to bulk more largely in deep-sea deposits than 
the siliceous remains. The Globigerina and Pteropod oozes and 

the Coral muds 

and sands owe 

their names to 

abundance in 




Fig. 116. 
Clathrocaniuin regintv, Haeckel. From the surface (magnified). 



Cinclopyra m is infiindi- 

hulum, Haeckel. From 
the surface (magnified). 

them of the re- 
mains of pelagic 



foraminifera (see 
Figs. 1 18 to 121), 
of pelagic molluscs (Figs. 122 and 123), or of coral fragments, 
while the valves of ostracods (Figs. 124 and 125), the spines 
of echinoids, the spicules of alcyonaria and tunicates, and 
the otoliths of fishes are among the most constant of the 
calcareous remains occurring in the deposits, though rarely 
found in any great abundance. Reference may also be made to 
the teeth of sharks (see Figs. 126 and 127) and the earbones of 
whales (see Figs. 128 and 129) found occasionally in all deposits, 
but characteristically in the Red clay areas especially of the 



I50 DEPTHS OF THE OCEAN 

Pacific Ocean, which have evidently lain there for a long period 




Fig. ii8. 
Globigerina bulloides, d'Orbigny. From the surface (magnified). 



of time, having become much decomposed or deeply impregnated, 
and in many cases thickly coated, by the peroxides of manganese 



IV DEPTHS AND DEPOSITS OF THE OCEAN 151 

and iron. It is remarkable how very few fish bones other than 
teeth and otoHths occur in marine deposits. 

The inorganic materials entering into the composition of Materials of 
deep-sea deposits may be conveniently considered under three o^J'^frT^''^ 




Fig. 119. 
Orbuli?ia utiiversa, d'Orbigny. From the surface (%"). 



heads: (i) terrestrial, (2) extra-terrestrial, and (3) secondary or 
chemical products. 

The terrestrial materials are either of volcanic or continental Terrestrial 
origin, the former being derived from submarine and subaerial 
eruptions, and, by reason of their areolar structure, widely 



Volcanic 
products. 



152 



DEPTHS OF THE OCEAN 



distributed over the ocean-floor, the latter being derived from 
the disintegration of continental land through atmospheric and 
physical agencies and distributed in comparatively close proximity 
to that land. Of volcanic products the most characteristic is 
pumice, which may float for a long time in the surface waters of 




Fig. 120. 
Hastlgerina pelagica, d'Orbigny. From the surface (\°). 

the ocean and may be carried far from its original source before 
finally becoming water-logged and sinking to the bottom. 
While floating on the surface these stones are knocked against 
one another by the waves, and the broken-off fragments fall to 
the bottom. Three varieties of pumice have been recognised 
among the fragments from the sea-bottom : liparitic, basaltic 



IV DEPTHS AND DEPOSITS OF THE OCEAN 153 

or basic, and andesitic. After pumice, the most striking volcanic 
products are fragments of basic volcanic glass (sideromelan) 
nearly always partly, sometimes entirely, decomposed and 
altered into palagonite, together with palagonitic tufas, generally 
associated with the deposition of the peroxides of manganese 
and iron, besides basaltic and other lapilli and volcanic ashes. 
Great slabs have been dredged showing sometimes distinct 




Fig. 121. 

pelagica, d'Orbigny. 



From the surface {^x)- 



layers produced by showers of volcanic ashes. Minerals of 
volcanic origin (volcanic dusts) may be carried great distances 
by the winds, and ultimately find a resting-place on the bottom 
of the sea. 

The continental products consist of fragments of continental Continental 
rocks and the minerals derived from their disintegration, the Products. 
characteristic mineral species being quartz. The rock-fragments 
are usually found only in close proximity to the continental 
land-masses, though exceptionally found in deep water far from 



154 



DEPTHS OF THE OCEAN 



Extra- 
terrestrial 
materials. 



land in those regions of the ocean affected by floating icebergs. 
The dust from deserts, Hke volcanic dusts, may be carried by 
wind to great distances from land, and can be detected in deep- 
sea deposits, for instance, off the west coast of Africa. 

The materials of extra-terrestrial origin, though extremely 
interesting, do 

not bulk largely ^'^^^^m ^ h 

in marine de- ^' ' 

posits ; indeed 
they are rather 
of the nature of 
rarities, and are 
noticed most 
abundantly in 
Red clay areas 
where, for many 
reasons, it is 
believed the rate 
of deposition is 

at a minimum. They consist of minute black metallic spherules 
and brown chondritic spherules, which may be extracted by 
the aid of a magnet when the Red clay deposit is reduced to 
a fluid condition by admixture of water. The black spherules 
(see Figs. 130 and 131) sometimes have a shining metallic 




V 



Canna/'/a lamarckii. Per 

of this species are occasionally met with 



Fig. 122. 
and Les. (From Steuer. ) 



The fragile shells 
deep-sea deposits. 




Fig. 123. 

Pterotrachea coi'onafa, Forsk. (From Leuckart, after Steuer. ) This species has no shell, 
and therefore does not enter into the composition of deep-sea deposits. 

nucleus of native iron (or an alloy of iron, cobalt, and nickel), 
surrounded by a shell of brilliant magnetic oxide of iron, to 
which the magnetic properties of the spherules are due. The 
brown spherules (see Figs. 132 and 133) have the lustre of 
bronze externally, and have a finely lamellatefd crystalline 
structure, with blackish -brown inclusions of magnetic iron, 
which account for their extraction by the magnet. A cosmic 



IV DEPTHS AND DEPOSITS OF THE OCEAN 155 

origin is attributed to both forms of magnetic spherules, which 
are supposed to have been thrown off by meteorites, or falHng 
stars, in their passage through our atmosphere. 

The secondary products entering into the composition of Secondary 
deep-sea deposits are (i) clay, (2) manganese nodules, (3) barium P'^°'^"^ts. 

and barium nodules, (4) 
glauconite, (5) phosphatic 
concretions, and (6) zeo- 
lites. 

The clayey matter in Clay. 
the deposits near land 
may have been trans- 
ported by rivers, etc., 
from the land, but most 
of the clayey matter 
present in the deposits 
far from land is believed 
to have been derived from 
the decomposition under the action of water of eruptive and 
metamorphic rocks and minerals, especially pumice and volcanic 
glass. The deep-sea clays, some of which are mostly made up 
of these decomposing volcanic materials, are usually coloured 
a reddish -brown by the oxides of manganese and iron — 

products of the de- 




124. 

Krithe producta, Brady. From the bottom-deposits 
(magnified). 




Fig. 125. 

From the bottom-deposits (magnified). 



composition of the 
same rocks that gave 
rise to the clayey 
matter — and a com- 
paratively small 
amount of clay may 
give a clayeycharacter 
to the deposit. 

The oxides of iron Manganese 

and manganese are "°'^"^^^- 
widely distributed in 



Cy there dictyon, Brady. , ^ ^ ,. 

marine deposits, and 
especially in deep-sea deposits. They occur in minute grains, 
and act as colouring matter in nearly all deep-sea clays, 
and in certain abyssal regions of the ocean they form con- 
cretions of larger or smaller size, which are among the most 
striking characteristics of the oceanic Red clay. Sometimes 
the oxides cover consolidated masses of tufa, fragments of 
rocks, portions of the deposit, branches of coral and other 



156 



DEPTHS OF THE OCEAN 



calcareous remains, or form irregular concretionary masses, 
though the commonest form is that of more or less rounded 
nodules (see Figs. 134 and 135), which at any one station have a 
general family resemblance and differ in form and size from 
those taken at another station, looking like marbles at one 
place, like potatoes or like cricket balls at other places. Gener- 
ally the nodules are concretions formed around a nucleus, con- 




FiG. 126. — Tooth of Carcharodon megalodon. 
"Challenger" Station 281, South Pacific, 2385 fathoms. 

sisting of a shark's tooth or whale's earbone, or portions of teeth 
or bone, a piece of pumice or fragment of volcanic glass, etc., 
though sometimes no nucleus could be detected. These nodules 
of iron and manganese are classed with the impure variety of 
manganese known as wad or bog manganese ore, and the 
greater part of the manganese and iron is believed to have been 
derived directly, along with clay, from the alteration of the rock- 
fragments and mineral particles containing manganese and iron, 
especially of those of volcanic origin, which are spread over the 



IV DEPTHS AND DEPOSITS OF THE OCEAN 157 

ocean-floor. Where basic volcanic rocks are in process of 
decomposition, manganese nodules may be relatively abundant 

in shallow water, and they are never 
numerous in Globigerina oozes, ex- 
cept where volcanic material is 
present in some abundance in the 
deposit. 

Sulphate of barium has been Barium. 
found to be present in most marine 
deposits and in manganese nodules 
in small quantities ; in terrigenous 
deposits up to about o. i per cent, in 
manganese nodules slightly more, 
and in Red clays up to about i per 
cent. Small round nodules have 
been trawled off Colombo, in 675 
fathoms, containing 75 per cent of 
barium sulphate. 

-Glauconite occurs in the terri- Giauconite. 
genous deposits typically in the form 
of minute rounded grains of a green- 
ish colour, usually associated with greenish or brownish casts of 
calcareous organisms (foraminifera, etc.) ; in fact, the rounded 




Fig. 127. — Tooth of Oxvrjj/xa 

TRIGODON. 

"Challenger" Station 276, Tropical 

Pacific, 2350 fathoms. 





Fig. 128. — Petrous and Tympanic Bone 
of ziphws cavirostris. 

"Challenger" Station 286, South Pacific, 
2335 fathoms. 



Fig. 129. — Section of a Mangan- 
ese Nodule, showing a Tym- 
panic Bone of Mesoplodon in 
the Centre. 
"Challenger" Station 160, Southern 
Ocean, 2600 fathoms. 



trace 



green grains are supposed to be casts which have lost all 

of the enveloping calcareous chambers. The individual grains 

of glauconite do not exceed one millimetre in diameter, though 



158 DEPTHS OF THE OCEAN 

occasionally they are cemented into nodules, several centimetres 
in diameter, by a phosphatic substance ; the grains are always 
rounded, often mammillated, hard, dark green, or nearly black, 
with sometimes a dull and sometimes a shining surface. Mixed 

with the rounded 
grains are pale 
green, pale grey, 
white, yellow and 
brownish internal 
casts ot the cavities 
and chambers of 
calcareous organ- 
isms, often asso- 





FiG. 130. — Black Spherule 
WITH Metallic Nucleus 
(¥)■ 

" Challenger " Station 285, 
South Pacific, 2375 fathoms. 



"iG. 131.— Bla( K Spue 
WITH Metallic Nucleus riated with 

en 

' Challenger " Station 9, North 
Atlantic, 3150 fathoms. 



amorphous organic 
matter of a brown- 
ish - green colour. 
Glauconite is principally developed in the interior of foramini- 
ferous shells and other calcareous structures, the initial stages in 
the formation of glauconite being probably due to the presence 
of organic matter in the interior of these shells. Glauconite is 




Fig. 132.— Spherule of Bronzite 

(V). 

"Challenger" Station 338, South 
Atlantic, 1990 fathoms. 




Fig. 133. — -A Lamella of a Spherule 

OF Bronzite (highly magnified). 

"Challenger" Station 338, South Atlantic, 

1990 fathoms. 



always associated with terrigenous mineral particles and rock- 
fragments, the decomposition of which, under the action of sea- 
water, would yield the chemical elements subsequently deposited 
•in the form of glauconite in the chambers of foraminifera and 
other calcareous organisms. The excreta of echinoderms appear 
sometimes to be converted into glauconite. 



IV DEPTHS AND DEPOSITS OF THE OCEAN 159 

Associated with the glauconite in certain localities, more Phosphatic 
especially off the Cape of Good Hope and off the Atlantic coast '^°"'^'^^ti°"^- 
of the United States, irregular concretions, largely made up of 
phosphate of lime, have been dredged. The concretions vary 
greatly in size and form, with a greenish or brownish glazed 
external surface, and are made up of 
heterogeneous fragments derived from 
the deposit containing the concretions 
(grains of glauconite and other minerals 
or remains of organisms), cemented 
by phosphatic material, which consti- 
tutes the principal part of the concre- 
tions. When the cemented particles 
are purely mineral, the phosphatic 
matter acts simply as a cement, but 
when the remains of calcareous organ- 
isms are included in the concretions, 
the phosphatic material plays a more 
important part, filling the internal 
chambers, and often the calcium car- 
bonate of the shell is pseudomor- 
phosed into calcium phosphate. When 
the filling up of a foraminifer, for 
example, and the pseudomorphism of 
its shell, are complete, the phosphate, 
attracted around this little centre con- 
tinues to be added at the surface, and 
thus a phosphatic granule is formed, 
the external appearance of which no 
longer recalls that of the organism 
around which the phosphate has 
grouped itself. These phosphatic con- 
cretions occur chiefly along coasts 
bathed by waters subject at times to 
great and rapid changes of tempera- 
ture, which cause the destruction on a 

large scale of marine life, the decomposition of the organic 
remains, sometimes thickly covering the sea-floor in such locali- 
ties, giving rise to the phosphate of lime to be permanently 
fixed in the phosphatic nodules. 

Just as the silicate glauconite occurs in the terrigenous Phiiiipsite. 
deposits, and is supposed to be a secondary product derived 
from the decomposition of continental rock fragments, so the 




Fig. 134. — Manganese Nodule 
with scalpellvm darwinil 
growing on it. 
" Challenger" Station 299, South 
Pacific, 2160 fathoms. 



i6o 



DEPTHS OF THE OCEAN 



silicate phillipsite occurs in the pelagic deposits, and is supposed 
to be a secondary product derived from the decomposition of 
volcanic rock fragments. Phillipsite is found in the various 
kinds of deposits in the deep water of the Central Pacific and 
Central Indian Ocean far from land, and is most abundant in 
some Red clay areas. It occurs in crystalline form, either as 
simple isolated microliths, crossed twins, irregular groups, or 
aggregated into spherolithic groups in which these zeolitic 
crystals are entangled together so as to form crystalline globules 
of sufficient size to be distinguished by the naked eye. The 
distribution of these crystals of phillipsite coincides with that of 
basic volcanic glasses and basaltic lapilli over the ocean-floor, 
the decomposition of which, under 
the action of sea-water, would give 
rise to the materials afterwards 
deposited in a free state as zeolitic 
crystals and aggregates. 




Radio-active Professor Joly has examined 

substances. ^^^ their radium contents a number 
of deposit-samples supplied by Sir 
John Murray. He finds that the 
deep-sea deposits are much richer 
in radium than the average terres- 
trial rocks. The Red clays and 
the Radiolarian oozes, which are 
laid down in deep water far from 
land, contain much more radium 
than the calcareous deposits like the Pteropod and Globigerina 
oozes. The radio-activity and percentage of calcium carbonate 
in the deposits stand in an inverse ratio to each other, and the 
■ Blue muds contain less than the calcareous oozes, though more 
than the continental rocks. It seems evident that the quantity 
of radio-active substances, of manganese nodules, with earbones 
of whales and sharks' teeth, of zeolitic crystals and cosmic 
spherules, is greatest where, for other reasons, we believe the 
rate of deposition to be least. 

Deep-sea In the neighbourhood of emerged land the material derived 

deposit types, f^^^^ |.j^^j- \^^^ jg spread over the sea-floor, becoming finer and 

finer in texture with greater distance and depth, whereas in 

the central regions of the great ocean basins land-detritus may 

be almost totally absent from the deposits, while the calcareous 



Fig. 135. — Manganese Nodule with 
TWO Tunicates and a Brachiopod 
attached. 
"Challenger" Station 160, Southern 
Ocean, 2600 fathoms. 



IV DEPTHS AND DEPOSITS OF THE OCEAN i6i 

and siliceous shells and skeletons of pelagic or plankton organ- 
isms may greatly predominate. This fact affords a ready Classification, 
means of dividing marine deposits into two main classes, viz. 
Terrigenous Deposits, largely made up of detritus derived 
directly from emerged land, with the remains of benthonic 
organisms, and Pelagic Deposits, containing little if any land- 
detritus, but largely made up of the remains of pelagic organisms. 
The former class of deposits must therefore form a border, 
varying in extent according to circumstances, around all the 
land-masses and islands of the world, while the latter class of 
deposits occurs in those regions so far removed from the land- 
masses and islands that very little material derived directly 
from the land can reach the position where they are found. 
The dividing lines between these two classes of deposits, and 
between the various types included in them, are not sharply 
defined, but the different kinds of deposits merge gradually the 
one into the other, so that frequently two names, and in some 
cases even three names, might equally well be applied to the 
same sample. It is the terrigenous deposits laid down in close 
proximity to the land, and in enclosed seas like the Mediter- 
ranean, that are represented in the geological series of rocks, 
but it is extremely doubtful whether the pelagic deposits laid 
down in deep water far from land have any analogues among 
the geological strata. 

After a careful study of all the available samples, Murray and 
Renard gave the following classification of marine deposits : — 



Marine Deposits 

' Red clay 
Radiolarian ooze 
Diatom ooze 
Globigerina ooze 
Pteropod ooze 

Blue mud 
Red mud 
Green mud 
Volcanic mud 
Coral mud 



Shallow - ^^'■ater Deposits, 1 o j i 

K^fw^^.. 1..,,. wof«. ^.ovi.. I Sands, gravels, 
muds, etc. 



Deep- Sea Deposits, 
beyond loo fathoms. 



I. Pelagic Deposits formed 
in deep water removed 
from land. 



Terrigenous 
formed in 



Deposits, 
deep and 



between low water mark 
and loo fathoms. 



3. Littoral Deposits, between 1 ^ 1 

, • , J , .1 Sands, gravels, 

high and low water \ a \ 

° 1 muds, etc. • 

marks. j 



shallow water close to 
land-masses. 



l62 



DEPTHS OF THE OCEAN 



Terrigenous 
deposits. 



Blue mud. 



Green mud 

and sand. 



Red mud. 



Volcanic mud 
and sand. 



Coral mud 
and sand. 



Pelagic 
deposits. 



The Terrigenous Deposits are characterised, as already- 
stated, by the abundance of land-detritus, and are subdivided 
into the following types, viz. : — 

Blue Mud. — This is the predominant type of deposit in the 
neighbourhood of continental land, and is principally made up 
of land-detritus (quartz being the characteristic mineral species), 
which becomes less and less abundant with increasing distance 
from the land, until the Blue mud passes gradually into one of 
the types of pelagic deposits. 

Green Mud is a variety of Blue mud, distinguished by the 
abundance of grains of glauconite usually associated with 
phosphatic concretions, and is found most characteristically on 
the continental slopes off high and bold coasts where currents 
from different sources alternate with the season, as off the 
Cape of Good Hope, off the east coast of Australia, off Japan, 
and off the Atlantic coasts of the United States. In the lesser 
depths the amount of clayey and muddy matter decreases and 
the deposits are called Green Sands. 

Red Mud is a local variety of Blue mud found in the Yellow 
Sea and off the coast of Brazil, where the great rivers bring 
down a large amount of ochreous matter, to which the deposit 
owes its colour and its name. 

Volcanic Mud occurs off those coasts and islands where 
volcanic rocks prevail ; the volcanic mineral particles are larger 
and more abundant in the shallower water near the land, and 
the deposits there are called Volcanic Sands. 

Coral Mud is found in the vicinity of coral reefs and islands ; 
fragments derived from the disintegration of the reefs are 
larger and intermixed with less fine material in the lesser 
depths, and the deposits are then called Coral Sands. 

The Pelagic Deposits are characterised by the fact that, 
with the exception of Red clay, their composition is largely 
determined by the pelagic or plankton organisms, which secrete 
hard shells either of calcium carbonate or of silica, the pre- 
dominance of the remains of one or other of these classes of 
organisms giving the names to the deposits. In fact, the 
deposits may be divided into those that are calcareous and 
those that are siliceous, the calcareous deposits (Globigerina 
ooze and Pteropod ooze) being characteristic of tropical and 
subtropical regions, where there is abundant secretion of calcium 
carbonate by plankton organisms, the siliceous deposits (Diatom 
ooze and Radiolarian ooze) being characteristic of polar and 
other regions, where there is a large admixture of clayey matter 



IV DEPTHS AND DEPOSITS OF THE OCEAN 163 

in the surface waters, and where there is abundant secretion of 

silica by the plankton 
organisms. Over wide 
areas in very deep water, 
however, neither cal- 
careous nor siliceous 
remains predominate ; 
the basis of the deposit 
then becomes Red clay, 
consisting of clayey 
matter derived from the 
decomposition of vol- 
canic materials ; quartz 
particles, so abundant 
in terrigenous deposits, 
are rare or absent. 

The pelagic deposits 
are subdivided into the 
following types, viz. : — 

Pteropod Ooze. — In Pteropod ooze. 
the shallower waters, 
oceanic ridges and cones, 




Fig. 136. — Pteropod Ooze. 

Valdivia" Station 208, Indian Ocean, lat. 6° 54' N. 

long. 93° 28'. 8 E., 162 fathonis (magnified). 



on 



usually far from continental land 
especially within coral 
reef regions where 
warm water with small 
annual range occupies 
the surface, almost 
every surface organism 
which secretes a hard 
shell or skeleton is 
represented in the de- 
posit, the dead shells of 
pteropods and hetero- 
pods being character- 
istic, and the deposit is 
hence called Pteropod 
ooze (see Fig. 136). 
About 35 species of 
pteropods and 32 
species of heteropods, 
as well as pelagic gas- 
teropods (see pp. 172- 
173), are known to live in the surface waters of the tropics, and 




Fig. 137. -Gi.onicERiNA Ooze. 
Valdivia" Station 45, Atlantic, lat. 2° 56'.4 N., 
long. 11° 40'. 5 W., 2728 fathoms (magnified). 



Globigerina 
ooze. 




f^^^ 



Fig. 138.— Globigerina Ooze. 

Station 162, Southern Ocean, lat. 43° 44'. 4 S. 



Valdivia 

long. 75" 33'- 7 E. 



1878 fathoms (magnified). 



164 DEPTHS OF THE OCEAN 

the shells of all these species may occur in the Pteropod ooze, 

but the extent of this 

type of deposit is not 

great. Shelled ptero- 

pods, except Lijuacina, 

are not found in the 

polar oceans. 

Globigerina Ooze. — 
The average depth of 
the ocean is about 2000 
fathoms, and the most 
widely distributed of 
the deposits in these 
average depths is Glo- 
bigerina ooze (see Figs. 
137 to 139), which is 
made up largely of the 
dead shells of surface 
foraminifera, the genus 
Globigerina often 
greatly predominating, 
hence the name. About 
twenty species of pelagic 
foraminifera (see p. 172) 
inhabit the surface 
waters of the tropical 
oceans, and their dead 
shells are found in the 
Globigerina ooze ^ and 
also in the Pteropod 
ooze, but towards the 
Arctic and Antarctic 
regions only one or two 
dwarfed species occur 
in the surface and sub- 
surface waters. I n very 
deep water, even within 
the tropics, the calcare- 
ous shells do not accu- 
mulate on the bottom, 

1 The names " Biloculina clay" and ." Orbulina ooze" will lie found in the literature of 
marine deposits, but these have been described from samples which had been passed through 
fine sieves, the larger shells having been retained while the smaller ones had passed through 
the meshes. 




Valdivia ' 
long, 



Fi<;. 13M. 1,1^ 'i.^.ij i\ > I )ozE. 
Station 154, Southern Ocean, lat. 6 
61° 15'. 9 E. , 1940 fathoms (magnified). 



45'.2 S. 



-f>' 



IV DEPTHS AND DEPOSITS OF THE OCEAN 165 

being apparently remov^ed through the solvent action of sea- 
water, and with in- 
creasing depth the 
Globigerina ooze 
passes gradually into 
another pelagic type, 
usually Red clay. 

Diatom Ooze. We Diatom ooze. 

have indicated that in 
the colder regions of 
the ocean, as in the 
great circumpolar 
Southern Ocean and 
along the northern 
border of the Pacific, 
diatoms flourish abun- 
dantly in the surface 
waters, and where de- 
trital matters are not 
very large in amount 
their dead frustules, 
falling to the bottom, 
make up a large part 
of the deposit called 
^^>t. I& Diatom ooze (see Fig. 

■/// Radio larian Ooze Radioiaiian 

;/ (see Fig. 141) has not °°^^- 

been recorded from the 
Atlantic Ocean, but is 
characteristic of deep 
water in the tropical 
regions of the Pacific 
and Indian Oceans, 
, where the surface 

\:,^' waters have rather a 

low salinity and carry 
clayey matter in sus- 
pension. It may be 
Fig. 141.-RA1.10LARIAN Ooze. regarded as a variety 

Valdivia" Station 237, Indian Ocean, lat. 4° 45' S. , P-r^ A \ «- ' ' 

long. 48° 58'. 6 E., 2772 fadioms (magnified). OI KeQ Clay COntammg 



Fig. 140. — Diatom Ooze. 
Valdivia" Station 140, Southern Ocean, lat. 54° 
long. 22° 13'. 2 E., 2207 fathoms (magnified). 



' It may be noted that Flint has recorded Diatom ooze from the tropical Pacific, but his 
samples have since been examined and classed by us as Radiolarian ooze. 



i66 DEPTHS OF THE OCEAN 

many radiolarian skeletons. The frustules of diatoms and 
skeletons of radiolarians may occur in all deposits, but gener- 
ally they do not become characteristic or predominant when 
calcareous shells are present in large numbers. 

Red Clay is characteristic of great depths, say beyond 2700 
fathoms (as Globigerina ooze is characteristic of moderate 
depths, between 1000 and 2500 fathoms), and is the most widely 
distributed of all the deep-sea deposits, covering a larger area 
of the sea-floor than any other deposit type. The basis of the 
deposit is the hydrated silicate of alumina, or clay, derived 
principally from the decomposition and disintegration of pumice 
and other volcanic products long exposed to the action of sea- 
water, often associated with secondary products derived from 
the same source, such as manganese-iron nodules and phillipsite 
crystals. Calcareous remains may be totally absent in the 
greatest depths, while in lesser depths the percentage of calcium 
carbonate may approach 30, and the deposit then passes gradu- 
ally into Globigerina ooze. If the calcium carbonate in a 
Globigerina ooze or a Pteropod ooze be removed by weak acid, 
the residue resembles closely a Red clay. In other places the 
siliceous remains of radiolaria may increase to such an extent 
that the Red clay merges gradually into Radiolarian ooze. The 
rate of accumulation is evidently at a minimum in the Red clay 
areas, for the calcareous shells falling from the surface waters 
have been gradually removed in solution either before, or 
immediately after, reaching the bottom ; the ear-bones of whales 
and teeth of sharks (some of them belonging to extinct species) 
are there found in the greatest profusion, impregnated with and 
coated by the peroxides of manganese and iron ; and there also 
occur in greatest abundance (though always rare) minute 
metallic and chondritic spherules supposed to have fallen from 
interstellar space, and found there more abundantly simply 
because of the sparse deposition of other materials. Radio- 
active substances are also found more abundantly in Red clay 
than in any other marine deposit, or in any continental rocks. 

A few facts relating to the horizontal distribution of marine 
deposits may now be Indicated. The terrigenous deposits 
include a number of varieties, but as a whole they surround all 
continents and islands in all latitudes, and extend to varying 
distances from the shore. The Coral muds and sands included 
in this class are limited to the coral-reef regions of tropical and 
subtropical latitudes, and the presence of the calcareous shells 



IV DEPTHS AND DEPOSITS OF THE OCEAN 167 

of pteropods and heteropods and pelagic foraminifera in terri- 
genous deposits indicates approximately temperate or tropical 
latitudes ; in the Arctic and Antarctic regions these shells are 
absent from the deposits. Green muds and sands appear to be 
limited to regions where there is a wide range of temperature 
in the surface waters of the ocean, while Red muds are limited 
to those localities where a large amount of ochreous matter is 
carried into the sea by rivers, and Volcanic muds and sands are 
limited to the neighbourhood of volcanic centres, both subaerial 
and submarine. But the most widely distributed of all the 
terrigenous types is Blue mud, which occurs in both the Arctic 
and Antarctic regions, and along the shores of continents and 
continental islands throughout the world, where not displaced 
by one or other of the varieties just mentioned. 

Broadly speaking, the terrigenous deposits close to land in 
shallow water contain more and larger mineral fragments than 
those farther removed from the land and in deeper water. 
Where great rivers enter the sea the terrigenous deposits may 
extend very far seaward, and a Blue mud may occupy the whole 
of the continental slope, extending perhaps some distance out 
over the deep bed of the ocean. On the other hand, along 
high and steep coasts oceanic conditions may approach close to 
the shore, and a Blue mud may pass into a Green mud or into a 
Pteropod ooze, and finally into a Globigerina ooze along the 
continental slope. 

Turning to the pelagic deposits, we find that Pteropod ooze 
is limited to the tropical and subtropical regions, usually in the 
neighbourhood of oceanic islands and on the summits and sides 
of submarine elevations ; it is found in relatively shallow water, 
and covers a relatively small extent of the ocean-fioor. 

Globigerina ooze is much more widely distributed ; in fact, it 
covers an area of the entire sea-fioor second only to that occu- 
pied by Red clay, extending as far north as lat. 72° N. in the 
Norwegian Sea and as far south as lat. 60° S. in the South 
Atlantic. A Globigerina ooze from a tropical locality differs 
greatly from one taken towards the polar regions, for the 
tropical sample may contain the representatives of more than 
twenty species of pelagic foraminifera as well as many species 
of pelagic molluscs, whereas the polar sample would include 
only one or two species of pelagic foraminifera and no pelagic 
molluscs. Globigerina ooze is the predominant type of deposit 
in the North Atlantic, covering all the deeper parts of that 
ocean except for two areas of Red clay, and it is there found 



i68 DEPTHS OF THE OCEAN 

in much deeper water than in any other of the great ocean 
basins. 

Diatom ooze occurs typically only in extra-tropical regions, 
forming a broad almost circumpolar band in the great Southern 
Ocean, outside the zone of Blue mud bordering the Antarctic 
continent, and a smaller band along the extreme northern border 
of the Pacific Ocean, along the Alaskan and British Columbian 
coasts of North America, and the Kamtchatkan and Japanese 
coasts of Asia and the intervening Aleutian Islands. 

Radiolarian ooze covers the sea-floor in certain portions of 
the tropical regions of the Pacific and Indian Oceans, being 
apparently entirely unrepresented in the Atlantic ; it occurs in 
a band of varying width in the equatorial eastern Pacific, 
approaching comparatively close to the shores of Central 
America, and in other smaller isolated areas. 

Red clay is the most characteristic and most extensive of 
the pelagic deposits, occupying the deepest portions of the great 
ocean basins except in the polar regions, extending beyond 
lat. 50'' N. and S. in the Pacific, and between lat. 40° N. and S. 
in the Atlantic. It is the typical deposit of the great Pacific 
Ocean, attaining there its maximum development, and being 
associated over wide areas with the characteristic manganese 
nodules; in the Indian Ocean it is also associated with much 
manganese, and therefore usually of a dark chocolate colour, 
while in the Atlantic it is generally intermixed with less 
manganese and usually of a light red-brown colour. 

As regards the vertical distribution of the deposits, we have 
already indicated how gradual is the transition between the 
various types and classes, so that frequently two or more names 
might be used to characterise samples from the border regions. 
It is therefore evident that no definite limits of depth can be 
assigned to the different types of deposits, but their general 
distribution m.ay be broadly outlined. 

The terrigenous deposits have for their upper limit the 
shore-line, while their lower limit varies according to local con- 
ditions. We have already pointed out that in certain localities 
Blue mud may be restricted to the continental slope within 
depths less than 1000 fathoms, while in other localities it may 
extend far into the abysmal area in depths exceeding 2000 
fathoms, and in some places approaching 3000 fathoms. Coral 
mud may extend into depths approaching 2000 fathoms before 
passing gradually into a Globigerina ooze, but sometimes it 
merges into Pteropod ooze in depths less than 1000 fathoms. 



IV DEPTHS AND DEPOSITS OF THE OCEAN 169 

while in the lagoons of coral islands it may be found in a few 
feet of water. Volcanic mud may be found extending into very 
deep water — in fact, some of the deepest Red clays might be 
called Volcanic muds, so abundant are the minute fragments of 
pumice and volcanic glass — but in the neighbourhood of volcanic 
islands the material from the land is generally masked by the 
accumulation of pelagic shells, and the Volcanic mud may pass 
into Pteropod ooze in depths of about 1000 fathoms, or into 
Globigerina ooze in depths of 1500 or 2000 fathoms. Green 
mud and Red mud generally occur in depths less than 1000 
fathoms, the seaward limit being about 1300 or 1400 fathoms. 

Of the pelagic deposits, Pteropod ooze is found in shallower 
water than any of the other types — from about 400 fathoms to 
about 1500 fathoms, its seaward limit being reached in about 
1700 or 1800 fathoms. Globigerina ooze may be found in all 
depths from about 400 fathoms to over 3000 fathoms, but 
occurs typically in depths between about 1200 and 2200 
fathoms, its deeper limit in the Pacific and Indian Oceans 
occurring at about 2800 or 2900 fathoms, while in the North 
Atlantic it is known in depths approaching 3500 fathoms. 
Diatom ooze occurs usually in depths of about 600 to over 
2000 fathoms, but in the North Pacific it is found in depths of 
4000 fathoms. Radiolarian ooze is a characteristically deep- 
water deposit, hardly known in depths less than 2000 fathoms, 
and covers the bottom at the greatest depths recorded by 
the "Challenger" and "Nero" in 4500 to over 5000 fathoms. 
Radiolarian ooze may, however, be regarded as a mere variety 
of Red clay, containing a notable proportion of these siliceous 
remains as a result of the favourable conditions in the surface 
waters. Red clay is the typical deep-water deposit, and covers 
wide areas in depths exceeding 2000 fathoms, occupying the 
sea-floor in all the "deeps" except in one or two cases in the 
North Atlantic, being displaced in certain parts of the Pacific 
and Indian Ocean by its variety, Radiolarian ooze. 

The rate of deposition of materials on the sea-floor is Rate of 
naturally beyond the range of direct measurement, at all events disposition. 
in deep water. The only observations bearing on this point 
have been recorded by Mr. Peake, who in 1903 on board the 
S.S. "Faraday" raised and repaired a telegraph cable lying in 
2300 fathoms in lat. 50^^ N. and long. 31° W. in the North 
Atlantic. This same cable had been lifted from a depth of 
2000 fathoms about 200 miles to the eastward in 1888 by 



ijo DEPTHS OF THE OCEAN chap. 

Mr. Lucas on board the S.S. "Scotia," and on portions of the 
cable recovered in 1903 being submitted to Mr. Lucas, he was 
quite convinced that no deterioration had taken place during the 
interval of fifteen years. This is ascribed to the fact that the 
cable when lifted in 1888 was covered by Globigerina ooze, 
which is believed to act as a preservative upon cables in 
contact with it. As in 1888 the cable had been submerged 
for thirteen years, this implies a rate of deposition of one 
inch of the deposit in some period less than thirteen years ; 
but as the deterioration noted in the cable, especially in the 
hemp serving, had probably taken some years to effect, it is 
perhaps fair to assume a period of ten years for the accumula- 
tion of a layer of the deposit one inch in thickness, in the 
position referred to. Another cable lifted from the bed of the 
equatorial Atlantic (lat. 2' 47' N., long. 30^ 24' W.) from a 
depth of 1900 fathoms in 1883, after having been submerged 
for nine years, was found to be in much better condition than 
the North Atlantic cables examined after having been laid for 
a similar period, and this is supposed to be due to the more 
rapid deposition of the Globigerina ooze in the warmer waters 
of the equatorial Atlantic than in the colder waters of the 
North Atlantic, so that the cable became more rapidly covered 
over by the Globigerina ooze.^ 

While, therefore, it may be assumed that the Globigerina 
ooze accumulates at the rate of about one inch in ten years in 
the central part of the North Atlantic in lat. 50° N., and at a 
still more rapid rate in the central part of the equatorial Atlantic, 
it would appear from the recent observations of the " Michael 
Sars " Expedition that the rate of deposition of sediment may 
be almost nil even at depths of 1000 fathoms in certain parts 
of the North Atlantic, where glaciated stones have been dredged 
in considerable quantities. Possibly, however, these glaciated 
stones may have been deeply covered by the ooze since the 
close of the glacial period, and may have been subsequently 
exposed by the action of deep tidal currents sweeping away the 
Globigerina shells from the top of a low ridge perhaps recently 
elevated by earth-crust displacements in the deep sea. We 
now know that tidal currents prevent the formation of muddy 
deposits on the top of the Wyville Thomson Ridge in depths 
of 250 to 300 fathoms, while just below the summit of the ridge 
on both sides mud is deposited. 

1 See Murray and Peake, On Recent Con/rihutions to our A'nozvledge of the Floor of the 
North Atlantic Ocean, extra publication of the Royal Geographical Society, London, 1904, 
pp. 21 and 22. 



IV DEPTHS AND DEPOSITS OF THE OCEAN 171 

As to the relative rate of accumulation of the different types 
of deposits, it may be assumed that the terrigenous deposits 
accumulate at a much more rapid rate than the pelagic deposits. 
Of the terrigenous deposits, the Blue muds situated near the 
mouths of large rivers may be supposed to accumulate at a 
relatively very rapid rate, for the various constituents of the mud 
show little trace of alteration, while the rate of deposition in 
the case of Green muds and sands must be much slower, since the 
mineral particles are generally profoundly altered, and there is 
an extensive formation of secondary products, like glauconite 
and phosphate of lime ; Coral muds and sands appear to accumu- 
late rapidly under certain conditions, and the same may be said 
of Volcanic muds and sands in the neighbourhood of active 
volcanoes, where the volcanic minerals are fresh and unaltered, 
but most of the deep-sea volcanic deposits far from land appear 
to accumulate at a relatively slow rate, for the volcanic particles 
show abundant traces of alteration accompanied by the deposi- 
tion of manganese peroxide. 

Of the pelagic deposits, the Globigerina and Pteropod oozes 
of tropical regions probably accumulate the most rapidly, from 
the greater variety of tropical pelagic species of foraminifera 
and molluscs, and the larger and more massive shells secreted in 
tropical as compared with extra-tropical regions. Diatom ooze 
appears to accumulate at a more rapid rate than Radiolarian 
ooze, since in addition to the siliceous remains it usually 
contains a considerable admixture of calcareous remains, but 
from all points of view it seems reasonable to suppose that the 
minimum rate of deposition of materials on the ocean-floor is 
reached in those characteristic Red clay areas farthest removed 
from continental land and in very deep water. The greater 
abundance of cosmic spherules, sharks' teeth, and ear-bones of 
whales, some of them belonging to extinct species, in the Red 
clays than in any other type of deposit, is ascribed to the fact 
that few other substances there fall to the bottom to cover them 
up. The state of profound alteration of the volcanic materials 
in the Red clay, accompanied by the secondary formation of 
clay, manganese nodules, and zeolitic crystals, is ascribed to the 
fact that these materials have lain for a long time exposed to 
the solvent action of sea-water. The presence of radio-active 
substances in this deposit, in much larger quantity than in other 
deposits, apparently also points to a very slow rate of deposition. 

It may be stated generally, with reference to the horizontal 



172 



DEPTHS OF THE OCEAN 



Distribution 
calcareous 
remains in 
pelagic 
deposits. 



Pelagic 
species of 
foraminifera. 



of distribution of calcium carbonate organisms, that they are most 
abundant both at the surface and at the bottom in warm tropical 
regions where the annual range of surface temperature is least. 
In the tropics the following genera and species of foraminifera 
are known to have a pelagic habitat, three or four of the species 
being rather doubtful : — 



Globigeruia sacculifera, Brady. 

aqicilateralis^ Brady. 
conglobaia, Brady. 
dubia^ Egger. 
rubra, d'Orbigny. 
bulloides, d'Orbigny. 
i/ijlata, d'Orbigny. 
digitata, Brady. 
cretacea, d'Orbigny. 
dutertrei, Brady. 
i>achyderfna (Ehrenberg). 
marginata (Reuss). 
linncBa?ia (d'Orbigny). 
helicina, d'Orbigny. 



Orbulina universa, d'Orbigny. 
Hastigerina pelagica (d'Orbigny). 
Pullenia obliquiloculata, Parker and 

Jones. 
Sphceroidina dehiscens, Parker and Jones. 
Candeina fiitida, d'Orbigny. 
Cymbalopora ( Tretomphalus) bulloides 

(d'Orbigny). 
Fulvmidina ?nenardii (d'Orbigny). 

,, tiimida, Brady. 

„ canariensis (d'Orbigny). 

„ michelmiana (d'Orbigny). 

„ crassa (d'Orbigny). 

„ patagotiica (d'Orbigny). 



The following genera and species of shelled pteropods and 
heteropods are pelagic : — 



Pteropods 



Pelagic species Limacina inflata (d'Orbigny). 
of pteropods. ,, triacaiitha {Y\?,z\vQx). 

helicitia (Phipps). 
antarctica, ^Voodward. 
helicoides, Jeffreys. 
lesueuri (d'Orbigny). 
australis (Eydoux and Soule- 

yet). 
retroversa (Fleming). 
trochiformis (d'Orbigny). 
bulinioides (d'Orbigny). 
Peradis reticulata (d'Orbigny). 

„ bispinosa, Pelseneer. 
Clio {C resets) virgida (Rang). 
„ ,, cotnca (Eschscholtz). 

„ ,, adcula (Rang). 

„ ,, duerchice (Boas). 

,, {Hyalocylix) striata (Rang). 



Clio {Styliola) siibida (Quoy and 
Gaimard). 
,, andrece (Boas). 
„ polita (Craven). 
,, balantiimt (Rang). 
,, chaptali (Souleyet). 
,, ai/stralis (d'Orbigny). 
„ sidcata (Pfeffer). 
,, pyramidata, Linne. 
,, cuspidata (Bosc). 
Ciivieri?ia colu7nneUa (Rang). 
Cavolinia trispinosa (Lesueur). 
,, qicadridentata (Lesueur). 
,, longirostris (Lesueur). 

„ globidosa (Rang). 
,, gibbosa (Rang). 
,, tride/data (Forsk^l). 

,, iindnata (Rang). 

„ i/iflexa (Lesueur). 



Heteropods 



Pelagic species Carinaria cristata (Linne). 

of heteropods. ^^ fragilis, St. Vincent. 

,, /a??iardiii, Peron and Lesueur. 



Carinaria depressa, Rang. 

,, australis, Quoy and Gaimard. 

,, galea, Benson. 



DEPTHS AND DEPOSITS OF THE OCEAN 173 



Carinaria cithara, Benson. 

,, punctata, d'Orbigny. 

„ gandichaiidii, Eydoux and 

Souleyet. 
,, atlautica, Adams and Reeve. 
„ cornucopia, Gould. 

Atla?ita peronii, Lesueur. 

„ turriculata, d'Orbigny. 
„ lesueurii, Eydoux and Souleyet. 
„ involuta, Eydoux and Souleyet. 
,, inflata, Eydoux and Souleyet. 
„ inclinata, Eydoux and Souleyet. 
„ helicitioides, Eydoux and Soule- 

_ yet. 
„ gibbosa, Eydoux and Souleyet. 



Atlanta gaudichaudii, Eydoux and Sou- 
leyet. 

,, fusca, Eydoux and Souleyet. 

,, depressa, Eydoux and Souleyet. 

,, rosea, Eydoux and Souleyet. 

,, quoyana, Eydoux and Soule- 
yet. 

„ mediterranea, Costa. 

,, violacea, Gould. 

,, tessellata, Gould. 

,, primitia, Gould. 

,, cunicula, Gould. 

„ souleyeti. Smith. 
Oxy gyrus keraudrenii (Lesueur). 

„ rangii, Eydoux and Souleyet. 



The gasteropod genus lantkina is also pelagic, while the 
species of coccolithophoridse are very numerous. 



Sea Surf a 




Fig. 142. — Diagram showing gradual disappearance of Calcium Carbonate 

WITH increasing DEPTH. 

The distribution of the dead shells of these pelagic organisms 
in different depths is peculiar and remarkable. If we suppose 
a cone to rise from a depth of 4000 fathoms up to within half 
a mile of the surface far from land in the warmer regions of 
the ocean (see Fig. 142), we shall find on the upper surface of 
this cone, and down its sides to about 1000 fathoms, nearly 
every shell of pelagic organisms represented in the deposit, 
even the smallest and most delicate. At about 1500 fathoms Disappearance 
many of the thinnest and smallest shells will have disappeared, carbl!nate\vith 
and the Pteropod ooze passes gradually into Globigerina ooze, increase of 
At 2000 fathoms there may not be a trace of pteropods, and *^'^^'^' 
some of the more delicate foraminifera will also have disappeared. 
At 2500 fathoms the larger and thicker foraminifera shells still 
remain, and the deposit becomes a Red clay with some carbonate 
of lime. At 4000 fathoms not a trace, or little more than a 
trace, of these shells can be found, and chemical analysis does 
not show I per cent of calcium carbonate. 

Now it has been shown by hundreds of observations that 



174 DEPTHS OF THE OCEAN chap. 

in the surface waters the Hving animals are as abundant over 
the Red clay areas, where not a trace of their shells can be 
detected in the deposits, as over the Pteropod ooze areas, where 
every one of them may be found. 

At about 2500 fathoms the percentage of calcium carbonate 
in the deposits apparently falls off more rapidly than at other 
depths. In some areas, as, for example, in the North Pacific, 
calcareous shells are not found in 2500 fathoms, while in 
the North Atlantic they are at the same depth sufficiently 
numerous for the deposit to be called a Globigerina ooze. 
Where the living organisms are most numerous in the surface 
waters, the dead shells are to be found at greater depths on the 
ocean's floor than elsewhere. Where cold and warm currents 
intermingle, shelled organisms are killed in large numbers, and 
the dead shells may be found in deeper water than in neigh- 
bouring regions. 

It must be remembered that while we know the crust of the 
earth on the continental areas to the depth of several thousands 
of feet, our knowledge of the crust under the oceanic areas is 
limited to one or two feet. Only in a few exceptional instances 
can we say that the sounding-tube has penetrated more than 
eighteen inches or two feet into the deposit. Sometimes, when 
the sounding-tube brings up a section over a foot in length, 
there are distinct indications of stratification.^ Even in great 
depths there may be a Globigerina ooze overlying a Red clay 
in the deeper part of the section. This arrangement may be 
explained by supposing that the calcareous shells have been 
slowly dissolved from the deeper layers, but this explanation 
will not suffice when a Red clay occupies the upper and a 
Globigerina ooze the deeper layer of the section. This latter 
arrangement appears to indicate that a large block of the earth's 
crust may have subsided to the extent of several hundreds of 
feet — from a depth at which a Globigerina ooze had been formed 
in normal circumstances to a depth at which a Red clay is laid 
down at the present time. 

There are not many cases on record of one type of deposit 
being superposed upon another distinct type, examples being 
more numerous of differences in colour and in composition in 
the different layers of the same type of deposit. Thus, in Blue 

1 From his examination of the samples collected during the German South Polar Expedition 
on board the " Gauss," Philippi believed that stratification on the sea-floor of to-day is not the 
exception but the rule, and that, where it seems to be wanting, the upper layer is probably 
thicker than the depth to which the sounding-tube penetrated. 



oceanic 
areas. 



IV DEPTHS AND DEPOSITS OF THE OCEAN 175 

muds it seems to be the rule that the upper portion should be 
thin and watery and reddish-brown in colour, in striking contrast 
with the stiff compact blue lower portion, and this is apparently 
due to the ferric oxide or ferric hydrate being transformed into 
sulphide and ferrous oxide in the deeper layers. Among our 
records there are seven cases of Red clay overlying Globigerina 
ooze, eight cases of Globigerina ooze overlying Red clay, thre*e 
cases of Globigerina ooze overlying Blue mud, two cases of 
Globigerina ooze overlying Diatom ooze, and four cases of 
Diatom ooze overlying Blue mud ; in twenty other cases the 
percentage of calcium carbonate was considerably higher in 
the upper portion of the deposit- samples than in the lower 
portion, while in six cases the lower portion was richer in 
calcareous remains than the upper portion. 

The examples of Red clay overlying Globigerina ooze point Subsidence in 
to subsidence in the region where they occur, and, indeed, there 
are many reasons for believing that the great earth-blocks in 
the oceanic areas for the most part undergo subsidence, while Elevation in 
similar earth-blocks on the continents are, on the whole, subject continental 

. ' ' J areas. 

to elevation. 

3. Some Chemical Reactions in the Deep Sea 

In Dittmar's well-known analysis of ocean-water^ the acids 
and bases are arbitrarily combined, but it is now known that 
the dissolved substances in sea-water are not accurately repre- 
sented by that table, inasmuch as they are present mainly as 
ions. The aggregate degree of ionic dissociation may be cal- 
culated from the freezing and boiling points of sea-water to be 
about 90 per cent. That is, only one-tenth of the total solids 
are present as salts pure and simple ; but these must comprise 
not only those named by Dittmar but all the possible combina- 
tions of bases with acids, among which calcium and magnesium 
sulphates will be relatively in largest proportion. The bulk of 
the solutes, however, consists of ions, and it would be more 
rational to write the composition of sea-water thus : — 



1 Sodium chloride 


27.213 grams per litre. 


Magnesium chloride . 


• 3-807 „ 


Magnesium sulphate . 


1.658 „ 


Calcium sulphate 


1.260 ,, ,, 


Potassium sulphate 


0-863 ;„ 


Calcium carbonate 


0-123 ,, 


Magnesium bromide . 


0.076 ,, 



35- 000 



176 



DEPTHS OF THE OCEAN 



Dissolved 
solids in 
sea-water 
as ions. 



Calcium 
sulphate. 



Calcium 
carbonate. 





Parts per 1000. 


Percentage. 


Na . . 


10.722 


30.64 


Mg 






1. 316 


3-76 


Ca 






0.420 


1.20 


K 






0.382 


1.09 


CI 






19.324 


55-21 


SO4 






2.696 


7.70 


CO, 






0.074 


0.21 


Br 






0.066 


0.19 








35.000 


100.00 



Dittmar's item CaCO^, which was presumably included in 
order to express the fact that there is on the whole an excess 
of bases over acids, is obviously incomplete as it stands. From 
the most recent measurements we gather that a 3 per cent sodium 
chloride solution, in equilibrium, as regards CO„-tension, with 
air (which holds good approximately for sea-water), dissolves at 
25° C. about 0.07 gr. of calcium carbonate per litre. Hence 
there cannot be as much as 0.13 gr. per litre in sea- water. The 
surplus base should rather be regarded as a mixture of calcium 
and magnesium bicarbonates, existing in equilibrium with a 
certain amount of free CO^, and of the products of their hydro- 
lytic dissociation, viz. calcium and magnesium hydroxides. It 
is the two latter which impart to sea-water its alkaline reaction. 

On considering sea-water in its relation to submarine 
deposits we note that, of all possible combinations of cation 
with anion, there are three which are much less soluble than 
any others, and are therefore closest upon saturation and pre- 
cipitation : these are calcium sulphate, calcium carbonate, and 
magnesium carbonate. 

From what is known of the solubility of gypsum in brines, 
and allowing for the excess of SO^, one would suppose that 
sea-water is very nearly saturated for this salt, and that addition 
of, for instance, a sulphate would precipitate it. But gypsum 
is unknown as a constituent of deep-sea deposits (unless of 
extraneous origin), so that its solubility-limit is evidently never 
exceeded under submarine conditions. 

Calcium carbonate, on the other hand, occurs, as already 
stated, in enormous quantities at the bottom of the sea over 
wide areas. All the lime in it has been derived, by the aid of 
organic agencies, from the calcium held in solution by sea-water. 



IV DEPTHS AND DEPOSITS OF THE OCEAN 177 

whilst the carbonic acid owes its origin more or less indirectly 
to the atmosphere and to infra-oceanic respiration. 

In considering by what agencies calcium carbonate may be 
precipitated from the sea, we can at once set aside two which 
are of importance in terrestrial geology, viz. removal of solvent 
by evaporation and change of temperature ; neither are operative 
in adequate degree in the hydrosphere. Turning to chemical 
processes we note, in the first place, that the solubility of calcium 
carbonate in water is nearly proportional to the cube root of the 
COg-tension,^ i.e. the amount of free CO^ present in solution. 
Calcium carbonate as such is scarcely soluble at all, but in 
presence of CO., the bicarbonate Ca(HC03).3 is formed, and 
this is soluble to a considerable extent. Hence, if CO^ be 
abstracted, calcium carbonate will tend to come out of solution. 
Here we have what seems to be the niodzis operandi of cal- 
careous algae. The plant absorbs CO., by way of nutrition, 
precipitates calcium carbonate, and thus builds its skeleton. 
That this process takes place in fresh water, where the bicar- 
bonate is the chief salt of calcium present, may be considered 
as established. The mosses Hypiium, Eucladimn, Trichostovia 
are cases in point, as also Chara. These plants deposit coral- 
like growths, known to mineralogists as tufa and travertine. 
Many occurrences have been noted in the Yellowstone Park 
and other American localities. In some instances the calcium 
carbonate is aragonitic, as at Carlsbad. The calcareous algae, 
which are well represented at the surface and at the bottom of 
the warmer oceans (coccolithophoridae), no doubt secrete their 
skeletons in the same way as the fresh-water algae enumerated. 

But there is another far more important agency at work. 
Calcium carbonate must separate out if the product of the con- 
centrations of its ions Ca"* and CO3" happens to exceed a certain 
definite limit. Small increases in the concentration of Ca" ions 
may be disregarded, since their concentration is already consider- 
able ; but small local accessions of CO3" ions, which, in the shape 
of alkaline carbonate, may and do occur, are more effective. 
Marine animals generate, as ultimate products of the metabolism 
of their proteid food, ammonia and carbon dioxide. These 
combine to form ammonium carbonate, which in aqueous solution 
is largely dissociated into NH^' and CO3" ions ; thus calcium 
carbonate is precipitated with liberation of ammonia, and a shell 
or coral growth may be formed. The reaction here described, 

1 Schloesing, Coinptes Retidiis Acad. Sci. Paris, vol. Ixxv. p. 70, 1872 ; Bodlander, Zeiischr. 
Phys. Cheni., vol. xxxv. p. 23, 1900. 

N 



178 DEPTHS OF THE OCEAN 

which, according to the older chemical notions, was expressed 
by the equation 

(NH,X,C03 + CaSO^=CaC03 + (NHJ,SO,, 

seems to have been first suggested in this connection by 
Forchhammer, and was fully proved and worked out experi- 
mentally, with respect to marine organisms, by Murray and 
Irvine.^ It accounts for the enormous amount of calcium 
carbonate at the bottom of the ocean, which once formed part 
of the tests or skeletons of living organisms. A limited 
amount of purely inorganic precipitation does, indeed, take place 
in coral reefs and some shallow-water deposits and in the Black 
Sea. In the Mediterranean, for instance, stone-like crusts are 
plentiful, consisting of clay cemented by calcium carbonate, 
which latter is produced by ammonium carbonate arising from 
the decay of organic matter in the mud below bottom-level 
meeting with fresh sea-water from above. We have further the 
lime-concretions of the Pourtales, Argus, and Seine banks, the 
"Challenger" casts of shells from the Great Barrier Reef,^ and 
so on. But all these must be regarded as rarities. A great 
many of the reactions here referred to are believed to be ruled 
by enzymes and catalytic substances. 

Whilst a great deal of calcium is thus being taken out of 
solution throughout the ocean, conversely the carbonate is 
continually being redissolved. Calcium and magnesium carbon- 
ates are held in solution mainly as bicarbonates ; but since 
these compounds are incapable of existence in the solid state, 
questions of precipitation and dissolution, so far as they can be 
approached on theoretical grounds, must be decided by the 
solubilities of the normal carbonates. The solubility of CaCOg 
in water (foreign salts being absent), and the equilibrium of 
the various molecules and ions concerned, have been fairly 
thoroughly elucidated.^ When MgCOg is also present and 
sea-water is the solvent, matters become so complicated that 
we cannot calculate, from first principles, how near sea-water 
is to saturation for calcium carbonate. . There are, however, 
direct empirical data on this point. From the experiments of 
Anderson with natural, and of Cohen and Raken with artificial, 
sea-water, it would appear that with regard to CaCOg, in the 
final stable modification of calcite, sea-water is saturated and 
incapable of taking up more, under conditions of stable 
equilibrium. Nevertheless the ocean does unquestionably dis- 

1 Proc. Roy. Soc. Edin., vol. xvii. p. 79, 1889. 
- Deep-Sea Deposits Chall. Exp., pp. 170, 172, 1891. * Bodlander, loc. cit. 



IV DEPTHS AND DEPOSITS OF THE OCEAN 179 

solve such calcium carbonate as it comes in contact with, 
especially dead shells and skeletons. Three reasons for this 
may be adduced : — 

(i) There may be local accessions of CO2, the dissolving 
power of which has already been referred to. The sarcode of 
molluscs and the albuminous binding material of their shells are 
decomposed, on the death of the animal, to CO2 and ammonia, 
the former being much in excess. The solvent thus provided, 
in the case of any given shell-forming- organism, can only, how- 
ever, be small relatively to the calcareous matter present. 

(2) The carbonate may be in a less stable, and therefore 
more soluble, form than calcite. This is eminently true of 
corals, which are mainly aragonitic. Some shells also are 
wholly or partially aragonitic, and marine aragonitic algae 
occur, such as Halimeda. Sea-water saturated for calcite 
would, needless to say, be unsaturated for aragonite. 

(3) It is a familiar fact that freshly precipitated calcium 
carbonate is much more soluble than the stable macrocrystalline 
modification. The older theory, which supposed the former to 
be basic or hydrated CaCOs, seems open to doubt, since there is 
no sort of evidence that such compounds exist. More probably 
the abnormal solubility is due to the exceedingly small size of 
the particles. Above a certain limit of size, the concentration 
of saturated solutions of a solid is constant, whether the 
particles be large or small ; below this limit the concentration 
becomes greater the smaller the particles, these stronger 
solutions being in perfectly stable equilibrium with solid 
particles of a definite magnitude. Experimental observations 
of this phenomenon, which may be an effect of surface-tension 
between solid and liquid, have in recent times been made on a 
variety of substances.^ The limiting size for abnormal solubility 
is about 2/u, diameter for gypsum, and will hardly be very 
different for calcium carbonate. It may be that what is called 
amorphous calcium carbonate is often merely calcite or aragonite 
in a state of extremely fine subdivision, whence the higher 
solubility. Abnormal solutions thus produced are of course 
supersaturated for larger particles, but there is evidence that 
they part with their surplus solute with extreme reluctance. 

In all probability, then, the particles of calcium carbonate of 
organic origin in the sea, which are protected, during life, by 
albuminoid matter, go into solution, in the course of their post- 
mortem descent, by virtue of their minute size, and leave trails 

^ See Hulett, Zeiischr. Phys. Cketn., vol. xxxvii. p. 385, 1901. 



i8o DEPTHS OF THE OCEAN 

of sea-water surcharged with Hme. This Hme, though in a 
metastable condition, finds no nuclei to deposit upon and 
remains in solution, being carried about until it reaches an area 
impoverished of lime by precipitation, when its condition 
becomes stable, or until it is itself reprecipitated by coming 
into the sphere of action of an ammonia-producing organism. 
Thus the ocean as a whole remains just about saturated for 
calcium carbonate. 

Oceanic calcium undergoes extensive circulation between 
the dissolved and undissolved states. When calcareous frag- 
ments fall on a clayey or muddy bottom, they fall into water 
which can take up lime, and are dissolved as the water passes 
over them, while on falling on distinctively calcareous deposits 
like Pteropod ooze they fall into water-layers, immediately above 
the bottom, which can dissolve no more lime. In either case 
the lime depends for its redistribution on the slow processes of 
diffusion by convection and other currents. In those areas 
covered by Globigerina and Pteropod oozes lime is being 
steadily withdrawn from the ocean. Over Red clay areas, on 
the other hand, lime is being returned to the ocean. From 
the state of saturation of sea-water we may infer that the 
aggregate accessions of lime to the bottom exactly balance the 
aggregate supply from land and from the direct decomposition 
of submarine rocks. On the whole, lime at the present time 
appears to be accumulating towards the equator. 

Another element present in the sea, magnesium, shares the 
vicissitudes of calcium, but in a very minor degree. Magnesium, 
in contrast with calcium, is very prone to form hydrated and 
basic carbonates, ahd when the carbonate is precipitated from ' 
solutions of magnesium salts, it comes down not in the anhydrous 
crystalline form, but mainly as a trihydrate. Now solubility- 
determinations in pure water and in salt-solutions indicate that 
MgCO., as bicarbonate, in equilibrium with trihydrate, is of the 
order of ten times more soluble than CaCOo. Hence the former 
is far less likely to be precipitated than the latter, even though 
there is about three times as much magnesium in the sea as 
calcium. Moreover, it is well known that magnesium carbonate 
is not readily brought down in presence of ammonia. Thus we 
find that in living shells, corals, and algse the proportion of 
MgCOg to CaCOg is usually below i per cent. It is observed, 
however, that in dead carbonates, e.g. Coral sands and muds 
and calcareous oozes which have been for a long time at the 
bottom, there are markedly greater admixtures of magnesium. 



IV DEPTHS AND DEPOSITS OF THE OCEAN i8i 

This enrichment in magnesium is a famihar phenomenon at 
shallow depths, notably in and about coral reefs. It has also been 
shown on the basis of the "Challenger" analyses that bottom- 
deposits contain more MgCOg in proportion to CaCO,, the less 
calcareous they are. Granted that accumulation of magnesium 
does take place, there are two explanations which have been 
offered, viz. (i) that deposited lime is dissolved away in prefer- 
ence to magnesia, and (2) that a kind of pseudomorphosis by 
the interaction of calcium carbonate and dissolved magnesium 
salts sets in. Both assume MgCOg to be less soluble than 
CaCOg, and both may well hold good. Even if MgCOg were 
precipitated as trihydrate, it would sooner or later change into 
the anhydrous form, or rather into dolomite, that being the most 
stable and final form. Perhaps this transformation has already 
been effected in the shell. But dolomite is well known to be 
less soluble in carbonated water than calcite. As regards 
enrichment by accession of magnesia, this could only take place 
if sea-water were nearly saturated for MgC03, a matter which 
has not hitherto been put to the test ; sea-water is certainly not 
saturated for the trihydrate, but it is conceivable that anhydrous 
calcium carbonate would determine the deposition of magnesium 
carbonate in the anhydrous form, which is relatively very 
insoluble. Now when calcium carbonate goes into solution, 
the concentration of CO3" ions in its neighbourhood is increased, 
whereby the solubility of any other carbonate is lowered ; thus 
a precipitation of MgCOg might ensue. However, if this action 
were capable of taking place generally, we should expect a far 
larger percentage of magnesia in the purer calcareous oozes. 
On the whole, therefore, the enrichment in magnesia in deep- 
sea deposits proper is rather to be sought in preferential 
dissolution of lime. 

The total magnesium carbonate at the bottom of the sea 
only amounts to a small percentage of the total calcium carbonate. 
Since the proportion of Mg to Ca, primarily in rocks and 
secondarily in river-waters, is much larger than this, it is clear 
that dissolved magnesium is accumulating in the ocean. 

Another of the more important constituents of sea-water, Sulphur. 
sulphur, suffers transference, on a modest scale, from the sea to 
the bottom. Nowhere in the deposits of the open ocean has 
sulphur been found to occur as sulphate, but in those very 
extensive landward areas where Blue muds form the deposit 
there is always a small percentage of ferrous sulphide and 
of free sulphur, which are directly or indirectly derived from 



i82 DEPTHS OF THE OCEAN chap. 

sea-water sulphates. In all deep-sea muds there is a certain 
amount of decaying animal and vegetable matter fallen from 
the hydrosphere, the proteids of which leave their sulphur, so 
far as it escapes oxidation, combined with the iron of the 
surrounding mud. But apart from this rather insignificant item, 
there are bacteria which, whilst living on sarcodic matter, seize 
on the dissolved sulphates of sea-water and reduce them to 
sulphides ; the latter react with whatever ferruginous material 
is present, and produce the highly insoluble compound ferrous 
sulphide. Free sulphur, when found, is to be accounted for by 
the partial oxidation of sulphides, either by dissolved oxygen or 
at the expense of ferric iron. The retention of sulphur in 
bottom-deposits can only occur where there is plenty of decaying 
organic matter, where the bottom-waters are stagnant, or nearly 
so, and not well aerated, and where there is not a copious hail 
of calcareous tests ; that is, mainly in the lower layers of muddy 
bottoms at shallow and medium depths. The sea- water 
imprisoned below the upper layer of mud becomes poorer in 
sulphate and richer in carbonic acid,^ whilst the mud is darkened 
in colour by very finely-divided and easily oxidizable ferrous 
sulphide. Under suitable conditions the ferrous sulphide may, 
as in Black Sea muds,-"' combine with free sulphur and attain a 
condition of higher stability in the form of pyrites. The essential 
chemical factor which renders possible the retention of sulphur 
is the power of the colloidal ferric hydroxide in clay to react 
with sulphides. A small quantity of ammonium sulphide added, 
in the laboratory, to ordinary Red clay from the deep sea, at 
once goes into reaction: the clay is darkened to a tint resembling 
that of Blue mud ; the original tawny colour is restored by 
atmospheric oxidation ; the darkened clay evolves sulphuretted 
hydrogen with dilute acid. At the same time it is well to 
remember that many Blue muds owe their colour to quite other 
causes than the presence of sulphur. 

The reduction of sulphates occurs only where there is a 
continuous deposition of detritus, and takes place, in the sub- 
marine muds, in the deeper layers. Consequently under 
normal conditions precipitated sulphur does not perform a cycle 
between bottom and sea, but remains irrevocably buried, 
accumulating as the deposit accumulates. No attempt seems 
hitherto to have been made to determine the ferrous sulphide 
in marine muds, but it is probably very minute in amount. 

' Murray and Irvine, Trans. Roy. Soc. Ediii., vol. xxxvii. p. 481, 1893. 
- Murray, Scot/. Geogr. Mag., vol. xvi. p. 673, 1900. 



IV DEPTHS AND DEPOSITS OF THE OCEAN 183 

Free sulphur has been found in a maximum of 0.003 P^^" cent 
in oceanic deposits,^ although inland and estuarine deposits may 
contain rather more. We may therefore take it that the 
aggregate influx of oxidized sulphur into the ocean greatly 
exceeds the fixation of reduced sulphur at the bottom. 

The elements silicon (as hydrated silica) and phosphorus 
(as calcium phosphate) are transported by biological agencies 
from the sea to the bottom, the former in large, the latter in 
small, quantities. The compounds referred to are capable of 
existing in solution in sea-water only to an infinitesimal extent, 
so that all the silicic and phosphoric acids carried into the 
ocean must eventually find their way to the bottom. 

The silica of organic origin in deep-sea deposits, which of sm 
course represents but a tiny fraction of the total silica present, is 
peculiar in having been derived not only from dissolved, but also 
from suspended, silicates.^ It takes the form of tests and skeletons 
characterising the important Diatom ooze and Radiolarian 
ooze areas, and of sponge spicules, which are ubiquitous but 
nowhere concentrated enough to give rise to a definite deposit. 
Chemically, this silica is in the hydrated colloidal condition 
not unlike opal. By what process the siliceous organisms 
convert their intake of dissolved silica and floating clay into 
structural silica is not clearly known ; as regards the former, it 
is evident that the organisms possess some means of coagulating 
to a hydrogel the silica which they receive either as SiO^'' ions 
or as a hydrosol of silicic acid ; whilst their argillaceous food is 
probably decomposed by some acid juice with elimination of 
alumina in solution and eventual deposition of coagulated silica. 
During life, siliceous tests are protected from dissolution by 
an admixture of albuminoid matter, which rots away after death. 
The hydrogel of silica then undergoes peptisation (that is, so 
much of it as does not fall to the bottom), probably by virtue of 
the free alkali in sea-water, and returns to the dissolved state. 
The conditions of dissolution of silica and, for instance, calcium 
carbonate are very different. Silica, as being a colloid, has not 
a definite solubility ; its existence as a hydrosol is limited only 
by the coagulating action of the electrolyte solutes of sea- water 
or by its precipitation in combination with a base. As to the 
former effect, we have no data except that sodium chloride is 
comparatively feeble as a coagulant. It is remarkable that no 
silica seems ever to reach the bottom as a chemical precipitate 

^ Buchanan, Proc. Roy. Soc. Ediii., vol. xviii. p. 17, 1891. 
- Murray and Irvine, Froc. Roy. Soc. Edin., vol. xviii. p. 229, 189 1. 



i84 DEPTHS OF THE OCEAN 

of calcium or magnesium silicate, although magnesium silicate 
is known to be soluble to only i part in 100,000 of sea-water.^ 
This perhaps indicates that the silica in solution in the sea is 
always below saturation-point, so that a local concentration large 
enough to determine precipitation never occurs. Or again, 
excess silica perhaps combines with what little alumina there is 
in sea-water and is deposited as clay ; if that were the case, the 
limit of dissolved silica would be set by the solubility of this 
substance, which may well be less than that of magnesium 
silicate. At any rate, the quantity of silica really dissolved in 
sea-water is extremely small. According to the most recent 
and trustworthy determinations," there is on the average about 
one part, and never more than two parts, per million in North 
Sea and Baltic waters. 

Although for obvious reasons vastly less silica is produced, 
by biological agencies, in the waters of the sea than calcium 
carbonate, the former, like the latter, is found in almost all 
submarine deposits. When siliceous remains fall into a calcareous 
deposit, the silica has little tendency to combine with lime, 
since silicic at low temperatures is an even weaker acid than 
carbonic ; but, the process of peptisation being accelerated by 
the higher alkalinity of the superjacent waters, we should expect 
the predominance of lime to favour the dissolution of silica. 
This seems to be borne out by the fact that silica is least 
abundant in the most calcareous bottoms of the open sea, and 
also by the almost total absence of silica in coral reefs and 
muds.^ Again, essentially siliceous accumulations (Radiolarian 
ooze) are characteristic of the very deepest parts of the ocean, 
where calcareous remains have such enormous columns of sea 
to fall through that they may fail to reach the bottom. There 
is thus a tendency for silica and calcium carbonate to be 
mutually exclusive. In terrestrial calcareous deposits (chalk) 
we find imprisoned silica going into solution, migrating to 
centres of coagulation and forming nodular segregations (flint). 
No such phenomenon is observed at the bottom of the sea, 
where the silica brought into solution has probably no difficulty 
in diffusing into the hydrosphere out of the comparatively loose 
deposit. 

The soluble silica of the sea is derived ultimately from 
felspathic minerals, and the greater bulk is introduced from 

1 Murray and Irvine, Proc. Roy. Soc. Edin., vol. xviii. p. 238, 1891. 
^ Raben, Wissensch. Meeresuntersiichiingeii, Kiel, vol. viii. pp. 99 and 277, 1905. 
^ The Atoll of Funafuti : Report of Coral Reef Committee of the Royal Society ; Chemical 
Examination of the Materials from Funafuti, by J. W. Judd, p. 370, 1904. 



IV DEPTHS AND DEPOSITS OF THE OCEAN 185 

land by means of rivers. Since the ocean cannot retain in 
solution more than a trace, all this silica must eventuate as 
organic deposits, especially Radiolarian and Diatom oozes. 
Furthermore, a certain quantity of suspended terrigenous clay 
is being continually converted into the hydrated silica of these 
deposits. Neglecting the latter source of biological silica and 
the comparatively inconsiderable radiolarian areas, we can say 
that the dissolved silica yielded by the continents is tending to 
accumulate on the frontiers of the temperate and polar zones, 
especially in the Antarctic Ocean. 

The amount of phosphorus in sea-water is comparable in its Phosphc 
tenuity to that of silica, Raben's determinations for North Sea 
and Baltic waters show a seasonal variation ranging from 
0.14 to 1.46 parts of PgOj; per million. Phosphorus originates 
as calcium phosphate in the form of apatite, passes through the 
ionized condition, and is deposited on the bottom of the sea as 
calcium phosphate. In the deposits this compound is of 
universal distribution ; all samples of whatever character contain 
from a trace to about 3 per cent of tricalcium orthophosphate. 
The clays and muds no doubt retain traces of undecomposed 
mineral phosphate. On the other hand, calcium phosphate is 
secreted to a greater or less extent by the living denizens of 
the sea, whence its presence in calcareous and siliceous deposits ; 
here we have the phosphorus withdrawn from aqueous solution 
and partly going through a cycle between the sea and the 
bottom, like lime and silica. 



If there were no organic life in the ocean, the deposit every- pecompos 
where would consist of a mud or clay, composed of mineral m^JJerais. 
detritus. As it is, this detritus is nowhere wholly absent, and 
large areas consist of little else. Whether the mud be brought 
into'the sea by rivers or through the agency of tidal erosion, or 
whether it be formed in sittt at the bottom, it is always of a 
dual nature. The one ingredient is more or less finely powdered 
original mineral matter produced by mechanical comminu- 
tion ; the other is a mixture of substances resulting from the 
chemical decomposition of rocks. It has not been found 
possible to disentangle these components quite satisfactorily by 
chemical analysis, but it is safe to state that the proportion of 
one to the other ranges from one quarter to three quarters. 

In chemically-produced mud we have the result of the action 
of water on crystalline silicates without the intervention of any 
solute except dissolved gases. Qualitatively, therefore, it is of 



i86 DEPTHS OF THE OCEAN 

the same composition whether formed in fresh water or in the 
sea. Quantitatively, it might be expected to show a difference 
for terrigenous and pelagic origin respectively, since the mother- 
rocks are in general not the same. Nevertheless, a remarkably 
close similarity is revealed by analyses, such as the " Chal- 
lenger" analyses of Blue muds and Red clays, or still better, of 
Clarke's ultimate analyses of averaged "Challenger" deposits.^ 
One notable point of difference is brought out, viz. the greater 
manganese-content of pelagic deposits. 

The action of unlimited water, oxygen, and carbonic acid 
on the earth's crust tends to lead to certain definite end-products, 
the nature of which is dictated by the abundance and the 
affinities of the elements concerned, and by their habit as 
regards solubility. All minerals, given time, succumb to these 
agencies. Reviewing the chief elements, we find the final con- 
ditions of stability under subaqueous influences to be as follows. 
The alkalies, being of a highly soluble tendency, go into 
solution and accumulate in the hydrosphere. Calcium and 
magnesium are rendered soluble by the presence of carbonic 
acid and become sea- water constituents, the former being 
ultimately redeposited by organic processes. Phosphorus 
behaves similarly. Ferric iron is very feebly basic, and therefore 
tends to the condition not of a salt but of a hydrated oxide 
(FeoOg.Aq) which, being very insoluble, remains in the 
residuum. Ferrous iron, which is a much stronger base, is 
leached out by the aid of carbonic acid, but is soon oxidized to 
ferric iron and rendered insoluble. Much the same holds good 
of manganese, which exists in minerals almost exclusively in the 
manganous state : it is dissolved as bicarbonate, undergoes 
oxidation, and comes to rest as hydrated peroxide (MnO^. Aq). 
Aluminium forms only one base, which is very weak, but has 
the property of combining with silica to form a highly insoluble 
substance, ideal clay (AI0O3. 2510,. 2H2O), which represents its 
final stable condition. Silicon exists as a weak acid (SiOo) of 
insoluble tendencies, which, after having been brought into 
solution, partly joins the residuum as clay and is partly re- 
deposited as hydrated silica through organic agency. 

The ultimate mineral residuum, then, consists, if we pass 
over the rarer elements, of aluminous clay, hydrated ferric oxide, 
and hydrated manganese peroxide. In all probability the two 
former substances should be considered together and submarine 
clay regarded as an ill-defined colloidal compound in which 

^ P)Oc. Roy. Soc. Edin., vol. xxxvii. pp. 167 and 269, 1907. 



IV DEPTHS AND DEPOSITS OF THE OCEAN 187 

silica and alumina play the chief part, but ferric hydroxide and 
even lime, magnesia, and alkalies are also represented. These 
minor constituents are, at any rate, so combined as to resist 
leaching out by dilute acids. Vast areas of the lowest depths of 
the sea are covered by such a clay in a state of considerable 
mechanical purity, a product of almost exclusively submarine 
disintegration, known as Red clay. 

The chemical action by which pelagic clay is derived from 
its volcanic mother- rocks must proceed, as compared with 
subaerial weathering, with the utmost sluggishness. The 
fundamental question, indeed, whether fresh or salt water exerts 
the more powerful action upon rocks must be regarded as not 
yet answered. Great experimental difficulties are encountered, 
and we find the results of Thoulet, who concluded that fresh 
water is a better disintegrant than salt, diametrically opposed to 
those of Joly.^ But several other considerations must be taken 
into account, and it cannot be doubted that rock silicates are 
degraded more slowly in the sea than on land. For instance, 
the clastic action of frost is never brought into play. There is 
no comminution of the minerals by moving water. The soluble 
by-products are removed, and the supply of oxygen and carbonic 
acid maintained, by diffusion only. 

At this stage the state of rest of the deep-sea residuum is 
not even yet necessarily final, but is capable of being disturbed 
locally by organic agencies. Aluminous clay, indeed, is per- 
manent once it is at the bottom, but, whilst floating, it is to 
some extent decomposed, as we have seen, by siliceous algse for 
purposes of nutrition. Iron and manganese oxides are suscept- 
ible to reduction by purifying sarcodic matter, whence result the 
ferrous iron of the Blue muds, and also many of the concretionary 
forms of these oxides. 

The Blue mud areas, which are of vast extent, afford a 
most important example of the reduction of submarine clay after 
deposition. We may indeed divide the floor of the sea, accord- 
ing to the relative abundance or paucity of dissolved oxygen 
in the bottom-waters, into oxidizing and reducing areas. Re- 
ducing conditions will prevail wherever there is a larger excess 
of putrefiable organic matter than can be coped with by what- 
ever supply of oxygen (depending on the circulation of the 
area) may be available. In general, therefore, the coast-lines 
of continents are girdled by reducing areas, and it is here that 

' It may be mentioned that the methods of leaching adopted by these experimenters are 
somewhat dififererit, and that Thoulet measures his effects by loss in weight, whereas Joly deter- 
mined the amounts taken up in solution. 



i88 DEPTHS OF THE OCEAN 

Blue muds characteristically occur. Oxidation of the organic 
matter is here effected at the expense of ferric iron, probably 
by bacteria] agency. A special case of this, viz, the bacterial 
production of ferrous sulphide and free sulphur, has already 
been referred to. It may be that sulphur plays an inter- 
mediate part in the formation of Blue muds, but the end- 
product is simply a clay, in which some or most of the iron 
has been reduced to the ferrous state, containing i or 2 per 
cent of amorphous black organic substance. To these two 
factors the distinctive dark colour is due. The organic sub- 
stance is associated with but little nitrogen and hydrogen, and 
it no doubt represents the final refuse of bacterial and higher 
forms of life. Blue muds are produced out of the deposit from 
the top downwards, as is evidenced by the reddish unreduced 
layer overlying the deeper Blue ones. Since Blue mud is of 
terrigenous origin, the undegraded silicate which it contains 
consists of continental minerals. 

From the general conditions obtaining in reducing areas it 
follows that carbonic acid must be unusually plentiful in the 
mud-waters. A consequence of this is that calcium carbonate, 
if deposited, is readily redissolved. Hence the Blue muds are 
on the whole poor in lime. It further follows that lime is 
tending to accumulate in the deposits of the moderate depths 
of the ocean, between the reducing areas and the abysses where 
it is dissolved before reaching the bottom. 

Doubtless the decay of minerals on the floor of the sea 
follows much the same course as subaerial weathering. Inter- 
mediate products, however, are comparatively rare, since the 
general conditions are not (as on land) subject to variation. 
The only substances of this category which form in any pro- 
fusion are zeolites, especially the one known as phillipsite. 
Here and there intermediate products are arrested by being 
surrounded with concretions. A notable instance is the mineral 
palagonite, which is frequently found at the centre of ferro- 
manganic nodules. Basic volcanic glass (an amorphous fused 
silicate of calcium, magnesium, and ferrous iron) has the 
property of combining with water continuously from the peri- 
phery inwards without crumbling, giving what is virtually a 
hydrated aluminium-iron silicate in a medium of opal. A 
coating of concretionary matter prevents the gelatinous silica 
from breaking away and dissolving, but offers no resistance to 
the diffusion of calcium and magnesium, which are leached out. 
Meanwhile the colloidal silica exerts its absorbing power on 



IV DEPTHS AND DEPOSITS OF THE OCEAN 189 

the potash and soda of sea-water, and these oxides enter to 
the extent of about 4 per cent each. The iron becomes ferric, 
and can no longer get away as bicarbonate. The resulting 
palagonite is a more or less homogeneous and transparent 
amorphous mineral. Exposed naked to the action of bottom- 
waters it rapidly breaks down to clay. 

Deep-sea conditions are, on the whole, more favourable to Synthetic 
the degradation of mineral matter than to the generation of new p'^^'^^'^^^- 
minerals. Nevertheless a few syntheses are being continually 
carried on in the muddy parts of the bottom and in the 
immediately superjacent layers of water; they fall into two 
groups, viz. true chemical syntheses of new classes of silicates, 
and mineralogical syntheses of concretionary minerals. The 
first group comprises glauconite and phillipsite, the second 
group ferromanganic and phosphatic concretions. 

Glauconite is a hydrous double silicate of potassium and Glauconite. 
trivalent iron, occurring in rounded grains said to be composed 
of minute felted crystals. The ideal composition (KFe SioO^. Aq) 
is claimed for it, but actually the purest marine glauconite 
hitherto analysed contains 1.5 per cent of AI0O3, 3.1 per cent 
of FeO, and 2.41 per cent of MgO, with only 'j.'] per cent of 
K20.^ The chemistry of its genesis is still a complete mystery ; 
all that can be said is that it appears to result from a meta- 
morphosis of ferruginous clay, and that, in view of its frequent 
formation inside the shells of foraminifera (and of its absence 
in the Red clay and Red mud areas), decomposing organic 
matter probably plays a part in its formation. On the score 
of abundance glauconite is a mineral of considerable importance 
in bottom-deposits, being the characteristic component of the 
Green sands and Green muds. Glauconite is a mineral belong- 
ing essentially to the reducing areas of the deep sea. 

The most notable geochemical change associated with 
glauconite is the withdrawal of potassium out of solution in the 
sea. This element has a remarkable tendency to be held in 
loose combination in amorphous and colloidal minerals (like 
palagonite), and all submarine muds and clays contain a small 
amount (less than i per cent) of absorbed potash ; the quantities 
thus progressively entangled at the bottom will be roughly 
proportional to the aggregate accessions of clayey matter, and 
can only be a tiny fraction of the total potassium imported into 
the ocean. In glauconite-producing areas, on the other hand, 

1 Collet and Lee, Proc. Roy. Soc. Edin., vol. xxvi. p. 238, 1905. 



I90 DEPTHS OF THE OCEAN 

the fixation of potassium must reach formidable dimensions, 
since the purest Green sands may contain 7 to 8 per cent of 
K2O. Nevertheless over the whole ocean it is hardly probable 
that deposition keeps pace with supply, and potassium may be 
regarded as one of those elements which are slowly concentrating 
in sea-water. 

The zeolite phillipsite is the only substance produced in 
well-developed crystalline forms at the bottom of the sea, where 
it is peculiar to the deepest Red clay regions. Marine phillips- 
ite is a hydrated calcium-aluminium silicate in which the 
principal minor bases are potash and soda (4 to 5 per cent each 
of KoO and NagO), with insignificant amounts of lime and 
magnesia. Like all zeolites, it must have been deposited out of 
a solution of its constituents, and it represents an intermediate 
stage in the degradation of rock-silicates to clay. Why should 
the process of degradation have been arrested at this stage ? 
In all probability because solutions containing silica, alumina, 
and the other elements in just the right proportions were 
imprisoned in interstices of the Red clay, secure from diffusion, 
and therefore available for the slow process of crystallisation. 
It is worthy of note that in point of percentage quantity the 
minor bases of marine phillipsite differ widely from those of the 
terrestrial mineral, in which latter calcium plays the chief part. 
Taking into account the well-known faculty possessed by zeolites 
of exchanging bases with solutions with which they are in 
contact we have here (especially in the high percentage of 
Na^O) an interesting effect of sea-water as a medium in the 
mineralogical world, comparable with its far-reaching biological 
effects. Why the crystallographical species phillipsite should 
be favoured rather than any other zeolite, we cannot in the 
present state of knowledge imagine. 

The chief submarine concretionary substances are, in 
descending order of abundance, manganese and iron peroxides, 
calcium phosphate, calcium carbonate, and barium sulphate. 
A tendency to assume concretionary forms argues proneness to 
supersaturation and feebly crystalline habit on the part of the 
substance concerned. The former property is very characteristic 
of the peroxides and of calcium phosphate, and is evidently 
connected with the reluctance to come to equilibrium in solution 
which so often goes hand in hand with high valencies.' 
Wherever concretions are found, we must suppose that there 
has at one time been a layer, or a chronological series of layers, 

^ See Van t'Hoff, Sitztmgsber. K. Akad. IViss. Berlin, vol. xxxiv. p. 658, 1907. 



IV DEPTHS AND DEPOSITS OF THE OCEAN 191 

of water surcharged with the substance, whence deposits have 
taken place on whatever nuclei offered, forming a hard radial 
aggregation, which would continue to grow until either the 
solution was exhausted or the supersaturation was relieved by 
external causes. The shape of the concretion must depend on 
the shape and number of its nuclei and the evenness of concen- 
tration in the surrounding solution ; in the ideal case of a small 
single nucleus and a uniform supply of substance from all sides, 
the concretion becomes an almost perfect sphere, like the 
manganese nodules met with in certain localities. 

Iron and manganese depend for the formation of super- Concretions 
saturated solutions in bottom-waters on the change of valency n\°nganesc. 
of which these elements are capable. Iron is brought into 
solution as ferrous bicarbonate by the decomposition of minerals; 
or again a solution of the bicarbonate may be produced locally 
by the action of decaying organic matter on ferric compounds. 
Now ferrous oxide is a base of strength comparable to, but 
rather less than, that of calcium oxide, and is subject to 
analogous conditions of solubility as bicarbonate. If oxygen 
were absent, and it the solubility were diminished, e.g. by with- 
drawal of carbonic acid, we should expect a deposition of ferrous 
monocarbonate (such as has often taken place on a large scale 
on land). As it is, the ferrous solution, diffusing out of the 
mud, meets with dissolved oxygen, and the change of valency 
to ferric iron rapidly supervenes. Ferric oxide, however, is a 
much weaker base, and the hydrolytic dissociation of its salts 
with a weak acid like carbonic is so complete as to render a 
ferric carbonate practically incapable of existence in presence of 
water. That is, the substance now in solution is ferric hydroxide. 
But this is a vastly less soluble body than ferrous bicarbonate ; 
therefore the iron in solution is now supersaturated. 

Non - manganiferous ferric concretions are comparatively 
rare, and have been reported only from the North Atlantic and 
the polar seas,^ where the terrigenous bottoms are poor in 
manganese. They attain no great size or hardness, contain 
much silica, and are rather balls of clay cemented with hydrated 
ferric oxide. 

As for manganese, the manner in which supersaturated 
solutions come into being is the same, in2itatis imitaiidis, as in 
the case of iron. The deposited peroxide has approximately 
the composition MnO., in deep-sea nodules, but shows notable 

1 Schmelck, Norwegian North Atlantic Expedition, No. IX. p. 52, 1882 ; Eoggild, 
Norwegian North Polar Expedition, Scientific Results, vol. v. No. XIV. p. T)%, 1906. 



192 DEPTHS OF THE OCEAN 

admixtures of lower oxides of manganese when laid down in 
landward waters/ where the supply of oxygen is competed for by 
much organic matter. The hydration MnOg-^H^O is assumed 
by Murray and Renard, and FCgOg. i^Hfi (limonite) for the 
accompanying ferric oxide. Deep-sea nodules are never purely 
manganic, but contain inclusions of clayey and other matters, 
and always a considerable proportion of iron. The mean of 
forty "Challenger" analyses works out at 29.0 per cent of 
MnO.2 and 21.5 per cent of Fe.^Og, soluble in hydrochloric acid. 
As a rule, then, surcharged waters hold both iron and manganese 
ready to be deposited simultaneously. The mode of formation 
of these nodules and the origin of the manganese from volcanic 
minerals have been thoroughly elucidated by Murray and Irvine.^ 

It should be noted that these oxides need by no means 
necessarily assume a concretionary form. They are very 
commonly found as thin incrustations on granular and frag- 
mentary objects. Furthermore many, if not most, of the pelagic 
clays contain intimate admixtures of finely-divided brown 
manganese and occasionally of limonitic iron. Here the super- 
saturation would seem to have been so high as to transgress the 
metastable limit, whereupon the oxides have precipitated them- 
selves without the intervention of nuclei ; they certainly must 
have been precipitated from solution. 

Manganese originates in the form of silicates and comes to 
rest exclusively in the form of peroxide. It is imported, on the 
one hand, from land as detritus or in solution ; but in the 
terrigenous areas of the bottom, where reducing conditions 
prevail, as a rule, it tends to exist in the suboxidized, i.e. soluble, 
form. Hence much of the terrigenous manganese will be 
carried on to the deeper oxidizing waters before it can deposit. 
There is thus a constant accession of manganese from land to 
the pelagic deposits. In the second place, manganese comes 
into the floor of the ocean from certain basic volcanic minerals 
of vitreous habit, and these are to be regarded as the principal 
source of ferromanganic nodules. These basic glasses are the 
only primary minerals in the deep sea which contain important 
amounts of manganese. It so happens that they are common 
in the Pacific, less common in the Indian Ocean, and rare in 
the Atlantic. Consequently the greatest abundance of manganese 
peroxide, pulverulent and nodular, is met with in mid-Pacific. 

Phosphatic concretions are of very localised occurrence and 

^ Buchanan, Trans. Roy. Soc. Edin., vol. xxxvi. p. 459, 1892. 
- Trans. Roy. Soc. Edin., vol. xxxvii. p. 721, 1894. 



IV DEPTHS AND DEPOSITS OF THE OCEAN 193 

are, in the last resort, of biological origin. The phosphoric Phosphatk 
acid in sea-water is derived chiefly from the skeletons and concretions. 
tissues of the marine fauna. At certain spots great masses of 
these skeletons are heaped up at the bottom, and here or here- 
abouts phosphatic nodules are presently formed. In order to 
explain why the phosphate of decaying bones goes into solution 
it is not necessary to postulate exceptional conditions in the 
surrounding sea- water. The solubility of tricalcium orthophos- 
phate in water is a matter which bristles with complications, and 
experimental difficulties have hitherto proved too great for its 
exact measurement ; but it seems to be of the order of deci- 
grammes per litre. The solubility is much enhanced by the 
presence of H' ions, i.e. of acids. The solvent action of carbonic 
acid which has been suggested seems, however, to be merely 
hypothetical. Carbonic acid is so weak that at best it can 
produce only a negligible concentration of H" ions ; moreover, 
there is experimental evidence that so long as excess of lime 
(as bicarbonate) is present, calcium phosphate is no more 
soluble in carbonated than in pure water. In all probability the 
rapid dissolution of the calcium phosphate and carbonate in fish- 
bones is simply due to the fine state of division. This effect 
has already been discussed with reference to sea-shells. The 
extreme fineness of the inorganic particles disseminated in the 
gelatinous matter of fish-bones is attested by the translucency 
of the mass. Or it may even be that the carbonate and 
phosphate are present in a colloidal form. In either case they 
will readily yield supersaturated solutions when the enclosing 
ossein rots away, and as soon as a nucleus presents itself the 
formation of concretions is ready to begin. Since phosphatic 
concretions usually occur, as already indicated, in positions where 
organic remains accumulate on the bottom at a rapid rate, as in 
areas having a great range of surface temperature, the trans- 
ference of matter from bones to nodules must have taken place 
without much delay. Consequently there has been little 
opportunity for differentia] diffusion of carbonate and phosphate, 
so that these calcium salts are invariably found to have been 
deposited simultaneously. The "Challenger" analyses show 
i^ to 3 parts of tricalcium orthophosphate to one of calcium 
carbonate. Magnesium phosphates being considerably more 
soluble than those of calcium, the phosphate of bones is re- 
deposited unchanged after its passage through sea-water ; only 
a trifling percentage of magnesium is shown by the analyses, 
and this is probably present as carbonate. 

o 



194 DEPTHS OF THE OCEAN 

4. Depth and Deposits of the North Atlantic Ocean 

The North Atlantic may be called a circumscribed ocean, 
being practically land-locked except towards the south. Its super- 
ficial area is small compared with the other ocean basins, but 
the area draining into it is enormous, since the Arctic Ocean, 
the Mediterranean Sea, the Baltic Sea, the Gulf of Mexico, and 
the Caribbean Sea all communicate with it. Indeed, it has 
been estimated that nearly one-half of the entire world drains 
directly or indirectly into the Atlantic Ocean ^ as a whole, or 
about four times the area draining into the great Pacific Ocean, 
and of this by far the larger portion drains into the North 
Atlantic as distinct from the South Atlantic ; the largest river 
of South America, the Amazon, enters the Atlantic just on 
the equator, and its outflowing waters, with their burden of 
sediment, are carried mostly into the North Atlantic. It has 
further been estimated that more than one-half of the total 
rainfall of the globe falls on the Atlantic drainage area, equal 
to more than three times the amount- falling on either the 
Pacific or Indian Ocean drainage area.^ Remembering these 
facts, and the relatively large area occupied by the continental 
shelf and continental slope, it is easy to understand why the 
deposits covering the floor of the North Atlantic partake more 
of a terrigenous character than those of the other ocean basins, 
and this character is further emphasised by the floating icebergs 
met with in the northern part of the ocean, and by the 
proximity to the southern part of the ocean of the great desert 
of the Sahara, the sand grains from which are sometimes 
carried far out to sea by the wind. The North Atlantic is also 
remarkable for the relatively high temperature of its waters at 
all depths from surface to bottom, as compared with the other 
oceans, and this is due partly to the influence of the dense 
warm water flowing out from the Mediterranean at the Straits 
of Gibraltar, and partly to the downward movement of the 
dense surface water of the Sargasso Sea. Another characteristic 
of the North Atlantic is the permanent anticyclonic area in the 
Sargasso Sea region, which largely determines the direction of 
the prevailing winds over a large part of that ocean, and hence 
of the great surface currents like the Gulf Stream. 

The bathymetry of the North Atlantic, according to the 

1 Scott. Geogr. Mag., vol. ii. p. 554, 1S86. - Ibid. vol. iii. p. 67, 1887. 



DEPTHS AND DEPOSITS OF THE OCEAN 195 

present state of our knowledge, is shown in Map HI. On Depths of 

the Nortt 
Atlantic. 



this chart the soundings in depths greater than 1000 fathoms '"^^ ^"""^^ 



are indicated by the hrst two figures, and they show that the 
North Atlantic is now well sounded — in fact, probably the 
best sounded of all the ocean basins. The recent soundings 
by the "Michael Sars " did not bring to light many new facts 
as to depth, and it is not likely that any great changes in the 
contour-lines will be revealed by future soundings, though it is 
possible that further submarine cones, like the Seine Bank and 
Dacia Bank and the Coral Patch, may yet be discovered. 

A comparison of this map with the depth map published by Maury's 
Maury in 1854, which is reproduced in Map I., brings out ^^P'^^ "^^p- 
at a glance the strides that have been made in our knowledge 
regarding the depth of the North Atlantic since that time — 
a progress from comparative simplicity to great complexity. 
Maury's 4000 -fathoms area in the North - West Atlantic, 
based upon some doubtful soundings (two of them exceeding 
5000 fathoms and another in 6600 fathoms), has disappeared, 
though the existence of very deep water in the neighbourhood 
is evidenced by the soundings in the Suhm Deep. These deep 
soundings laid down by Maury were among the early attempts 
at deep-sea sounding, and the records of such depths as 6600 
fathoms, no bottom, were due to the uncertainty as to when 
the sounding-tube touched bottom. The only part of the 
North Atlantic where the depth is now known to exceed 4000 
fathoms (in the Nares Deep north of the West Indies) is 
blank on Maury's map, but the northern portion of the mid- 
Atlantic ridge, on which the Azores plateau is situated, is 
correctly indicated, though since modified in outline ; the 
continuation southward of this ridge was, however, unknown 
in Maury's time. 

Reference has already been made to the relatively large area 
occupied throughout the world by the continental shelf, which 
is equal to about 7 per cent of the entire ocean-floor. The 
continental shelf apparently attains its maximum development Continental 
in the North Atlantic basin, if we include the tributary seas J^J[i;" ^^^ 
(x^rctic Ocean, Mediterranean, etc.). The total area of this Atlantic, 
basin may be estimated at about 23 million square miles, and of 
this area no less than about 6 million square miles (or 26 per 
cent) lies between the shore-line and the lOO-fathoms line. 
While the gentle gradients of the continental shelf cover such Continental 
an extensive area, the continental slope beyond the lOO-fathoms ^T°PtV" * " 
line seems, on the other hand, to be relatively very steep, for Ati 



in the 



th 
antic. 



iq6 



DEPTHS OF THE OCEAN 



Abyssal area 
of the North 
Atlantic. 



Deeps of th' 

North 
Atlantic. 



the area between the lOO-fathoms Hne and the 500-fathoms Hne 
is only a little over 2 million square miles (or 9 per cent), and 
the area between the 500-fathoms line and the looo-fathoms 
line is only about i million square miles (or 4 per cent of the 
total area). It thus appears that the area with depths less than 
1000 fathoms within the North Atlantic basin, as already defined, 
is equal to about 9 million square miles (or 39 per cent of the 
total area), and of this the continental shelf covered by water 
less than 100 fathoms in depth occupies 6 million square miles 
(or 26 per cent). 

Proceeding into the abysmal region, we find that the area of 
the North Atlantic sea- floor covered by water between 1000 
and 2000 fathoms in depth is about 5 million square miles (or 
22 per cent), the area covered by water between 2000 and 
3000 fathoms in depth is about 7^- million square miles (or t,^ 
per cent), and the area covered by more than 3000 fathoms of 
water ("deeps") is about i^ million square miles (or 6 per cent 
of the total area). These figures show what a large proportion 
of the North Atlantic sea-fioor is covered by shallow water less 
than 1000 fathoms (equal to two-fifths of the entire area), and 
by deep water between 2000 and 3000 fathoms (equal to one- 
third of the entire area). 

The deeps of the North Atlantic number fourteen, and cover 
an area of about i J million square miles, as already indicated. 
The larger and more important of these, Nares Deep, Moseley 
Deep, and Chun Deep, have been briefly described on pages 
141, 142, and 143. The smaller ones are : Makaroff Deep in the 
West Indian seas; Bartlett Deep in the Caribbean Sea; Mill 
Deep and Keltie Deep in the sea between Bermuda and the 
American coast ; Suhm Deep, Libbey Deep, Sigsbee Deep, 
and Thoulet Deep, to the south of Nova Scotia and Newfound- 
land ; Peake Deep to the west of Cape Finisterre ; Monaco 
Deep to the south of the Azores ; and Hjort Deep immediately 
to the east of the mid-Atlantic ridge in lat. 20° N. 



The 

Norwegian 

Sea. 



The Norwegian Sea is bounded on the east by Spitsbergen, 
Bear Island, the banks of the Barents Sea and the Norwegian 
coast ; on the south by the North Sea, the Shetland and Faroe 
Islands, and the submarine ridges between the Shetlands and 
Faroes and between the Faroes and Iceland ; on the west by 
Iceland and Greenland ; and on the north, about lat. 80° N., 
by a submarine ridge supposed to separate the two deep basins 
called the Norwegian Sea and the Polar Sea. 



IV DEPTHS AND DEPOSITS OF THE OCEAN 197 

The Norwegian Sea has a superficial area of 2.58 milHon 
square kilometres, nearly two-thirds of which consists of a deep 



Fig. 143.— The Norwegian Sea, showing Depths. 

200 metres. — • looo metres. 

600 ,, — 2000 ,, 

3000 metres. 



198 



DEPTHS OF THE OCEAN 



basin (see Fig. 143), more than 3000 metres deep in the central 
portion. From this depth the floor rises gradually towards 
the continental slope on either side. The main features of the 
continental slope and shelf along the coast of Norway will be 
grasped by reference to the accompanying diagram (Fig. 144). 
The term "coast banks" is usually applied to the higher parts 
of the submerged continental plateau or continental shelf, which 
are frequented by fishermen ; there is often a marked "edge" 
between the plateau and the continental slope. 

The continental shelf fringes to a greater or less extent the 
whole of the coasts of the Norwegian Sea, and occupies alto- 
gether about a third of its entire superficial area. This shelf 
is covered by depths down to 200 metres with channels down 
to 600 metres. In water shallower than 200 metres there 

are only comparatively 
small banks, the great- 
est being at Lofoten 
and Romsdal and 
round the Faroes and 
Iceland. Deeper than 
600 metres the con- 
tinental slope is steep ; 
the bathymetrical 
curves for 600 and 
1000 metres lie every- 
where in close prox- 
imity to one another, and the area of the sea-bottom between 
them is no more than 5.4 per cent of the whole extent of the 
Norwegian Sea. 




G. 144.— Diagrammatic Section off the Norwegian 

Coast. 
Continental slope ; b, continental edge ; c, continental shelf 
or plateau ; d, coast bank ; e, fjord ; f, coast. 



Deposits of 
the North 
Atlantic. 



The distribution of the deposit-types over the floor of the 
North Atlantic is shown on Map IV., an examination of which 
bears out the statement that the terrigenous deposits are 
relatively more important in the North Atlantic than in the other 
oceans, in correlation with the relatively large area covered by 
shallow water. Thus of the total area of 23 million square miles, 
one-half, about ii|- million square miles (or 49 per cent), is 
covered by terrigenous deposits. This area is to a very large 
extent occupied by Blue mud, no attempt having been made to 
indicate on the map the small areas occupied by Green mud off 
the coast of the United States, off the Spanish and Portuguese 
coasts, and in the vicinity of the Wyville Thomson Ridge, nor 
the small areas occupied by Volcanic mud in the neighbourhood 



,v DEPTHS AND DEPOSITS OF THE OCEAN 199 

of the Azores, Madeira, etc. The position of the Coral mud 
deposits of the West Indies and Bermuda is, however, indicated 
on the map, and these deposits cover an area of about half a 
million square miles (or 2 per cent of the total area). 

After the Blue mud, the principal type of deposit in the 
North Atlantic is Globigerina ooze, which covers an area of 
about 9 million square miles (or 39 per cent of the total area). 
A glance at the map shows what an extensive area is occupied 
by this type of deposit in the open ocean, where it is found in 
greater depths than is usually the case in the other ocean-basins 
(the "Michael Sars " deepest sounding in 2966 fathoms, for 
example, gave a Globigerina ooze with 64 per cent of calcium 
carbonate) ; it also occurs in the Caribbean Sea, in the Gulf of 
Mexico, and in the Norwegian Sea in lat. 63° N. to 72° N. 

Red clay, which covers such an enormous area of the sea- 
floor in the great Pacific Ocean, plays a subordinate part in the 
North Atlantic, being estimated to occupy about 2^ million 
square miles (or 1 1 per cent of the total area) ; it occurs in two 
areas on either side of the mid- Atlantic ridge : the larger to the 
west of the ridge, surrounding Bermuda and extending from 
lat. 13° N. to 40° N., the smaller to the east of the ridge in lat. 
8^ N. to 28° N., with a subsidiary area in the Caribbean Sea in 
lat. 13^ N. to 15' N. 

Pteropod ooze, though widely distributed throughout the 
basin, covers in the aggregate a comparatively very small area, 
estimated at about 200,000 square miles (or i per cent of the 
total area) ; it occurs in the open ocean in the neighbourhood of 
the Azores, Canaries, Bermudas, and West Indies, as well as 
in the Mediterranean, Caribbean, and Gulf of Mexico. The 
other two types of pelagic deposits, Radiolarian ooze and 
Diatom ooze, are not represented in the North Atlantic. 

Although the "Michael Sars" Expedition did not add "Mic 
greatly to our knowledge either of the depth or of the deposits s^ampies!^°'''' 
of the North Atlantic, still both the soundings and the deposit- 
samples are of value, many of the deposit-samples, indeed, being 
extremely interesting. A detailed description of all the samples 
will be reserved for a later publication, but in this place we may 
refer to the more interesting points brought out by a study of 
the m.aterial. 

In the first place, reference may be made to the stones and 
rock fragments brought up from several stations, which form 
the subject of a report by Drs. Peach and Home appended to 



hael 



200 DEPTHS OF THE OCEAN 

this chapter ; from another station the ear-bone of a whale and 
two sharks' teeth were obtained. 

Of the twenty-seven samples submitted to detailed examina- 
tion, nineteen were Globigerina oozes, six were Blue muds, one 
a Pteropod ooze, and one a Globigerina ooze overlying Blue 
mud. The Globigerina oozes occur over the route followed by 
the " Michael Sars " as far west as long. 44° W. ; the Globigerina 
ooze overlying Blue mud occurred to the north of the Rockall 
Bank ; the Pteropod ooze near the Canary Islands ; and the 
Blue muds in the Eastern Atlantic from the Faroe Channel to 
the Straits of Gibraltar. The " Michael Sars " samples show 
that the Globigerina ooze approaches nearer to the coasts of 
the British Islands than was previously supposed, having been 
found at the following depths along the continental slope off the 
European and African coasts: 547 fathoms (Station 4), 1256 
fathoms (Station 25 A), 1 122 fathoms (Station 25 B), 1422 fathoms 
(Station 35), 746 fathoms (Station 41), 688 fathoms (Station 93), 
981 fathoms (Station 95), 742 fathoms (Station 98), and 835 
fathoms (Station 100). Globigerina ooze and Pteropod ooze 
were found in the neighbourhood of the Canary Islands in 
positions where they were previously unrecorded. 

An interesting point in connection with the " Michael Sars" 
deposits is the number of instances where the sounding-tube 
had plunged deeply into the sediment, bringing up sections 
varying from two to fourteen inches in length, and in some 
cases marks observed on the outside of the sounding-tube 
indicated that it had penetrated still farther into the deposit. 
Though in most cases the material was apparently uniform 
throughout, some of these long sections gave distinct evidences 
Stratification, of Stratification. Thus at Station 10 in the Bay of Biscay, at a 
depth of 2567 fathoms, the sounding-tube brought up a section 
about five inches in length, of which the upper portion to the 
depth of about three inches was of a uniform fawn colour, 
representing apparently an ordinary Globigerina ooze with 
66 per cent of calcium carbonate, while the lower inch or two 
had a mottled appearance, with light and dark brown patches, 
the dark brown material giving only ;^2> P^^ cent of calcium 
carbonate when analysed. At Station 49 C, from a depth of 
2966 fathoms, the sounding-tube brought up a section about 
fourteen inches in length, showing distinct traces of stratification, 
especially towards the upper end, although the lower end 
presented a mottled appearance with patches of lighter and 
darker brown ; towards the upper end there were small patches 



IV DEPTHS AND DEPOSITS OF THE OCEAN 201 

of a dark brown colour which proved to be Red clay, with only 
25 per cent of calcium carbonate, though the mass of the sample 
was a Globigerina ooze with 64 per cent of calcium carbonate. 
At Station 100, in 835 fathoms, the sounding-tube brought up a 
section about nine inches in length, which was extremely interest- 
ing because of the great difference between the upper and lower 
portions, the upper portion, to the extent of three or four inches, 
being a Globigerina ooze with 58 per cent of calcium carbonate, 
while the lower portion was a Blue mud with only 26 per cent 
of calcium carbonate. At Station 88, in 1703 fathoms, the 
sounding-tube brought up a section about fourteen inches in 
length, which showed little difference to the naked eye, although 
the colour was darker in the lower portion, the upper portion 
being rather lighter in colour, less coherent, and more granular ; 
the deposit was a Globigerina ooze, containing 83.79 per cent of 
calcium carbonate in the upper portion, 73.66 per cent of calcium 
carbonate in the middle portion, and 62.1 per cent of calcium 
carbonate in the lower portion. It is curious that at this 
station the trawl brought up a large quantity of empty pteropod 
shells (chiefly Cavolinia trispinosa), while in the samples from 
the soundjng-tube submitted to examination no pteropods were 
observed. It is possible that the trawl may have worked 
over shallower depths than where the sounding was taken. 
Similarly, at Station 23, where the depth was 664 fathoms, the 
Petersen net sent down with 820 fathoms of line and towed 
throughout the night of 5th and 6th May brought up a large 
amount of empty pteropod shells (principally Cavolinia inflexa) ; 
indeed, the pteropod shells at this station differ strikingly 
in general appearance from those taken at Station 88, ten 
degrees farther north. At Station 34, in 1185 fathoms, the 
middle portion of the section from the sounding-tube, about six 
inches below the upper surface, showed dark-coloured patches 
containing a large proportion of volcanic glass splinters, to 
which the dark colour was due ; the volcanic glass was quite 
fresh and unaltered, as though the products of a volcanic eruption 
(probably submarine, since the glassy fragments showed no trace 
of friction or decomposition but were perfectly angular) had 
been overlain by new material to the depth of six inches. 

We append the detailed description of a typical Globigerina 
ooze taken by the " Michael Sars " to the south of the Azores: — 

"Michael Sars" Station 55. loth June 1910. Lat. 36° 24' N., 
long. 29° 52' W. ; depth, 3239 m. (1768 fathoms). 



202 DEPTHS OF THE OCEAN 

Description of GlOBIGERINA Ooze — dirty white colour, coherent, granular. 

typical deposit Calcium CARBONATE — 78,59 per Cent; pelagic and bottom-living 

kcTidVy°the foraminifera, ostracods, coccoliths, and rhabdoliths. 

"Michael RESIDUE, 21.41 percent: — 

Sars." Siliceous Organisms — 2 per cent ; radiolaria, sponge spicules. 

Minerals — 4 per cent, m. di. 0.09 mm., one angular fragment of 
volcanic glass exceeded 2 mm. in length ; quartz, plagioclase, 
volcanic glass, augite (?), magnetite, mica. 
Fine Washings — 15.41 per cent; amorphous clayey matter with 
minute mineral particles. 
Note. — The sounding-tube brought up a roll about 9 inches in length 
of a creamy white colour throughout. 

All the rock fragments dredged during the " Michael Sars " 
Expedition, as well as those collected by H.M. ships " Knight 
Errant" and "Triton" in 1880 and 1882, have been carefully 
examined and studied by Dr. B. N. Peach. ^ Drs. Peach and 
Home have prepared the folio w^ing note on the general results: — 

Rock frag- The materials collected by the " Michael Sars " Expedition fall under 

ments dredged |-^q categories: (i) those whose presence on the sea -floor is due to 

"\lichael natural agencies, and (2) those distributed by human agencies. The 

Sars." materials belonging to the first group consist chiefly of rock fragments, 

the remains of floating or swimming organisms that lived at or near the 

surface of the sea (such as barnacles and the ear-bone of a whale), and 

fragments of wood. The members of the second group are mainly 

furnace clinkers and pieces of coal, small pieces of glazed pottery, and 

oyster-shells, together with a cannon-bone of a small ox. 

By far the most interesting collection of the " Michael Sars" series 
was obtained from Station 95, which lies about 230 miles south-west 
of Mizen Head, Ireland, at a depth of 5886 feet, or a little over a mile. 
The rock fragments, comprising over 200 specimens, included upwards 
of 100 of sedimentary origin, 58 of igneous origin, and 40 belonging 
to the metamorphic series. Some of the specimens were referred to the 
Cretaceous and Carboniferous periods by means of their fossil contents ; 
the remainder were grouped with the Devonian or Old Red Sandstone 
and Silurian systems solely on lithological grounds. 

The fragments regarded as of Silurian age include greywacke- 
sandstones, dark shales, and black lydian stone identical in lithological 
characters with rocks that floor a large part of the southern uplands 
of Scotland and the north of Ireland. Those referred to Devonian 
time resemble the Glengariff grits of the Dingle peninsula in the south- 
west of Ireland. The carboniferous specimens comprise encrinital 
limestones with chert, like those of Galway and Clare. One sandstone 
fragment was crowded with ScJiizodus and Edinondia similar to rocks 
occurring in places along the Solway shore in Scotland and in London- 
derry and Tyrone in Ireland. The specimens of chalk and chalk-flints 
are like the rocks in the Antrim plateau. 

^ See detailed report in Proc. Roy. Soc. Edin., 19 12. 



.V DEPTHS AND DEPOSITS OF THE OCEAN 203 

Among the metamorphic series there are representatives of crystalline 
o-neisses and schists which could be matched from the Lewisian gneiss 




Fig. 145.— Glaciated Stone from "Michael Sars " Station 95. 

and Moine schist areas in the North-West Highlands of Scotland. 
Associated with these are specimens indicatmg a low grade of meta- 
morphism, such as phyllites and sheared greywackes and igneous rocks, 



204 DEPTHS OF THE OCEAN chap. 

which resemble types to be found along the south-eastern border of the 
Highlands and the north of Ireland. Indeed, some may have been 
derived from the south of Ireland. 




Station 95. 



The evidence furnished by the igneous materials is no less remarkable. 
The plutonic rocks are represented by granites resembling those of 
Lower Old Red Sandstone age in Scotland and the north of Ireland, 
and also by a specimen of nepheline-syenite which cannot be matched 



IV DEPTHS AND DEPOSITS OF THE OCEAiN 205 

with any known rock of this type in the North Atlantic basin. The 
lava - form and intrusive types of the basic materials have marked 
affinities with the tertiary volcanic rocks of the Inner Hebrides and the 
north of Ireland. 

Of special interest is the evidence pointing to the conclusion that the 
rock fragments from this station must have been transported by floating 
ice during some phase of the glacial period. More than half of the 
specimens are glaciated, the larger part of the remainder are angular, 
and a number are well rounded. A typical example of one of the 
glaciated stones is shown in Fig. 145, which is a portion of a larger boulder 
broken off before being embedded. Irregular striae appear on this 
specimen, but on one surface it is facetted and the striae thereon |are 
more or less parallel. It is noteworthy that the glaciated and ice- 




FiG. 147. — Surface of Specimen No. 4 in Fic. 146, enlarged to show 
" Chatter-marks." 

moulded specimens include nearly every rock type represented in the 
collection from this particular station. The stones resemble those found 
in boulder clay or " moraine profonde," indeed in some instances the 
clayey matrix of this deposit has been cemented to some of them by 
calcareous matter. 

Some of the rounded specimens, consisting of Silurian greywackes, 
carboniferous limestone, chalk -flint, dolomite, and vein - quartz, are 
shown in Fig. 146. These must have been rounded before they reached 
the position from which they were dredged. 

An enlarged part of specimen No. 4 in Fig. 146 (chalk-flint) is repre- 
sented in Fig. 147, to illustrate the bulbs of percussion or " chatter-marks " 
which it displays. Such evidence indicates that the stones had originally 
been dashed against each other by torrent or wave action, 

A careful examination of the specimens points to the conclusion that 
all had been partially embedded in a Globigerina ooze on the sea-floor. 



206 



DEPTHS OF THE OCEAN 



as shown by the attached marine organisms and by a slight coating 
of manganese oxide on the exposed parts. In Fig. 148, which represents 
a specimen composed of carboniferous Hmestone and chert, the arrow 

points to the man- 
ganese staining where 
the exposed and un- 
exposed parts meet. 

The average size 
of the stones is about 
three inches ; only a 
very few reach six 
inches in length. As 
the sounding - tube 
brought up from the 
sea-floor at this station 
a core of ooze nine 
inches long, we may 
infer that the tube 
pierced the deposit to 
a greater depth than 
that reached by any 
of the stones. It is 
therefore clear that 
none of the stones can 
be in situ. They must 
have been dropped 
from above into the 
ooze. 

Many of the speci- 
mens, as represented 
in Fig. 149, must have 
stood on end in the 
ooze, which is not the 
natural position they 
would have assumed 
if dropped on the 
present surface of that 
deposit. The infer- 
ence seems obvious 
that originally they 
fell into a soft ooze 
in which they were completely buried. The stones would naturally be 
arranged along the lines of least resistance to friction, so that many 
would be entombed end on or edge on, like those illustrated in Figs. 
149 and 1 50. Subsequent current action has removed part of the 
material in which they were embedded, and has been powerful enough 
to prevent further accumulation of ooze at the spot where they were 
dredged. Since the ooze contains IJ per cent of insoluble material, the 
theory of the removal of the deposit by solution is improbable. 

Among the materials distributed by human agency dredged from 




Fig. 148. — Stone with staining ok Manganese, the 
arrow showing the position of the surface of 

THE DEPOSIT IN WHICH THE SPECIMEN HAD BEEN 
EMBEDDED. 




IV DEPTHS AND DEPOSITS OF THE OCEAN 207 

this station (95) about 200 specimens of furnace clinkers were found, Furnace 
together with fragments of unburnt coal, also a portion of an earthen- clinkers, coal, 
ware jar and a cannon-bone of an ox. This station lies along the route ^^^' 
of the Atlantic Liners, from which these specimens were probably 
dropped. 

At Station 10, on the south side of the Bay of Biscay, and nearly 
200 miles north of Cape Finisterre, 
at a depth of over 15,000 feet, an >^>>^ I 

assemblage of stones was obtained, 
numbering in all 339, most of 
which were glaciated and almost 
identical in lithological characters 
with those just described. 

At Station 48, lat. 28° 54' N., 
long. 24° 14' W., in about 2800 
fathoms, chalk - flints and ice- 
moulded metamorphic rocks were 
collected, showing that floating 
ice had dropped materials over 
that part of the sea-floor. They 
were associated with fragments 
of pumice carried thither by the 
descending branch of the Gulf 
Stream. An ear-bone of a finner- 
whale was also found at this 
locality. 

Just outside the Straits of 
Gibraltar, at Station 23, in 664 
fathoms, a curious assortment of 
materials was dredged, comprising 
dead lamellibranch shells (some 
of them bored by gasteropods), 
barnacles dropped from whales, 
furnace clinkers, and an American 
blue point oyster that had fallen 
from a passing ship. The dead 
lamellibranch shells point to 
subsidence of that part of the 
sea - floor in recent geological 
times. 

The materials dredged at 
Station 70, south of the New- 
foundland Banks, in 600 fathoms, 

indicate that this part of the sea-floor is within the range of the present 
Arctic ice-drift. 

The rock fragments obtained from Stations 100 and loi, in 835 and 
1013 fathoms, seem to point to the conclusion that they were transported 
thither by ice that passed over the Orkney and Shetland Isles. 





40 



so 



120 



160 MM. 



Fig. 149. — Diagrams drawn to scale show- 
ing POSITIONS OF Stones embedded in the 

DEPOSIT, the shaded PARTS INDICATING 
THE PORTIONS PROJECTING ABOVE THE 
DEPOSIT. 



Important evidence was gathered from the Wyville Thomson Ridge 



208 



DEPTHS OF THE OCEAN 




Rock frag- at depths ranging from 318 to 3420 feet during the expeditions of H.M. 
merits dredged ships "Triton" and "Knight Errant." It suggests that the glaciated 
stones on the ridge are or have been embedded in a boulder clay. The 
stones are composed chiefly of Lewisian gneiss and the Moine schists 
lying to the east of the post-Cambrian displacements in the Highlands 
of Scotland. A large proportion consists of Caithness flagstones and 
other Old Red Sandstone rocks, like those occurring in place in the 

Orkney and Shetland 

' ^^^ Isles. A considerable 

number of Jurassic and 
Cretaceous types occur 
in the collection, together 
with two carboniferous 
specimens, the age of 
which is determined 
by their fossil contents. 
The assemblage of fossil- 
iferous stones are similar 
to those found by Messrs. 
Peach and Home in the 
boulder clays of Caith- 
ness and Orkney. 

On the Faroe Banks 
the volcanic rocks of the 
Faroe Isles are not re- 
presented among the 
rock fragments dredged, 
which would seem to 
point to the extension of 
the combined Scottish 
and Scandinavian ice- 
sheets over that part of 
the sea-floor during the 
glacial period. 

Just inside the Rock- 
all Bank, at Stations 
100 and loi (" Michael 
Sars "), only one Old Red 
Sandstone boulder was 
found in the materials 
collected, but the sand 
grains occurring in the 
ooze are either red or green. The ooze also contained fragments of 
brown glass, resembling the slaggy volcanic rocks of Iceland. Such 





AO 



80 



— I — 
120 



6 //YCHES 



160 MM. 



Fig. 



50. — Diagrams drawn to scale showing positions 
OF Stones embedded in the deposit, the shaded 

PARTS indicating THE PORTIONS PROJECTING ABOVE 
THE DEPOSIT. 



distributed by floating ice. 

At Station 3 ("Knight Errant"), at a depth of 318 feet, many 
dead shells of shallow-water habitat were got, which clearly indicate a 
subsidence of the sea-floor since the glacial period. The absence of 
raised beaches in Orkney and Shetland, the submerged peat-mosses, 



IV DEPTHS AND DEPOSITS OF THE OCEAN 209 

the depth and steepness of the sounds between the Faroe Islands, the 
great depth at which the seaward extension of the fjords in Iceland cut 
the marine shelf, the submergence of shell banks between Iceland and 
Jan Mayen referred to by Nansen, all point to the same conclusion. In 
all probability there was either land connection with Greenland during 
the glacial period, or a confluent ice barrier which prevented the Gulf 
Stream from flowing into the Polar basin and deflected it towards 
the south. 

J. M. 




Hooke's Sounding Machine and Water-Bottle, 1667. 
(See page 2. ) 




CHAPTER V 



PHYSICAL OCEANOGRAPHY 



In the middle of last century the idea of "physical oceano- 
graphy " did not exist, but in the course of a few decades it 
has become a widespread branch of knowledge, with a copious 
literature and bulky text-books. A few figures may serve to 
show how important is the study of the sea. The waters of the 
globe cover more than two-thirds of its surface, and their 
volume is about 1300 millions of cubic kilometres, or thirteen 
times that of all the land above sea-level. The mean height 
of the land is 700 metres, while the average depth of the sea 
is 3500 metres. Sea-water contains various salts in solution, 
the total weight of which is nine times that of the earth's 
atmosphere. 

The reason why the ocean, which plays such an important 
part in the economy of the earth, has not been investigated 
until recently is because of the special difificulties which are 
encountered in making investigations. One great difficulty is, 
as has been previously mentioned, that it is impossible to 
observe directly what is going on beneath the surface, and it is 
necessary to have a special set of apparatus that can be relied 
upon. The methods have developed with phenomenal rapidity, 
but the observations are still few in proportion to the extent of 
the ocean, and consequently it is often difficult to obtain a 
complete and true image of the actual conditions. Many of the 
results obtained are therefore merely preliminary, and further 
study may alter our views on various points ; for the solution of 



PHYSICAL OCEANOGRAPHY 



sending down 
instruments. 



many important problems we have not yet sufficiently numer- 
ous observations. In a rapid sketch like this, only some of 
the principal facts can be dealt with ; we shall first examine 
the methods employed in physical oceanography, and then 
endeavour to draw some conclusions from the observations 
available. 

In the first place, one must have a line with which to send Lines for 
down the instruments and draw them up again. Formerly 
hemp lines were used, but they have now been superseded by 
wire ; steel piano-wire is used for sounding, and wire rope 
for thermometers, water-bottles, etc. For general use the wire 
need not be more than 2 to 3 mm. in 
diameter, and it will, nevertheless, bear 
the weight of several hundred kilograms 
without breaking. The old hemp line 
was marked at regular intervals for the 
determination of the depth, but this can- 
not well be done with the wire, which is 
run out over the metre- or fathom-wheel Metre-wheel. 
(see Fig. 151), and this is both a con- 
venient and accurate method. The 
wheel communicates with a clock-work 
arrangement with dials and hands, by 




means of which the length of wire run 



Fig. 151. — Metre-Wheel. 



out can always be read off correct to 
within a metre. When, however, an 
observation is to be taken at a depth of 
1000 metres, it is not enough to run out 
1000 metres of line. The line must be 
"up and down," and this is not always 
easily managed, especially in a wind or strong current, when 
the ship is drifting. Some manoeuvring is then required, and 
the apparatus must either in itself be sufficiently heavy to 
straighten the line, or an extra weight must be added. Many Several 
of the instruments are so constructed that they may be attached lIsed's'imuK 
to the side of the line as well as at the end, and thus several taneousiy. 
instruments may be used simultaneously. They are fastened at 
certain intervals on the line as it is being paid out, and a 
number of observations are made at the same time at different 
depths. By this method a comprehensive series of observations 
from the surface down to two or three thousand metres may be 
taken in a couple of hours. This method was employed during 
the "Challenger" Expedition. 



212 



DEPTHS OF THE OCEAN 

7vo/]xyod 




When several series of observations have been taken in a 
certain region, they are usually represented for diagrammatic 



PHYSICAL OCEANOGRAPHY 213 

purposes in horizontal plans and vertical sections. It is To show 
necessary, in order to be able to see anything in the sections, ^oSfo^g i,^ 
to exaggerate the scale of depth in comparison with the scale of diagrammatic 
horizontal distance. This is shown in Fig. 152, which represents necessary' to 
the floor of the Atlantic Ocean along the parallel of 40" N. exaggerate 
The upper line (A) shows the section drawn to the same scale scaie.^'^''^^ 
for depths and horizontal distances ; the variations in the depth 
are represented by a thin uneven line, indicating how relatively 
small is the depth of the Atlantic Ocean compared with hori- 
zontal distances on the earth's surface ; the lower diagram (B) 
shows the section with the depths exaggerated 500 times. 
Drawing the depth on a larger scale brings out the details of Section across 
the relief of the ocean-bed : thus off Portugal there is seen a Atk^dc* 
narrow continental shelf, and then a rapid falling-off towards 
the deep water (the continental slope) ; farther west (about the 
middle of the figure) there is a corresponding slope, on the 
summit of which the Azores appear ; then another fall towards 
the western basin of the North Atlantic, followed by the 
continental slope on the American side, where again a narrow 
continental shelf borders the coast. The continental shelf is 
seen to be wider on the American side than on the European 
side of the section. This exaggeration of the vertical scale 
allows of the representation of a number of details, but, of course, 
the lines look very much steeper than they really are. One 
must not imagine that the continental slopes are so marked as 
they appear in the figure, for the angle is usually not so much 
as two degrees, the slope being similar to that of our common 
roads and railways ; real submarine precipices do occur, but 
mostly as rare exceptions. 

At a comparatively early date it was known that the The temp^^ 
temperature^ of _ike_-jseazsuiiace_w^ by ti-,e tureo t esea^ 

c urre nts. In the beginning of the seventeenth century, for 
instance, it was noticed that there was a sudden change of 
temperature on passing from the cold Labrador current south 
of the Newfoundland Banks to the adjacent warmer waters of 
the Gulf Stream. Benjamin Franklin, who made a careful Benjamin 
study of the Gulf Stream (see Fig. 153), advised ships' officers Ji^'cuif ""'"^ 
to use the thermometer in order to find out when they entered Stream. 
the Gulf Stream, so that they might take advantage of the 
current when voyaging eastward, and steer clear of it when 
sailing westward. 

The American naval officer M. F. Maury (i 806-1 873), Maury. 



214 



DEPTHS OF THE OCEAN 



one of the founders of physical oceanography, used the surface 
temperatures recorded from different places in the sea in his 
examination of the currents. He organised an extended 
collection of temperature-observations for the benefit of navi- 
gation ; he studied the winds and the drift of vessels, and in 
the middle of the nineteenth century he published his Ex- 
planations and Sailing Directions to accompany the Wind and 
Ctwrent Charts. He also wrote an extremely interesting book, 
The Physical Geography of the Sea and its Meteorology, which 
has appeared in many editions and in several translations. 
Maury's work had important consequences, for ship-masters 
following his directions shortened the voyage between North 




Fig. 153.— Benjamin P^ranklin's first chart of the Gulf Stream. 

America and England by ten days, that from New York to 
California by about forty-five days, and that from England to 
Australia and back by more than sixty days. The profit 
derived from the use of Maury's charts by British ship-owners 
on the East India route alone amounted to 10 million dollars 
yearly. 

On Maury's suggestion it was decided, at an international 
congress at Brussels in 1853, that numbers of log-books should 
be sent out with captains of ships for the purpose of entering 
observations of wind and weather, of currents, and of tempera- 
tures at the sea-surface. This plan has been followed ever 
since, the notes being as a rule entered once every watch, so 
that a formidable pile of material has now been amassed. Up 
to 1904 the Meteorological Office in London had collected 7 
millions of these notes, the Deutsche Seewarte in Hamburg 



PHYSICAL OCEANOGRAPHY 



215 



De Bilt 3J millions, the Hydrographical Bureau in Washington 
51^ millions, and so on. Add to this the surface observations 
made by scientific and other expeditions, and it will be evident 
that in the course of the last sixty years a good deal of know- 
ledge regarding the surface of the sea has been gained. 

Making surface -temperature observations is very simple Temperature 
work. All that is necessary is to haul up a bucket of sea-water observations 

dn • /* 1 * 1 ''■ ^LlG suri3.cc 

measure the temperature by means 01 an ordmary thermo- of the sea. 

meter. It is a far more difficult thing to record the actual 

temperature of the deeper layers. In 1749 Captain Ellis Temperature 

brought up water from 11 90 metres and from 1645 metres to beneath \h? 

the south of the Canaries, and, on measuring the temperature surface. 

of the water inside the water-bottle after it had been hauled 

up, found it to be 17.2° C. lower than the temperature at the 

surface. Some investigators coated their water-bottles with an insulating 

insulating substance, so that the temperature might remain water-botties. 

unaltered during the process of hauling up. This principle has 

recently been developed to a high degree of perfection in one 

of the water-bottles now most used, viz. the Pettersson-Nansen 

water-bottle, which will be described later. 

Attempts were also made to insulate the thermometer itself insulating 
by surrounding the bulb with a stout sheath of caoutchouc or thermometers. 
wax. This insulated thermometer was lowered to the depth 
desired, where it was left for hours to assume the temperature 
of the water ; it was then hauled up quickly and the temperature 
read off. In this manner de Saussure was able, in 1780, to 
determine correctly the temperature in the Mediterranean at 
585 metres, finding it to be 13° C. Thermometers made on 
this principle have been much used until our own times, but they 
have one serious drawback, for the operation takes a very long 
time, and this makes them unsuitable for use in expeditions, 
where the work must be done as quickly as possible ; they may, 
however, do good service in cases where the very greatest 
accuracy is not required, and where there is unlimited time at 
disposal, as on light-ships. 

Nearly a hundred years ago some one thought of employing Maximum 
Six's maximum and minimum thermometer for temperature S'-^ermom"""^^^ 
observations in the sea, various modifications being introduced, 
until finally in 1868 it became quite serviceable as made by 
Casella under the direction of Dr. Miller. The Miller-Casella Miiier- 
thermometer (see Fig. 154) was the one principally used on board Caseiia. 
the "Challenger" and during other great expeditions. At the 



2l6 



DEPTHS OF THE OCEAN 



top there are two glass bulbs, united by a bent capillary tube ; 
the left-hand bulb is filled with creosote, the capillary tube 
contains some mercury, and the right-hand bulb constitutes a 
vacuum except for a little creosote. When the thermometer is 
heated, the creosote on the left side expands, driving the 
mercury through the tube so that it rises in the right-hand 
branch ; the mercury lifts a small index, a pin 
that is so constructed that it sticks at the place 
where the mercury leaves it. When the ther- 
mometer is cooled the creosote contracts, and the 
creosote-vapours in the right-hand bulb propel 
the mercury farther into the left-hand branch, 
where there is a similar index. In this way the 
index on the right shows the maximum tempera- 
ture, and that on the left the minimum tem- 
perature. The thermometer is fastened to a 
rectangular plate carrying the temperature scale, 
and the whole instrument is put inside a protect- 
ing tube of copper. The maximum and minimum 
thermometer needs about twenty minutes for 
adjustment, and is slow enough not to change 
appreciably during a rapid hauling up from 
moderate depths, but if it has to be brought from 
great depths, erroneous results may be recorded, 
e.g. in waters where the temperature does not fall 
or rise uniformly towards the bottom. In Arctic 
and Antarctic seas, for instance, the temperature 
generally falls to a minimum at about 50 or 70 
metres below the surface, rising to a secondary 
maximum at a depth of a few hundred metres, 
finally falling again towards the bottom, and this 
implies two maxima and two minima. In such a 
case Six's thermometer would show only the 
highest maximum and the lowest minimum en- 
countered, and not the intervening values. This 
thermometer has, however, done very good service ; it is, 
for instance, astonishing how correct the temperature determina- 
tions taken on board the " Challenger" have proved to be. In 
the great depths of the ocean the variations of temperature from 
year to year are so small that it is possible to verify now the 
observations of earlier expeditions. 

The French physicist Aime about seventy years ago intro- 
duced the reversing thermometer, which is caused — either by a 




HlI^SE 



Fig. 154. 
Miller-Casella 
Thermometer. 



PHYSICAL OCEANOGRAPHY 



217 



sliding weight (" messenoer ") or by a propeller-release — to turn 
upside down at the depth where the temperature is to be deter- 
mined. The temperature is thereby regis- 
/^^^^^\. tered, and can be read off at any time after the 

(l'i^\\ instrument has been hauled up. Aime's instru- Aime. 

ment was, however, rather intricate. In 1878 
Negretti and Zambra of London constructed a Negretti and 
reversing thermometer, which has played a ^'^"^b''''^- 
prominent part in physical oceanography. In 
this form there is a narrowing of the tube just 
above the bulb ; the mercury fills the tube 
above the narrowing to a greater or lesser 
extent according to the temperature, and when 
the thermometer is tipped over, the mercury 
breaks off at the narrowing, the portion which 
was above that point sinking down to the end 
of the tube (Fig. 155); the scale on the tube 
indicates the temperature at the moment of 
inversion. The thermometer must be able to 
withstand the pressure of the ocean depths, 
and is therefore placed inside a strong glass 
tube, with some mercury round the bulb of the 
thermometer in order to secure a rapid conduc- 
tion of heat. 

The Negretti and Zambra reversing thermo- 
meter has latterly been widely used, but it has 
been found that occasionally the mercury broke 
off not exactly at the narrowing, but at some 
other place in the tube, while sometimes addi- 
tional mercury might overflow during the pro- 
cess of hauling up. Certain improvements 
have therefore been introduced to remedy 
these defects, like the recent modifications by 
C. Richter of Berlin, who altered the breaking- Richter. 
off arrangement so as to render it quite trust- 
worthy, and formed the tube in such a way that 
no superfluous mercury could enter it during 
the ascent (see Fig. 156). The severed 
column naturally lengthens or shortens some- 
what according to the temperature changes to 
which it is subjected : suppose, for instance, the 
thermometer to be reversed in water of 2.00'' C, and then 
hauled up through warmer water and read off in the air at a 



le 



H 



4yj> 



Fig. 155. 

Negretti-Zambra 

Thermometer, 

after reversing. 



2l8 



DEPTHS OF THE OCEAN 



temperature of 20° C, 
the mercury - thread 
would have expanded a 
Httle, giving a reading 
perhaps of 2.25° C. in- 
stead of 2.00° C. This 
secondary change is 
easily calculated when 
the temperature of the 
mercury at the reading- 
off is known, and so 
inside the protective 
tube Richter has placed 
a small auxiliary ther- 
mometer (d), which 
gives the reading tem- 
perature, and thereby a 
correction for the read- 
ing. 

In many cases it is 
necessary to have the 
temperature determined 
with the highest possible 
degree of accuracy, and 
Richter's reversing ther- 
mometer is very satis- 
factory in this respect. 
During the " Michael 
Sars" Atlantic Expedi- 
tion the temperature 
series were taken almost 
exclusively by the aid of 
these thermometers, and 
in most instances two 
thermometers were used 
simultaneously, so as to 
make quite sure of the 
determinations. When 
the readings were cor- 
rected it was found that 
the mean difference be- 
tween the values given 
by the two thermome- 





FiG. 156.— Richter's Reversing Thermometer. 
The mercury breaks at e ; the figure on the left and the 
upper one on the right show the position of the mercury 
before reversing. The lower figure on the right repre- 
sents part of the thermometer immediately after reversing. 



PHYSICAL OCEANOGRAPHY 219 

ters in about 600 double determinations was only y-J^" C, so 
that the temperature of the greatest ocean depths can now be 
determined with great accuracy. 

A common form of reversing mechanism is a brass tube Reversing 
which can turn over within a frame. A pin retains the tube "mechanism. 
(into which the thermometer is placed) in an upright position ; 
when the pin is withdrawn, the tube is tipped over by the aid 
of a steel spring. The pin is removed either by means of a 
propeller or by a messenger. The propeller is so adjusted that 
it does not move during the descent, but when the apparatus 
is pulled upwards it revolves, drawing out the pin along with 
it. Formerly this propeller-release was employed with many 
kinds of oceanographical apparatus, but it is not always reliable, 
especially in a rough sea, and the apparatus must be hauled 
up some distance before the propeller works. It is, therefore, 
gradually being superseded by the messenger, a small weight 
which is fixed on the line and let down after the apparatus has 
reached the desired depth. When the messenger reaches the 
reversing mechanism it knocks out the pin and the thermometer 
is turned upside down. One of the wa£er-bottles used during 
the "Michael Sars " Expedition is reversed together with the 
thermometer ; in other words, this water-bottle is a reversing 
mechanism for taking a temperature and a water-sample at the 
same time. 

The Pettersson-Nansen water-bottle has a very high in- Pettersson- 
sulating capacity, and the temperature of the water-sample is ^!au?.bottie. 
not affected by conduction even when hauled up from a depth 
of several hundred metres, though the apparatus may be 
drawn through water-layers having very different temperatures. 
Pettersson originally used an ordinary thermometer, which was 
inserted into the water-bottle after it came up. Then Nansen 
thought of fixing a thermometer inside the water-bottle, and 
in this way the temperature at any depth was determined more 
easily as well as more exactly. The Nansen thermometer is 
very delicate, and is protected by a strong glass tube against 
the great pressure. 

In making temperature-observations, however, one special Effect of great 
precaution must be taken. When a liquid is exposed to great P'^'^'^^"'^^- 
pressure its volume is slightly diminished, and, some heat being 
liberated, the temperature of the liquid rises. Lord Kelvin 
studied this question carefully, and arrived at a formula by 
which such changes of temperature maybe calculated. Con- 
versely, the volume of a liquid released from great pressure 



220 DEPTHS OF THE OCEAN 

increases, and by this process some heat is taken up which is 
drawn from the Hquid, lowering its temperature. When, there- 
fore, a water-sample is drawn up in an insulating water-bottle 
from a depth of looo metres, the temperature of the water- 
sample sinks a little. Nansen first called attention to this fact, 
and has drawn up tables for the corrections according to Lord 
Kelvin's formula. The corrections prove to be quite consider- 
able. When employing an insulating water-bottle, account must 
be taken, not only of the alteration of volume in the water- 
sample, but also of that taking place in the solid parts of 
the water-bottle. A water-sample, for instance, brought up 
in an ordinary-sized Pettersson-Nansen water-bottle from a 
depth of looo metres in the Norwegian Sea, is cooled 0.06" C. 
while being hauled up ; a sample from the same depth in the 
Mediterranean is cooled 0.17' C. This difference is due to the 
fact that the amount of cooling depends on the temperature of 
the water, which at 1000 metres in the Norwegian Sea is about 
— 1° C. and in the Mediterranean +13° C. 

We are here confronted with a problem of considerable 
interest. When a body of water sinks from the surface down 
to great depths, its temperature rises a little because of the 
compression. The " bottom -water " of the Atlantic Ocean 
averages nearly 2^° C. ; supposing that it has sunk from the 
surface to a depth of 3000 metres, it has been heated about 
0.27° C. in the course of its descent, by reason of the increasing 
pressure. If it should appear at the surface again, the reduc- 
tion of pressure will have lowered the temperature by the same 
amount, — 0.27 C. There are various other conditions which 
produce changes in the temperature, as, for instance, mixing 
with other bodies of water, in the upper layers absorption of 
solar heat, near the bottom possibly a very slight influence 
from the internal heat of the earth. It is, of course, difficult 
in such a combination of factors to single out the effects of one 
of them individually. 

During the "Michael Sars " Expedition in the North 
Atlantic we made a certain number of observations in the 
deeper layers with a Richter reversing thermometer, which 
seemed to prove in several cases that the temperature increased 
slightly towards the bottom. The following extract from the 
" Michael Sars " tables shows the number of the station, the 
depth, the temperature (measured in szhi), and the temperature 
that the water would acquire — on account of the reduction 
of pressure — if it were raised to the surface. The latter 



PHYSICAL OCEANOGRAPHY 



221 



temperature has by the author of the present chapter been Potential 
called \\-\^ potential temperature, a term used in meteorology. temperature. 



Station. 
Depth to the bottom. 


Depth of observa- 
tion in metres. 


Temperature 
in situ. 


Potential 
Temperature. 


lO A 

4700 m. 


3000 
4500 


2.43° c. 
2.55° 


2.16° c. 

2.08° 


49 C 
about 5400 m. 


3950 
4950 


2.42° 
2.46° 


2.03° 
1.92° 


63 

5035 m- 


4000 
4850 


2.35° 

2-37° 


1-95° 
1.85° 



From these and many similar observations it is seen that 
the temperature in the deepest strata of the North Atlantic is 
about 2^° C. (as a rule a little lower). The temperature of the 
deepest strata below 2000 fathoms appears to remain almost 
constant through long periods of time, the variations probably 
not amounting to more than a few hundredths of a degree. 
Very delicate instruments are necessary to detect them, and as 
yet we have insufficient observations to enable us to study 
the details. 

It is apparent from the tables that the temperature would 
fall several tenths of a degree if the "deep-water" were raised 
to the surface without being heated by mixing on the way. 
This we have been able to prove in a direct way by means of 
the insulating water-bottle, which we used at Station 91 at a 
depth of 4750 metres, the temperature inside the water-bottle 
after hauling up being only 2.00° C, whereas the water at that 
depth was in reality several tenths of a degree warmer. When 
ill situ the water has the temperature indicated by the reversing 
thermometer, but when brought to the surface it has the 
potential temperature nearly indicated by the thermometer 
inside the insulating water-bottle. Granted that no other 
change has taken place, the bottom-water must have had a 
temperature of about 2° C. at the time when it began sinking 
down from the surface ; as it sinks the temperature gradually 
rises, and at Station to A, for instance, it was found to be 
0.12° C. higher at 4500 metres than at 3000 metres. Some 
such increase of temperature towards the bottom has long 
been suspected as an effect of the internal heat of the earth ; 
as early as about 1840 Aime looked for it, but his methods 



222 



DEPTHS OF THE OCEAN 



were not sufficiently accurate. More recently several indica- 
tions of a rise of temperature towards the bottom have been 
observed. The pressure and the internal heat having the 
same effect, it is difficult — at our present stage — to determine 
how much is due to the internal heat of the earth. In any case 
the bottom-water temperatures would be considerably lower but 
for the effect of pressure on the sinking waters. 

It may be stated as a general rule that the temperature of 



- 


?" 


0° 


r 


4" 


6° 8° 10° 


ir 14" 1 


6- /a: 


?0" 




re 














1 


f 


r 


,^^ 


\/ 








500 










y 






•i 
















^ 




■^ 




// 


J 


/ 












^ 


1 








/J 


^ 


















' J 








v/ 




















1 






/ 


{ 






PE^ 




<I06 ^fl 














.1/ 








Jl 




/OA '^ ^W 












' 


If 








i^ 


fc 


'^^ ^JB 






fSOO 








if 






~~ 


f 


-64 




1 








j 






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i 










1 ^.. 




^1 






?onn 






10 





















Fig. 157. — The distribution of Temperature at four different Stations 

IN THE Summer of 1910. 

The positions of the Stations are shown in the small inset map. 



ocean water is in summer highest at the surface, and decreases 
gradually towards the bottom. Fig. 157 shows the distribution 
of temperature as observed at four stations during the " Michael 
Sars " Atlantic Expedition, the position of the stations being 
indicated on the little inset map. Station 64 is situated in the 
Sargasso Sea westward of the Azores, Station 87 in mid-ocean 
between France and Newfoundland, Station 10 1 between 
Scotland and Rockall, and Station 106 in the Faroe-Shetland 
Channel north of the Wyville Thomson Ridge. Station 106 
belongs to the region of the Norwegian Sea, whereas the other 



PHYSICAL OCEANOGRAPHY 223 

three belong to the Atlantic proper; Stations 87, loi, and 106 
all lie within the precincts of the " Gulf Stream." At all four 
stations the temperature is highest at the surface : 22°-23*' C. in 
the Sargasso Sea (24th June), over 18° C. at Station 87 (17th 
July), 13°- 1 4° C. westward of Scotland (7th August), and 13° C. 
at the station west of Shetland (loth August). It is worthy of 
note that a temperature of about 13° C. was observed at the 
surface near Scotland, while the same temperature occurred at 
a depth greater than 500 metres in the Sargasso Sea. 

From the surface downwards the temperature falls very 
rapidly for the first 50 or 100 metres; at 100 metres it is from 
4" to 6° C. colder than at the surface. Beyond 100 metres the 
temperature decreases at first much more slowly, then rapidly 
again, and then very slowly until the great depths are reached, 
where the temperature changes very little. The layers in Discontinuity 
which the temperature changes very rapidly are called " dis- ^^y^^^- 
continuity-layers" (by the Americans " thermocline," and by 
the Germans " Sprungschicht "). They are particularly marked 
at Station 106, where there is such a layer immediately below 
the surface, and another extending from 450 to 750 metres. 
Between the two (from 50 to 450 metres) there is a fairly 
uniform stratum, and another one under the deeper layer, from 
750 metres to the bottom. At the other three stations the 
upper discontinuity-layer is also very strongly marked, but the 
lower one is not so sharply distinguished from the adjoining 
water-strata. 

It will be noticed that the temperatures in the deep strata 
(below 800 or 900 metres) were, at the same depths, nearly 
identical at the three stations in the Atlantic proper, the differ- 
ences not exceeding 1° C, although these stations are situated 
far apart ; but at Station 106 in the Norwegian Sea the temper- 
ature was 7°-8° C. colder. This is due to the form of the 
bottom, the Wyville Thomson Ridge separating the deep layers wyviiie 
of the Atlantic from the deep layers of the Norwegian Sea, so ^1^°™^°" 
that at a depth of 1000 metres the temperature is 6'-7° C. in 
the Atlantic Ocean, and below o" C. in the Norwegian Sea. 
That implies two widely different deep-sea regions : a warm 
one south of the ridge, and a cold one to the north of it, with 
great differences in the deep-sea fauna of the two regions. 
The influence of the Wyville Thomson Ridge is very clearly 
seen in a section across the ridge (see Fig. 106, p. 124), from 
Station loi to Station 106 ; in the upper strata, down to 500 
metres, there is little difference, but the deeper strata are like 



224 DEPTHS OF THE OCEAN chap. 

two different worlds, the Atlantic world south of the ridge, the 

Arctic world north of it. 
Decrease of The surface-tempcrature is naturally high in the equatorial 

temperature Tegious, decreasing toward the poles, where it falls below o° C. 
from equator Kriimmel has calculated the mean surface-temperatures for each 
to poles. lo-degree zone throughout the great ocean basins, his figures 

for the North Adantic being : — 

Zone . . o^-io" io°-20° 2o°-30° 3o''-4o"" 40^-50° 5o''-6o" 6o°-7o° N. lat. 
Temp. . . 26.83 25.60 23.90 20.30 12.94 8.94 4.26 X. 

It is interesting to compare this horizontal distribution of 
temperature with the vertical distribution in tropical waters. 
The following temperatures, for instance, were recorded by the 
German Antarctic Expedition in July 191 1, at a station in lat. 
7|-° N. in the middle of the Atlantic : — 



Depth . 





100 


200 


400 


800 


1000 metres. 


Temp. 


. 26.86 


18.57 


10.71 


7.70 


5-13 


4.81 °C. 



At a depth of 100 metres the temperature is seen to be the 
same as the average surface-temperature in about 40° N. ; the 
mean surface-temperature at 50° N. is the same as that found at 
200 metres in the tropics, and the mean surface-temperature at 
60° N. corresponds to the temperature at a depth of 700-800 
metres in the tropics. In other words, we have a horizontal 
distribution of temperature from the equator towards the poles 
similar to what we have vertically from the surface towards the 
bottom in the tropics. Near the equator one need only send a 
thermometer down to 800 metres in order to find the same 
temperature that one would have to travel 60° northwards to 
find at the surface, but the other physical conditions are widely 
different. In the deep water at the equator there is an 
enormous pressure and unchanging darkness, but at the surface 
far north and south there is a pressure of only one atmosphere 
and good light, at least in summer. Thus the physical condi- 
tions in the deep layers of the tropical waters are really very 
different from those at the surface towards the poles, and in 
consequence the conditions of life also differ ; organisms living 
in the surface-layers of high latitudes are found in far deeper 
water in low latitudes, in so much as they are capable of adapting 
themselves to the excessive pressure and the infinitesimal 
quantity of light. Some organisms seem to be mainly depen- 
dent on the degree of light, the temperature being of less 
importance to them. We shall return to the questions of light 



PHYSICAL OCEANOGRAPHY 225 

and pressure, and the geographical distribution of animals, 
later on. 

The high temperature at the surface evidenced by the curves Absorption of 
in Fig. 157, is principally due to the absorption of heat-rays from surtaceJ!? Ae 
the sun. In places the water is heated by contact with warm sea. 
air, but this source of heat is of less importance, the temperature 
of the surface-water being, as a rule, higher than the temperature 
of the air. The sun's rays penetrate into the water and are 
absorbed ; the dark heat-rays are absorbed in the uppermost 
layers, while the light rays, which also convey a little heat, 
make their way down to a depth of several hundred metres 
before disappearing altogether. The action of the sun's rays is 
strongest in the tropics, declining towards the north and south, 
and this in a general way explains the distribution of the surface- 
temperature. 

A fine example of the heating action of the sun's rays is storage of 
afforded by the Norwegian oyster-basins. Along the west jj^nl" ""^""^"^ 
coast of Norway there are in many places salt-water basins, 
separated from the outer fjord by a sill, which is covered only 
at high water. At the surface the water of the " poll " — as 
such a basin is called in Norway — is comparatively fresh, 
and consequently light ; from a depth of about one metre to the 
bottom it is very salt and heavy. The sun's rays in summer 
penetrate into the water and heat it, mostly at the surface, but 
also to some extent down to a depth of a few metres. The 
surface-water is cooled during the night, but at a depth of one 
or two metres beneath the surface the heat will not be given 
off so readily, because the heavy water there does not reach the 
surface. When this has gone on for some time, the temperature 
at a depth of a few metres may be remarkably high, sometimes 
fully 35° C, while the temperature at the surface might be 
about 20° C. In these "polls" the surface-layer of relatively 
fresh water prevents the layers below from coming into contact 
with the cooling air, and such polls may indeed be compared to 
hot-houses, the fresh surface-layer corresponding to the fixed 
transparent roof, under which heat is stored.^ in these 
oyster-basins absolutely tropical conditions are developed in 
summer. It is significant that Gran once found in one of them 
a small crustacean, which according to G. O. Sars belongs to 
the Guinea Coast. Fig. 158 shows the temperatures and salini- 
ties in an oyster-basin in the early part of the summer before 

1 Compare Murray and PuUar, Bathy metrical Sui~i<ey of the Fresh- Water Lochs of Scotland, 
vol. i. pp. 580, 581, and 587, Edinburgh, 1910. 

Q 



226 



DEPTHS OF THE OCEAN 



Conduction 
of heat. 



the maximum temperature has been reached, but already on the 
loth June (1903) the water of this poll is seen to be 5° C. 
warmer at a depth of 2 metres than at the surface. 

To understand how such a high temperature can be preserved 
for a length of time at a depth of 2 metres, one must bear in 
mind the fact that the conduction of heat plays an altogether 
subordinate part in the thermal conditions of the sea. Kelvin 
and Wegemann have made some calculations on the trans- 
mission of heat in water by conduction ; Wegemann commences 
with a sea 5000 metres deep, with a temperature of 0° C. 
throughout ; the surface is supposed to be in contact with a 





5 n%o 23%.o 24%o 25%o 26%o 17%o Zd%o Zr/oo 30%^ 3/%c 
^ t /3° /4° /5° /6° 17° 16- 19" ZOO ^,6 ZZ^''^ 












1 

1 

t J 


















V 


^~- 




^J 


— -__ 


____ 
























^ 


















.^"^ 


R 
















t_ 


^""^^ 






\ 


5 










^^^ 
















/_ 




^ 

/ 











































Fig. 158.— The Vertical Distribution of Temperature [t) and Salinity {s) 

IN THE KvERNE-POLL, IOTH JUNE I903. 

source of heat at a temperature of 30' C. No forces inter- 
vening other than conduction, no heating effect would be 
perceived at a depth of 100 metres after 100 years, and after 
1000 years the temperature at 100 metres would only have 
reached j.^, C, and at 200 metres 0.6° C. It is thus seen 
that transmission of heat by conduction is practically negligible 
in the sea. The heat conveyed by the sun to the uppermost 
water-layers cannot therefore be propagated into deep water by 
conduction, but only through movements of the water — waves, 
currents, convection "currents," etc. Where there is no such 
motion, and where the sun's rays cannot penetrate, heat cannot 
be transmitted by conduction, and hence we find temperatures 
as low as 2" C. or less in deep water even under the equator. 



PHYSICAL OCEANOGRAPHY 



227 



In winter, heat will be radiated from the sea-surface to the 
colder air, and the temperature will be lowered. In Figs. 159 
and 160 two maps of the North Atlantic, one for February and sea. 
one for August, are reproduced from Atlantischer Ozean, ein 
Atlas, published by the Deutsche Seewarte in Hamburg. 
In the February map the isotherm of 25' C. runs from the 
Antilles towards the east and a little to the south, in the 
direction of Africa, whereas in August this line lies, in the 
western part of the ocean, as much as twenty degrees of latitude 



Radiation of 

heat from the 

rface of the 




Fig. 159.— Surface Temperature of the North Atlantic in February. 

farther north. In the same way the other isotherms have 
more northerly positions in summer than in winter. The 
difference between the surface-temperature in February and in 
August is about 5° C, in some places less, in others considerably 
more. Near land the annual variations are much greater, as in 
the coast- water within the Norwegian skjsergaard (" skerry- 
guard," literally: "fence of islands"), where the surface- 
temperature in summer is i5°-20 C, and in winter only a few 
degrees above zero. Beneath the surface the variations 
gradually decrease, and at a depth of a few hundred metres no 
marked seasonal variations can be traced. 



Reversal of 
seasons at a 
depth of 200 
metres. 



228 DEPTHS OF THE OCEAN chap. 

At a certain depth a displacement of the seasons is often 
found. Repeated observations have been made by the 
"Michael Sars " at a station outside the entrance to the 
Sognefjord in different seasons and in different years. In 1903, 
measurements were made at this station in the months of 




Fig. 160.— Surface Temperature of the North Atlantic in August. 

February, May, August, and November, and the following 
temperatures were found : — 





February. 


May. 


August. 


November. 


Surface .... 


4.8° c. 


7-3° C. 


13.8° c. 


8.7° c. 


100 metres . . . 


6.8° 


6.4° 


6.9° 


9-3° ' 


200 ,, ... 


7-9° 


7.0° 


.6.7° 


7-9 


300 „ . . . 


6.3° 


6.5° 


6.4° 





At the surface it was coldest in February and warmest in 
August — the difference being 9^ C. At 100 metres it was 
coldest in May and warmest in November, with a difference of 
2.9° C. At 200 metres it was coldest in August, warmest in 
February and November, the difference being 1.2° C, so that 



PHYSICAL OCEANOGRAPHY 229 

at this depth the seasons were reversed : it was " winter " in 
the water in the middle of the summer, and "summer" in the 
middle of the winter. Murray's observations in Upper Loch 
Fyne in 1888 gave similar results. At 300 metres at the 
" Michael Sars " Station there were hardly any variations at all, 
the temperature being very much the same as the mean annual 
temperature of the air, as Nordgaard has shown to be the case 
with regard to the bottom-water of the Norwegian tjords. 

When sea-water is cooled its density increases, and it often vertical 
happens in winter that the surface-water becomes heavier than "^'g^^^'wat'erl 
the water below. The surface-layer then sinks, and the under- 
lying water comes to the surface. By this vertical circulation 
the conditions are equalised, so that exactly the same salinities 
and temperatures are found as far down as the vertical circulation 
extends ; wind and current aid in the process. This takes place 
especially from January to March ; in April the weather again 
becomes warmer and the temperature begins to rise at the 
surface. A very good example of this phenomenon is afforded 
by the "Michael Sars" observations taken to the westward of 
Plymouth in April 1910 ; at the very surface the temperature 
had risen slightly, but otherwise practically the same salinities 
and temperatures prevailed at every station down to a depth of 
150 metres or more. Later on in spring the surface tempera- 
ture gradually rises, and a marked discontinuity-layer is formed. 
In many places near the coast, where the salinity is low at the 
surface and high beneath the surface, a brisk vertical circulation 
cannot be set up ; the comparatively fresh water on top is so 
light that, even when considerably cooled, it does not change 
places with the salt and heavy water below. But farther out 
to sea the vertical circulation may extend down to a depth of 
200-300 metres or more. 

It is thus not only the surface-water that may give off heat Effect of heat 
to the air, but a great body of water extending to several f^eTea.^^^ 
hundred metres in depth, and hence the great influence of the 
sea on winter climates. The capacity for heat of water is very 
great compared with that of the air. Supposing that we have 
I cubic metre of water giving off enough heat to the air to 
lower the temperature of the water one degree, this heat would 
be sufficient to raise the temperature of more than 3000 cubic 
metres of air by one degree. An example will show the 
importance of this. Suppose a body of water, 700,000 square 
kilometres in extent and 200 metres deep, to give off enough 
heat to the air in winter to lower the water-temperature one 



230 DEPTHS OF THE OCEAN 

degree, then the heat given off would be sufficient to raise the 
temperature of a stratum of air covering the whole of Europe 
to a height of 4000 metres on an average ten degrees. This 
Gulf Stream, explains how the Gulf Stream renders the climate of northern 
Europe so much milder in winter than would be expected from 
its northerly latitude. We shall see later on that the oceano- 
graphical researches of the last few years give reason to hope 
that it will even be possible to predict the winter temperature 
of northern Europe from the temperature of the sea some time 
in advance. 



The salts of 
the sea. 



Salinity 
determined 
from water - 
samples. 

Obtaining 
samples from 
surface and 
shallow water. 



Obtaining 
samples from 
deep water. 



Buchanan's 

stopcock 

water-bottle. 



There are many different salts in the sea. Salinity means 
the total amount of salts in a given quantity of sea-water, and 
is usually stated in parts per thousand (per mille), indicating how 
many grams of salt are contained in one kilogram of sea-water. 
The salinity of the sea varies considerably both horizontally 
and vertically, and its distribution is determined by examining 
samples of water from different parts and different depths ; these 
samples are secured by means of various water-bottles. From 
the surface a sample may be drawn with an ordinary bucket. 
For shallow waters down to 30 or 40 metres a common glass 
bottle is often employed ; the Hne is bound to the neck of the 
bottle and a weight is suspended underneath. The stopper is 
fastened to the line a little way above the bottle, and is inserted 
when the bottle is lowered. When this simple water-bottle has 
arrived at the depth from which the sample is to be taken, the 
line is given a sharp pull, so that the stopper is drawn out and 
the bottle fills. In hauling up, a little water from the upper 
layers may, of course, enter the bottle, but this simple method 
does well enough for shallow water 
variations are so great as to render 
necessary. 

Many varieties of water-bottles for investigations in deep 
water have been constructed. A few of those most in use, and 
most effective in working, may be described, and the different 
principles involved explained. 

We will begin with an apparatus designed by J. Y. Buchanan 
for the "Challenger" Expedition, a so-called stopcock water-bottle 
(Fig. 161). It consists of a brass tube (A), which can be closed 
at both ends by means of metal stopcocks (B,B) ; the latter are, 
through two levers (D,D), connected with a rigid rod (0,0). 
When the side-rod is in the upper position, as seen in the left- 
hand and central figures, the cocks are open. A tilting plate 



near land, where the 
extreme accuracy un- 



PHYSICAL OCEANOGRAPHY 



2.^,1 



(E) is hinged on to the rod. In the left-hand figure the plate 
is tilted upwards, and it remains in that position while the 




C.^^ — ^- 



^ 



Fig. i6i.— Buchanan's Stopcock Water-Bottle. 



apparatus is' being lowered. But as soon as it is pulled upwards 
the water presses against the plate, tilting it into the position 
shown in the middle figure ; the rod is then forced downwards, 



232 

and 



DEPTHS OF THE OCEAN 



Pettersson s 

insulating 

water-bottle. 



Pettersson- 

Nansen 

water-bottle. 



along with it the levers, closing both stopcocks simul- 
taneously. The plate then falls into the position seen in the 
right-hand figure. This simple arrangement allows of enclosing 
a water-sample at any depth required. This water-bottle has 
done very good service ; it was much used on board the 
" Challenger," and has also — with a few small improvements — 
been employed a good deal in later times. 

In a stopcock water-bottle of this construction the 
temperature of the water-sample may alter during the hauling- 
up process, and it is impossible to get a record of the temperature 
in situ with the water-sample, without having a special apparatus 
for the thermometer. Buchanan himself, and later on Nansen, 
modified this water-bottle by adding an arrangement for a 
thermometer, which would be reversed the moment the cocks 
were closed. In the meanwhile Otto Pettersson had adopted 
F. L. Ekman's old idea of making a water-bottle which should 
be insulating, so that the water- sample would retain its 
temperature unchanged, even when drawn up from a great 
depth. Pettersson availed himself of the circumstance that the 
water itself is an excellent insulator, its power of conduction 
being small and its capacity for heat very great. This water- 
bottle consisted of a bottom-piece, a cylinder, and a lid ; these 
three parts could be separated by lifting up the cylinder and 
the lid along two brass rods forming the sides of the encom- 
passing frame. The cyHnder is a composite one ; inside a 
strong cylinder of ebonite there are various other cylinders of 
celluloid and brass, one inside the other like a set of Chinese 
boxes. Between these concentric tubes are narrow cylindrical 
spaces which fill with water when the apparatus is lowered into 
the sea, and in this way a system of excellent water-insulators 
is formed. The outer cylinder may alter in temperature con- 
siderably in the course of hauling-up, the inner ones less and less, 
until in the central chamber the temperature will not change at 
all for some time, although the water-bottle be strongly heated 
from without. On the bottom and on the lid Pettersson 
attached a number of parallel plates, which likewise enclose 
insulating water-layers. 

Nansen has introduced several improvements, and the latest 
model — the so-called Pettersson -Nansen water-bottle — is an 
excellent apparatus, which is now very widely used (see Fig. 
162). On the left it is seen open, as it is let down into the 
water ; the lid is suspended in the upper part of the frame, and 
supports the cylinders as well as a weight hanging below the 



PHYSICAL OCEANOGRAPHY 



233 



apparatus. When a messenger is sent down the line and strikes 
the water-bottle, the Hd is released, and the weight draws both 
lid and cylinders down, clasping the 
apparatus together and closing it her- 
metically. The right - hand figure 
shows the water-bottle closed and 
ready for hauling up. The Nansen 
thermometer is seen in the left- 
hand figure, and is — as mentioned 
above — a thin delicate instrument, 
fitted inside a strong protective glass- 
tube in order to withstand the enor- 
mous pressure of the deep sea. The 
Pettersson-Nansen water-bottle is so 
well insulated that the temperature of 
the water-sample is not influenced 
from without, even when being hauled 
up from a depth of 1000 metres. 
But the temperature is lowered 
slightly, in consequence of the reduc- 
tion of pressure during the process of 
hauling up, as has already been men- 
tioned. This circumstance asserts 
itself quite appreciably in the case of 
the insulating water-bottle when used 
at great depths. The water-bottle 
is, however, fitted with a frame for 
carrying a reversing thermometer, so 
that a double determination may be 
made. During the "Michael Sars " 
Expedition we very often employed 
the insulating water-bottle, and took 
temperatures both with the Nansen 
thermometer and with the Richter 
reversing thermometer simultaneously. 
As an example, an observation made 
at Station 10 1 in 1400 metres may 
be mentioned : after correction the 
Nansen thermometer read 4.45'' C, 

the Richter thermometer 4.59° C, that is 0.14' C. lower in the 
first case than the second. The water in the water-bottle 
should, according to the calculation by Lord Kelvin's formula, 
have been cooled 0.12° C. ; granting that the determinations 




Fig. 162. — Pettersson - Nansen 

Water-Bottle. 

Shown open in the left-hand figure, and 

closed in the right-hand figure. 



234 



DEPTHS OF THE OCEAN 



are absolutely correct, the cooling of the 
solid parts of the apparatus accounts for 
the difference of two -hundredths of a 
degree, which is a very probable value. 
This is an instance chosen at random 
from a vast number of observations, and 
proves how accurately deep-sea tem- 
peratures can now be determined. 

V. W. Ekman has constructed an 
apparatus to serve as a reversing 
mechanism and a water-bottle at the 
same time. The apparatus is made of 
brass, and consists of a frame carrying 
inside a cylinder pivoted on an axle at 
the middle of the frame (see Fig. 163). 
At either end of the cylinder there is a 
lid, to which are attached two pairs of 
levers fastened to the frame near the 
axle of the cylinder. The cylinder can 
be placed in such a position that both 
lids are open, and it is kept in this 
position by means of a small pin, seen 
at the top of the frame on the right. 
Thus adjusted the water-bottle is let 
down into the sea. A messenger is 
sent down after it and knocks out the 
pin ; the cylinder is poised in such a 
way that it turns over in the frame. 
The levers gradually draw the lids 
closer, and when the cylinder is wholly 
reversed it is held fast by a catch and 
encloses the water-sample hermetically. 
To the side of the cylinder is attached 
a metal sheath for holding a reversing 
thermometer, which is consequently 
reversed along with the water - bottle. 
This apparatus may be fastened any- 
where on the line, and a number of 
them may be used at the same time, in 
which case the messenger - release is 
arranged in the following manner : In 
the figure a messenger is seen hooked 
on to a small bar underneath the water- 



' 



1 



Fig. 163. — Ekman's Reversing 
Water-Bottle in process 
OF being reversed, and 

SHORTLY after BEING RE- 
LEASED. 



PHYSICAL OCEANOGRAPHY 



235 



bottle ; when the water-bottle is reversed the bar is withdrawn, 
and the messenger is let go. The next water-bottle is knocked 
over, releasing in its turn the following messenger, and so on. 
It is indispensable with this, as with all other water-bottles, that 
when closed it should be absolutely water-tight, otherwise water 
might get in from the higher layers and vitiate the sample.^ 

The water-sample, when brought on board, may be dealt 
with at once, and its salinity, etc., determined, but it is generally 
the best plan to store the samples for examination in a shore 
laboratory. In this case the samples must be preserved Preservation 
absolutely air-tight, so that they shall not suffer any change g^nT^^^^s for 
in the interval. As a rule, the water may be kept in good glass examination 
bottles with lever stoppers, like those used in soda-water bottles. °" ^^°''^- 
Cork stoppers will not do, unless capped with paraffin or wax, 
as it is difficult to avoid some degree of evaporation which 
would invalidate the results. 

The chemical composition of sea-water has been very care- Chemical 
fully determined. Wellnigh all known elements are found in o?'^ea°^at°en 
solution in the sea, but most of them in such small quantities 
as to be detected only by the most delicate methods. A 
kilogram of sea-water contains about 35 grams of solid sub- 
stances altogether ; the quantity varies slightly in different 
places, but on an average there are about 35 weight-units of 
solids in 1000 weight-units of sea-water (35 per thousand). 
According to the results of Dittmar's analyses of the " Challenger" 
water-samples there are on an average in 1000 grams of sea- 
water : — 





Grams. 


Percentage on 
total solids. 


Sodium chloride (NaCl) . 
Magnesium chloride (MgCl.,) 
Magnesium sulphate (MgSO^) . 
Calcium sulphate (CaSO^) . 
Potassium sulphate (K2S0^) 
Calcium carbonate (CaCOg) 
Magnesium bromide (MgBr^) . 

Total .... 


27.213 
3.807 
1.658 
1.260 
0.863 
0.123 
0.076 


77.76 
10.88 

4-74 
3.60 
2.46 

0.34 
0.22 


35.000 


100.00 



^ The highest perfection must be exacted with regard to this point. It formerly frequently 
occurred that the instruments leaked a little ; as the knowledge of the sea has grown, many 



236 DEPTHS OF THE OCEAN 

The numerous other substances in solution are present in 
such extremely small quantities that they may be disregarded. 
Although the total salinity may vary widely, the composition of 
the dissolved solids proves to be practically the same every- 
where. Hence if in a sea-water the percentage of any one 
component, say chlorine, be known, the total salinity can be 
ascertained by calculation. 

The direct determination of salinity by evaporating a known 
volume of water to dryness does not give accurate results, unless 
the amount of chlorine is carefully determined before and after 
the evaporation, because in the last stages of evaporation and 
in drying the residual salt uncertain amounts of chlorine are dis- 
engaged in the form of hydrochloric acid. Such a determination 
is very circumstantial, and it is therefore necessary to resort to 
indirect methods, which may be physical or chemical. 

An old-established physical method consists in determining 
the density by means of the hydrometer. This is a glass cylinder 
which floats in the water and has a graduated stem, on the scale 
of which densities are read off The temperature of the water 
must be determined at the same time. Densities so found are 
recalculated by means of tables to a standard temperature, 
generally 17.5° C. Now, owing to the uniform composition 
of sea -salts, a definite density at 17.5° corresponds rigidly 
to a definite salinity. Hence by referring to tables the 
salinity of a sea-water can be found from its density at standard 
temperature. 

The hydrometric method is easily applied on board ship, 
and may be made to give densities correct to four places of 
decimals. Densities can be determined to a yet higher degree 
of accuracy by means of the pycnometer, but this method is 
practicable only in a laboratory on land, and is not often 
employed. 

Two other physical methods have been tried by way of 

errors have been detected in earlier determinations referable to the leaky condition of the 
water-bottles. 

When the forms of apparatus described above are to be used, the vessel must be stopped and 
hove to as long as the work goes on. Recently several investigators have studied the problem 
of constructing a i apparatus to be used while the ship is under way. Water-bottles have been 
made which can be let out when the ship is going at full speed, with the line running'freely so 
as to allow them to sink. On checking the line the apparatus is closed by a mechanism like 
that used by Buchanan in his water-bottle. The water-bottle being insulating, a temperature- 
reading is secured together with the water-sample. In such an experiment a metre-wheel 
showing how much line has run out is no use ; one must have a special depth-gauge, usually 
one to measure the compression suffered by a certain volume of air from the weight of the water. 
These new instruments are not in common use as yet, being still in the experimental stage, 
but the time is not far off when we shall have automatic water-bottles working with absolute 
precision. That will mark an important step forward, as much time will then be saved in 
an expedition. 



PHYSICAL OCEANOGRAPHY 237 

experiment, but are not in general use. The one consists in 
measuring the refractivity of the water, i.e. the deflection under- 
gone by a ray of monochromatic hght when passing from air to 
water ; this quantity, again, stands in definite relation to the 
salinity of the sample. The other method is based on the 
electrolytic conductivity of sea-water, and has the advantage 
that no sample need be brought up, a pair of electrodes being 
simply sent down to any required depth and the readings being 
taken on board. This method has been applied by Martin 
Knudsen with good results in shallow water. 

The most convenient, and on the whole the most satis- Chemical 
factory, method of determining salinity is a chemical one, and is '"^^^^o^^- 
based on the fixed relation between the chlorine contained in 
a sea-water and its total salinity. 

The amount of chlorine can be determined by a rapid and chlorine 
easy method. When a solution of silver nitrate is added to ^^^'^^^'o"- 
sea-water, the chlorine is thrown down as a white precipitate of 
silver chloride. If a few drops of yellow chromate of potassium 
are added it is easy to see when all the chlorine is precipitated, 
for the silver nitrate will then act on the chromate so that the 
yellow colour is changed into red. When the chlorine content 
of a water-sample is to be determined, a certain quantity 
{e.g. 15 c.c.) is measured off and poured into a glass; a few 
drops of the yellow chromate solution are added as an indicator, 
and then nitrate of silver from a burette, that is, a graduated 
glass tube with a stopcock (for discharge) at the lower end 
(see Fig. 164). When the red colour appears, the burette is 
read off to find out how much silver solution has been added, 
and it is easy from this value to calculate the amount of 
chlorine. From Knudsen's Hydrographical Tables the salinity 
or the specific gravity, corresponding to this chlorine-value found 
by titration, may be determined. All this can now be done 
quickly and accurately ; in fact, the salinity of a water-sample 
is determined in less than five minutes to within about j-^ per 
iiiille, i.e. i centigram of salt per kilogram of sea- water. The 
modern method of chlorine titration is a great improvement on 
former methods, and it has been much used in recent oceano- 
graphical work, thousands of such determinations being now 
made yearly. 

The density of sea-water depends both on the salinity and Density of 
on the temperature ; the water is comparatively light when ^ea-water. 
the salinity is low and the temperature high, and increases 
in density with a rise of salinity and a fall of temperature. 



DEPTHS OF THE OCEAN 




Fig. 164.— Titration Apparatus. 

On a shelf there is a large bottle for the silver solution, which can flow through a glass tube into the 

burette ; the latter is provided with cocks for regulating the inflow and the outflow of the solution. 

Fresh water has its greatest density at 4 C, which is taken 
as unity. Salt water becomes heavier the lower the temper- 



PHYSICAL OCEANOGRAPHY 239 

ature, the density of sea - water with a sahnity of 35 per 
thousand and at a temperature of 0° C. being 1.028 13. By 
means of Knudsen's Tables the density is quickly found when 
both salinity and temperature are known. The value of most 
interest to us is the density at the potential temperature (see 
above, p. 221) corresponding to the temperature in situ. It has 
been found that this density always increases from the surface 
downwards to the bottom, even when the compression is left 
out of account. If this were not so, in order to attain equilibrium 
the heavier overlying water and the lighter underlying water 
would have to change places, and this is what actually 
takes place in winter, when the density at the surface exceeds 
that of the waters below. The layers will always arrange them- 
selves in such a way that the lighter water is on the top and 
the heavier water underneath. 

Salt water freezes at a lower temperature than fresh water ; Freezing- 
thus sea-water with a salinity of 35 per thousand freezes at p°"^'" 

— 1.9° C, so that temperatures below zero are found in the sea, 

— I J° C, for instance, being a common temperature in the polar 
currents. When the salinity exceeds 24.7 per thousand the 
water becomes heavier on being cooled, until the freezing-point 
(below zero) is reached. This implies an essential difference 
between salt water and fresh water. In the deep water of lakes 
temperatures below 4° C. are never found, while in the bottom- 
water of the ocean considerably lower temperatures prevail, as, 
for instance, — 1° C. or still lower recorded in the Norwegian 
Sea, and about + 2° C. recorded in the Atlantic. Thus it is, as 
a general rule, colder in the great depths of the ocean than it is 
at the bottom of deep lakes. 

We shall now indicate in a general way the distribution of Distributioi 
salinity. It must be remembered that the salinity is raised by of^^^™')- 
evaporation, and lowered by dilution with fresh water either 
from rainfall or from rivers. Where the evaporation outweighs 
the supply of fresh water the salinity increases, as is the case, 
for instance, in the Mediterranean and in the Red Sea, where 
the air is dry and hot, and in the ocean north and south of the 
equator, where the warm trade-winds blow, producing a strong 
evaporation. In such places a high salinity will be found. 
There is a steady inflow of Atlantic surface-water with a salinity Medi- 
of about 36 per thousand into the Mediterranean Sea, where the t^rranean. 
water removed by evaporation is far greater than the supply of 
fresh water, so that the salinity rises to 38 per thousand, accom- 
panied by an increase in density, which is accentuated by the 



Coastal 
districts. 



240 



DEPTHS OF THE OCEAN 



cooling down in winter, and the surface-water becomes so 
heavy that it sinks and forms the bottom - water of the 
Mediterranean. 

On the other hand, there are coastal districts where the 
many large rivers constantly carry more water into the sea 
than what is evaporated from it. In such places the salinity is 
decreased, as, for instance, off the coasts of Scandinavia. A 
great part of the rain falling in Northern and Central Europe, 
as far south as the Alps, is carried by rivers into the Baltic 
and the North Sea, where it is mixed with the salt water, 
producing the so-called " coast- water " of comparatively low 
salinity. The density of the coast- water is so low that it 




-The Sognefjord Section, May 1904. 
Salinities above 35.0 per thousand shown by single hatching ; salinities above 35.20 per 
thousand shown by cross hatching. 

always floats on the top, and often glides along a substratum of 
more saline water. Such coast-water forms the Baltic current, 
running out of the Baltic Sea through the Kattegat and 
Skagerrak, continuing on its way along the coast of Norway, 
above the Salter and heavier Atlantic water carried north by the 
" Gulf Stream." 

Fig. 165 represents a section from the mouth of the Soo-ne- 
fjord (near Feje) westwards to a little north of the Faroe 
Islands. The Atlantic water is marked by hatching, and we 
see the coast-water lying on the top, close to the land on the 
right. This section has been examined through a succession 
of years in the month of May, and we have measured the coast- 
water section in square kilometres. The top curve (I.) in 
Fig. 166 shows how this section has varied from year to year. 
Now it proves to be the case, as was to be expected, that 
these variations to a certain degree correspond to the varia- 
tions in the rainfall. The other curves show the divergences 



PHYSICAL OCEANOGRAPHY 



241 




(per cent) from the normal annual rainfall, (H.) for Chris- 
tiania, (HI.) for Bergen, (IV.) for Germany; (V.) shows the 
divergences in Norway during the months of October, November, 
and December. On the whole, the rainfall corresponds well 
with the transverse section of the coast-water some time after- 
wards. The rainfall was comparatively small in 1902, and the 
coast-water had a small transverse section in May 1903 ; the 
rainfall was large in 1903, and there was much coast-water in 
May 1904, and so on. The effect of the rainfall on the land is 
not immediately felt in the coast-current off western Norway ; 

there is a delay which 

lani tars') /<xnQ zona. /on.^ ^ > 

seems to make it possible 
to predict some time be- 
forehand if there is going 
to be much or little coast- 
water. This is an ex- 
ample of the predictions 
likely to be undertaken in 
the future, when the sea 
and the air have been 
more closely studied. 

We shall now, after 
these introductory re- 
marks, examine the ver- 
tical distribution of salinity 
in some different places, 
as found in the cruise 

Fig. 166.— Curves showino the Variations in of the " Michael Sars." 

I. the transverse section of the coast-water off Feje pTJo- i f\i rp-nrf^cp^ntc fhf^ 

(May); II., III., IV., the annual rainfall for Chris- ^ ^- , ^y icpiCbCllLb LUC 

tiania, Bergen, and Germany respectively; V., the phySICal COnditlOnS a little 

. . ^_.-,___ xr ^-.. ._. ^^ ^^^ north of the Sar- Sargasso Sea 

gasso Sea, at Station 65, ""^sion. 
on 25th June 19 10. In this, as well as in the following 
figures, the continuous line indicates the salinity, the broken 
line the temperature, and the dotted line the density.^ We 
see that the salinity is greatest at the surface, 36.43 per 
thousand; this is the result of the strong evaporation. It 
decreases downwards, at first rapidly, then more slowly, more 
rapidly again, and finally very slowly ; in the deep layers below 
1250 metres the salinity is less than 35 per thousand, and 
throughout the great body of the deep water 34.9 per thousand. 

^ The density is given in abbreviated form, e.g: 25.56 instead of 1.02556, and is indicated by 
the Greek letter a (o-j being the density at the temperature zn situ disregarding the compression). 





/900 


1901 /902 /903 1904 1905 


% 


















120- 










/ 


\^^ 


HlX 




//O- 




^ 






// 


\ ^ 


/ 




ZOO- 




^ 


^ 




/J^ 


K\ 


V 




90- 




^^ 






\ \ 


A/ 




SO 








'\|/ 


/ / 












V 


\^ 


^ /v 




yo 

An 










\ 


-^ 





rainfall in Norway dtu-ing October, November, and 
December. 



Between 
Scotland and 
Rockall. 



242 DEPTHS OF THE OCEAN chap. 

The density increases from the surface to the bottom, but with 
varying rapidity ; 
through the first 
100 metres it in- 
creases rapidly, 
and also inthedis- 
continuity - layer 
between 600 and 
1 100 metres. 

Fig. 168 shows 
the conditions on 
the 7th August 
1910, at Station 
loi, between 
Scotland and 
Rockall, in that 
branch of the Gulf 
Stream which 
flows towards 
northern Europe. 
The salinity at the 
surface is here i 



°5 

T 




25J0 
ifSO 
0° 


20 30 4« 


2600 2650 
3S00 3550 
5° 6° 7° 6° 9° 10° 1 


2700 2750 
ibOO 3650 yoo 
" U'U-H" 15''16°17»16''19°20°C. 


6O0 
1000 
1500 

9 firm 






























I 

/ 
/ 

/ 


/ 


f- 




















/ 


/ 


/ ,-' 


,• 


>r. 


-^y 


























/ 


/ 

/; 
/ 












































/ 

i 


































\ 



Fig. 167.— Temperature (broken line), Salinity (continu- 
ous line), and Density (dotted line) at Station 65, 
a little north of the Sargasso Sea (25th June 1910). 
Depth in metres. 



per thousand lower than at Station 65 near the Sargasso Sea, 

^otaiwa 101. 



2&S0 ihno 

A-no dioo 

o' I" 2° 3' 4' S" 6° T 



Zbso 

iiiO 

■ 9" 10' // 



dbon 3bSO%o 

' /d" /T' /S" /S/" ?U' C 



1 '■ 


1 F 7^. + 







Fig. 168. — Temperature, Salinity, and Density at Station ioi, a little 
east of Rockall (7th August 1910). Depth in metres. 

due to admixture of fresh water ; but from about 900 metres 
down to the bottom the salinity, temperature, and density 



PHYSICAL OCEANOGRAPHY 



243 



are all very much alike in these two places, nearly 2000 
nautical miles distant from each other. There is thus a 
marked difference as far as the upper layers are concerned, 
both salinity and temperature decreasing northwards, while in 
the deep layers below 500 fathoms the conditions are the same 
throughout the middle and north-eastern part of the North 
Atlantic. Northwards from Station 65 to Station loi the 
decrease of temperature in the upper layers is more marked 
than that of the salinity, so that the density of the surface-layer 
increases from 1.0254 at Station 65 to 1.0266 at Station loi. 
As a general rule, the upper water- layers, on being cooled, 
become gradually heavier from the tropics toward the poles. 

Fig. 169 shows the conditions at Station 106, loth August Faroe 
19 10, in the Faroe- Shetland Channel to the north of the ^^^""^^• 

Station 106 



t 




0° 


„ 


„ 


' i 


2boo 


(,' 7' e- s 


^ 


0' 1 


r /Z' /3' 1 


Zloo 


21S0 
7' >8^ B'^^'o^^C 






^8oo 






















1 


/ 


r 


- 
















-, 




















Ix 


'' 


'-' 


■" 


'{ 




'^ 


/' 
































... 




< 








! 




















































Lj 



Fig. 169.— Temperature, Salinity, and Density at Station 106, in the 
Faroe-Shetland Channel (loth August 1910). Depth in metres. 

Wyville Thomson Ridge, about 300 miles north-east of 
Station loi. At Station 106 some fresher water was found at 
the surface, but otherwise the salinity, temperature, and density 
were the same at both stations as far down as 500 metres ; the 
water had grown slightly colder and heavier in these 300 miles, 
but the difference was very small. Below 500 metres, however, 
there is a great contrast, the temperature of the deep water 
being, as already indicated, much lower north of the Wyville 
Thomson Ridge than south of it, and the density is therefore 
greater on the north side. The deep water of the Norwegian 
Sea is thus colder and heavier than that of the Atlantic, but, 
strange to say, there is no difference in the salinity of the 
deepest layers of the two regions. 

At all three stations the surface -layers are occupied by a 
warm, comparatively saline, northerly current. On proceeding 
northwards, there is a fall of temperature and of salinity and 



244 



DEPTHS OF THE OCEAN 



an increase of density, but the differences are not so great as 
to forbid the inclusion of the three stations in one region with 
regard to the upper water-layers ; it is a region with a southern 
character. 

The conditions are widely different when we come to a 
northerly region, like that where the East Greenland Polar 
Current and the Labrador Current bring down great water- 
masses from the Arctic seas. On our passage to and from 
St. John's we sailed across the Labrador Current and took a 
number of observations at different places in it. Fig. 170 shows 
the conditions at Station 76, due east of St. John's, towards the 
eastern margin of the cold current. Here the temperature at 
the surface was about 6° C, falling rapidly to —0.35° C. at 55 
metres (30 fathoms), rising again, at first rapidly, to 3^ C. at a 



M. 

/oo 



Ji6o 
33 



■ees 

33 6 
Z" . 3° 



g7o 

3i.o 

4' .5" 



J'fS 



i'ao 






Fig. 170. — Temperature, Salinity, and Density at Station 76, in the eastern part 
OF THE Labrador Current, off Newfoundland (9th July 1910). Depth in metres. 



little more than 200 metres, and then slowly to 3.4" C. towards 
the bottom in about 400 metres. If the depth had been 
greater, we should have found that the temperature fell 
again as we penetrated into the deep water. This is an 
example of the usual conditions in Arctic and Antarctic regions, 
where in summer the temperature decreases gradually from the 
surface to a minimum at 50 to 70 metres, then rises to a 
secondary maximum at 300 to 400 metres, falling again towards 
the bottom, and it is in a case like this that the ordinary 
maximum and minimum thermometer is inadequate (see p. 216). 
At Station 76 the water was warmer through the influence of 
the Gulf Stream ; it was much colder, for instance, at Station 75 
farther west, where we found -1.43° C. at 55 metres, and at 
Station 74, just off St. John's, where the temperature was —1.52° 
at 91 metres. As a rule, it may be said that in a polar current 



PHYSICAL OCEANOGRAPHY 245 

in depths between 50 and 100 metres the temperature is below 
zero, and where there are banks at these depths they are 
covered wath ice-cold water ; hence the great difference between 
such banks and those which lie within the region of the warm 
currents. Fig. 95, p. 1 10, represents a section across the New- 
foundland Banks from the Gulf Stream (Station 69) northwards 
to a point just outside St. John's (Station 74). On the northern 
part of the bank it is very cold, for there we are in the middle of 
the Labrador Current; on the southern slope it is much warmer, 
because of the vicinity of the Gulf Stream. There are accord- 
ingly great differences in temperature and salinity in different 
parts of the Newfoundland Banks, especially in the deeper 
parts. 

From Fig. 170 we see that the salinity was below t,t, per 
thousand at the surface, that it increased rapidly downwards (to 
34.6 per thousand at 200 metres), and afterwards more slowly, but 
it nowhere attained the salinity of the " Atlantic water," viz. more 
than 35.0 per thousand. This is characteristic of the Arctic and 
Antarctic regions, especially in summer. The water brought by 
the currents from the North Polar basin is a kind of coast- 
water. The great rivers of Siberia and of the north of America 
empty volumes of fresh water into the Polar Sea, where it 
mixes with the salt water, diminishing the surface salinity, 
which is further reduced by the melting of the drifting ice in 
summer. The low salinity at the surface renders the density 
comparatively small, but it increases rapidly downwards, so 
that the water at 100 metres is heavier than at any of the three 
stations within the warm water region just mentioned. We 
have not in any of these examples taken into consideration the 
fact that the density is slightly increased with increase of depth 
by the pressure due to the weight of the overlying water. 

The pressure in the sea increases by about i atmosphere The pressure 
for every 10 metres of depth. Thus there is a pressure of '''^^^^^^■ 
about 100 atmospheres 1000 metres below the surface, and of 
500 atmospheres at a depth of about 5000 metres. When 
differences in pressure occur in adjacent areas at the same level 
below the surface, various currents arise, just as air-currents 
are produced by differences of barometric pressure. The 
circumstance that the water is not equally heavy everywhere is 
one of the main causes of the ocean currents, and, the water 
being easily moved, small differences of pressure will be sufficient 
to produce a sensible motion. By the great pressure the water 



246 



DEPTHS OF THE OCEAN 



itself, and all the materials carried into deep water, are com- 
pressed. Water is, however, only to a slight extent compressible, 
so the effect of pressure is not so great as is popularly supposed. 
Tait and Buchanan have shown conclusively that compressi- 
bility decreases slightly but sensibly with increase of pressure. 
V. W. Ekman has recently made a very careful investigation on 
the compression of sea- water, and has published Tables for Sea- 
Water under Pre sszcre. From his tables we may easily compute 
the actual density with compression, when depth, salinity, and 
temperature are known. 

Let us take, as an example, the conditions at Station 63, 
near the Sargasso Sea, 22nd June 19 10, as shown in the 
following table, giving for the depths specified: (i) the 
temperature, (2) the salinity, (3) the density disregarding the 
compression (calculated by means of Knudsen's Tables), and 
(4) the actual density with compression (calculated from 
Ekman's Tables) : — 



Depth. 


Temp. 


Salinity 

per 
thousand. 


Density. 


■ Metres. 


Fathoms. 


Without Actual density 
compression S. Sj. 



183 
366 
549 
732 

915 
1830 
3000 
4000 




100 

200 

300 

400 

500 

1000 

1640 

2187 


22.30 
16.71 
15.22 

^2.35 
8.41 
5-97 
3-54 
2.90 

2-35 


36.44 
36.27 
36.00 

35-54 
35-11 
35-16 
34-94 
34-92 
34.88 


1.02525 
1.02658 
1. 02671 
1.02696 
1.02732 
1.02770 
1. 02781 
1.02786 
1.02787 


1.02525 . 
1.02741 
1.02835 
1.02943 
1.03067 
1. 03190 
1. 03631 
I.04171 
1. 04621 



It is seen that the density is practically identical, for instance, 
at 3000 metres and at 4000 metres when leaving compression 
out of account, whereas a considerable difference was actually 
produced by the compression. At 4000 metres the effect of 
the pressure of 400 atmospheres was so great that the density 
increased from 1.02787 to 1.0462 1, equal to an increase of 
weight of if per cent. As a matter of fact the water at 4000 
metres has become only if per cent heavier by reason of the 
compression ; a fairly delicate weighing would have been 
necessary to detect this increase. The case may also be stated 
thus : I litre of water at 4000 metres weighs 1046 grams ; if 



PHYSICAL OCEANOGRAPHY 247 

this litre were brought up to the surface, it would expand so 
that its volume would be increased by 18 cubic centimetres; 
subtracting the 18 c.c. and weighing the remaining litre we 
find a weight of 1028 grams. Thus even at a depth of 4000 
metres the difference caused by pressure is not great. 

Now, what is the effect of this increase of density on a solid Sinking of a 
body lowered into the sea ? Let us suppose a piece of solid ^^^''^ ^""^y* 
iron, weighing 1000 grams in the air, to be sent down to 4000 
metres at Station 63. When it is lowered just beneath the 
surface it becomes lighter by 131 grams, thus weighing 869 
grams. When it has reached a depth of 4000 metres the 
buoyancy is 134 grams, so that the piece of iron there weighs 
866 grams — a difference in weight of 3 grams for a piece of 
iron weighing 1000 grams in air. This is merely 0.3 per cent 
of the weight, and consequently quite insignificant. In other 
words, metals and other solid substances are practically just as 
heavy in deep water as they are at the surface, and will sink as 
rapidly there as in shallow water. This may be proved by 
direct observation, for if a messenger is sent down to close a 
water-bottle at a depth of 2000 metres it will be found to take 
four times as long as when sent down to 500 metres. 

But suppose that, instead of a massive piece of iron, we take sinking of 
a perfectly tis^ht capsule of thin iron filled with air, and lower it ^n air-fiiied 

i. J <j X ' C3.DSUIg. 

down to 4000 metres ; in the course of the descent the pressure 
increases, forcing the walls of the capsule together. The 
volume of air within the capsule may be so large that it only 
just sinks at the surface, its total specific gravity being then 
very little greater than that of the water ; but when it has 
reached a depth of 10 metres the air is compressed to half its 
original volume, granted that the capsule is collapsible, and the 
weight of the iron then acting more freely, the capsule will sink 
faster and faster ; when it reaches a depth of 4000 metres it is 
exposed to a pressure of 400 atmospheres, and the compressed 
air having hardly any buoyancy left, the capsule will sink almost 
as fast as if it had been made of solid iron throughout. 
Collapsible solid bodies containing air will accordingly sink 
faster in deep water than at the surface. A piece of wood 
floats at the surface because it contains a large amount of air, 
but there is nothing to prevent it from sinking when it is sent 
down into deep water ; therefore wood and cork are not 
suitable for floats at great depths. It is the same with the dead 
bodies of marine animals, etc., for when the air is compressed 
they will easily sink. 



248 



DEPTHS OF THE OCEAN 



The penetra- 
tion of light 
into the sea. 



Absorption of 
light rays. 



Intensity of 
light at 
different 
depths. 



Fol and 
Sarasin. 



When the sun's rays fall on the surface of the sea, some of 
them are rejected, and the rest penetrate into the water, though 
in a somewhat altered direction. The direction is not much 
altered when the sun is high in the heavens, as at noon in the 
tropics. When the sun is just above the horizon its rays are 
most strongly deflected, the few rays penetrating into the water 
forming an angle of about 42" with the surface. As the sun 
rises and the light becomes more intense, the deflection from 
the course in the air gradually decreases, so that the rays do 
not penetrate so deep as might be expected, even if the 
angle with the surface increases. When the sun is 60^ above 
the horizon, the refraction in the water is about 8°, the angle 
between the surface and the penetrating rays then being about 
68°, and when the sun is at its zenith, the rays are not bent at 
all, but proceed perpendicularly into the water. 

The rays making their way into the water are, however, 
gradually absorbed, some quickly, others more slowly, accord- 
ing to the wave-length of the ray and the limpidity of the water. 
The sun's light, of course, consists of many different kinds of 
rays : the dark heat-rays, imperceptible to the eye, lie beyond 
the red end of the spectrum, and are therefore called ultra-red 
rays ; then comes the visible spectrum with the colours in the 
well-known order — red, orange, yellow, green, blue, indigo, and 
violet ; beyond the violet end are the ultra-violet rays, remark- 
able for their chemical action, but having no effect on our 
senses. These different rays are refracted and absorbed in 
different degrees. The red rays are refracted somewhat less 
than the blue and violet rays, and are much more quickly 
absorbed. The dark heat-rays are absorbed in the very upper- 
most water-layers. The light rays also convey some heat, and 
they penetrate deeper before disappearing — the deeper the 
nearer the blue end of the spectrum is approached. Light at a 
certain depth in the sea has not the same composition as on 
the surface of the earth, there being fewer of the red rays 
and more of the blue, which proportion becomes gradually more 
pronounced with increasing depth. 

Attempts have been made to determine the intensity of the 
light at different depths, especially in the Mediterranean, by 
means of the action of the rays on photographic plates. 
Ordinary plates are most influenced by the rays at the blue end 
of the spectrum, and by the ultra-violet rays, and only slightly 
by the red. Fol and Sarasin, working off the Riviera, traced 
an effect on the plate as far down as between 465 and 480 



PHYSICAL OCEANOGRAPHY 



249 



metres ; Petersen found that in the neighbourhood of Capri a Petersen. 
plate was influenced by the rays at a depth of 550 metres, 
Luksch made some investigations in the eastern part of the Luksch. 
Mediterranean, exposing his plate for fifteen minutes, and found 
that the limit of the light-rays must be drawn at 600 metres. 
In these experiments the influence of the collected rays on an 
ordinary photographic plate was studied. 

In order to make some investigations on this subject in the 






jjy pii 



Fig. 171.- 

On the left, as it is sent down 



-Helland-Hansen's Photometer. 
in the middle, open for exposure ; on the right, closed and 
ready for hauling up. 



'Michael Sars " Atlantic Expedition, the author constructed a Heiiand- 

- - - - . . - . . . „. , Hansen's 

photometer. 



new kind of photometer, which is represented in Fig. 171. In ^^"sens 



the centre figure — at the lower part — is seen a brass cube ; the 
four sides and the top have square " windows," and on each of 
them a small square frame with a similar window (2x2 cm.) 
can be screwed fast ; the screws and openings are seen in the 
figure. The cube rests on a larger brass plate, or rather on an 
india-rubber mat covering the brass plate. The plate and cube 
are fastened inside a frame, along which they can be moved up 
and down. At the top of the central figure is seen a larger 



250 DEPTHS OF THE OCEAN 

metal cube without any base ; it is intended to cover tightly 
the lower cube to which the photographic plates are fastened. 
On the left the apparatus is seen closed, with the cubes suspended 
at the top of the frame, the smaller one inside the larger. In 
this position the apparatus is lowered into the water. A 
small messenger is sent down the line and releases the inner 
cube, which drops to the bottom of the frame (see the middle 
figure). The plates are thus exposed. After a certain time a 
larger messenger is sent down, releasing the large cube, which 
falls like a shutter over the plates, as seen in the figure on the 
right. The apparatus is then ready for hauling up, and the 
cubes are taken out of the frame into the dark-room for develop- 
ment and change of plates. 

In all previous photometric apparatus for use in the sea the 
plates were hermetically closed behind a strong glass pane, in 
order to shield them against the great pressure, but in the 
photometer here described a totally different principle was 
applied. The gelatine-film was covered with a glass plate and 
inserted into a small envelope of thin caoutchouc, with a square 
opening in front through which the light is admitted. The 
envelope with the plate was then placed on one of the sides of 
the inner cube, and the corresponding brass frame was screwed 
on tightly. The water could penetrate both outside and inside 
the cube, so that there was the same pressure on both sides of 
the film and the glass cover. The rubber envelope would be 
pressed tightly on to the glass plate, so that no water could enter 
and spoil the film. By this arrangement the apparatus might 
be exposed to any pressure without any special protection, and 
it was used at various depths down to 1700 metres without a 
single plate being cracked or spoilt by water. 

Highly sensitive pan-chromatic plates (4x4 cm.) were 
employed in the experiments — the windows being, as mentioned 
above, 2x2 cm. In several experiments a gelatine colour 
filter was inserted between the photographic plate and the glass 
cover. Wratten and Wainwright's three-colour filters (red, 
green, and blue) admit respectively only a certain portion of the 
spectrum. This made it possible to study the rays present 
within the separate fields of the spectrum, as well as the total 
intensity of the rays. These investigations were carried out in 
the southern stretch of the cruise, and though time and weather 
did not allow of many experiments, those that were made gave 
interesting results. 

Some of the plates exposed are represented in Fig. 172. In 



PHYSICAL OCEANOGRAPHY 251 

the upper row are seen some results without a Hght-filter at Results at 
Station 51. The plate on the left (No. 10), exposed for 40 'j'^p^hTluh 
minutes at 500 metres, was strongly influenced by the rays, and without 
The next plate (in the middle of the upper row), exposed foj- '^o °"''-*i f^''^- 
80 minutes at 1000 metres, was also blackened by the light-rays. 
The third plate was exposed for 120 minutes at 1700 metres, 
and showed no effect whatever. These experiments were made 
at noon on the 6th June with a clear sky, and show that a good 
deal of light penetrates to a depth of 1000 metres — considerably 
deeper than was previously supposed. The limit of light 




Fig. 172.— Photographic Plates exposed at different depths. 
The upper row from Station 51, the lower row from Station 55. 

sufficient to influence the plate in the course of two hours lies 
at a less depth than 1 700 metres. 

The lower row in Fig. 172 shows some plates from Station 
55, all exposed for forty minutes at a depth of 500 metres. The 
plate on the left was used without filter, and shows the same 
strong effect as the corresponding plate from Station 51, in the 
upper row. The next plate (in the middle of the lower row) 
was exposed with the blue filter ; an influence of the blue rays 
is visible on the original plate (a faint Roman V), but not so 
clearly in the reproduction given here. The right-hand plate 
in the figure was exposed with a green filter, and shows no 
effect. A plate with the blue filter needs an exposure six times, 
and one with the green filter eighteen times, as long as a plate 



252 



DEPTHS OF THE OCEAN 



CHAP. 



is therefore difficult to compare the plates 
it may at least be maintained that there 



with no filter. It 
quantitatively, but 

must be many blue rays, though hardly any red ones, at a 
depth of 500 metres. Series of experiments with and without 
filters were also made at a depth of 100 metres ; in forty minutes 
all the plates were over-exposed, those with a red filter only a 
little, those with a blue one very much, so that there are many 
rays of all kinds at 100 metres, though fewest of the red. When 
plates without colour-filters were exposed on the top and on 
the sides of the cube simultaneously, the plate on the top proved 
to be more strongly influenced than the others. This fact is 
not without interest, as it shows that the rays in the clear 
tropical waters have a distinct direction at 500 metres, not 
having yet become altogether diffuse ; shadows should, then, 
be thrown even at that depth. 

Regnard constructed an apparatus for determining the length 
of the day at different depths, in which a clockwork arrange- 
ment inside a cylinder causes a photographic film to pass before 
an aperture. At the end of March 1889 the Prince of Monaco 
made some experiments with Regnard's apparatus in the harbour 
at Funchal, Madeira ; the water was not so clear as in the open 
sea, so the times recorded may be rather short. At 20 metres 
the day lasted eleven hours ; at 30 metres it began at 8.30 a.m. 
and ended at 1.30 p.m., the sky becoming overcast ; at 40 metres, 
with the sun shining brightly, the film exhibited only a slight 
influence of light for a quarter of an hour about 2 p.m. These 
and a few other experiments show that the day becomes 
gradually shorter, and the intensity of light decreases, as the 
depth increases. 

The Swiss naturalist, Hermann Fol, has several times gone 
down in diving dress off Nice to examine the bottom. At a 
depth of 10 metres the solar light disappeared quite suddenly in 
the afternoon a long time before sunset. At 30 metres the 
light was so bad that it was difficult to gather the animals on 
the bottom ; he could see a stone only at a distance of 7 or 8 
metres, whereas shining objects in favourable positions could 
be discerned at a distance of 25 metres. He also noticed that 
dark red animals (like Muriccea placornus) looked quite black, 
while the green and green-blue algse appeared lighter in colour. 
This is explained by the fact that the red light disappears much 
sooner than the blue. A coloured object will always look black 
when untouched by rays of its own colour. As the white sun- 
light contains all colours, objects display in it their proper tint, 



PHYSICAL OCEANOGRAPHY 253 

but when the red rays, for instance, are cut off, a piece of red 
paper will look black. 

The usual method of studying the transparency of the water Transparency 
is to lower a large white disc, noting the depth at which it of^ea-water. 
disappears from view. The degree of transparency is found 
to vary greatly, for in the clear dark-blue water in the middle 
of the ocean near the tropics the white disc can sometimes 
be seen as far down as 50 metres below the surface, or even 
more, while in those places where rivers bring down large 
quantities of detritus from the land the disc may occasionally be 
invisible a couple of metres beneath the surface. The enormous 
quantities of small plankton organisms inhabiting the upper 
layers may also render the water relatively opaque. The 
penetration of light thus varies according to circumstances, but 
few direct observations of the light-intensity have as yet been 
made. It would be of the greatest interest to know the amount 
of light at different depths in different seas, and thereby gain a 
better understanding of the conditions of life, for instance, as 
regards the development of the plankton, as the small plankton 
algae need light for the processes of assimilation. 



Sea-water normally contains oxygen, nitrogen (with argon). Gases in the 
and carbonic acid. These gases are absorbed at the surface ^^^• 
from the atmosphere, and are carried by currents even into the 
deepest parts of the ocean in varying amounts. A study of these 
variations is of considerable interest, and may be briefly dealt 
with here, although no gas-analyses were made during the 
"Michael Sars " Atlantic Expedition. There are several good 
methods of analysis. For the three gases named, the method 
introduced by Bunsen, and further developed by Pettersson and 
Fox, may be employed, the water-sample being boiled at a low 
pressure, and the escaping gas collected and analysed. The 
oxygen may be determined by a very simple titration, according 
to Winkler's method, or Krogh's method of examining the 
tension of the several gases in solution may be applied. 

Oxygen is not so readily soluble in salt water as in fresh ; Oxygen. 
the higher the salinity the less the absorption of oxygen by the 
water. It is also a well-known fact that cold water dissolves 
more air than warm. This is clearly seen in the following 
excerpt from Fox's tables, showing the cubic centimetres of 
oxygen in i litre of water at different temperatures and sali 
when the water is saturated with this gas : — /C^\ 




254 



DEPTHS OF THE OCEAN 



Temperature. 




Salinity. 












per thousand. 


20 per thousand. 


35 per thousand. 




0. in c.c. per litre. 


0. in c.c. per litre. 


0. in c.c. per litre. 


o°C. 


10.29 


9.01 


8.03 


10° c. 


8.02 


7.10 


6.40 


20° c. 


6.57 


5.88 


5-35 


30° c. 


5-57 


4.96 


4-5° 



At 30° C. a litre of water which is saturated with oxygen 
contains little more than half as much as at 0° C. There is 
therefore normally more oxygen in the cold water-masses of the 
Arctic and Antarctic regions than in the warm water-masses of 
the tropics. The salinity is not such an important factor in the 
solubility of oxygen as the temperature. 

Marine animals need oxygen for respiration, and therefore 
consume some of that contained in the water. By the act of 
respiration carbonic acid is produced and dissolved in the water. 
The same thing goes on through the respiration of plants. 
These are some of the principal oxygen-consuming processes. 
But plants assimilate besides breathing ; that is to say, they 
make use of the carbonic acid by dissociating it into oxygen 
and carbon ; they employ the carbon for building up cells, while 
the oxygen is again dissolved in the water. This is the chief 
oxygen-producing process, but it is carried on only through the 
influence of light-rays. It is doubtful what rays are the most 
important for marine plant life, and in what quantity they are 
necessary. Experiments have shown that many higher aquatic 
plants assimilate much better in yellow light than in blue or 
violet light ; this is the case with most adherent green algse, 
and hence they are found in the upper water-layers near the 
surface, where there is enough yellow light. The red alga^, on 
the other hand, assimilate better in blue light than in yellow, 
and therefore live in deeper water than the former. We know 
nothing of the assimilation by the plankton-algae of the various 
light-rays ; we only know that they need light, and that they 
are found in the upper water-layers, but not in deep water. 
The production of oxygen in the sea is thus limited to the 
upper layers, while the consumption of oxygen takes place 
wherever there are living organisms (excepting certain bacteria). 
Now, supposing the processes of assimilation and of respiration 



PHYSICAL OCEANOGRAPHY 



255 



balanced, the quantity of oxygen in the water is not altered 

however many or- 
ganisms are pre- 
sent. But if there 
is an excess of 
animal life the 
amount of oxygen 
decreases (as it 
always does in the 
dark) ; if there is 
an excess of plant 
life the amount of 
oxygen increases, 
provided there is 
light enough. 

Knudsen a n d Knudsen and 

Ostenfeld made o^t<^"f^>d's 



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I 


f 


^. 


.£• 


1 


/ 


X 


\ 




A 




\ 


)\ 


i 


-, \ 


VA "^^^ 


sv 






1^ ^ 


^ / 


\\\\- 




^ / 


\ \. 


^ ^^ 






c;:^o3 ■f.-t^. 


^ \ 


V 


' ^ 


\\ 




^ 


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y , 



r: Q 



O ^ 



experiments. 



some expermients 
g ;S to prove this. 
3 S. They filled some 
'^ S bottles with a 
K I capacity of i litre 
z § with sea-water, and 
z J into one they put 
t \ some living crus- 
o ^ tacea (copepods). 

o After three hours 
§ ^ there was 3.88 
^ I cubic centimetres 

1 & less oxygen in this 
S I bottle than in the 
y I' others, while the 
^ £ quantity of car- 

l bonic acid had 
" increased. They 
'i filled two litre- 
bottles with sea- 
water, and intro- 
duced equal quan- 
tities of vegetable 
plankton (dia- 
toms), covering 



one 



of them with tin-foil so as to shut out the light. 



After 



256 DEPTHS OF THE OCEAN chap. 

three hours it was found that the diatoms had consumed 
2.34 cubic centi- 
metres of the 
oxygen in the dark '^• 
bottle (the amount 
of carbonic acid 
being shghtly in- 
creased), whereas 
in the uncovered 
bottle thequantity 
of oxygen had 
increased by i i.oo 
c.c. (the amount of 
carbonic acid 
being decreased). 
Brennecke has 
compared the 
results of a num- 
ber of oxygen-de- 
terminations from 
the Atlantic 
Ocean, and in 
Figs. 173 and 
174 his two sec- 
tions showing the 
vertical distribu- 
tion of oxygen in 
the Atlantic (from 
the surface to a 
depth of 1 500 
metres) between 
lat. 60° N. and 50 
S. are reproduced. 
The first section 
shows the quan- 
tity in cubic centi- 
metres per litre. 
A little north and 
south of the equa- 
tor the value is ^ 
only 1-2 c.c. per 
litre in the water 
between 200 metres and 600 or 700 metres ; on the equator, 




PHYSICAL OCEANOGRAPHY 257 

where the cold water from below comes comparatively near the 
surface, it is a little more ; the highest value, over 6 c.c. 
per litre, is found in high northern and southern latitudes. 
The second section shows the deficiency from saturation in 
cubic centimetres per litre at the temperature and salinity 
ill situ. In the upper 50-100 metres the water is nearly 
saturated all over the Atlantic, while in greater depths the 
oxygen is deficient, especially in tropical waters^ at a depth 
of about 500 metres in lat. 10" N. and S. the deficit amounts to 
five or six cubic centimetres per litre. This is explained by the 
abundant supply of oxygen in the surface-layers, through absorp- 
tion from the atmosphere, and through assimilation by the rich 
plant life, while the oxygen is being constantly consumed at 
greater depths, where plant life is scarce and animal life in 
excess. As a rule, where there is a great deficit of oxygen the 
water is characterised as " stale," a long time having elapsed since 
it was aerated at the surface or purified through the action of 
plants. 

The disappearance of the oxygen is not, however, due only 
to the respiration of animals, but may also be caused by various 
hydro-chemical processes. In the Black Sea oxygen is found 
only in the upper 150-200 metres (about 100 fathoms) of water ; 
below this it has disappeared totally, whereas sulphuretted 
hydrogen is present in increasing quantities down towards the 
bottom. The Black Sea is separated from the Mediterranean Black Sea. 
by the Bosphorus ridge, so that the water in its deep basin lies 
stagnant, unrenewed by the influx of other water. Similar con- 
ditions prevail in several Norwegian " threshold fjords," or on a Norwegian 
smaller scale in the oyster-" polls." In such places the bottom fj^JS^aSi 
is thickly covered with organic matter ; a slimy black mud is oyster- ^ 
formed, swarming with bacteria that produce sulphuretted ^° ^' 
hydrogen, which spreads through the water, combining with 
the oxygen to form various sulphates. This causes the oxygen 
to decrease and finally to disappear altogether, when the 
sulphuretted hydrogen begins to appear free in solution. It 
gradually spreads upwards, until the water is devoid of oxygen 
and contains free sulphuretted hydrogen, at a depth of only 
100 fathoms in the Black Sea, and in the oyster-basins in 
autumn often at merely a couple of metres below the surface. 
In summer the "bottom-water" of the oyster-" polls " lies 
stagnant, but in the course of the autumn and winter it is 
generally renewed by the supply of comparatively heavy water 
from without ; then the sulphuretted hydrogen disappears and 



258 



DEPTHS OF THE OCEAN 



the oxygen returns, producing thus an annual change in the 
gaseous conditions of the deeper parts of the oyster-" polls.'* 
In autumn the state of things may become critical for the oysters, 
which are suspended in baskets at a depth of i-J-2 metres ; it 
happens occasionally that the animals all die at this time by 
suffocation through want of oxygen or by sulphur poisoning. 

The water may, on the other hand, become over-saturated 
with oxygen, as occurs sometimes in the Kattegat, or in spring 
in some parts of the oyster-" polls," where plant life is particularly 
luxuriant. 

Carbonic acid. Carboiiic add occurs combined as carbonates and bicar- 

bonates, and only in very small quantities as a free gas. The 
quantity varies considerably, among other things because of the 
activity of plants and animals, as above mentioned. Usually 
there is about 50 c.c. of carbonic acid in i litre of sea-water, 
but of this only a few tenths of a cubic centimetre is free gas in 
solution. 

Carbonic acid has probably been present from the formation 
of the primitive ocean, together with the salts of the sea, but 
the quantity varies from place to place and from time to time, 
depending on the number of plants and animals, on the com- 
position of the bottom, and more especially on atmospheric 
conditions. At times considerable quantities of carbonic acid 
gain access to the water through submarine volcanic activity, 
but this has probably less influence on the variations than the 
atmospheric conditions. August Krogh has made some very 
valuable investigations on this point, and has arrived at the 
conclusion that the sea is a sort of regulator for the amount of 
carbonic acid in the atmosphere. When there is much carbonic 
acid in the air, much will be absorbed by the sea ; this is the 
case near land, and especially where there is a dense population 
and extensive industrial activity, or near active volcanoes. The 
tension of carbonic acid is everywhere small, but it is on the 
average greater over the land than over the sea. Now, if the 
tension in the air over a certain portion of the sea is smaller 
than it is in the sea, the latter will give off carbonic acid to the 
air. The sea thus has a regulating influence on the variations 
in the carbonic acid of the atmosphere. Many important 
questions arise with regard to these relations, but we cannot 
enter into further detail here ; investigations on the subject 
are few. 

Nitrogen. NUrogeu is SO inert a gas that it is of little importance in 

oceanography. It is absorbed from the atmosphere in con- 



Krogh's 
investigations. 



PHYSICAL OCEANOGRAPHY 259 

siderable quantities, i litre of water at a temperature of 10° C. and 
with a salinity of 35 per thousand, for instance, containing when 
saturated 12 c.c, of nitrogen. It is possible that marine bacteria 
partly dissociate nitric compounds so as to liberate nitrogen, 
and partly bind free nitrogen in various salts. These variations 
are always small, and not easily demonstrable. As a rule, 
though not without exception, the surface-water is saturated 
with nitrogen from the air, and when the water leaves the 
surface it carries down with it practically the same amount of 
nitrogen. 

A vessel running a certain course at a speed measured by Currents ii 
the log often proves to have arrived at another point than that ^^^ ^^^' 
which would be expected from the reckonings. This will be 
the case when there is a strong wind, but even in a calm a dis- 
placement is frequently experienced, which is then caused by a 
current, and when the calculated position is compared with that 
actually arrived at, the difference will indicate the effect of the 
current on the ship. In sailing across the Gulf Stream off the* 
east coast of North America, for instance, the ship is carried 
north or north-east of its latitude according to the compass and 
the log. The deviation is then an expression of the direction 
and velocity of the current, and much information with regard 
to the set of the currents has been obtained in this way. But 
the method is not trustworthy when there is a wind acting on 
the ship. The drift of various objects floating on the sea. Drift of 
wreckage for example, has also been studied. When wreckage ^'^eckage. 
belonging to the *' Jeanette," which foundered in the Arctic Sea, 
was found in the North Atlantic, Nansen concluded that a 
current must run from the polar basin between Greenland and 
Spitzbergen into the Atlantic Ocean, and on this supposition 
he planned the " Fram " Expedition. In the Atlantic Ocean 
wrecks are often encountered drifting about with wind and 
current. These are reported, and from such reports one can 
follow the movements of wrecks for a long time. Fig. 175 shows 
some such wreck-courses ; many of the wrecks have drifted 
from North America towards Europe, thus showing the effect 
of the Gulf Stream ; others have been carried eastward in the 
direction of the Azores, then south, and finally west back towards 
America again. But in these cases the wind always plays an 
important part, so that it is difficult to form a correct idea of the 
movements of the water. In the far north and far south we Floating 
can follow the drift of the icebergs ; one, for instance, breaking ''^^^^''g^- 



26o DEPTHS OF THE OCEAN chap. 

loose far north on the west coast of Greenland would float 
towards the south along the coasts of Labrador and Newfound- 
land, and even farther south, thus proving the existence of the 
Labrador Current. An iceberg lies deep in the water, a fraction 
only of its bulk rising into the air, so that the wind will have 
little influence on its motion, which will practically express the 
aggregate effect of the currents through which the foot of the 
iceberg stretches. 

It has occurred more than once that vessels have been 
locked up in the ice east of Greenland, and have been carried 




Fig. 175. — Drift of Wreckage in the North Atlantic. (After Kriimmel.) 

along with the drifting ice far towards the south. In the year 
1777 a number of whalers were caught in the ice north of Jan 
Mayen, and all their efforts to free themselves were in vain, 
many of the ships being crushed, while most of the men 
perished; when the last ship was lost it had drifted iioo 
nautical miles in 107 days, or an average of 10 miles per day. 
On the second German Arctic Expedition one of the ships, the 
" Hansa," was locked up in the ice in lat. 74° 6' N. and long. 
i6j^ W. on the 6th September 1869, and was carried southwards 
until it was crushed on the 19th October. The crew took 
refuge on an ice-floe, and drifted on till the 7th May 1870, 
when they were able to land in Greenland in lat. 61° 12' N. 



PHYSICAL OCEANOGRAPHY 261 

They had been carried 1080 nautical miles in 246 days, that is, 
4,4 miles per day on an average. 

Information about the currents is also obtained from objects 
found drifting along with them. At Lofoten golf-balls have 
been found which must have come across from Scotland. In 
the Norwegian Sea drift-wood from Siberia is occasionally met 
with ; once we came across the trunk of a Siberian tree thickly 
covered with littoral diatoms, which had thus travelled right 
through the polar sea, so that the log had come from the 
northern coast of Asia with the same current that carried the 
" Fram " through the northern waters. 

In order to study the currents, drift-bottles have often been Drift-bottles. 
employed, in which are enclosed slips of paper with directions 
to the finder to send the note to the address given, with ■ 
information about when and where it was found. Fig. 176 
shows the results of some of the bottle-experiments made in the Fulton's 
North Sea by Fulton, who has in this way been able to give a ^"-p^"'"^" ^• 
more complete account of the currents of the North Sea than 
was previously possible. In this case the method gave quite 
trustworthy results, because there were shores all round where 
it was comparatively easy to recover the bottles within a short 
time. As regards the great oceans, the method often gives 
rather doubtful results. In the first place, one cannot know the 
route followed by the bottle from the time it was thrown over- 
board till the time it was found, and then it may lie for years 
on the shore before it is found, so that no one can tell how long 
it has been on its journey. 

These methods give a certain amount of information about 
the motion of the superficial layers, but none about the deeper 
currents. We can also study the set of the water-masses 
by means of their physical or chemical qualities, especially 
temperature and salinity and gaseous contents. It is, for 
instance, known that the Gulf Stream carries much salt water 
(with a salinity above 35 per thousand) from the Atlantic into the 
Norwegian Sea, and the course of this salt water can be traced 
farther north ; it forms a band along the coast of Norway, and 
branches off in several places. The position of this salt water 
indicates the course of the current itself, not at the surface only, 
but also in the deeper layers. 

From a study of the distribution of salinity and temperature 
the average direction of the drift of the water-masses may be 
deduced, and an idea of the velocity obtained by calculation, ^j^j^,^ 
Mohn, and more recently especially Bjerknes, have greatly Bjerknes. 



262 DEPTHS OF THE OCEAN chap. 

aided oceanographical work by giving the mathematical basis 




Fig. 176. — Results of Dr. Fulton's Drift-Bottle Experiments in the North Sea. 

for these investigations. This method, however, is indirect, 
and is in many cases insufficient for obtaining an exact know- 



PHYSICAL OCEANOGRAPHY 263 

ledge of the motions of the sea, for which purpose direct 
current-measurements are necessary. 

Measuring the currents at different depths in the sea is 
much more difficult than might appear at first sight, and re- 




Ekman's Current-Meter. 



quires good apparatus. Many excellent current-meters have 
been constructed, the one made use of during the cruises of 
the " Michael Sars " being that invented by V. W. Ekman, Ekman's 
represented in Fig. 177. The apparatus consists ot a double 
wing (A), that points in the direction of the current. In front 



current- meter. 



264 DEPTHS OF THE OCEAN 

is a propeller which is moved by the current, the velocity- 
determining the number of revolutions in a certain period. 
The propeller works some small cog-wheels connected with 
hands showing on a dial the number of revolutions. The 
mechanism for indicating the direction of the current is very 
ingenious. Some small shot are inserted into a tube leading 
to one of the cog-wheels, which is provided with notches each 
holding one little ball. The balls are carried round by the 
wheel, and after half a revolution are discharged through 
another tube into the centre of a metal box, in which is poised 
a magnetic needle with a groove along the top of one branch. 
As the shot fall, they roll along the needle and drop off its point 
into the box. Their path may be traced in the figure. The 
bottom of the box is divided into thirty-six small partitions, and 
the balls fall into one or other of these according to the position 
of the needle. The position of a ball in the box thus indicates 
the angle between the axis of the apparatus and the magnetic 
meridian, that is, the direction of the current. When the 
apparatus is lowered into the water, the propeller is set and 
fixed, and is subsequently released by a small messenger so 
as to spin with the current ; when desired, a larger messenger 
is sent down to arrest the propeller before hauling up. With 
this current-meter a great number of observations have now 
been made, many of which have given very important results. 

In order to obtain good results it is necessary that the 
apparatus should hang practically still, without being carried 
along by the ship or the water, or — if this be unavoidable — 
that the drift should be perfectly well known. The boat 
from which the work is done must be very firmly anchored. 
In the Norwegian investigations we have, as a rule, worked 
from a small boat with anchors fore and aft, and it was possible 
in this way to hold the boat, even when more than 500 metres 
over the bottom, the most exact bearings showing that the 
boat did not drift sufficiently to influence the current-meter ; 
one anchor alone is usually not sufficient, for the boat may 
swing, thus affecting the apparatus. When measuring the 
currents in the Straits of Gibraltar, we tried double staying 
with the life-boat, using a strong hemp line about one inch in 
circumference, but the current was so strong that the line broke 
again and again, and we had to give it up. When the current 
(or the wind) is very strong, good results may be obtained by 
means of a single anchor forward, so we dropped one of the 
large anchors of the "Michael Sars," and the steamer lay so 



PHYSICAL OCEANOGRAPHY 265 

still that we could work with the current-meters from deck, but 
the strain on the wire was enormous. Double staying is much 
too difficult at great depths, although a single line may some- 
times do. At Station 58, south of the Azores, we had the 
trawl out in about 900 metres of water, when it caught on 
something and stuck fast on the bottom, holding the ship 
practically still (the compass was carefully observed the whole 
time) ; we improved the occasion by making a series of current- 
observations, and the results, which will be discussed farther 
on, prove the drift or the swing to have been insignificant, so 
that the observations are fairly reliable. 

In the deep ocean, where current-measurements would be 
of special interest, it is impossible to anchor the ship on the 
bottom, but the drift of the vessel may, when exactly known, 
be allowed for, and measurements may be made at any depth. 
We tried this two or three times. At Station 19, in the Medi- 
terranean, all the nets and young-fish trawls were towed at the 
same time. The speed of the vessel then just balanced the 
surface current ; the motion appeared to be quite steady, and 
some observations were made at different depths to determine 
the deeper currents in comparison with the surface current. 
Again, at Station 49 C, west of the Canaries, we employed the Current- 
large bag-net (3 metres in diameter) with the wire as a drift- "o?he w^st^of 
anchor. The net was lowered to a depth of 1000 metres and the Canaries, 
held there for many hours ; the drift of the vessel was fairly 
steady, and the compass showed the swing to be trifling. The 
depth of water was about 5000 metres, and measurements were 
made at different depths down to 1830 metres (1000 fathoms) 
with two Ekman current-meters, the results being indicated 
in Fig. 178. It may be interesting to see how an attempt at 
determining the currents above so great a depth turned out. 

The cardinal points of the compass are shown by dotted 
crosses, and arrows are used to indicate the velocity and 
direction according to the current- meters sent to different 
depths, a broken line for 915 metres (500 fathoms) and 1830 
metres (1000 fathoms), and a thin line for 10 metres. Now, 
we know nothing directly about the currents in deep water in 
the open ocean between 500 and 1000 fathoms, but we must sup- 
pose the movements to be comparatively insignificant when the 
depth to the bottom is very great, say more than 2000 fathoms. 
Supposing there were no current at these depths, the apparatus 
would act as a log, showing the velocity and direction of the 
drift of the vessel. Granting this to have been the case, the 



266 



DEPTHS OF THE OCEAN 



lo-metre arrow will represent the resultant of the two com- 
ponents : the actual current at lo metres and the actual motion 



IOtti 



915 772y 



10171 z.^izi.'^.o^ani 




Fig. 178.— Current-Measurements at Station 49 C (ist-2nd June 1910). 

of the ship, as indicated by the deep-water measurements. 
The actual current at 10 metres is then easily determined ; it 



PHYSICAL OCEANOGRAPHY 267 

is here indicated by the thick arrows. Two measurements 
were made at 1830 metres (Nos. I. and IV. in the figure), and 
two at 915 metres (Nos. II. and III.), and at the same time 
observations were made at 10 metres with another apparatus. 
The time by the watch is noted in the figure. The arrows 
in V. show the currents thus found at 10 metres after allowing 
for the assumed drift of the vessel, and it is seen that the 
variations both in velocity and in direction are large. This 
method is, however, uncertain so long as the currents in deep 
water are unknown ; if these are considerable, the thick arrows 
in Fig. 178, v.. do not give the actual currents at 10 metres, 
but only the relation between these currents and those in deep 
water. Still one thing is at least clear from the figure : the 
thick arrows alter their direction regularly, and the change is 
counter-clockwise. A continuous alteration of set is one of 
the characteristics of tidal currents, and the conclusion is in all 
probability admissible that our measurements at Station 49 C 
prove the existence of tidal currents in the Atlantic Ocean, 
even where it is very deep. 

Tidal motion in the sea is due to the attraction exercised Tides and 
by the sun and moon on the water-masses, which varies from ^'^^^ currents. 
place to place. It would take us too far to enter into the 
theories of the tides here, and besides, we have not yet a clear 
solution of the problem, because, among other reasons, we have 
no observations from the open sea, but only those from the 
coasts. The rise and fall of the surface, known as tides, are 
accompanied by currents, and the study of these currents in 
the open sea would be of great importance for the comprehen- 
sion of tidal phenomena. In the "Michael Sars " Expedition, 
as mentioned above, we made a number of current-measure- 
ments, the principal object being to find out if it were possible 
to make trustworthy observations of the veldcity and direction 
of tidal currents in the ocean. This has not been done 
before in deep water. Buchanan in 1883 made some interest- Buchanan. 
ing measurements on the Dacia Bank, off the west coast of 
Morocco, and found marked tidal currents during the couple 
of hours the observations lasted. Afterwards R. N. Wolfenden Woifenden. 
discovered tidal currents on the Gettysburg Bank. Beyond 
these and a few other observations, we have no observations 
from the open ocean far from land and none at all in deep water. 

We usually figure to ourselves the attraction of the moon Tidal waves, 
and the sun producing a tidal wave which can develop freely 
in the Southern Ocean, where a zone of water encircles the 



268 
earth 



DEPTHS OF THE OCEAN 



This wave has a very great length, with high - water 
at the crest and low- water in the trough. Its form remains, 
fettered by the moon, while the earth revolves beneath it. 
Passing the opening between Africa and South America, it 
gives rise to a lateral wave moving from south to north through 
the Atlantic. This tide-wave reaches the coasts of northern 




Fig. 179. — The Currents on the Ling Bank in the North Sea (7th-8th August 1906). 

Europe, producing tidal effects there. But besides this wave 
coming from the Southern Ocean there is formed an Atlantic 
tide-wave following the movement of the sun and moon from 
east to west. As already remarked, these things are somewhat 
enigmatical, but as there is a connection between tidal waves 
and tidal currents, we may hope that careful current-observations 
will contribute to the unravelling of these problems. 



PHYSICAL OCEANOGRAPHY 



269 



In August 1906, a series of current-measurements was made c 

by the "Michael Sars " 
the Ling Bank in the North Sea, 
Sea. Fig. 179 shows the 
currents at depths of 2, 20, 
and 75 metres (the depth of 
water being 80 metres). In 
the lower row the direction 
j- and velocity of the current 
^ are indicated by arrows for 
^ every hour from 5 p.m. on the 
? 7th August to 6 A.M. on the 
? 8th August. It is seen how 
I the water moved at the differ- 
^ ent depths, varying in direc- 
j tion and velocity ; in the 
I course of twelve or thirteen 
^ hours the direction of the 
5 current had passed through 
I all the points of the compass. 
I In the top row all the arrows 
5 are joined, thus forming a 
^ line which shows roughly the 
I motion of the water during 
^ the period of thirteen hours. 
I The course proved to be 
'^ somewhat elliptic, the water 
S returning very nearly, but 
^ not quite, to its point of 
J departure. This is a typical 
^ case, for tidal currents are, as 
]* a rule, characterised by this 
g turning, the water arriving at 
": its Starting-point again after 
^ a period of about twelve and 
a half hours. The displace- 
ment in the course of this 
time, as exhibited by the 
current-lines, is attributable 
to a general motion of the 
water, towards the east at 
2 metres, north-east at 20 
metres, and north - north - east at 75 metres. But this 




measurements 
n the North 



270 



DEPTHS OF THE OCEAN 



general motion is quite insignificant compared with the tidal 
current. 

In Fig. 180 we see some current-lines of a totally different 
form, the results of a number of measurements made on 
Storeggen, westward of Aalesund, on the 12th and 13th July 
1906. A line is drawn for each of the following depths below 
the surface: 2, 20, 50, 100, and 200 metres (the depth of water 
being 260 metres). It is seen that the current on the whole 
flowed in a north-easterly direction at all depths, but the 



Stat 58 

12 VI 



to meters 
1910 




Fig. 181. — Result of Current-Measurements at io metres at Station 58, 
SOUTH OF THE AZORES (i2th June 1910). 

direction was not constant, as implied by the bends in the lines. 
The variations of direction were due to the tides, but here the 
tidal current was weak compared with the general motion of 
the water-masses. In this place the coast-current of the upper 
75 or 100 metres, and that portion of the Gulf Stream which 
traversed the layers below, both ran towards the north-east ; 
had there been no tide-motion on the bank, the lines would 
probably have been straight, not sinuous. 

The measurements at these two stations give an idea of the 
movements of the water -masses in the sea, and show that 
current-lines may have very different courses, largely determined 



PHYSICAL OCEANOGRAPHY 



271 



by the relation between the tidal current and the general drift of 
the water. 

We have already mentioned that the observations made at 



J ^einf25f.) 



JT -^Sdmfioof) 





jn: 732/72 f9^6?y^J 



\i 



7.1 2 ant, 




'%. 



iO 20 50 



Fig. 182.— The Currents at different Depths at Station 58, 
SOUTH OF the Azores (12th June 1910). 

Station 49 C lead us to infer that tidal currents exist even in 
the deep sea. Again, at Station 58, south of the Azores, we 
made a number of current-measurements from the ship at 
anchor throughout one complete tide-period. With one of the 



measurements 
to the south 
of the Azores. 



272 DEPTHS OF THE OCEAN 

Current- current-metcrs we took regular observations at 10 metres, 70 in 

all, from i a.m. till 2.45 p.m. on the 12th June. Fig. 181 shows 
the variations at this depth, which recall the current-lines on the 
Ling Bank. The tidal current predominated, attaining a maxi- 
mum velocity of 38 cm. per second (0.7 knot per hour) ; there 
was also a general drift of the water towards the south-east, with 
a mean velocity of 8-9 cm. per second (0.2 knot per hour). 
Simultaneously another apparatus was employed to determine 
the current at different depths down to 732 metres (400 fathoms), 
the depth of water exceeding 900 metres. Some of the results 
are represented in Fig. 182, which shows the current at different 
depths: I, at 46 metres (25 fathoms); H. at 183 metres (100 
fathoms) ; and HI. at 732 metres (400 fathoms). At all depths 
the velocity and direction varied constantly,^ the changes in 
direction being clockwise, and it is notable that the direction 
shifted about 180'' in the course of half a tide-period. In this case 
there is no doubt that tidal currents prevailed throughout the 
whole body of water from the surface to the bottom ; they were 
unmistakable even at 732 metres ; at this depth a velocity of 
more than 27 cm. per second (more than ^ knot. per hour) was 
once measured, showing that the tide can make its influence felt 
down to considerable depths. This is particularly the case 
where a plateau or ridge obstructs the passage of the tidal 
wave ; in such places the current near the bottom is probably 
increased. This would explain the remarkable fact that on 
many submarine slopes and ridges no fine mud is deposited, 
because the strong current sweeps the bottom clean. 

Another interesting result of these measurements is repre- 
sented in Fig. 183, where the arrows show the currents at several 
depths simultaneously: I. at 3.35 a.m., and II. at 7.12 a.m. on 
the same date. We see that the currents set in different 
directions at the different depths. In the upper layers the 
direction shifted more and more to the right with increasing 
depth, but from 100 fathoms (183 metres) down to the bottom 
the direction was reversed. Thus the current at 500 metres ran 
in the opposite direction to that of the upper layers, which again 
approached that of the currents at the greatest depths. At a 
certain moment the currents are, then, arranged in the fashion 
of spiral staircases, the whole system turning in clockwise 
direction from top to bottom. 

These observations in the Atlantic give rise to many inter- 
esting ideas about the currents in the sea, and show that there 



PHYSICAL OCEANOGRAPHY 



27: 



is still much to be done in this line. But the fluctuations of the 
ocean-currents are determined by more influences than tides, 
for many other forms of motion supervene, rendering the whole 
picture highly complicated. A careful analysis of the measure- 
ments made on Storeggen in 1906, led to the conclusion that 
there were certain regular variations which took the form of 




3, 55a.77t. 



JT 772 a.m. 



Fig. 183. — The Currents as determined by simultaneous measurements 

(3.35 A.M. AND 7.12 A.M.) at different DePTHS AT STATION 58. 

pulsations in the current. When the effect of the tide was Puis 
subtracted it appeared that the ordinary current at lo metres "^ ^^ 
ran for some time with considerable velocity (up to ^ metre 
per second) ; then the velocity decreased during seven or eight 
hours until it approached zero, increasing again during the next 
seven to eight hours, and so on. The fluctuations had thus a 
period of about fifteen hours, but we are as yet ignorant of the 
particular cause, though it may be a usual phenomenon in the 

T 



274 



DEPTHS OF THE OCEAN 



Wind- 
produced 
currents. 



Boundary- 
waves. 




sea. Supposing the coexistence of two different periodical 
variations, one with a period of about twelve and a half hours, 
the other with one of about fifteen hours, an infinite number of 
variations would ensue, to which might be added the more 
casual influence of the wind and other factors, causing among 
other things incessant dislocations of the boundaries between the 
different water-layers or currents. 

The wind may produce a current, particularly in the surface 
layers, thus altering the direction and velocity of the existing 
current. We know very little, however, about the relation 
between wind and current, through lack of detailed observations, 
although the question is naturally of the first importance from 
an oceanographical point of view, as well as from its bearings on 
the conditions of everyday life. This is one of the principal tasks 
for the oceanographer of the future ; such observations are 
diflicult to make, no 
doubt, but with modern 
methods much can be 
done. 

A wind blowing over 
the sea will carry the 
surface water along with 
it. In the open ocean 
the current thus pro- 
duced is generally somewhat deflected from the direction of the 
wind itself. During the drift of the " Fram " over the North 
Polar Sea, Nansen found that the ship, as a rule, was carried to 
the right of the wind's course. V. W. Ekman has studied the 
question theoretically, arriving at the conclusion that such a deflec- 
tion is a result of the earth's rotation. Later, Forch, by extracting 
the records from a number of ships' journals, found the same 
deflection to the right in the Mediterranean and in the North 
Atlantic, while, as might be expected, there is a deviation to 
the left in the southern hemisphere. Now, as the surface-water 
is carried along by the wind, the deeper layer will approach the 
surface at the place of origin of the wind-current. In Fig. 184, 
which represents one of Sandstrom's experiments, we see how 
the wind may raise the boundary between the upper and lower 
water-layers. When the wind ceases this rise again subsides, 
producing a boundary-wave which will proceed farther. A wave 
like this may attain a considerable height, without being 
perceptible at the surface ; its dimensions will depend on the 
distribution of density. A boundary-wave in the Norwegian 



Fig. 184.— Sandstrom's Experiment for producing 
A Submarine Wave by a gust of wind. 



water. 



PHYSICAL OCEANOGRAPHY 275 

Sea 100 metres in height would manifest itself as a surface- 
wave about 5 cm. high, that is, practically imperceptible, as the 
wave is very long and proceeds slowly. Several of the 
"Michael Sars " investigations indicate such boundary-waves, 
but here also precise observations are lacking. They are, "Dead 
however, known in one particular form, viz. as the boundary- 
wave producing "dead water." When a comparatively fresh 
and light water-layer, 2 or 3 metres thick, rests on a salt 
and heavy layer, a passing ship may give rise to a boundary- 
wave between the two layers. This wave may stop the ship, 
so that it lies in dead water hardly able to move at all. Ekman, 
who has investigated these phenomena, has demonstrated the 
dead-water wave by the following experiment (see Fig. 185). 
He put salt water, coloured dark, into a long basin, and on the 
top he poured a thinner layer of fresh water ; when he slowly 
towed a small model of a ship through the upper layer, a 




Fig. 185.— Ekman's Experiment to show the wave producing Dead-water. 

boundary-wave arose, as seen in the figure, which, when strongly 
developed, checked the speed considerably. 

Naturally when a wave like this passes a certain spot on the 
sea, the undulating boundary between the two water-layers will 
at one moment be vertically nearer to that spot, at another 
moment farther down. Similar vertical oscillations may 
arise in other ways, as we shall now briefly indicate before 
describing some observations made during the cruises of the 
" Michael Sars," which prove that such undulations do exist 
in the sea. 

We may first mention one of the effects of the rotation of Effect of the 
the earth. By reason of the earth's rotation a body moving rotation 
freely in the northern hemisphere in any direction will 
be deflected to the right, and with great velocities this de- 
flection is quite considerable. There are many examples of 
it : a swinging pendulum constantly turns ; the wind does not 
blow straight towards a cyclonic area, but in a spiral direction, 
bending to the right in the northern, and to the left in the 
southern, hemisphere ; the effect of the earth's rotation is also 



276 



DEPTHS OF THE OCEAN 



seen in the direction of the trade-winds, monsoons, etc. The 
rivers of Siberia flowing northwards to the Polar Sea, eat into 
their eastern beaches as an effect of the rotation of the earth. 
It is the same influence which directs the course of the great 
ocean-currents. In the North Atlantic the warm currents from 
the south bend in general to the right, that is to the east, and 
the cold currents from the north likewise bend to the right, that 
is to the west ; thus the Gulf Stream flows across to Europe, 
and the polar currents to Greenland and Labrador. Let us 
now suppose that we take observations at a couple of stations 
right across a current. This may be represented roughly by a 
vertical section, as in Fig. 186 ; we must here imagine that the 
motion takes place in the direction from the eye through the 
paper, that the motion is swiftest at the top, and that we are in 
the northern hemisphere. The rotation imparts to the water 

A ^ 3 A _^ B 

'^ — "^^r 



--^ t 



M 



Fig. 186. 



(represented by the horizontal arrows) the water-layers 
acquire a slanting position, determined by the difference of 
velocity and density in the different layers. 



mass a tendency to 
move to the right ; 
J there will be a pressure 
in that direction (indi- 
cated by the arrows), 
forcing the layers down 
at Station B, raising 
them nearer to the 
surface at Station A. 

By reason of the deflecting influence of the earth's rotation "FU.'c rr\\Te'c tVio K/->iir>.-1 

i^^r^^^^^^tc^A K„ ^^r.^ i,„,-w„„toi ovK,^,.,e\ ti.a ,.,oto,- io„^.-c ^ ^ib ^ives loe UOUnQ" 

ary-layers a slanting 
position, as shown by 
the broken lines, the incline being slight if the surface- 
current is slow (I.), and strong if the current is rapid 
(II.). Consequently the light water will go deep at B, the 
station situated to the right in the current, while at Station A, 
on the left, the heavy water from below will come nearer to the 
surface. Wherever there is a strong current in the upper 
water-layers the following rule will apply in the northern 
hemisphere : on the right-hand side the water is comparatively 
light, on the left-hand side comparatively heavy ; the conditions 
are reversed in the southern hemisphere. There are many 
examples illustrating this. Off the west coast of Norway the 
current runs north, and the water to the right, near the coast, is 
light, while that to the left, in the middle of the Norwegian 
Sea, is heavy. In the Gulf Stream off the east coast of North 
America the water is light (warm) on the right side of the 
current, and cold (heavy) on the left. The southern hemisphere 



PHYSICAL OCEANOGRAPHY 



277 



affords many other examples ; the distribution of temperature in 
the remarkable Agulhas Current, for instance, is explained in 
this way. 

The Norwegian coast-current presents a good example of 
the effect of the earth's rotation on the inclination of the water- 



zoo . 




/S03 
MAY.22-25. 



Fig. 187.— The Sognefjord Section in May 1903. 
(Fig. 165 shows the same section in May 1904.) 

layers. Fig. 187 shows the conditions in May 1903 along a 
section through the Norwegian Sea from the mouth of the 
Sognefjord to the west ; on the right, close to the land, the 
coast- water attains a depth of about 100 metres. By heating 
in the course of spring and summer this water becomes lighter 

Om. 



zoo : 




Fig. I 



The Sognefjord Section in August 1903. 



and acquires a greater tendency to spread over the surface. 
This tendency counteracts the deflecting force of the earth's 
rotation, and finally causes the surface-layers to extend towards 
the west, becoming less thick in proportion. Fig. 188 shows the 
conditions along the same section in August 1903, when we 
repeated the investigations. The coast- water now lay much 
farther from the land than in May, reaching only to a depth of 



278 



DEPTHS OF THE OCEAN 



60 metres near the coast, the water naturally having become 
lighter and its tendency to spread westwards having overcome 
the effect of rotation acting eastwards. When the coast-water 
is cooled down in autumn it becomes heavier again, is not then 
so much lighter than the Atlantic water, and has consequently 
not such a great tendency to spread westwards over the surface 
as in summer ; it is then forced towards the land (to the right) 
again by the rotation of the earth. Thus there are in the 
course of the year periodic lateral movements of the coast- water, 
which are of importance, for instance, in their effect on the 
distribution of the young fish. 

The water-layers, then, slant differently according to the 
strength of the surface-current and the vertical distribution of 
density. Supposing the surface-current to run sometimes fast 
and sometimes slow, the layers will respectively be lowered or 
raised. Again, regarding Fig. 186, the layers that in I. are 
comparatively deep at Station A, by an increase of the surface- 
current (as in II.) will rise considerably higher. Thus vertical 
oscillations are set up as a consequence of the fluctuations of 
the current ; at a certain fixed point the movement will be like 
that of a submarine wave. Such vertical oscillations may be 
imagined to arise in other ways. It is, for instance, highly 
probable that there exist in the sea standing waves with one or 
more nodes, similar to the undulations of a violin string. Forel, 
Chrystal, and others have found these standing waves in 
lakes, the Japanese have shown them to be present in their 
seas, and we have several indications of their existence in the 
Norwegian Sea. 



We cannot dwell any longer upon this question, but will 
now examine some observations made during the "Michael 
Sars " Expedition, which show marked vertical oscillations of 
one kind or another. We made a number of careful measure- 
ments in the course of twenty-four hours at Station 115, in the 
eastern part of the Faroe-Shetland Channel, near the slope west 
of Shetland, in 570 metres of water. Here we anchored a buoy, 
near which the steamer kept as long as the observations lasted. 
We made continuous observations of temperature and salinity 
at the same depths, and were thus able to see whether or not 
the conditions at a certain depth varied. At the same time 
similar measurements were made by the Scottish research 
steamer, the "Gold-Seeker," on the Faroe side of the channel. 
By these simultaneous investigations we hoped to determine 



PHYSICAL OCEANOGRAPHY 



2/9 



whether the variations were due to a progressive wave, or to 
fluctuations in the current, or to standing waves. The results 
have not yet been worked out, so we can only discuss some of the 
" Michael Sars " observations. Unfortunately it was impossible 
to make direct current-measurements, as the weather was too 
rough. 

During the twenty-four hours we made 86 observations at 
the buoy, care being taken that the line was absolutely vertical. 
Surface-observations apart, most of the measurements were made 
at a depth of 300 metres (19 observations). The temperatures 
found at this depth are noted in Fig. 189 along the vertical scale, 
while the hours are put down along the horizontal scale. There 
were considerable variations : on the 13th August at 5.8 p.m the 
temperature was 5.60° C, and on the 14th August at 12.25 a.m. 



l3 Vllt /9/0 



















































\ 


\ 








/■ 


/ 






1 


\ 








^• 


^ 








/ 






\ 




\ 


- 




/ 
















V, 




" 




^ 


*\ 


^- 


/ 
























































^ 



Fig. 189. — Temperature Variations at 300 metres at Station 115 
(13th- 14th August 1910). 

it was 4.73" C. — a difference of 0.87° C. When the mean 
temperatures of the different water- layers are calculated and 
represented in curves, it is easy to see how much the tempera- 
ture altered for each metre of depth. At about 300 metres the 
temperature decreased with increase of depth to such an extent 
that a difference in temperature of 0.87° C. corresponded to a 
difference in depth of about 35 metres. In the other layers 
there were similar variations, indicating vertical oscillations of 
between 15 and 35 metres. These observations go far to prove 
the presence of such undulations of the water-layers, which is 
indicated also by the form of the curve in the figure, among 
other things. But these variations are not comprised in one 
single period, as if they were due to an ordinary progressive 
wave, or an ordinary standing wave alone. The shape of the 
curve points to complicated fluctuations of the velocity as the 
cause of the variations, but it is possible, nay probable, that we 



28o DEPTHS OF THE OCEAN 

are here confronted with an inter-play of several different factors. 
It is, by the way, worthy of notice that there is an interval of 
twelve or thirteen hours between the two principal maxima of 
temperature ; this agrees with the tide-period, and we know that 
the velocity of the current varies with the tide. 

In previous investigations in the Norwegian Sea we have 
several times encountered variations which are most naturally 
explained by supposing that there are great undulatory move- 
ments of the water-layers, and the investigations just described 
strongly corroborate this supposition. The problem is one of 
the greatest importance, and its solution will, in more ways than 
one, lead to a fuller comprehension of the science of the sea, in 
the first place with regard to the dynamics of the water-masses, 
and in the second place with regard to certain biological 
questions. The discontinuity-layer is often a boundary between 
two different worlds of living organisms, and it is a point of 
interest for the study of these to know if this boundary is 
moving up and down, for this would probably imply that the 
organisms themselves (possibly even shoals of fish) were also 
being moved up and down. On the continental slope, just 
below the edge, there live multitudes of marine animals, the 
warm water having one characteristic fauna, and the deeper 
cold water another. Now, if the fairly definite boundary 
between the two water-masses swings up and down, one must 
expect that there is a comparatively broad transitional region, 
where the particularly hardy individuals of either of these 
characteristic domains would live together. Where the change 
of temperature is slow and regular the effect upon the organisms 
would be of little importance ; not so, however, where there is 
a marked discontinuity-layer, as for instance in the Norwegian 
Sea. The proof that there are such oscillations would also be 
of very great importance for our methods of studying the sea. 
Let us look, for example, at Fig. 190, showing a section from 
Shetland to the Faroe Islands, taken during the " Michael 
Sars" Expedition on the loth and nth of August. The 
positions of the stations are shown in Fig. 104, p. 122. 
Isotherms are drawn at intervals of two degrees Centigrade ; 
single hatching indicates salinities between 35.00 and 35.25 per 
thousand, and cross-hatching salinities above 35.25 per thousand ; 
in the deep layers the salinity was below 35 per thousand. 
The lines both for temperature and salinity are strikingly wave- 
like in the intermediate water-layers. The saltest water has 
come from the Atlantic in the south, and the cold deep water 



PHYSICAL OCEANOGRAPHY 281 

from the Norwegian Sea ; the boundary between these layers 
hes deeper at Station 106 than at the neighbouring stations, the 
difference of level amounting to 200 metres. In order to get 
as true a picture of the conditions as possible the stations were 
placed at short intervals of only 20 nautical miles ; there may 
be great differences within 20 miles, as from Station 105 to 
Station 106, and fewer stations at longer intervals might have 
given a totally false representation. Knowing the distribution 
of salinity and temperature, we may now draw conclusions as 



'06 /05 /04 /03 




200 



300 



400 



500 



Fig. 190.— The Southern Section in the Faroe-Shetland Channel 
(loth-iith August 19 10). 

to the nature of the currents, their direction, breadth, and depth. 
Our section has a rather irregular look, suggesting complicated 
conditions ; it seems, for instance, as if the Gulf Stream were 
divided into two branches, one close to Shetland, and one in 
the middle of the channel. In the present case the variations 
from one station to another are probably in part caused by 
the vertical oscillations mentioned, but they are evidently in 
part due also to another important phenomenon, viz. vortex 
movements. 



One of the objects of our joint-research with the Scottish Vortex 
investigators in the Faroe-Shetland Channel was to throw light '"ovements. 



282 



DEPTHS OF THE OCEAN 



on possible vortex movements. Four parallel sections were 
made, the two in the middle by the " Michael Sars," the 
southerly one being represented in Fig. 190, and the northerly 
one in Fig. 191. In the map of the stations (Fig. 104, p. 122) the 
position of the sections is seen, the distance between them being 
20 to 25 nautical miles. Although the sections were so close 
together they differed greatly. In the northern section the 
lines are fairly regular; high salinities of more than 35.25 per 
thousand are found only in the neighbourhood of Shetland, not in 




^00 



600 



600 



Fig. 191 



-The Northern Section in the Faroe-Shetland Channel 
(nth- 14th August 1910). 



the middle of the channel. Vertical oscillations may have had 
great influence on the appearance of the section. The two 
sections might not have presented such great differences if the 
observations had been taken at other times, but in any case they 
point to other irregularities, in the first place to vortices with 
vertical axes, similar to those known in rivers, only very much 
larger. These vortices have rendered the motion of the water 
highly complicated. The "Atlantic water" has moved towards 
the north, having a breadth of 50 or 60 miles in the neighbourhood 
of Shetland; between Stations 105 and 106 the water of the 
upper layers has probably moved southwards, between Stations 
106 and 107 to the north, and so on. Previous investigations 



PHYSICAL OCEANOGRAPHY 



28- 



have shown that there are great vortices in several places in the 
Norwegian Sea. Fig. 192 shows the distribution of salinity at 
a depth of 100 metres in the southern part of the Norwegian 
Sea and the northern part of the Atlantic in May 1904. The 
arrows mark the probable direction of the movements. There 
are several vortices of different dimensions, one being drawn in 




Pio. 192. — The DioTribltion of Salimiy in the ^ORrHERN part of the Atlantic 
Ocean and the southern part of the Norwegian Sea at a depth of ioo 
METRES (May 1904). 



the Faroe-Shetland Channel ; similar conditions prevailed in 
this place in August 19 10. 

Nansen and the writer have discussed^ at some length the Currents and 
oceanographical conditions of the Norwegian Sea on the basis J,°onvegkV^'^ 
of earlier investigations. Fig. 193 shows the currents and Sea. 
vortices in the Norwegian Sea. We arrived at the conclusion 
that there must be many forms of motion of great and far- 
reaching importance, though hitherto hardly known at all, 

^ The Norwegian Sea, Bergen, 1909. 



284 



DEPTHS OF THE OCEAN 



among them vertical oscillations of the water-layers and vortex 
movements. Many things go to prove that these are phenomena 
of general occurrence. We must picture to ourselves great 




^Ihi" 






■^^'i© 



v_> 



.y 



-, 11//// 










Fig. 193.— The Currents of the Norwegian Sea. 

submarine waves moving through the water-masses, alterations 
of depth in the layers according to changes in the velocity of 
the currents, standing waves, and great vortices. We must 
further conceive of constant fluctuations in the velocity, pardy 



PHYSICAL OCEANOGRAPHY 285 

also in the direction, of the great ocean currents, not only by 
reason of the tides and as the effect of the wind, but also because 
the currents are subject to a sort of pulsation, the nature and 
origin of which are as yet unknown. There is an interplay of 
many different forces, producing an extremely variegated picture ; 
the sea in motion is a far more complex thing than has hitherto 
been supposed. Physical oceanography is confronted with a 
host of new problems, the solution of which will be a matter of 
the highest interest. It was to attack a few of these general 
problems that the physical and chemical investigations of the 
"Michael Sars " Atlantic Expedition were undertaken. 

We shall now consider the investigations made during the 
" Michael Sars " Atlantic Expedition into the physical conditions 
in the Straits of Gibraltar. At the current-measurement station current- 
(Station 18) on the 29th and 30th April we obtained a series of "jj'^th^e StS^ 
observations from different depths throughout one complete tide- of Gibraltar. 
period. Some of the results are represented in the accompany- 
ing three figures. Fig. 194 shows the direction and velocity of 
the movement at different depths on the 30th April : (i) at 10 
metres (about 5 fathoms), (2) at 46 metres (25 fathoms), (3) at 
91 metres (50 fathoms), (4) at 183 metres (100 fathoms), and 
(5) at 274 metres (150 fathoms). The arrows are drawn in the 
true directions ; the velocities are seen by the scale. The 
current 10 metres below the surface (i) had a westerly set on the 
30th April between 2 and 4 a.m., afterwards — until 4 p.m. at 
least — running without interruption eastwards (between south- 
east and north-east), that is into the Mediterranean. The 
velocities were at times very considerable, being greatest about 
9 A.M., when we measured velocities up to 118 cm. per second, 
corresponding to 2.3 knots per hour ; velocities of about i metre 
per second, or 2 knots per hour, were found during the whole 
time from 7 to 1 1 a.m. Later in the day the current slowed 
down ; at noon it was only 40 cm. per second (0.8 knot per 
hour), increasing a little later; at 4.30 p.m. it was 70 cm. per 
second (1.4 knot per hour) ; then the observations were broken 
off, but it was ascertained that the velocity was decidedly on 
the increase. The current thus ran into the Mediterranean 
with no very fixed set, the uncertainty of direction being pardy 
due to the formation of vortices on the sides of the strait. 
Early in the morning the current set from the Mediterranean 
into the Atlantic, as mentioned above ; the velocity at 2 a.m. 
was 47 cm. per second (0.9 knot per hour), but it was then 



286 



DEPTHS OF THE OCEAN 






Ji- s. 




Fig. 194.— The Currents in the Straits of Gibraltar on the 
30TH April 1910 at different depths. 

1 at 10 metres, 2 at 46 metres, 3 at 91 metres, 4 at 183 metres, and 5 at 274 metres. 



PHYSICAL OCEANOGRAPHY 287 

decreasing. These periodic changes, between a strong current 
running east and a much weaker one running west, are caused 
by the tides, which are strong enough to reverse the current. 
The tide-period being nearly twelve and a half hours, one might 
expect the turning of the current about 2 in the afternoon ; at this 
time it was, however, still setting east, though with comparatively 
small velocity. It was thus only once in the day that the 
current at 10 metres ran out of the Mediterranean; in other 
words, there was a difference between the two tide-periods in the 
same day. It is probably connected with the so-called "daily 
difference " of the tide, well known in many places, which 
manifests itself by each alternate high-water being conspicuously 
greater than the intervening one. We must, however, bear in 
mind that these results, of course, only apply to the particular day 
on which the observations were made, and we must therefore 
beware of drawing general conclusions until observations during 
a longer period and at different times of the year are available. 

On the preceding afternoon (29th April) we obtained from 
the life-boat some measurements of the velocity of the current 
at a depth of 5 metres. At 5,15 p.m. the velocity was 113 cm. 
per second (2,2 knots per hour), and was then on the increase, 
being more than 150 cm, per second (nearly 3 knots per hour) 
at 6 P.M., and the current then set eastwards. This corresponds 
to the increasing velocity eastwards at a depth of 10 metres half 
a day and a whole day afterwards. Some observations in the 
deeper strata were also made from the life-boat about 6 p.m. on 
the 29th April, the velocity at 25 metres being 124 cm, per 
second (2,4 knots per hour), and at 50 metres 138 cm. per 
second {2.7 knots per hour) ; at both depths the current set in 
a north-north-easterly direction. Unluckily the observations were 
then interrupted for many hours by the breaking of the anchor- 
cables, otherwise we should have had continuous observations 
during two whole tide-periods. 

On the 30th April we obtained some series of measurements 
from the steamer down to the bottom in about 200 fathoms of 
water. The current often ran so fast that the wire with the 
apparatus was brought into a slanting position, and the first 
messenger was not sent down for some minutes to allow time 
for adjustment. This rendered the determination of depth 
somewhat uncertain ; the depths quoted refer to the length of 
wire out, and may sometimes exceed the actual depth, but it 
was useless to apply corrections, as we did not know the lie of 
the line in the water. Fig, 194, 2, shows the current at 46 



288 DEPTHS OF THE OCEAN chap. 

metres (25 fathoms) below the surface between 6 a.m. and 2.20 
P.M. In the forenoon the current ran east in the same manner 
as at a depth of 10 metres ; about 8 a.m. the velocity was more 
than 90 cm. per second (1.8 knot per hour); about 11 a.m. it 
was slackening considerably, and at 2.20 p.m. it was merely 
9 cm. per second (0.2 knot per hour) ; the current then set to 
the north. The variations in velocity correspond to those 
found at 10 metres. 

Similar results (Fig. 194, 3) were obtained at 91 metres (50 
fathoms), where the current ran into the Mediterranean in the 
forenoon with velocities attaining 105 cm. per second (2 knots 
per hour) ; but between 2 and 3 p.m. it turned to the north-west, 
that is, mainly towards the Atlantic and contrary to the current 
at 10 metres. 

Fig. 194, 4, shows the results obtained by sending down the 
current-meter with 183 metres (100 fathoms) of wire. The 
observations were made between 6.40 a.m. and 11.26 a.m., and 
all this time the current ran out from the Mediterranean in the 
direction opposite to that of the higher layers, the greatest 
measured velocity being rather more than 40 cm. per second 
(0.8 knot per hour). The transition from the current running 
into the Mediterranean to that running out must have been 
somewhere above 100 fathoms. 

The observations with the apparatus out with 274 metres 
(150 fathoms) of wire are particularly interesting (see Fig. 
194, 5). They were made from 2.15 a.m. to 3.30 p.m., and 
the current all that time ran west, from the Mediterranean into 
the Atlantic. At 2.15 a.m. the enormous velocity of 227 cm. 
per second (4.4 knots per hour) was observed ; at this time the 
current at 10 metres had also a westerly set. Then the velocity 
decreased ; at 8.49 a.m. — half a tide-period later — a velocity of 
only 17.5 cm. per second (rather more than 0.3 knot per hour) 
was measured ; at this time the current in the opposite direction 
at 10 metres ran its fastest. Later on, the deep current 
increased in velocity, running at 3.27 p.m. — after another half- 
tide period — 83 cm. per second (1.6 knot per hour). There 
was a similar difference between two successive tides at 
274 metres and at 10 metres. These observations gave this 
important result : that when the surface current ran fastest to 
the east the under current setting west was at its slowest, and 
vice versa. 

At 12.22 P.M. one of the current-meters was sent down with 
366 metres (200 fathoms) of wire, but after working for ten and a 



PHYSICAL OCEANOGRAPHY 289 

half minutes it was hauled up in a wrecked condition. The wings 
were battered and bent, and the compass was gone ; it was 
clear that the apparatus had been bumping against the stones 
on the bottom. The propeller had made 280 revolutions, 
implying a velocity of 1 1 cm. per second (0.2 knot per hour), so 
that the water had moved along the bottom at that rate at 
least, probably faster, as the propeller must have revolved too 
slowly after being injured. This separate measurement gives 
the interesting result that there may be an appreciable current 
even along the bottom. 

Now, in what relation do these currents stand to high and 
low water ? The tide-tables show that at Cadiz and Algeciras 
high water and low water on 30th April 19 10 occurred at the 
followinp- hours : 





High Water. 


Low Water. 


Cadiz 
Algeciras . 


4.51 A.M., 5.16 P.M. 
5.15 A.M., 5.40 P.M. 


11.04 A-J^I- 
11.28 A.M. 



In the straits high water may with sufficient accuracy be 
referred to about 5 a.m., low water to a little after 11, and the 
next high water to about 5.30 p.m. It follows that the water ran 
fastest into the Mediterranean about four hours after high 
water, i.e. at falling tide, and that it ran fastest out from the 
Mediterranean three or four hours after low water, that is, with 
a rising tide. 

In Figs. 195 and 196 the current-conditions between the sur- 
face and the bottom are shown, in the first for the 30th April at 
9 A.M., when the current into the Mediterranean was running at 
its maximum, and in the second the mean for the movements at 
2 A.M. and at 3 p.m., when the current out of the Mediterranean 
attained its greatest velocity. The velocities at the different 
depths have been calculated with regard to the longitudinal 
direction of the strait, the varying directions of the current 
having been taken into account ; the actual velocities are shown 
in Fig. 194. The two diagrams give a good picture of the 
relation between the upper and the lower current in the middle 
of the straits, the former about four hours after high water, the 
latter three or four hours after low water. It is seen that the 
boundary between the two currents lay at a depth of about 160 
metres when the inflow into the Mediterranean was greatest, and 

u 



290 DEPTHS OF THE OCEAN chap. 

that it approached the surface when the inflow was least, 






wo 

Fig. 195. — The Motions in the different layers in the Straits of Gibraltar 
(calculated for the longitudinal axis of the straits) when the current 

WAS SETTING INTO THE MEDITERRANEAN AT ITS STRONGEST (30th April I910). 



SO 









\ 














1 Z Z I 










^__^ 




_ — — _ _ 


















































- 


























— — — — 


1 


























^^^ 



Fig. 196. — The Currents along the longitudinal axis of the Straits of Gib- 
raltar ON the 30TH of April 1910, when the current set strongly towards 
the Atlantic. 



moving 100-150 metres up or down in the course of half a 
tide-period. 



PHYSICAL OCEANOGRAPHY 



2QI 



Together with the current - measurements four series of Temperatures 



water-samples and temperatures were taken 
efiven in the following: table : — 



the results are 



ind salinities 
in the Straits 
of Gibraltar. 



Depth. 
Metres. 


Station 18 A. 

29 IV. 114 A.M. - 

12^ P.M. 


Station 18 B. 
29 IV. 2-2i P.M. 


Station 18 C. 
29 IV. 11-12 P.M. 


Station 18 D. 
30 IV. 9i-ioi A.M. 




Temp. 


Salinity. 


Temp. 


Salinity. 


Temp. 


Salinity. 


Temp. 


Salinity. 


o 


17.0 


36.12 


16.6 


36.14 


16.6 


36.02 


17.4 


36.17 


25 


15.16 


36.19 


14.89 




15.6 




16.18 




50 


13.29 


37.80 


13-35 




15.09 


36.20 


15-39 




100 


12.92 


38.30 


12.92 


38.33 


14.38 


36.28 


14.09 




200 


12.91 


38.39 






13.II 


37-97 


12.94 


38.36 


300 


12.87 


38.39 






12.89 


38.39 







Here also we see considerable variations from time to time 
at the different depths, variations corresponding to a difference 



2800 



•28-50 



2900 



38-50%, 




Fig. 197. — Temperature (broken line), Salinity (continuous line), and Density 

(DOTTED line) AT STATION I9, IN THE MEDITERRANEAN (2nd May I910). 

of level between the layers of 100-150 metres. On the 29th 
April, about 2 p.m., the current running in must have been 
feeble and that running out must have been strong, judging 
from the later current-measurements, and the salt Mediterranean 
under current extended up towards the surface, whereas on the 
30th April, between 9.30 and 10.30 a.m., the upper current was 
very strong and the undercurrent from the Mediterranean very 
feeble in comparison, and the salt water from the Mediterranean 
lay about 100 metres deeper. The vertical distribution of 
salinity and temperature is seen to accord with the currents. 
Two days after these observations in the Straits of 



Observations 
in the Medi- 
terranean. 



292 DEPTHS OF THE OCEAN chap. 

Gibraltar, the "Michael Sars " entered the Mediterranean, and 
took observations at Station 19, the hydrographical conditions 
being shown in Fig. 197. The surface temperature varied from 
1 6° to 1 7' C, and the salinity was nearly 36.4 per thousand. The 
temperature decreased and the salinity increased downwards, 
until we struck the Mediterranean deep water at a depth of 
about 160 metres ; from this point downwards we found exactly 
the same temperatures and salinities as in the undercurrent in 
the straits. This was on the 2nd May, between 10 a.m. and 
I P.M. ; the observations in the uppermost 300 metres were 
made between 10.30 and 11. 30 a.m. Judging from the previous 

measurements the in- 
flow in the straits 
should then be about 
its strongest. Be- 
tween 5 and 6 p.m. 
some of the observa- 
tions were repeated, 
and the boundary be- 
tween the surface- 
layers and the deep 
water then lay some- 
what higher; it might 
be a matter of 10 or 
15 metres. The 
under current setting 
out of the straits was 
then very strong and 
the surface current 
comparatively feeble. 
So there were fluctua- 
in the Mediterranean 
the fluctuations in the 



^^^^^i^H 


■1 


^^^^^^1 


^^^^^^^^^^v 


27. ^H 


^^ 


^^^^m 


19a^ 


m ""•' ^?.J^ 




'—v-^^i |k, 




/' ^^ ' 20^Kk 


^ 


29, •^'^^H 


^^^^^^^ 


^^^^ 


^^^^^I^^^^H 






^^^^^^^H 


^^^^^^^^^^H 


30^ ^^^k 


^^H 


.^^^^^^^^1 

^^^^^H 


^^H 


J2^^^^^H| 


^1 



Fig. 198. — "Michael Sars" Stations in the Spanish 

Bay between Spain and Morocco in May 1910. 

The lines indicate the positions of the two sections represented 

in the two following figures. 



tions in the position of the boundary 

eastward of the straits corresponding to 

straits, only considerably smaller, because the current-velocities 

naturally would be much smaller where the basin was broad. 

A few days later a number of observations were taken in 
the Spanish Bay westward of the straits. The positions of the 
stations are indicated in Fig. 198, and the salinities and tempera- 
tures are shown in the two sections: Fig. 199, in an east and 
west direction, and Fig. 200, in a north and south direction. In 
the east to west section the salt Mediterranean water with a 
salinity exceeding '}y^ per thousand is seen stretching out through 
the Straits of Gibraltar, its salinity, however, soon decreasing 



PHYSICAL OCEANOGRAPHY 



293 



to little more than 36 per thousand. Agreat mixing process must 
be going on here, as might be expected with the mighty sub- 
marine current rolling its saline waters into the strata occupying 




the Spanish Bay. By admixture with the somewhat colder and 
considerably less saline water, the temperature is slightly, and 
the salinity greatly, reduced ; thereby the density also decreases, 
becoming lower than that of the deepest layers of the Atlantic 
region, although higher than that of the surface layers. This 



294 



DEPTHS OF THE OCEAN 




PHYSICAL OCEANOGRAPHY 



295 



({ id 60 
5 d550 
t 



5tatLoa 17 
2750 

3600 3650%, 



mixed water enters like a wedge between the other water- 
masses at a depth of about 1000 metres, as clearly shown in the 
two sections. In this part of the Atlantic Ocean the salinity 
and temperature first decrease for some hundred metres below 
the surface ; then both increase a little through the influence of 
the outflow from the Mediterranean, below which they again Outflow of 
decrease. The admixture of water from the Mediterranean can fj^ter^^jo"^^" 
be widely traced over the eastern part of the North Atlantic, as the North 
already pointed out by Buchanan and Buchan. It is also ^'^^"^^'^• 
evident from our ob- 
servations at a number 
of stations, for instance 
at Station 17, off the 
coast of Portugal, as 
shown in Fig. 201. In 
the map showing the 
physical conditions at 
the depth of 500 
fathoms (given in Fig. 
202), we can trace it 
by the comparatively 
high salinities and 
temperatures reaching 
north towards Ireland 
and west towards the 
Azores. This ad - 
mixture is far more in 
evidence along the 
coasts of Europe than 
along those of Africa ; 
this signifies a drift 
towards the north, 
which might be ex- 
pected as an effect of the earth's rotation and the consequent 
deflection to the right. It appears, however, that some of this 
mixed water is carried far to the south-west by the great 
currents running between Madeira and the Azores. 

This wedge of mixed water from the Mediterranean is not 
met with near the surface nor in the greater depths. Thus it 
is not seen in the map (Fig. 203) showing the physical condi- 
tions at a depth of 200 fathoms (366 metres). At this level the 
saltest water (with a salinity above 36 per thousand) is found in the 
south-western part of the North Atlantic (excluding the fresher 



1000 



1500 



)° " 


a gc go IQO ,10 1^, jy , 


If" 1 


yc- 












( 


y 


S 






/■ 


1 
















\ 


\ 




1 
1 

\ 








\ 


















y 


1 

; 
; 
/ 
/ 


f 




y 


J 


^ 








\ 




^ 


'■^ 

























Fig. 201.— Salinity, Temperature, and Density at 
Station 17, west of Portugal (23rd April 1910). 



296 



DEPTHS OF THE OCEAN 



American coast-water). Farther north the salinity decreases, 
being a little more than 35.5 per thousand off the south-western 
coasts of Europe, and between 35.0 and 35.5 per thousand farther 




north off the British Isles towards the Faroe Islands and Iceland. 
In the northern part of the ocean the saltest and warmest 
water is found on the European side, the Gulf Stream making its 
influence felt there, whereas the less salt and much colder water- 
masses south of Greenland are derived from the polar currents. 



PHYSICAL OCEANOGRAPHY 



297 



In this map (200 fathoms) the lines south and east of the 
Newfoundland Banks have a peculiar form. The warm and 




Alternating 
currents off 
Newfound- 
land Bank. 



ON 



salt water-masses appear to be cleft in two by a colder wedge 
from the north-east. This indicates a current towards the 
south-west, forcing its way between the other water-masses 
flowing in the opposite direction. Now, it is quite possible 



298 



DEPTHS OF THE OCEAN 



that the Hnes in the map are wrongly drawn, because had 
there been many more stations the Hnes might have formed a 
number of vortices, Hke those mentioned above, p. 282. How- 
ever that may be, it is a fact that we fell in with a current 
running south-west, in the midst of the water-masses following 
the direction of the Gulf Stream towards the north-east, and 
this singular circumstance may be dealt with in greater 
detail. 

The section shown in Fig. 204 stretches from the Sargasso 
Sea along: the track of the " Michael Sars " northwards to the 



Newfoundland bank 

Stal 72 71 70 




3 7 2-3A 95 



Fig. 204. — Section from the Sargasso Sea to the Newfoundland Bank. 

Newfoundland Bank. At Stations 64 and 65 the conditions 
were uniform, resembling those found during the cruise from 
the Canaries westwards (see Fig. 63, p. 84). All this part of 
the Atlantic in and about the Sargasso Sea belongs to an 
oceanographically homogeneous region, but at Station 66 we 
suddenly met with very different conditions, for it was much 
colder in all the layers above the deep water, and the salinities 
were much lower. On proceeding farther north we again 
found, at Station 67, the same warm and salt water-masses 
as farther south at Stations 64 and 65. There was a decided 
difference also as regards the pelagic flora and fauna, which 
had a more northern facies at Station 66 than at Stations 



PHYSICAL OCEANOGRAPHY 299 

65 and 67. Now, when we consider the position of the 
water-layers and the effect of the earth's rotation, as treated 
above (p. 276), we come to the following conclusion : the 
current in the upper water-layers sets towards the north-east 
between Stations 65 and 66, another current runs tow.ards the 
south-west between Stations 66 and 67, then a current runs to 
the north-east again towards Station 70. 

As we were working at Station 67 on the afternoon of the 
27th June, a gale arose, increasing in the course of the night 
to a hurricane from the south-west, veering later on to the 
west. There was a rough sea with choppy waves, as is usual 
with the wind blowing against the current. We kept the 
ship's head to the wind all night, and it was as much as we 
could do under heavy steam pressure to stem the storm with- 
out drifting off. Next morning the wind fell somewhat ; it was 
fresh from the west when we occupied Station 68. When the 
captain got an observation, it proved that we had been carried 
southwards about fifty nautical miles from Station 67 to 
Station 68. This agrees excellently with our conclusions from 
the distribution of temperature and salinity, and it is established 
beyond doubt that in this place there was a strong current 
running towards the south-west. The west wind caused the 
ship to drift more to the south than the course of the current. 
Peake and Murray^ and Schott tell us that a current running 
south-west has been met with before in the same region ; thus, 
the cable - steamer " Podbielski," in May 1902, drifted 53 

1 " The climate of the British Isles being influenced to such a large extent by the warm water ot 
the Gulf Stream, the movements of this great body of water, the course of its main current, and 
the manner in which this spreads itself over a very large portion of the North Atlantic, should 
be a subject of special interest to the inhabitants of these islands. Among those who have not 
carefully studied the observations that have been made on this subject, a general impression 
obtains that after leaving the American coast the Gulf Stream consists of a body of warm water 
moving steadily across the North Atlantic in the direction of the Irish coast. An increasing 
number of observations tend more and more to show that this is not the case ; the movement of 
this great mass of water is more probably somewhat in the form of bands of current which 
curve and recurve on one another, forming swirls of large area whose strength and direction 
change almost daily. A glance at the current charts shows how the Gulf Stream in its passage 
across the Atlantic spreads itself out at the surface like a fan, and forms what is known as the 
Gulf Stream drift. 

" It will also be noticed that on the line of observation given herewith, an easterly current was 
met with considerably farther to the westward than would have been expected from the 
Admiralty current charts ; this, however, merely exemplifies the variations which occur in the 
course of even the main body of the stream at the surface, the course as shown on the Admiralty 
current charts being its average direction. 

" In the appended list of observations the total ' sets ' are given, and these are again corrected 
for the pressure of the wind and the force of the sea, leaving a ' set ' due to current only. 
The correction for wind and sea is necessarily only an approximation, but the result approaches 
more nearly to the current effect than would have been the case had no correction been 
attempted. The direction of the current as observed between the Azores and North America 
is shown on the accompanying map by arrows " (Peake and Murray, " On the Results of a Deep- 
Sea Sounding Expedition in the North Atlantic during the Summer of 1899," extra publication of 
the Roy. Geog. Soc. London, 1901, pp. 13-14). 



.^oo 



DEPTHS OF THE OCEAN 



miles to the south-west in the course of twenty-four hours in 
lat. 40' N. and long. 55' W. It would be interesting to know 
whether these conditions are constant in this region, as it 
might then be of importance for navigation, or whether there 
may be certain irregularities, perhaps one or more progressing 
vortices. 

As a matter of fact, the general current was here split into 
two branches. Whether it proceeds as two separate currents 
or not is difficult to judge from our investigations, as we had 
too few stations in the neighbourhood, and there are no 
previous observations. Our section from Newfoundland to the 
Bay of Biscay (Fig. 99, p. 115) has a suggestion of a similar 
division at Station 85, but it is too 
slight to base any conclusions upon. 
It is, however, known that farther 
south there occur " bands " of water 
with comparatively low temperatures 
in the surface - layers of the Gulf 
Stream. But we are on many points 
deficient in our knowledge of this most 
important ocean current, among other 
things also with regard to the yearly 
variations to which it is subject. 





/^K^ 




^ \ 


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L \ \ 


"r \^4 


^ X 


I ^ 2 t 


v_ ^ 


.^^ t 


V 




\, 


I t 


^ 




3 


I ~i 


v_ 


• ^ i - 


A 


>^Ji -J 









Fig. 205. — AlR-rEMPERATURE AT 

THE Faroe Islands 
G, when the wind blew from the 
"Gulf Stream" region; and P, 
when the wind blew from the East 
Iceland Arctic-current resfion. 



It is a well-known fact that the 
climatic conditions of northern 
Europe are influenced by that branch 
of the Gulf Stream which flows north- 
wards along the shores of the British 
Isles into the Norwegian Sea. In places with such a maritime 
climate as that of the Faroe Islands this influence is especially 
felt. Martin Knudsen has examined some meteorological 
observations from the Faroe Islands, and has found (see Fig. 
205) a conspicuous difference between the temperature of the 
air when the wind blew from the Gulf Stream region in the 
south and west, and when it blew from the north, over the 
Arctic East Iceland current. The difference was greatest in 
winter (as much as 6V C.) and least in summer (smallest 
difference ij" C). Pettersson at an early period entered on 
the study of questions regarding oceanic influence on the 
climate of Scandinavia, and his work on this subject has 
been more conducive than anything else to the establishment 
of the international investigations of North European waters. 



PHYSICAL OCEANOGRAPHY 301 

Figs. 206 and 207 show some of his results. At that time (in 
the nineties) no systematic investigations of the Norwegian Sea 
through any length of time had been carried on, so he could 
only study the surface-temperatures noted at three Norwegian 
lighthouses. 

In Fig. 206 we see the variations in the surface-temperature 
off the west coast of Norway (indicated by the thick line) and 
in the air-temperature at Orebro in Sweden (indicated by the 
thin line), both for January during the years 1874 to 1892. The 
vertical scale indicates the deviation from the mean temperature, 
which for the coast-water is 5.3° C. and for the air 3.4" C. 
On the whole the curves agree well, a high temperature in the 

74 7S 76 77 76 yjj 80 01 az ,yj {If 65 iih d7 6d dV 90 91 9^, 



M 







































3° 


\ 




























/ 


1 




'i° 














\ 
















/ 


\ 




J° 














\ 




1 










/ 




\ 




Z° 














\ 




1/ 






/ 


^ 


/ 




\ 






\ , 


^ 


; 


\ 






/ 




J 




1 


/ 
^ 


n\ 


/ 


/ 


^1 




Ocean 5^'C 


V 


w 




^ 




\\ 


/ 








r 










\ 


^ 


Htmoiph.i ^ 




\ 




\ 


/i\ 










1 










-r 

"6° 














































\ 


































\ 



























































Fig. 2o6. 

The thick line shows the variations in January of the surface temperature off the west coast of Norway 

from year to year ; the thin line the variations of the air-temperature at Orebro (Sweden). 

surface-water corresponding to a high temperature in the air. 
Pettersson further pointed out that a certain deviation from the 
normal temperature of the air, as a rule, lasts for a length of 
time ; a cold period, for instance, often lasts for weeks, or 
even months. Now, there are many relations on the land 
which are influenced by the deviations of the air-temperature 
from the normal, among other things, the duration of the snow- 
covering, the time of blossoming of many plants, the time for 
beginning field-labour in spring. Pettersson found the varia- 
tions in some of these particulars to agree with the variations 
in the temperature of the air and of the surface-water off the 
west coast of Norway some time before. Fig. 207 shows an 
example of this agreement ; the lower curve gives the variations 



302 DEPTHS OF THE OCEAN 

in the temperature of the sea-surface off the Norwegian light- 
houses for the month of February, while the upper curve shows 
the variations of the date at which the coltsfoot {Ttissilago far- 
fara) began to blossom in central Sweden (Upsala). This plant 
begins to blossom, on the average, about the 9th April, the 
exact date varying in different years from the i8th March to 
the 28th April. The two curves agree in many points ; when 
the water off the lighthouses was relatively warm in February 
the flowering commenced early, and when it was cold the 
blossoming was late. 

Pettersson had at his disposal only observations from the 
water in the immediate vicinity of these coast stations, but since 



7^ 75 76 77 7a 79 SO 61 82 83 8H 85 86 87 68 89 90 9/ 92 93 9^ 95 96 



^ 



13 - 

9 — 

30mrf5 

zo — 



6' 



Fig. 207. 
The upper curve shows the time of blossoming of Tz/ssi/ago /ar/ara at Upsala during a series of 
years. The lower curve shows the surface-temperature of the sea off the west coast of Norway, 
in the month of February of the same years. 



regular investigations were started in the Norwegian Sea in 
1 900, we have excellent series of observations during a succession 
of years, not only in the coast-water, but also in that branch of 
the Gulf Stream which flows into the Norwegian Sea. Nansen 
and the writer have found, by going through all the observations 
made in the years 1900 to 1905, that there are great variations 
in the temperature-conditions of this Atlantic current, and that 
these variations are apparently followed by corresponding 
variations in many other conditions ; for example, the temper- 
ature of the air, the year's harvest, the growth of the trees, and 
various circumstances touching the appearance of great shoals 
of fish. One or two instances may be referred to here. 

During the Norwegian investigations a section was run 



PHYSICAL OCEANOGRAPHY 



303 



from the mouth of the Sognefjord westwards, in the middle of 
May, every year from 1901 to 1905. One of these series is 
figured on p. 240. Nansen and the writer have calculated the 
mean temperatures in the Atlantic water of this section, both 
for the surface and for the deeper water. The variations in the 
surface-temperature are represented in curve L, Fig. 208, curve 
H. showing the variations in the growth of the pine in eastern 
Norway during the following year. The low surface-temperature 
in May 1902 corresponded to the small growth of the pine in 
the succeeding year, 1903, and the high temperatures in the 
surface of the Gulf Stream in May 1905 corresponded to a 
great addition to the height of the pine trees in the year 1906. 
This is explicable by the fact that the annual growth of the pine 
is not determined by the meteorological conditions of the same 
year, but by those of the year 
before, when the bud was 
formed, the growth mainly 
depending on the formation 
of the bud. Continued inves- 
tigations will prove whether 
the agreement strongly sug- 
gested by the figure is really 
a general rule, in which case 
it may be possible, on the 
basis of investigations in the 
Norwegian Sea, to predict 
with a high degree of probability how much the Norwegian pine 
will grow in the following year. 

By calculating the mean temperature of the Atlantic water- 
masses below the surface in the Sognefjord section, and 
multiplying the ascertained value by the area of the transverse 
section of these water-masses, an expression is obtained for the 
amount of heat in the northern branch of the " Gulf Stream." 
This has been done from the observations made during the 
May cruises, and the results are exhibited in curves I. and II. in 
Fig. 209 ; the two curves are obtained by two different methods 
of calculation which need not be discussed here. The lower 
curve shows the variations in the mean temperature of the air 
in Norway during the winter months from the ist November to 
the 30th April. The coincidence is striking ; when, for instance, 
the amount of heat in the Gulf Stream was great in the 
month of May, the air-temperature in Norway was high in the 
following winter. This holds good throughout six years, 



X 


1901 


1902 


t90i 


190^ 


1905 


JL 1902 


/903 


190^ 


J905 


/906 








' 






a ■ 














\ 


V 


J"^ 


-y 


/' 


7°- 




v/ 









Fig. 208. 
mean temperature of the surface of the ' ' Guh 
Stream " in the Norwegian Sea (Sognefjord 
section, May) ; II., mean growth of the pine 
in eastern Norway. 



304 



DEPTHS OF THE OCEAN 



but, of course, that is too short a period from which to draw 
definite conclusions. Anyhow, these preHminary results point 
to possibilities of no little importance, and we may in the future 
be able to predict, months beforehand, whether the coming 
winter will be warmer or colder than the normal. Many 
similar relations could be pointed out between the conditions in 
the sea and facts of interest bearing upon our daily life, but the 
above examples give an indication of the problems to be faced 
in modern oceanography. 



The Atlantic current flowing northwards over the Norwegian 

Sea, which in our waters 

/SOO /so/ t902 /S03 /S04 /SOS . ' , >-> i r 

IS also called the Gulf 
Stream, is thus subject to 
considerable variations in 
temperature and total 
amount of heat. This cur- 
rent is, however, a mixture 
of water from the Atlantic 
proper with water from the 
northern currents penetrat- 
ing intothe Norwegian Sea, 
north of the Faroe Islands, 
and the character of the 
" Gulf Stream " will de- 
pend on the conditions of 
mixture, and on the indi- 
vidual temperature of each 
of these currents, factors of 
It 
is highly probable that the 
Gulf Stream of the Atlantic also shows annual variations, 
and, though they may not be of much importance in their 
effect on the small branch in the Norwegian Sea, they may 
prove to be of great climatological significance for the 
countries on both sides of the Atlantic Ocean ; a thorough 
study of this current in the immediate future is therefore 
looked forward to with great expectations. That there are 
large annual variations in the caloric conditions of the huge 
water-masses of the North Atlantic was suggested by the 
observations of the "Challenger" nearly forty years ago, and 
has been confirmed during the recent cruise of the " Michael 
Sars," these two vessels having made investigations in the 




Fig. 209. 
I. and II. , the annual variations in the amount of 
heat in the "Gulf Stream" (Sognefjord section, 
May); III., variations in the air- temperature of which WC knOW little. 

Norway (November to April). 



PHYSICAL OCEANOGRAPHY 



305 



same oceanographical region. In July 19 10 observations were Comparison of 
made bv the " Michael Sars" at Stations 60 to 6s in the vicinity " ^^^^l^,"^v." ',' 

r 1 ./j—-i 11 M r- • ^ r T o in. t i "^ ^"^^ "Michael 

ot the " Challenger Station 65 ot June 1873. Now, the temper- Sars" 
atures of the great depths beyond 1000 fathoms prove to be oSvSont 
identical in these two years, showing that the thermometers 
worked properly, but in the upper layers it was much colder in 
1 9 10 than it was thirty-seven years before, the difference in 











TEMPERATURE °C 




^* 


€ 


8' 10' 


12" 14- 16° 18° 20" 


22° 


100 








fr^ 


^^ 


200 








I J 




300 








^^y / 




400 






, 


.4^ / 




500 






y^ 


^/"^ 




1 

t 600 






^^ 






5 


1 


'/ 


•CHALLENGER' -21 6.1873 36' 33 N. 47" 58 W. 




700 


/ 


1 

/ 


x'MICHAEL sars' 25. 6. I9IO 37° Is'N 4a" 30'w. 




eoo 


/ 


/ 








900 


/ 










1000 


i 











Fig. 210.— Comparison of the Temperatures taken by the "Challenger" 

IN 1873 AND BY THE " MiCHAEL SaRS " IN I9IO. 



some cases amounting to about 5' C. at a depth of 700-800 
metres (400 fathoms). Fig. 210 shows the temperature-observa- 
tions at the "Challenger" Station 65 and the "Michael Sars" 
Station 65, between the surface and a depth of 1000 fathoms. 

Observations were taken at the " Michael Sars" Station 51 
in June 1910, in the vicinity of the "Challenger" Station 354 
in May 1876. Fig. 211 shows the conditions at these two 
stations, which varied only to a slight extent ; at certain depths 

X 



3o6 



DEPTHS OF THE OCEAN 



it was a little colder in 1876 than in 19 10, at other depths a 
little warmer, but no general difference appears between the two 
series of temperatures — one series taken thirty-four years after 
the other. There have probably been many variations in the 
course of these years of which we have no knowledge. In this 



TEMPERATURE C 
10' 12° 14" 




'CHALLENGER 6.5. 1876 32° 41 N. 36 6' W 
("MICHAEL SAR5' 6 6. 1910 3l' 20N 35°7'W 



Fig. 211 — Comparison of the Temperatures taken by the "Challenger" 

IN 1876 AND BY the " MICHAEL SaRS " IN I9IO. 

and in many other respects the Atlantic Ocean calls for further 
and more detailed investigation ; as we said at the beginning of 
this chapter, very much more work will have to be done before 
we shall be able to solve the many interesting and important 
problems relating to the great ocean waters. 

B. H.-H. 



CHAPTER VI 

PELAGIC PLANT LIFE 

Not many years have elapsed since the scientific world became Historical 
aware that the sea contains plants in abundance floating on and introduction. 
beneath its surface, and that they build up the organic sub- 
stances upon which marine animals depend. In the open sea 
the plants are too minute to be detected without the microscope ; 
so that, until this instrument came to be regularly employed by 
biologists, it was impossible to know anything about them. 

The first to use the microscope for studying unicellular 
organisms in the sea was the celebrated Danish zoologist, 
O. F. Mtiller, who, in 1777, described one of the most important o. f. Muiier. 
plants of our northern waters, namely, Ceratimn tripos. He 
was succeeded by the microscopist Ehrenberg, who laid the Ehrenberg. 
foundation of our knowledge regarding the multiplicity of forms, 
their wide distribution, and their significance in the economy of 
nature ; and also discovered the coverings of diatoms together 
with coccoliths and the skeletons of various unicellular animals 
(radiolaria, foraminifera) in deposits on the sea-bottom and in 
geological strata from previous ages. Ehrenberg aroused 
interest by pointing out the wonderful structure of these 
coverings, and improvements in the microscope have resulted 
in fresh wonders being disclosed, which have induced quite a 
number of capable amateurs to take up the study of diatoms. 

Classification of these algae dates from about the middle of the 
nineteenth century. It is based on the shape and structure of the 
cell-wall, less attention having been given to the living contents 
and to the biology. The pelagic forms have as a rule thinner 
coverings, and a more indistinct structure, than the robust species 
nearer the coast, and have therefore been less studied. How- 
ever, occasional samples have now and then been collected from 
the surface with nets, and researches have been carried out by Bailey. 
J. W. Bailey in the waters off Kamchatka, by Brightwell along Brightwdi. 

307 



3o8 DEPTHS OF THE OCEAN 

Lauder. the shorcs of England, by Lauder at Hong-Kong, and by Cleve 

cieve. in the North Polar Sea and at Java. A regular gold mine in the 

Waiiich. way of rare pelagic forms was found by Wallich in the intestinal 

canals of salpse, and this source has subsequently been utilised 

for procuring forms that our apparatus could not capture. 

Pelagic algae which have no skeletons of durable mineral 

constituents, such as silicic acid or lime, were in those days 

neglected. A few, no doubt, of the larger peridinese were 

Nitsch. described by Nitsch, Ehrenberg, Bailey, Claparede, and 

ciaparede. Lachmaun ; but there was very little progress made, and it 

Lachmann. ^as uot till 1 883 that T. R. von Stein published his first 

Stein. comprehensive monograph, a great deal of the material for 

Bergh. which had been taken from the stomachs of salpse. R. S. Bergh 

had already issued, two years previously, a text- book on the 

organisation of these algse. 

Since 1870 important expeditions have been undertaken, 
one object of which was to study the pelagic organisms 
" chaiiengei •' systematically. The "Challenger" Expedition, in particular, 
Expedition. collected quantities of material from all the seas of the world ; 
though attention was still chiefly directed to those forms whose 
coverings are met with in deposits on the sea-bottom, that is to 
say, diatoms with their silicious coverings, and the remarkable 
little organisms forming the microscopic calcareous bodies which 
Ehrenberg had already designated coccoliths and rhabdoliths. 
John Murray. Murray pointed out that coccospheres and rhabdospheres, as 
they were termed, are really self-existent organisms in the 
surface-layers. He could obtain them by allowing a glass of 
sea-water to stand for a few hours, so that they sank to the 
bottom and attached themselves to threads placed there for 
purposes of experiment ; and he also found numbers of them in 
the stomach-contents of salpse, of which they often formed an 
essential part. It was possible, too, by noting the occurrence 
of their coverings in the bottom-samples, to obtain definite 
information regarding their geographical distribution. He 
observed that, while they are abundant in all tropical and sub- 
tropical waters in the open ocean, they are not found in arctic 
and antarctic waters having a temperature below 45° F., nor are 
they to be found in the deposits of the polar oceans. Murray 
further ascertained that diatoms are irregular in their occurrence, 
and that they are more numerous in coastal areas than out in 
Castracane. the oceau. Unfortunately Castracane, when examining the 
diatoms collected by the expedition, was unable to find any 
conformity in the distribution of the different species. 



PELAGIC PLANT LIFE 309 

The other expeditions that were sent out about the same 
time as the "Challenger" carried out their investigations on 
similar lines. G. O. Sars, who was a member of the Norwegian g. o. Sars. 
North Atlantic Expedition in 1 876-1 878, made a study on 
board ship of the luxuriant plant life near the ice-limit, and re- 
marked, like QErsted before him, that plants are really the basis CErsted. 
upon which the nutriment of animals is founded. It was not, 
however, till twenty years afterwards that an examination was 
made of the algae in the comparatively small number of samples 
then collected. 

Soon after 1880 Hensen commenced a physiological study Hensen. 
of the sea, and essayed principally to estimate its production of 
nutritive substances at different seasons. As a result the plants 
came more into notice than they had previously done ; and it is 
significant that Hensen found it necessary to introduce the new 
name of " plankton " to designate generally all pelagic organisms, "Plankton 
both plants and animals, regarded as one universal community. 
The term "plankton" is now used for all floating organisms 
which are passively carried along by currents, while "nekton" "Nekton." 
— a term introduced by Haeckel — is used to designate all 
pelagic animals which are able to swim against currents. 
During Hensen's Plankton Expedition in 1889 Schlitt made Schutt. 
the first investigations regarding the general biology of the 
plankton - algse. His ingenious descriptions and admirable 
drawings explained the different ways in which the alga; adapt 
themselves to their floating existence. 

An endeavour was made by Hensen to find a method of Qu; 
calculating the quantity of pelagic organisms occurring in 
different localities. He constructed nets to be drawn up for 
certain distances through the water, that were supposed to 
filter the whole column of liquid through which they passed, and 
to retain all the organisms existing therein. The total amount of 
these organisms was then measured by determining the volume, 
and a most careful enumeration was made of the number 
of individuals belonging to each species. The nets were drawn 
vertically through the whole zone where plant plankton is abund- 
ant, that is to say, from a depth of 200 metres to the surface ; 
and Hensen attempted to utilise the results for measuring the 
production of life in a column of water whose superficial area is 
one square metre. He tried at the same time to solve import- 
ant problems, such as the rate of augmentation of algse, or what 
proportion of individuals disappears owing either to consump- 
tion by other organisms or unfavourable conditions of existence. 



uantitative 
estimations. 



lO 



DEPTHS OF THE OCEAN 



Aurivillius. 



Pettersson. 



Hensen's work must not be disparaged because his aspirations 
have been more difficult to reaHse than he at hrst imagined. 
The difficulties are far from insurmountable, while Hensen 
himself will be always looked upon as one of the founders of the 
science of marine physiology. 

In the biology of the sea we have also to consider the 
geographical distribution of the different species and their 
dependence upon ocean currents. The Swedish scientists, 
Cleve and Aurivillius, brought these two questions into special 
prominence, though no doubt they had been previously con- 
sidered by others. But with the hydrographical investigations 
of Otto Pettersson and others the whole subject assumed a 
new aspect. Thanks to improved methods they succeeded in 
following the movements of the water-layers, by determining 
their salinity, temperature, and other hydrographical character- 
istics ; and from this time forward the plankton was also 
enlisted as a supplemental means of characterising water- 
masses of different origin. Cleve with his marvellous power 
of distinguishing forms was able in a short space of time to 
determine numbers of species, animals as well as plants, and 
it is to him we owe the foundation of our knowledge regarding 
the distribution of plankton-algaj. 

Since the international marine investigations were commenced 

nvestigations. ^bout ten years ago, researches have been carried out in the 

Northern Atlantic, North Sea, and Baltic ; and specialists from 

the different countries of North Europe have gradually extended 

our knowledge, as far as northern species are concerned. 

Simultaneously great improvements have taken place in our 
methods of studying plankton. Lohmann has made it clear that 
the catches in the silk nets originally used incompletely repre- 
sented the flora of the sea, owing to the fact that whole series of 
the most diminutive organisms slip through the meshes of even 
the finest straining-cloth. He devised methods for catching them 
by means of the filter and the centrifuge, and could thus estimate 
their numbers in a given quantity of sea-water. Coccolitho- 
phoridse, which the " Challenger " Expedition claimed to have 
discovered, but which Hensen refused to recognise as self- 
existent plankton organisms, because he did not capture them 
himself, were now investigated, and Lohmann was able to 
declare confidently that they really are algae, furnished with 
brown pigment granules, the physiological equivalent of 
chlorophyl, thus confirming the ecrlier discoveries of Sir John 
Murray, George Murray, Blackman, and Ostenfeld. Lohmann 



International 



Lohmann. 



G. Murray 
Blackman. 

Ostenfeld. 



PELAGIC PLANT LIFE 311 

has further, by his quantitative investigations of the variations in 
the plankton of Kiel Bay and off Syracuse, taught us the value 
of exact studies of this description. 

Our future investigations will have to be conducted on three 
main lines : — 

(i) In the first place, much study must be devoted to the 
biology, in the restricted sense of the word, of the algae. We 
will have to learn how the forms adapt themselves to their 
conditions of life, and in particular to their floating existence. 
Here, however, a great advance should most certainly be made, 
now that W. Ostwald has shown us a new factor affecting their Ostwaid. 
floating power, namely, the varying viscosity of sea-water, and 
since the instructive writings of Wesenberg-Lund have directed Wesenberg- 
our attention to the seasonal modifications which the species ^""^• 
adopt to suit variations in viscosity. 

(2) In the second place, the distribution of the species 
throughout the seas of the world requires further investigation 
at different seasons, and this must be founded on a careful 
characterisation of the different species. In recent years the 
peridineae, after a long period of neglect, have received due paviHard 
attention at the hands of Ostenfeld, Ove Paulsen, Pavillard, jorgensen. 
Jorgensen, Broch, and Kofoid. A great deal, however, still Broch. 
remains to be accomplished. Kofoid. 

(3) In the third place, we will have to deal with the laws of 
production in the sea. This great physiological question calls 
for observations on a very comprehensive scale, if we are to be 

in a position to discuss the interesting theories put forward by ^^^^^^^ 
Brandt, Nathansohn, and Putter. A brief discussion of their Nathansohn 
theories will be found at the end of this chapter. piuter. 

During the Adantic Expedition of the " Michael Sars " we 
were able to make observations on all these three aspects of 
the subject ; and in what follows I shall endeavour to summarise 
our results, and to consider, while doing so, the attitude at 
present taken up by the scientific world with regard to these 
three lines of investigation. 

Most of the ocean plants exist in countless myriads of General bio- 
minute individuals, though they are invisible to the naked eye. p°e^g°c aiga. 
Still, small as they are, they are in a way highly organised, 
and their organisation is in strict accordance with the particular 
conditions of life. On land' a higher plant consists of a 
community of separate cells, each of which has a special function 
to perform in the service of the whole. It establishes an under- 



312 



DEPTHS OF THE OCEAN 



ground system of roots to collect moisture and nourishment 
from the soil, and its leaves are raised aloft on slender stems 
to derive benefit from the rays of light and build up organic 
substance out of carbonic acid and water. Ocean plants have 
no such point cTapptii \ they find their nourishment dissolved in 
sea-water and distributed uniformly all around them, and they 
get most benefit from the sunlight when they are regularly 
spread throughout the whole bulk of the water in the photic 
zone. Their diffusion is also their best defence against their 
enemies, for, while animals have no great difficulty in 
finding and consuming the larger plants, these creatures, 
scattered everywhere like dust amidst the immeasurable 
water-masses, are not so easily available. The majority of 
the floating plants pass their lives as single cells, though they 
are frequently far more highly organised than the single cells 
that go to form a higher plant. 

As pelagic algse have generally a greater density than the sea- 
water in which they live, they would sink out of range of the 
rays of light, and perish, if it were not for the fact that they are 
kept from descending either by their own exertions or by 
suspension organs which act as a parachute. The most notice- 
able features in their organisation are their different forms of 
structure, which are directly connected with the floating existence 
they lead. In what follows I shall describe the most important 
types, belonging to a limited number of classes, most of which 
have variously shaped pigment granules or chromatophores, 
consisting of brown colouring matter instead of green chlorophyl. 
Comprised in their number are diatoms, peridineae, and brown 
flagellates, amongst which last we also include calcareous 
flagellates or coccolithophoridse. In addition there are a few 
pelagic representatives of the green and blue-green algse, which 
I will discuss separately. 



A diatom can be distinguished from other algse by its 
silicated cell-wall. This is composed of two quite similar 
halves, or valves as they are called, that are united to one 
another like the top and bottom of a pill-box (see Fig. 212). 
Inside the valves the protoplasm lines the wall like a thin sort 
of bladder, while the nucleus is frequently in the very centre 
surrounded by a denser mass of protoplasm connected to the 
bladder by bridges or strings. The rest of the cavity is full of 
a clear cell-fluid. The pigment granules, which are organs of 
nourishment, enable the diatom to collect rays of light and build 



PELAGIC PLANT LIFE 313 

up' organic substance out of carbonic acid. They usually 
lie in regular order along the cell-wall (Fig. 213, <?) ; but if the 
light becomes too strong for them, they are able to huddle 
more closely together, either in the middle of the cell or 





Fig. 212. — Cell-wall of a Diatom {Coscinodiscus subbuluens), ^i"*. 
(7, External view ; b, vertical section ; c, section in cell-division. 

at some point where they can mutually protect each other from 
the harmful effects of the rays (Fig. 213, ^ and c). This has been 
demonstrated by Schimper. The assimilation of carbonic acid 
produces a fat oil, which may form into comparatively large drops. 

Cells are produced by 
r^^i division. The nucleus and 
protoplasm divide into two 
parts, the valves are pushed 
a little apart, and two new 
valves develop within the old 
ones. Thus each of the 
daughter-cells gets one of the 
valves from the mother-cell 
and a new valve that joins on 
to it (see Fig. 212, c). When 
once the valves have acquired 
their shape they seem incapable 
of expanding, so that the cell 
generations will gradually be- 
come contracted in the plane 
in which division takes place. 
It follows that the cavity of 
the cell will also be dimin- 
ished, though at the same time 
the perpendicular axis of the plane of division is frequently 
slightly prolonged. Algse can, however, regenerate their 
original size, by throwing off their old valves, growing into a 
larger bladder with a thin expansible skin, and forming within it 
new valves that are two or three times as large as the old ones. 
This is the so-called auxospore development (see Fig. 214). 
Diatoms occur in quantities over the whole world in both 



Schimper. 
Cell division. 




Fig. 213. 
b, Lauderia annnlata. a, Cell with the pig- 
ment granules (chromatophores) in normal 
position, collected early in the morning ; b, 
chain from the surface of the sea, 3 P. M. , 
chromatophores congregated at the ends of 
the cells ; c, Detonula schrxderi in the same 
condition. All ^\^. 



Auxospore 
development. 



314 



DEPTHS OF THE OCEAN 



fresh and salt water, and they are found not merely as floating 
forms, but also along the coasts, some of them attached to the 
bottom or to other algse and animals ; some are capable of 
motion, gliding over the mud in enclosed bays or among grains 
of sand near the seashore. The coast forms, however, are 
essentially different from the pelagic forms in their structure. 
Littoral diatoms are apt to have a comparatively thick and 
extremely silicated cell-wall with the characteristic patterns, 
ribs, and pores, that have made them such an attractive object 
of study to amateur scientists. Bilateral symmetry prevails, 
especially amongst forms that are capable of motion, which are 
as a rule pointed at the ends like the bows of a boat. Diatoms of 




Fig. 214.— Auxospore-formation of Thalassiosira gravida. 
a. Showing in the centre a newly-formed auxospore, the old cell-walls still lying outside (-y-) ; b, 
showing on the left a cell before auxospore-formation, succeeded by an auxospore during its 
first cell-division, the chain of five cells having originated from an auxospore (-"^-). 

this kind have a highly organised locomotion apparatus, which 
is differently constructed in the different genera, such as 
Navicula and Nitzschia. Attached forms show more variation. 
Symmetry with them depends upon the mode of attachment. 
LicmopJio7'a and Gomphonema are fastened at one end to a 
gelatine-like stalk, and their cells are wedge-shaped, narrow at 
the bottom and widening out towards the top. Others, like 
Epit hernia, are convex on the one side and straight on the 
other, the straight side being the one by which they are attached. 
And there are others again that consist of more or less highly 
organised and often ramifying colonies, composed of series of 
cells, or sheaths of mucilage, within which the cells are able to 
move past one another. 



PELAGIC PLANT LIFE 315 

Pelagic forms usually have thinner cell-walls, and the f 
characteristic ornamentations on their silicated valves are not 
so prominent, though in their case too a high magnifying power 
will nearly always render them visible. The families that are 
endowed with locomotion organs are very scantily represented, 
and even amongst the few that are thus favoured, several species 
make use of them for quite a different purpose, employing them 
as organs to secrete mucilage and thus keep the cells united in 
chains. Most of the pelagic diatoms belong to families that 
lack organs of locomotion, though by way of compensation 
various types have highly developed suspension organs, which 
increase their superficies and consequently their friction against 
the surrounding water-masses. It is possible, too, that these 
algae are able to reduce excess weight by evolving specifically 
lighter matter, such as fat, within the cells or air-bladders outside 
them, but this has not yet been properly investigated. 

The suspension organs, however, have been most carefully 
studied, especially by Schlitt, who was one of the members of Schutt. 
Hensen's Plankton Expedition in 1889, and the different cell- 
forms, with their numerous contrivances for maintaining a 
floating existence, may be grouped under four heads : — 

(i) TJie Bladder Type.— In these the cell is comparatively large, p'our types of 
while the cell-wall and protoplasm are merely thin membranes round a suspension 
big inner cavity which is filled with a cell-fluid of about the same specific °''S'^"^- 
gravity as sea-w^ater. Among diatoms the best instances of this type 
are species of the genus Coscinodiscus, whose structure resembles 
cylindrical boxes, sometimes fairly flat-shaped, and sometimes more 
elongated and rounded at the top and bottom. In most forms the cell- 
wall is quite thin, though it is strengthened by means of a fine mesh- 
work of more or less regular hexagons. One of the biggest, Coscinodiscus 
rex {Et/unodiscus rex, Antelinine/lia gigas), is over a millimetre in diameter, 
and is quite a common form in "the warmer parts of the Atlantic (see Fig. 
215). A series of species with stouter structure, and more distinct orna- 
mentations on the cell-wall, occur especially in the deeper water-layers, 
at about the lowermost limit of plant-life (lOO to 200 metres), and 
belong to a characteristic twilight-flora, of whose existence Schimper 
became aware during the " Valdivia " Expedition. 

(2) The Ribbon Type. — The surface is enlarged owing to the cell 
being flattened down into a plane, which is often bent or twisted to a 
certain extent. Diatoms of this type (see Fig. 216) are scarce. We 
have, along the coasts especially, a few species with flat cells, which are 
associated in ribbon-shaped colonies, such as Fragilaria and Climacodimn. 
The cell-walls of these species are extremely thin, and not of a particularly 
distinct structure. 

(3) The Hair Type.— The cells are very much prolonged in one 
direction, or else they are united in narrow, elongated colonies. Diatoms 



i6 



DEPTHS OF THE OCEAN 



furnish many varieties of this type. Sometimes the length axis is situated 
in the division-plane of the cells, as, for instance, in Thalassiothrix 
longissivia, one of the characteristic forms in colder seas ; at other times 
division takes place across the elongated cell, as in the genus RJiir:osolenia, 
of which there are many species (see Fig. 217). Hair-shaped cells of this 
kind create a great deal of friction when horizontal, but would sink 
rapidly when perpendicular, if it were not for the fact that they are 
either slightly curved, or else their terminal faces are sloping ; so that 




jO ' 


; 


[0 ' 


■01 


La. 


<>J 


[O ' 


1^ 


fa 


' «J 




Fig. 2\^.~Coscixodisc.us rex (-'V')- 



Fig. 216. — Pelagic Diatoms of the 
ribbon-type {-^?^). 

Chain of Navicula vanhoffeni, the cells con- 
nected by a band of mucilage ; b, part of a 
chain of Frasrilai-ia oceaiiica. 



the resistance of the water soon restores them to an almost horizontal 
position, and they sink slowly in long spiral sweeps. 

(4) The Branching Type. — The surface of the cell is enlarged by 
various kinds of hair-shaped or lamelliform outgrowths. To this type 
belongs the genus CJicetoceras with its numerous species (see Fig. 218).. 






j5^«fe«> 



Fig. 217.— Pelagic Diatom of the hair-type, Rhizosolenia hebetata-semispina. 
a, Entire cell (^oo) ; b, end of a cell (^f «). 

Every cell has four long setiform outgrowths, and the cells are besides 
nearly always associated in chains, so that these setae radiate in every 
direction. When the chain is straight and stiff it is frequently furnished 
with special terminal setae, which are stiffer than the others, and act as 
a sort of steering apparatus. 

In addition to the actual outgrowths from the cell many 
diatoms can secrete long filaments of mucilage from special 



PELAGIC PLANT LIFE 



317 



secretion pores. These filaments act as an effective suspen- 
sion-apparatus (see Fig. 219). During unfavourable conditions 




Fig. 218.— Chain of Ch.f.toceras decipiens ('f-"). 

of existence, especially when there are considerable changes in 
the salinity, sufficient mucilage is secreted to form a protecting 




Fig. 219. — Chain of Thalassiosira gravida (-f")- 
Showing on the right five cells with filaments of mucilage. (Mangin. ) 

sheath round the cells. This I have myself observed in the 
case of species of Thalassiosira on the Norwegian coasts. 

Adjustment of their organisms to the conditions of their 



3i8 DEPTHS OF THE OCEAN chap. 

floating existence affects the whole structure of these alg^, 
though it is not always carried out to the same degree in the 
different genera and species. If we examine into their distribu- 
tion we shall find that no particular region is distinguished by 
specially well -equipped species. Genera with the greatest 
numbers of species have their representatives in both the 
warmest and the coldest areas of the sea, and no essential 
difference in the development of their suspension-apparatus is 
to be found between the species of ChcEtoceras and Rhizosolema 
which live near the confines of the polar sea, and their relatives 
in the tropics. The greatest abundance of forms is to be met 
with in coastal waters, where, too, the majority of the species 
have their home. I shall return later on to the special biology 
of these coast-forms. 

Many species of diatoms show variations indicating that 
within certain limits the algae can adapt their floating power to 
the demands made on them. Their tendency to sink increases 
with a rise of temperature, and decreases with an increase of 
salinity. It is not alone the specific gravity (density) of 
sea-water that is here the determining factor; no doubt we 
must bear specific gravity in mind also, but its variations are 
comparatively small. Ostwald has shown that the internal 
friction or viscosity of sea-water is the most important con- 
sideration, and this diminishes with an increase of temperature. 
Other things being equal, sea-water at 25° C. offers only half the 
resistance that it would at freezing-point. Salinity, on the 
other hand, is of less account. A rise of i per cent in the 
salinity will produce no more than an increase of 2 to 3 per 
cent in the internal friction, and as salinity in the open sea is 
subject to what are after all quite inconsiderable variations, it 
follows that it is really temperature which indirectly affects the 
development of the suspension-organs. In areas of the sea 
where there is a big difference in temperature between summer 
and winter, we find a number of species with distinct summer 
and winter forms, that have sometimes even been supposed to 
belong to totally different species. And the same variation 
occurs also in species with a wide distribution, the warm-water 
types corresponding to the summer forms, and the cold-water 
types to the winter ones. The summer forms have usually 
thinner cell-walls, and a more slender structure ; their excess 
weight appears to be reduced, though at the same time 
their surface is comparatively larger. As, however, diatoms 
vary greatly in their dimensions throughout their life-cycle, 



PELAGIC PLANT LIFE 



319 



their cells diminishing by being divided and increasing again 
owing to the formation of auxospores (see Fig. 220), it is 




Fig. 220.— Colonies of Thalassiothrix nitzschiowes (^f^). 
(/, With long cells shortly after auxospore formation ; b, with shorter and thicker cells. 

difficult to show in the case of many species to what extent 
variations are due to adaptation and regulation of their floating 
power, though in the case of some chain-forming species it is 




Fig. 221. — Parts of two chains of Chmtoceras decipiens (^f^). 
a. From the Atlantic off the coast of Spain, April 1910 ; b, from Christiania-Fjord, March 191 1. 

evident enough. Chcetoceras decipiejis, one of the commonest 
species in the northern Atlantic, consists of straight chains 
of flattened, almost rectangular cells, every one of which is 



,20 



DEPTHS OF THE OCEAN 



furnished with four long setse. Each of these setae is attached 
at the root to its fellow from the neighbouring cell, the result 
being the formation of the chain. The terminal faces of the 
cells are otherwise separate, so that there are openings between 
them. In the winter and spring Chcetoceras decipiens is furnished 
with thick cell-walls and stout setae, and the interstices between 
the cells are quite inconsiderable (see Fig. 221,^); but in summer 
the walls are thin and the setae extremely fine, and the openings 
in the chain between the cells then become large, round or 
oval gaps, which are almost as big as the cells themselves (see 
Fig. 22\,d). Corresponding variations occur in other species 
of Chatoce7'as, and in other diatoms, such as Biddulphia 
aitrita. Along the arctic coasts, for instance, BiddzilpJiia has a 
rather gross structure, and is almost cylindrical, with short 
conical projections at the corners, but off the south of Norway 
it has a comparatively much larger surface, and the corners 
develop into long, slender outgrowths. 

We find a variation of a different nature in the case of 



Fig, 222. — Cell of Rhizosolenia hebetata-semispina {^^^). 

One end of the cell belongs to the typical arctic hebetata (on the right), the other 

to the Atlantic form semispina. 

Dimorphism. Rhizosoletiia hebetata. It occurs in two perfectly distinct forms, 
that were formerly regarded as good species. The first, which 
belongs to arctic waters, is thick-walled and gross, and is the 
true R. hebetata. The second, R. semispina, has thinner walls 
and is proportionately longer, and it is furnished with a long 
hair-like point at each end. Its distribution extends over 
practically the whole Atlantic, though it is chiefly to be found 
in the neighbourhood of the cold currents. These two 
" species " can originate from one another reciprocally as the 
result of one cell-division. During the course of transition a 
cell may be hebetata at the one end and semispina at the other 
(see Fig. 222). Dimorphism of this kind is known, moreover, 
in the case of other species. 

Still, in the open sea conditions of existence are compara- 
tively uniform compared with what we find in coastal waters, 
where the temperature and salinity vary considerably. Most 
of the diatoms which belong particularly to the coastal waters 
Resting- have a special adaptation, the so-called resting -spores, which 
spores. must be regarded as a means of protection against such altered 

conditions. The contents of the cell can shrink into a denser 



PELAGIC PLANT LIFE 321 

mass in the middle, and become enwrapped in a new thick wall 



of characteristic shape within the old cell-wa 
carded as soon as the resting-spore 
is completely developed (see Fig. 
223). The spores have now ac- 
quired an increased specific weight, 
as compared with their original cell, 
and sink down into deep water, 
where they may be found months 
after they have disappeared from 
the surface-layers. The majority of 
them, however, rest on the bottom 
in shallow coastal waters, until con- 
ditions of existence again occur 
which induce them to make a fresh 
start. 

The germination of the resting- 
spores has not yet been described, 
though Hensen states that Lohmann 
has observed the first stages on 
several occasions. It will be a great 
advantage when we can follow their 
development-history through all its 
stages, and study the conditions of 
existence that lead to germination. 
Resting-spores are unknown in the 
true oceanic species ; but, as already 
stated, they are found in most of 
the species belonging to coastal seas, 
not aware of them till quite a short 



^hich 




Fig. 223. — Chain of Chmtoceras 
constrictum, with three rest- 
ing - spores and one normal 
cell (the end - cell of the 

CHAIN) {*-r-). 




In some cases we were 
time ago. It is only 
recently that they have 
been discovered in Lep- 
tocylindrus danicus (see 
Fig. 224), in which the 
cylindrical cells are 
broken across in the 
Fig. 22af.—LEPTocYuxDRus danicus, WITH RESTING- process of spore-forma- 
sFORE(i"/^). ^j^^^ g^ ^^^^ ^^^ spores 

are liberated, and in Chcetoceras pseudocrinitum, in which the 
resting-spores originate in auxospores. 

So far as we are able to ascertain, the auxospores of pelagic 
diatoms are always formed without any sexual act. There is, 
however, another kind of organ, the so-called microspores, Microspores. 

Y 



,22 



DEPTHS OF THE OCEAN 



Bergon. 
Karsten. 



Peridineae. 



which, according to Bergon's investigations^ would seem to be 
zoospores, and which Karsten assumes to be sexual cells. 
Karsten has observed the formation of microspores in an 
antarctic diatom, Corethroii valdivicE (see Fig. 225), and in the 
same microscopic preparations found amalgamations of small 
cells resembling microspores. We cannot yet, however, consider 
this conclusively settled. We do not know the life-history of 
the numerous small spores after they have emerged from the 
mother-cell. We can only hope that the centrifuge will enable 
us to study the 
most diminutive 
andsensitivecells 
immediately after 

capture, and that ^ ^ ¥ } II ^ 

we shall thus suc- 
ceed in solving 
this problem in 
the biology of 
diatoms. 




H 






Fig. 225.— Microspore-formatio.\ 01 Cokethron valdivi.e 
in different development stages (="-1"). 

Ripe microspores in the cell to the right. (Karsten.) 



Peridinese are 
mobile algae fur- 
nished with two 
cilia. Several 
species can pro- 
duce brilliant 
phosphorescence. 
Their cells are 
highly organised, 
with adistinctdif- 
ference between 
the anterior and 
posterior ends, and between the dorsal and ventral faces. 
The cell-wall is built up entirely of organised matter, which 
dissolves soon after the death of the cell. Peridinese are 
therefore not noticeable in the deposits of the ocean -bottom, 
which is one of the reasons why, until quite recently, they were 
but slightly and imperfectly known. A number of laminae, 
characteristic in shape and position, compose the cell-wall. On 
the posterior side there is a characteristic furrow, with a pore 
for one of the cilia, which can be withdrawn spirally into a 
sheath (see Fig. 226). The ventral furrow is often protected 
by curtain-membranes. Another furrow encircles the cell, and 



PELAGIC PLANT LIFE 323 

is known as the ring -furrow. It is guarded by projecting 
borders on the anterior and posterior sides, called ring-borders. 
It is in this furrow that the second cilium lies and vibrates. 

These principal organs appear in a great variety of shapes. 
The genus Ceratmm has the anterior end drawn out into a long Ceratmm. 
horn, which is open at the top ; its posterior end has also nearly 
always two horn-like projections, which in most species bend in 
a forward direction. The species of Ceratmm are well supplied 
with brown pigment granules, and they occur in the upper 
water-layers, where they constitute an essential part of the plant 

life. The horns must be regarded 
as suspension-organs, even though 
the mobility of the cell makes an 
adaptation of this kind less indis- 
pensable. We frequently find 
them, especially in the species 
of tropical seas, transformed into 
very consummate suspension - 
organs. Sometimes they are 
decidedly long and hair - shaped, 
sometimes flattened, and in a 
few species actually terminate in 
radiating branches. Kofoid has Kofoid. 
shown that the species of Cera- 
tmvi can regulate their floating 
power, and that when, owing to 
the movement of the water 
masses, they enter colder or 
Yio. 2z(y.-PERiDiNiuM DEPREssvM {^\^). warmcr layers of water, they can 

(Schlitt.) .^ r u • u 

shed portions 01 their horns or 
prolong them at will (see Fig. 227). They have also still 
another mode of improving their floating power. The cell wall 
grows in thickness during the whole life of the algse, and 
simultaneously ribs and pores are constantly developing ; but 
as soon as the cell gets too heavy, one or even several laminae 
peel off from the cell armour, and new extremely thin plates 
take their place. 

The species of Ce^^atiimi are also formed by division, and 
with them, too, the daughter-cells each retain half of the 
membrane of the mother-cell, the other half being new. This 
does not, however, take place within the cell- wall of the mother- 
cell, and there is therefore no gradual diminution in the bulk of 
the individual. Sometimes the cells hang together in chains. 




>24 



DEPTHS OF THE OCEAN 



and it is then quite evident that the direction and shape of the 
horns may vary considerably from one generation to another. 




Fig. 22-J.—CERATIUM TRICHOCEROS. 
Showing progressive and proportionate reduction of the horns in autotomy (^ f-). (Kofoid. ) 





0.0 



0.2 0-3 mm. U 

Fig. 228. — Ceratium platycorne. 
, Forma cojnpressa ; 2, 3, forma normalis. 




In other cases, where the cells separate immediately after 
division, it is more difficult to tell which variations are due to 
hereditary dissimilarities and which are the result of direct 



PELAGIC PLANT LIFE 



325 




adaptations from one generation to the othier. Still, now and 
then even this, too, is possible. I found during the Atlantic 
expedition of the " Michael Sars " that the subtropical Ceratium 
platycorne, both of the posterior horns of which are developed 
ordinarily into flat wing-like suspension-organs, changed gradu- 
ally into a form with cylindrical horns belonging to the Gulf 
Stream in the Norwegian Sea, that I 
had myself previously described under 
the name of Ceratium compresstnn (see 
Fig. 228). 

Discontinuous variations have been 
found as well as continuous ones in the 
species of Ceratitim. Lohmann has Lohmann. 
shown that the ordinary Baltic form, 
C. tripos, can set up an intermediate 
generation of a totally different type, 
much smaller and with short, straight 
horns, corresponding to the forms de- 
scribed under the name of C. lineatttm. 
Kofoid has met with similar variations 
in American species (see Fig. 229). The 
signification of these development forms 
has not yet been discovered. Jorgen- jcirgensen. 
sen, who has recently published a mono- 
graph on the genus, is inclined to 
regard them as degenerate forms that 
have been produced under abnormal 
conditions of existence. It seems to 
me, however, more probable that these 

Only one cell IV. I shows the charac- , , i -i n 1 

ter of the type, the others (I. -III.) Small, extrcmely mobile, cells are normal 
belonging to the type of pm//««/ formations, which have a definite func- 

cali forii tense {^\"). (Kotoid. ) . - . , . _ , - 

tion to perform m the imperfectly known 
development - cycle of the species of Ceratium. It is still 
questionable whether peridinese propagate sexually, even though 
Zederbauer claims to have discovered sexual propagation in the Zederbauer. 
ordinary fresh-water form [Cei^atium hirundinella\ But, a 
priori, it is quite possible that the above described inter- 
mediate generation may be a sex-generation. Just as little as 
these "mutations" do we understand the significance of the 
gemmation which Apstein has lately described in Ceratium Apstein. 
tripos, nor do we know what conditions of existence cause 
gemmation instead of normal cell-division. 

Another important genus with many species, Peridirmtm, Peridinium. 




Fig. 229. 
Ch.vin of Ceratium tripos. 



¥. 



326 DEPTHS OF THE OCEAN 

differs in various ways from Ceratittm, though systematically it 
is not far removed from it. The cells, however, lack the brown 
pigment-granules (at any rate, this is so in the case of marine 
species), and the contents are pale yellow or pink. It is im- 
probable that it can assimilate carbonic acid, and it must there- 
fore somehow or other obtain organic matter for its nourish- 
ment. Unfortunately nothing is known regarding its mode of 
nourishment. These forms do not live so close to the surface 
as the species of Ceratiuvi, but all observations made hitherto 
indicate that they belong exclusively to parts of the sea to 
which light penetrates, where they exist along with the other 
algae. Their cells are much grosser than 
those of the species of Ceratmm, and the 
projections corresponding to the horns of 
Ceratiuin are short or entirely wanting. 
The membrane-curtains along the furrows 
are only slightly developed, and the cell 
itself is much more globular. The species 
of Peridiniu77i, and some other genera 
{Goiiymilax, Goniodoina), have thus at 
best only imperfect suspension-organs, 
but the mobility of the cells makes up for 
„ this deficiency. The way they are formed. 

Fig. 230. • y-rr [ u 

GoNYAULAx poLYGRAMMA. too, IS dinerent from what we notice m 
The cell-contents form a zoo- Ceratium. There is no proper cell - 

spore, shed out from the burst- ,. . , , , 11 1 • 

ing cell-wall (^1 2). (Schiitt.) Qivision, but the Cell changes its contents 
to one, two, or four naked spores, which 
are shed out from their original covering (see Fig. 230). Each 
spore afterwards gradually evolves a new cell-wall for itself, 
within which it develops as the wall expands, and bands, due to 
accession of growth, intervene between the laminae composing 
the structure. This has been demonstrated by Broch. The 
genus Peridinmiu includes a large number of species distributed 
throughout all the seas of the world, but the systematic arrange- 
ment of the species is extremely difficult, and has not so far 
been sufficiently investigated. A large amount of material has, 
however, been brought home by our expedition, and it is to be 
hoped that we shall now be able to ascertain the characteristics 
to which we can ascribe chief systematic importance. A good 
beginning, at all events, has been made by Kofoid and Broch. 

The family Dinophysidae possesses the most remarkable 
suspension-organs of all the peridineae. In northern waters 
its representatives are limited to a number of species all 




PELAGIC PLANT LIFE 



327 



resembling one another and all belonging to the same genus, 
namely, Dinophysis. The commonest of these, D. acuta (see Dinophyi 
Fig, 231), has a small tongue-shaped mobile cell without particu- 
larly well-defined suspension -organs. Its ring- furrow and 
protecting borders are situated at 
the forepart of the cell, and its 
sides are flattened to such an 
extent that the ventral furrow is 
on quite a sharp edge, where it is 
guarded by two membrane-cur- 
tains. The cell is formed by 
division, which takes place per- 
pendicularly to the ring- furrow. 
Within the cell are several brown 
chromatophores, showing that 
Dinophysis is one of the peri- 
dineae that assimilates carbonic 
acid. 

In warmer waters this funda- 




FiG. 2-^1.— Dinophysis acuta. 

From the west coast of Norway (-?--)• 

(Jorgensen. ) 



Fig. 232. 

a, Amphisolenia globosa ; 

b, Amphisolenia tenella, n.sp. {^\^ 



mental type shows strange variations. Amphisolenia (see Fig. Amphisolenia. 

232) has its w^hole cell drawn out to a hair, the ring-furrow is 

situated right in front on a little head, and the ventral furrow 

is on a narrow neck with slightly developed membrane-curtains 

like a kind of collar. The cell widens out slightly like a spindle 

in the middle, and posteriorly ends in a globular knob by way 

of balance, or in two or three ramifications. Triposolenia (see Triposoienia. 

Fig. 233) has a similar anterior structure, but the middle part is 



,28 



DEPTHS OF THE OCEAN 



more expanded, and the two bent legs which issue from it do 
not lie in quite the same plane, with the result that in sinking 
the cell describes very long sweeps. Besides these we get other 
genera, where the suspension-organs are not formed by the 

Oniithocercus. Cell itself, but by the membrane-curtains. In Ornithocei^cus 
splendid2is the ring - borders are transformed into an un- 
mistakable parachute, stiffened by a network of ribs (see Fig. 
234, a), and in some species, such as O. steinii and O. qtiadratus, 
the membrane-curtains are ventrally or posteriorly most highly 
developed (see Fig. 234, b). The 
majority of these more different- 
iated forms are without chromato- 
phores, but some of them by way 
of compensation are in almost 
constant symbiosis with small 
brown naked cells that are prob- 
ably immobile stages of brown 
flagellates. In Oriiithocercus 
7nagniJicuSy for instance, we find 
these naked cells in the space 
between the ring-borders, where 
they are well protected against 
harm (see Fig. 235) ; and in a 
series of species of the remarkable 

Histioneis. tropical genus Histioneis this 
home of theirs is expanded pos- 
teriorly into a cavity which may 
be of considerable dimensions 
as compared with the cell. In 

Citharistes. Citkaristes the cavity takes up 

the whole of what should be the central portion of the cell, and 
the cell-membranes are merely the outer skin like the shell of 
a guitar (see Fig. 236). 

A remarkable subdivision of the peridinese is the genus 

Pyrocystis. Pyvocystis, which Sir John Murray discovered during the 
"Challenger" Expedition. Pyrocystis noctihica (see Fig. 237) has 
large globular cells with a thin layer of protoplasm along the 
cell-wall, a denser mass round the nucleus, and brown pigment 
granules. Murray stated that the genus was abundant in all 
tropical and subtropical waters, where the temperature exceeds 
68° F., and where the salinity at the surface is not lowered 
by the presence of coast or river water. The cells have 
no organs of motion, but belong to the most brilliantly phos- 




■Triposolenia b/cora'is m^). 
(Kofoid.) 



PELAGIC PLANT LIFE 



329 



phorescent of the algae ; biologically they are of the "bladder- 
type." Other species are elongated (see Fig. 238), straight, 
or crescent-shaped. Within their cells they form big zoo- 




^r^f -rr T^ 




Fig. 234. 
a, Ornithocercus splendidus [-\-) ; b, Ornithocercus steinii (^-f^). (G. Murray and Whitting. ) 

Spores, built up exactly like the peridinese type with a ring- 
furrow and two cilia, for which reason the species of Pyrocystis 
are included among the peridinese, though their fully-developed 
cells are really of a quite different type. 






'■'"'%. 



M^mK 



330 DEPTHS OF THE OCEAN 

Besides these highly-organised forms, which I have given 
as instances, the peridineae include many with a far more simple 
structure. There are, especially in the samples collected by 
means of the centrifuge, numerous series 
of small forms, both coloured and colour- 
less, and often with very poorly de- 
veloped cell -walls. These, too, have 
already got or will shortly be given 
names, although many of them are prob- 
ably nothing more than development- 
stages of the larger forms. We can 
recognise the whole series by their char- 
acteristic ring-furrow, so that we are 
seldom left in doubt as to the classifica- 
tion of even the simplest types. Still a 
good deal remains to be done before we 
With brown flagellate cells in the cau claim a thorough acquaintance with 
^4^0^ ^""jr^" ^f'"^"'^"'''^*'" their development-history and systematic 
' ' '^ " ' arrangement. 

The third series of pelagic algae consists of brown flagellates, 
the chief place amongst which is occupied by calcareous 
flagellates or coccolithophoridse (see Fig. 239). Their cells are 




Fig. 235 

Ornithocercus magnif/ccs. 



>:^^/^: 





Fig. 236. 

a, Citharistes apsteini (^-) ; b, Histioneis gubernaiis {-\^), both with cells of 

brown flagellates in special chambers. (Schiitt. ) 

generally nearly globular, with one or two cilia and one or two 
brown chromatophores, and they are protected by remarkable 
shields of lime which unite into a complete defensive covering, 
though sometimes with a big opening in front. The cell does not 



PELAGIC PLANT LIFE 



331 



always occupy the whole internal space, but lies sometimes, as 
it were, at the bottom of a hollow hemisphere or up at the 
mouth-opening in a conical sac. The shields of lime can be 
dissolved by the weakest acids, and the cell then remains as 
an insignificant mass with undefined boundaries. Still, these 
shields are very characteristic, and have been found in such 
enormous quantities in the deposits on the ocean-bottom that 
they aroused the attention of scientists 
long before the algae themselves were 
known. The commonest forms {Cocco- 
lithophora, Pontosphcera) have an almost 
globular lime-covering, and are there- 
fore without special suspension-organs, 
though their surface is big in proportion 
to their bulk, if we consider their extra- 
ordinarily minute dimensions (5 to 20 \x 




if' 




Fig. zyj.—PvKOCYSTis noctilvca. (From Chun.) 



Fig. 238. 
pvrocvstis fusiform is (^j"). 

( From ' ' Challenger " Narrative. ) 



in diameter). But in forms like Rhabdosphcsra the calcareous 
shields have each a more or less large spike in the middle. In 
Discosph(^ra we find trumpet-shaped spines, in Scyphosplicsra 
barrel-shaped outgrowths, and during the "Michael Sars" Expedi- 
tion I succeeded in discovering even stranger forms. Ophiaster 
has a tuft of slightly spiral flexible calcareous filaments. 
Michaelsarsia carries in the front of its cell a sort of parachute 
or pappus of hollow jointed calcareous tubes arranged in a 




332 DEPTHS OF THE OCEAN 

wreath. Calciosolenia 7nurrayi resembles, to some extent, the 
shape and structure of Rhizosolenia, as the shields of lime are 
not rounded like those of most other species, but rhomboid and 
spirally bent, so that between them they form a cylindrical tube, 
pointed at either end, and furnished at the extremities with one 
or two fine calcareous setae. 

Notwithstanding their small dimensions these microscopic 

calcareous algae oc- 
C\^ \ I cupy a very important 
place in the economy 
of the sea, and their 
shields of lime, which 
may be met with in 
geological deposits 
dating from as far 
back as the Cambrian 
period, show that they 
have retained their 
shape practically un- 
altered through im- 
measurable ages. 
They are almost en- 
tirely oceanic, and 
mostly belong to the 
warmer seas. In 
coastal waters, where 
the salinity is lower, 
they are scarcer, but 
the commone st 
species, the little 
Pontosphcera ktixleyi, 
has been found even 
in the Baltic, and 
there were such immense quantities of it in the inner parts of 
the Christiania fjord during the hot summer of 191 1 (5 to 6 
million cells per litre) that the calcareous cells with their strong 
refraction gave the sea quite a milky appearance. 

The naked flagellates in the sea are still only imperfectly 
known, though, no doubt, the part they play is quite a consider- 
able one. In coastal waters they occur sometimes in such 
abundance that we have actually been able, even with our present 
defective methods, to discover and describe a number of species. 
In the open sea we are best acquainted with the passive and 



Fig. 239. 



-Different Types of Coccolithophorid.^i. 

Mickaeharsia elegans ; 2, Ophiaster formosi/s ; 3, Rhabdo 
spheera claviger ; 4, Syracosphcsra frolongata ; 5 
leriia murrayi ; 6, 7, Coccolithophora leptopora ; 
sphcera ktixleyi. 



Calcioso- 
, Portio- 



PELAGIC PLANT LIFE 



usually almost globular development-stages that live in symbiosis 
with various animals, and, in particular, with radiolaria. Of 
these radiolaria, which would seem from Brandt's investigations Brandt. 
to derive special benefit from the assimilation-products of algae, 
we occasionally get the colony-forming species and Acantho- 
metridae in such myriads among the surface-layers, that they 
contribute a very large proportion of the organic substance 
produced. I have previously stated that the brown algae also 
regularly associate with a whole series of Dinophysidae. Another 
family of brown flagellates includes the species of Phceocystis, 
which form large colonies visible to the naked eye, and enveloped 
in a loose slime (see Fig. 240). In cold waters these have actually 

been known to occur in sufficient 
numbers to stop up the mieshes of 
silk nets, and render them ineffec- 
tive in working.^ 

It is the brown algae that, 
properly speaking, characterise the 
plant-world of the sea. Still there 
are two other important series, the 
cyanophycese and the chloro- 
phyceae, which preponderate in 
fresh water, and are, no doubt, re- 
presented in salt water also, though 
by only a few species. 

The Cyanophyceae are chiefly Cyanophyce^. 
to be met with in warmer seas, if 
we except the brackish water forms 
that may be found along the coasts 
of North Europe in the height of the summer. The genus 
T7Hchodesmmm appears as clusters of threads, composed of Tnchodes- 
brownish-yellow or red cells, which are either parallel to one """'"' 
another, or twisted together, or matted and tangled, and 
radiating in all directions. Wille, who described these forms wnie. 
collected by the German Plankton Expedition in 1889, showed 
that all the types may belong to the same species, Tricho- 
desinium thiebaulti, under different development-forms. The 
clusters may be seen sometimes when they collect near the 
surface in calm weather, and resemble yellowish-brown snow- 
flakes. Like the different kinds of fresh-water forms, they can 
raise themselves in the water by means of vacuoles that, accord- 
ing to Klebahn, contain air. When abundant they sometimes Kiebahn 

^ See Summary of Results Chall. Exp., p. 499, 1895. 




Fig. 2^0.— PiiyEOCYSTis povcheti. 
(Lagerheim.) 



134 



DEPTHS OF THE OCEAN 



cover the surface in one unbroken layer, a phenomenon which 

CErsted. CErsted observed in 1849, and which led him even then to 

look upon microscopic plants as the basis of production in the 
sea. Besides the species of TricJiodesmi2Lm we have another 

Katapiymcne. gcuus, Katagjty 7716116, with Spiral series of cells in sheaths of 
slime. Mention must also be made of 

Riciieiia. the remarkable little alga, Richelia 
iiiti^acellulai'is, described by Jobs. 

Schmidt. Schmidt, which lives in cells belonging 
to various species of Rhizosole7iia (see 
Fig. 241). These diatoms appear to 
have no difficulty in accommodating 
their guest, which apparently repro- 
duces itself within the cell, and is thus 
transferred to new generations of the 
hospitable plant. The riddle is, how 
did it originally manage to get in ? 
Most likely this happened at a stage 
when the Rhizosoleiiia had not yet 
developed the silicated cell-wall of the 
hermetically sealed chamber with which 
we are acquainted. 

The green colour which predomin- 
ates in plants on land is practically 
only to be found at sea in the globular 

Haiospiuzra. HalospIicE7'a vi7'idis (see Fig. 241). 

Schmitz. This has been described by Schmitz 
from Naples, where the people call it 
" punti verdi," that is to say, green 
spots. It is or may be lighter than 
sea-water, so that it floats quite close 
to the surface. On the other hand, 
Hensen's expedition found it at pro- 
found depths, even at 1000 metres, 
away down near the limit of the pene- 
tration of sunlight, but if this denotes anything in its life- 
history, it must be at any rate in a state of resting. HalospJi(E7'a 
is reproduced by zoospores, though we do not know how they 
proceed to form the small globular cells that little by little 
grow up to the normal size. The cell-wall is so firm and 
thick that its outer part is burst at last in the course of 
growth and discarded, and the inner elastic parts are thus 

cieve. enabled to expand. Cleve has also observed thick -walled 




Y\G. 241. — Chains of Richelia 

INTRACELLULARIS WITHIN THE 
CELLS OF RHIZOSOLENIA STVLI- 

FORMIS. (Karsten.) 



PELAGIC PLANT LIFE 335 

resting - cells. Halosphcsra occurs over the whole Atlantic 
Ocean, and follows the Gulf Stream to its farthest ramifica- 
tions in the north near the coasts of Norway and Spitzbergen. 
In the North Sea there are quantities, especially in the winter, 
and they form their zoospores in May, and thereby commence 
their new generation. 

Just as HalosphcEra differs from all the rest of the pelagic 
algae in having a pure green colour, so, too, it has its own special 
mode of reproduction. The other forms, whose development- 
history we know, are reproduced by division, and this goes on 
incessantly, the rate of increase depending upon different 
conditions of existence. Halosphcera does not undergo division, 
but continues to grow for a comparatively lengthy period, and 
then finally transforms all its contents, 
as has just been stated, into a great 
number of zoospores. 

In addition to Halosphcera viridis 
there are one or two similar species 
that have been described, but they do 
not call for any particular discussion. 

In the foregoing I have sketched 
the most important types of pelagic 
algae and their biology, but the picture 
Fig. 2ifi.—HALospHMRA VIRIDIS, would not be complete if I omitted to 

™a1m?T''''^"'°''''''^''''" describe the drifting species of sea- Floating sea- 
weed. These do not really belong '''^^^^• 
to the open sea. They grow along the coasts in the littoral 
zone, and their gas - filled bladders assist them in main- 
taining their position whatever be the state of the tide. 
The violence of the waves finally tears them loose, and then 
these same gas-bladders keep them for a long time floating 
on the surface. These patches of-- seaweed are to be met 
with in every coastal sea, the chief kinds along the coasts 
of North Europe being Fuais vesicidosus and Ascophyllum 
nodosum, and in the Mediterranean species of Cystosira. 
They may also drift right out into oceanic waters, and in 
the Sargasso Sea we have an immense eddy where the 
patches of weed often collect in enormous quantities. The 
prevailing weed is Sargassuni baccifertivi, but one fre- 
quently gets patches of AscophyllMm nodosimi as well, the 
whole being derived from the coasts of Central America. 
The Sargasso weed is easily recognisable, owing to its 




136 



DEPTHS OF THE OCEAN 

side branches 



(see 



berry - like bladders on special small 

Fig- 243)- 

One cannot help being struck by the fact that the drifting 
Sargasso weeds are destitute of the ordinary organs of repro- 
duction. This seems to be invariably the case with attached 
algae that have been torn loose from their support. They con- 
tinue to grow vegetatively, but are deprived of all power of 
forming new reproduction organs, until they can attach them- 
selves afresh. The same holds good, too, with those strange 

broken-off masses of 
algae that one finds 
drifting about along 
the bottom in bays, the 
constant movement of 
the water-masses pre- 
venting them from 
attaching themselves 
to the soft mud or 
sand. 

The Sargasso 
weed continues to 
grow as it drifts, but 
the gas -bladders are 
not formed in the 
same proportion as 
on the ordinary 
branches, the result 
being that one finds 
newly detached 
patches close up to 
the surface, whereas 
the older patches with 
a greater specific 
weight have sunk lower down. These last have, moreover, 
thinner branches and a lighter olive-brown colour. Finally, 
the power of floating ceases altogether, and the patches sink 
into deep water and perish. Their disappearance is, however, 
quite imperceptible, since fresh patches of weed are constantly 
arriving from the coast. 

It is quite usual to find smaller algae fastened to the Sargasso 
weed, and there is, besides, a characteristic animal-life amidst its 
branches, but none of these organisms properly belong to 
the ocean, notwithstanding their being found there so invariably. 




Fig. 243. 



-Branch of Sargassum bacciferum. 
(From Kerner.) 



PELAGIC PLANT LIFE 337 

This is true also of the attached algae, which develop upon 
driftwood, vessels, and other large objects. They show that 
germs of littoral organisms abound in the open sea, and are far 
more numerous than our random samples would seem to 
indicate. In May 1904, when cruising in the Norwegian Sea, 
in lat. 67° N., where the bottlenose whales are annually shot, 
we came across some wadding from a whaler's gun drifting in 
the sea, the lower side of which was thickly overgrown with 
attached forms of littoral diatoms. 

Castracane, after examining the first big collection of pelagic Geographical 
diatoms from all the seas of the world made by the " Challenger " offhe^^gia'^c 
Expedition, came to the conclusion that there was no essential aigje. 
difference between the flora of the different areas. In this, 
no doubt, he was right to a certain extent, since many species 
are very widely distributed ; still a closer study has shown us 
that there are definite marine areas and conditions of existence 
in which they develop in vast numbers, whereas in other localities 
they occur perhaps in such small quantities that only their 
skeletons in the bottom-samples furnish evidence that they have 
actually been present. Besides, we often find that species with 
a wide distribution have different forms in the different areas, 
though we have not yet the means of deciding whether these 
forms diverge from the main type by virtue of hereditary 
characteristics, or whether they merge into one another through 
constant modifications. But in any case these forms are 
characteristic of the flora of a given locality, and any one 
who examines plankton-samples will become aware that it is 
nearly always possible to determine the area from which they 
have come. During the German Plankton Expedition under 
Hensen in 1889, Schiitt convinced himself that the different Schutt. 
currents had their characteristic flora, and he was at a loss 
to understand how it is that local boundaries of distribution 
can continue, seeing that the currents are ever carrying off the 
microscopic plant-life from one part of the ocean to another, 
and it might consequently be expected that all differences would 
be obliterated. 

Schutt has also given a good description of the character of 
the plant-life in different parts of the Atlantic, but the honour 
of being the first to systematically investigate the distribution of 
all the different species, and the influence exerted upon them 
by ocean currents, must be assigned to the Swedish biologist cieve. 
Cleve. A chemist by profession, he had for many years made a 

z 



33< 



DEPTHS OF THE OCEAN 



special study of diatoms before he commenced co-operating about 
1890 with the well-known hydrographers, Otto Pettersson 
and Gustaf Ekman. They commenced their labours in the 
Skagerrack, that remarkable little sea where so many different 
water-masses meet and pass each other ; and it very soon became 
clear that different currents might each possess synchronously its 
own particular flora, and therefore there was the possibility of 
ascertaining where the water-masses came from, by determining 
their flora.^ All that was requisite was to know the distribution 
of the different species in contiguous parts of the sea. The 
investigations were accordingly extended, and samples were 
collected by ordinary steamers in the North Sea, the Norwegian 
Sea, and the Northern Atlantic, in addition to the collections 
that were gradually formed chiefly through the efforts of 
Swedish, Norwegian, and Scottish scientific expeditions. 
Cleve also studied the annual changes in the plankton, and had 
weekly collections made at selected stations on the Swedish 
coast. The scope of his investigations was further enlarged, 
for his unique knowledge of forms enabled him to determine, 
not merely all pelagic plants, but also little by little, a whole 
series of animal-families which proved no less useful than the 
algse as " guiding forms " to determine the character and origin 
of the plankton. 

Cleve believed that he could distinguish a series of plankton- 
types characteristic of defined marine areas. Particular species 
were therefore assigned by him to one or other of these main 
types. But whereas outside the Skagerrack each of the plankton- 
types had its own characteristic distribution, within this sea the 
same types were found to predominate, each in its own character- 
istic season. From February to April there were the same 
species that we have learnt to connect with the coasts of Green- 
land and Spitzbergen in the Polar Sea, and from May to June 
there was a plankton resembling that of the Western Baltic. 
During the course of summer and autumn there were, first of all, 
species like those belonging to the southern part of the North 
Sea, and afterwards Atlantic and more northerly forms. Cleve 
was led to conclude that these changes in the Skagerrack were 
due to the fact that it is supplied during the course of the year 

1 " While passing through the Japan Stream the tow-net observations indicated water from 
two different sources. When in the colder streams there were very many more small diatoms, 
Noctilucce, and Hydromedusse than in the warmer streams, where the same pelagic animals that 
were obtained all the way from the Admiralty Islands prevailed. Many similar instances 
occurred during the cruise, where the approach to land or the presence of shore water was 
indicated by the contents of. the tow-nets" (Narrative of the Cruise, Chall. Exp., vol. i. 
p. 750, 1885 ; see also Summary of Results Chall. Exp., pp. 893 and 895, 1895). 



PELAGIC PLANT LIFE 339 

in regular rotation with water-masses from the marine areas 
to which these plankton-types belong. 

Subsequent investigations have shown that Cleve's view, 
which he endeavoured to apply even more widely, was pre- 
conceived. His eagerness to discover how far the distribution 
of particular species depended on sea currents, made him apt to 
forget that algae are living organisms which are incessantly in 
process of formation. Accordingly, when the conditions of 
existence in the flowing water-masses gradually alter, it is the 
new conditions of existence that decide the character of the 
flora, since the species best qualified to endure them will very 
soon get the upper hand over the others. When, therefore, in 
a sea like the Skagerrack we find northern and southern forms 
alternating during the course of the year, we are not compelled 
to assume that the flora is being periodically recruited from 
different areas. The periodic alterations in the conditions of 
existence, and particularly in temperature and sunlight, which 
in our latitudes follow the course of the seasons, sufficiently 
explain why at one time northerly species predominate and 
thrive in low temperatures, and why southern forms succeed 
them and benefit by the warmth which they find necessary for 
their proper development. Of course it is absolutely essential 
that germs should be present ready to develop whenever the 
conditions of existence become favourable. A certain proportion 
of these, no doubt, may be introduced by currents from else- 
where, but there is nothing to prevent them from remaining in 
a particular area, even though the water-masses are in constant 
motion. Recent hydrographical researches have shown us that 
eddies are far more common than was at one time believed. 
Even in areas where huge masses of water are constantly 
streaming in one direction, which one might naturally suppose 
would carry away with them all germs belonging to a local flora, 
these eddies act as a retaining factor, preventing any complete 
replacement till germs sufficient to maintain the local flora have 
been transferred to the supplanting water-masses. In coastal 
seas, moreover, many of the species are able to evolve resting 
bottom-stages, which lie waiting to reproduce the local flora, as 
soon as the conditions of existence are congenial. 

Still Cleve's investigations have been of great value, and 
his plankton-types provide us with a biological division of 
species which is yet in the main quite serviceable. All that 
we have to say by way of qualification is that Cleve looked 
upon his types as representing communities of species limited 



340 DEPTHS OF THE OCEAN chap. 

to definite marine areas, whereas in reality the areas of distri- 
bution of the different species encroach so upon each other, 
that a division of this kind is hardly practicable. This is true, 
not merely of the altering flora of ocean-currents, but also of 
the attached flora along the coasts and on land. Unless the 
areas are exceedingly remote from one another, the forms 
common to the areas usually exceed those peculiar to each 
area. Cleve's types, on the contrary, have no species in 
common, and therefore do not record the species in any 
definite area, but merely group them in accordance with their 
conditions of existence. If we adopt his principles we can 
certainly obtain a biological division of the species that is 
satisfactory in the main ; but when we come to details it will, 
in some cases, be difficult to decide whether a species is to be 
assigned to this or to that type. 

Biogeographically, the pelagic alga; may be divided, firstly 
according to the latitudes in which they are distributed, which 
is generally tantamount to saying according to their need of 
warmth and light, and secondly according to their occurrence 
along the coasts or in the open sea. This latter classification 
gives us the most distinct boundaries, and we will therefore 
consider it first. There is a whole series of species which 
unmistakably belong to coastal waters, and occur there in 
myriads at definite seasons of the year. Out in the ocean we 
do not find them, except when salinities or other physical 
properties indicate that they must have drifted from the coast. 
iiaeckei. These have been termed neritic on the suggestion of Haeckel. 
Opposed to them are the oceanic species, which belong to 
the ocean and float over profound depths, from which 
occasionally they are swept by the currents into coastal seas 
and there usually perish. 

Neritic It is possible to imagine various reasons why the neritic 

species. species keep in the vicinity of the coasts. Some may derive 

benefit from the low or fluctuating salinities, which enable them 
to outstrip the more easily affected forms. Others, perhaps, 
require the abundant supply of nourishment from the land 
in order to grow and multiply as fast as such organisms should 
do. There may be other species, again, whose development- 
history makes it necessary for them to remain on the bottom 
at one stage of their existence, like the hydroid medusae and 
all pelagic young-stages of littoral animals. Most of the neritic 
algae have a bottom-stage, in so far as they form resting-spores 



PELAGIC PLANT LIFE 341 

that sink to the bottom in the shallow coastal seas, where they Resting 
rest until conditions of development become favourable again, ^p^""^^- 
This has been observed by many naturalists since Schlitt first 
noticed in the Western Baltic that a species which begins to 
form resting- spores disappears shortly afterwards from the 
surface-layers. He showed, too, that the resting-spores sink 
down to the bottom, and, although their germination has not 
been carefully studied, we may be sure, all the same, that it 
does take place ; further, when we subsequently find the same 
species once more in abundance, we have every reason for 
surmising that the resting-spores on the bottom were the 
principal source from which these forms have been derived. 

Ability to form resting-spores must be of the utmost 
importance for the existence of the species in coastal waters. 
The chief difference between coastal seas and the ocean, so 
far as hydrographical conditions are concerned, lies in the 
extreme and rapid changes in such fundamental conditions 
of existence as salinity and temperature in coastal waters, 
Resting-spores, therefore, must be the means by which many 
species continue in coastal seas, notwithstanding the fact that 
there conditions of existence are only favourable for a limited 
portion of the year. The arctic diatoms, for instance, which 
are sometimes to be found in the plankton of the Skagerrack, 
are very easily affected by a rise in temperature, but their 
development takes place during the winter months from 
February to April, when the temperature is at its minimum. 
In the summer they are not to be seen, but their resting-spores 
are then most probably on the bottom. In the same way a 
whole series of warmth-loving species pass through the winter 
as resting-spores, and are to be found along our shores only 
in the warmest months of summer and autumn. 

The neritic species may often be met with a long way Neritk 
out at sea, still continuing to increase, though they are ^i^t°i"- 

• -y^ rir- 1 P^ ^^' 

seldom m any great quantity. One of the few mstances that 
I know of, where we regularly find an immense production of 
neritic diatoms in the open sea, is in the Gulf Stream north 
of Shetland and the Faroe Islands during May. I made this 
discovery as long ago as 1895, and it has often been confirmed 
since then during the international investigations. When the 
snows begin to melt in the spring, the surface-layers of water 
are carried far away out from the land, and the neritic algae are 
taken with them. I shall presently show that it just happens 
to be in the spring that conditions of nourishment favourable 



diatoms in the 



342 DEPTHS OF THE OCEAN 

to an abundant plant-life exist in the Northern Atlantic, and 
the somewhat exacting neritic species benefit accordingly. 
This explanation, at any rate, seems to me the most reason- 
able one. 

Another well-known instance is in the Polar Seas during 
the summer. Close to the melting polar ice, where it meets 
the warmer water- masses, a rich flora of neritic diatoms 
sometimes develops, while littoral species form a brown layer 
over the floes and broken lumps floating between them. 
Blessing, who took part in Nansen's expedition during 1893- 
1896, has given a good description of this latter phenomenon. 
We must look upon the Polar Seas as coastal waters in 
the biological sense. They have the extreme variations of 
temperature and salinity, and probably also the abundant 
supply of nourishment, that we would expect to find in a 
coastal sea. The resting-spores are enclosed in the ice, as 
I was able to show after examining the material collected 
by Nansen. 

In the warmer parts of the Atlantic there are neritic 
diatoms nearly everywhere, but never in any great quantity, 
except where rivers enter the sea in the tropical regions. As 
a rule, too, they are smaller and weaker in structure than 
those we meet with in coastal waters under similar conditions 
of temperature. The cell -walls are very often only slightly 
silicated, and the form itself is so indistinct that it is difficult 
to distinguish species, which in their properly developed 
condition have unmistakable characters. It is not easy to 
tell whether this degeneration is merely a sign of insufficient 
nourishment, or whether other causes are also responsible. 
Certainly in one case want of nourishment is not entirely to 
blame. Out in the water-masses of the Atlantic to the south 
of Iceland we get a community of neritic diatoms that occur 
especially in the spring and autumn. Most of them are species 
of Chcetoce7'as. The prevailing forms have been long ago 
determined, and are undoubtedly C. schilttii and C. /aciniosum. 
Still they are so dwarfed in structure, and so much the reverse 
of typical, that one might very well say that they were separate 
species (see Fig. 244). During this last expedition of ours we 
succeeded in finding this diatom-flora again, though in smaller 
quantities, in the Gulf Stream off the east coast of North 
America, so that it is practically certain that the neritic diatoms 
of the Atlantic south of Iceland are derived from the American 
coastal sea. As they are borne passively northwards towards 



PELAGIC PLANT LIFE 



143 



the shores of Iceland, they commence to develop at a great 
rate, with the result that the plankton in those parts frequently 
yields abundant though monotonously uniform samples of these 
degenerate forms. The altered conditions of existence, which 
obviously must have supervened, have thus resulted in an 
extensive production of algse, though without investing them 
with their normal robust appearance. The strings of cells 
are of much smaller diameter than usual, so that the formation 
of auxospores cannot have taken place at the stage that is ^^^^^^^^^ 
usual elsewhere. Wesenberg-Lund has told us that pelagic Lund. 




Fig. 244. 
la, ChcBtoceras laciniosum : ifi, forma pela^ica ; 2a, C. schiittii : zb, forma oceanica. 



fresh - water diatoms, such as Asterionella gj'-acillinia and 
Fragilaria crotonensis, keep on reducing their dimensions in 
the Danish lakes for months, sometimes even for over a 
year, and then suddenly return to their maximum measure- 
ments, and that this is undoubtedly due to the formation of 
auxospores. All are not, however, affected alike by such a 
change, and the species occur thereafter in two different sizes, 
making it necessary to express the measurements of their 
cell-dimensions by means of divergent curves. This goes on 
uninterruptedly, moreover, and the smallest forms diminish 
and seem to degenerate more and more, until in Wesenberg- 
Lund's opinion they lose all power of regaining their normal 



344 DEPTHS OF THE OCEAN 

dimensions and of reproducing their kind. The degenerate 
forms of neritic diatoms met with in the open sea appear to 
me to lack the stimulus which in some unknown manner leads 
to the formation of auxospores ; consequently their ultimate 
extinction is only a matter of time, even though they may 
continue reproduction through a whole succession of genera- 
tions. This is, of course, merely an unsupported surmise, for 
the few random investigations we have hitherto made do not 
afford sufficient material to settle questions of this nature at 
all definitely ; but my idea is that the hypothetical views of an 
author are of more value than the enumeration of solitary facts 
that have no apparent connection. 
Resting-spores When the neritic diatoms evolve resting-spores out in the 
sea^^^°^^^" open sea, which occurrence w^e have been able to observe on 
more than one occasion, it might be supposed that the spores 
would be destroyed after sinking down to profound depths. 
This is not, however, necessarily always the case, since they 
appear to sink slowly, and remain within the region of light 
for weeks if not for months. The spores after leaving their 
cells are so minute that they are rarely caught in silk nets, 
so that little has been done as yet to throw light upon this 
question. But now that we have adopted the centrifuge- 
method it is possible to collect them, and we discovered numbers 
of resting-spores of species of Chcstoceras in our centrifuge- 
samples from the Atlantic. In a litre of sea-water from Station 
87 (lat. 46° 48' N., long. 2f 46' W.), from a depth of 100 
metres, I secured altogether. 1 160 resting-spores belonging to 
three different species of ChcBtoceras, though the forms them- 
selves were not present at that time in a vegetative state either 
in the surface-layers or deeper down. Most probably what we 
got were representatives from the last remnants of the diatom- 
masses that throng the surface-layers there during the spring. 
Distribution. Nentic species include a very large number of diatoms — 

a class by far the most characteristic in coastal seas. In the 
majority of these neritic diatoms we have now been able to 
prove the existence of resting-spores. The peridinece, on 
the other hand, are mainly oceanic, especially the species of 
Ceratmni. One of the best-known neritic peridineae is the 
comparatively low species Prorocentrimi micans ; but there are 
probably, too, whole series of small forms, as yet imperfectly 
known, which prefer the neighbourhood of the coasts. The 
coccolithophoridse, again, are undoubtedly oceanic, whereas 
most of the naked flagellates are most likely domiciled in 



PELAGIC PLANT LIFE 345 

shallower waters, Halosphara is oceanic, and so also are the 
species of Trichodesmium ; but there are several blue-green 
species that are brackish-water forms, and they must of course 
be accounted neritic [Anabcsna baltica, Nodtilaria spumigena, 
Aphanizoinenon flos-aqiics). 

Several of the neritic algai practically only occur locally. 
Detonida cystifera, for instance, appears in the Limfjord in 
Denmark and along the south coast of Norway, while Litho- 
desinium juidulatuniy Coscinodiscus granii.Navicula memb^^anacea, 
and Streptotheca thamensis belong to the English Channel and 
to the southern portion of the North Sea. I could mention 
additional examples, but the greater number of them are far 
more widely distributed. It has been found possible to allocate 
all the species along the coasts of the Northern Atlantic to 
three comprehensive main groups, namely, the arctic, temperate, 
and tropical. This is perhaps rather an arbitrary arrangement, 
as these groups encroach to a very great extent upon one 
another ; so that we get northern forms a long way south in 
the winter, and in the autumn the southern forms extend 
northwards. Further researches, too, might result in a stricter 
classification, while it is known that there are species which, 
biologically speaking, unite the groups, and might with equal 
reason be assigned to the one or to the other. 

(i) Arctic neritic species are mainly those which Cleve termed Sira- Arctic neritic 
plankton, and consist principally of diatoms. The characteristic forms species. 
are the species of Thalassiosira from which this name was derived. 
They are composed of long strings of short cylindrical cells united by 
a central thread of slime. Thalassiosira hyalina has its southernmost 
limit off the north of Norway, while T. gravida and T. nordenskioldii 
occur in winter as far south as Central Europe. A series of species 
belonging to the genera Fragilaria, Achnantes, Navicula and Amphiprora 
are also distinctly arctic forms, and are characterised by having their 
cells bound together like ribbons. These include Fragilaria oceanica, 
F. islandica and F. cylindrus, Achnantes tceniata, Navicula septentrionalis, 
N. vanJwffenii and A", granii, and Amphiprora liyperborea. The 
usually predominant genus Chcetoceras is only represented by two 
purely arctic species, namely, Chcetoceras furcellatum and C. mitra. 
We must likewise add the well-known Biddulphia aurita. Besides 
these diatoms, there are the peridinean Gonyaulax triacatttha, and the 
brown flagellate PhcEocystis poucheti, with its naked cells in large slimy 
round or lobate colonies. 

(2) Temperate neritic species are even more numerous. The warmth- ^J^^I^Pf^'^^^^g 
loving species fall under Cleve's designation of Didymus-plankton, with "*-» ^c species. 
CJicBtoceras didymum as the most characteristic form. It is, however, a 
better arrangement, perhaps, to associate with them a series of other 
species with a sUghtly more northerly character, that cannot be really 



346 



DEPTHS OF THE OCEAN 



called arctic. Here, too, diatoms predominate, and CJicetoceras takes 

first place. The commonest forms include : — 

{a) Northerly : Ch(£toceras teres, C. constrictuin, C. diadema, C. debile, 

C. crinitum, C. pseudocrinitum, C. scolopendra, C. sociale, C. simile, 

Rhizosolenia setigera, TJialassiosira decipiens, CosciJiosira polychorda, 

Leptocylindriis daniciis. 

ip) Southerly : ChcBtoceras weissflogii, C. contortiim, C. didymuvi, 

C. laciniosmn, C. schnitii, C. curvisetum, C. cinctum, C. afiastoinosans, 

C. radians, Laiideria anmdata, Ceratatdina bergonii, Biddidphia mobi- 

liensis and B. regia, Eucampia zodiacus, Dityluni brightzvellii, Guinardia 

fiaccida, Asterionella japonica, the peridinean Prorocentruvi inicans, and 

the brown flagellate Phceocystis globosa. 
Tropical (3) Tropical neritic species have had far less study devoted to them ; 

neritic species, g^ii} ^yg j^^y denote by this term a whole series of species that have 

their northernmost limit on the coasts of the Mediterranean. Of these 

we may mention : — 

Chcetoceras furca, C. diversum, C. femur, Hemiaulus hauckii and 

H. heibergii, Detonula scJirdderi, Asterionella notata, Rhizosolenia 

cylindrus. 

The neritic flora off the coasts of the Atlantic in the southern 
hemisphere has also been comparatively little studied as yet. 
Still we are justified in saying that the neritic diatoms of the 
antarctic, from the ice barrier northwards, differ in the main 
from species belonging to the northern hemisphere. The 
difference indeed is so great, that hardly a single species is 
common to both arctic and antarctic waters. The investiga- 
tions of Cleve, Karsten, and Van Heurck show that the 
following neritic diatoms may be considered characteristic of 
the antarctic : — -ChcEtoceras radiculum, Moelleria a^itarctica, 
Eucampia balatistitun, jFi'agilaria antardica, Thalassiosira 
anlarclica, and probably several others whose biology is as yet 
only slightly known. 



Neritic dia- 
toms in the 
Antarctic. 



Oceanic 
species. 



Oceanic plankton algai are much more widely distributed 
than neritic algae, and it would almost seem from our material 
that each species may be met with in all the seas of the world, 
wherever there are favourable conditions of existence. The 
diatoms are apt to occur irregularly. Sometimes we find 
enormous quantities of them, and at other times they may 
be so scarce that it is difficult to detect them. The peri- 
dinese are more evenly distributed, and this is true especially 
of the species of Ceraliuni, which are fairly abundant and hardly 
ever absent from oceanic-samples, unless perhaps in arctic 
waters. They may well be used as guiding forms to express 
the character of the plankton. It is possible that the different 



PELAGIC PLANT LIFE 347 

species and varieties of the genera Peridinium and Gonyaulax 
might be employed with equal advantage, but they are more 
difficult to determine, and so little studied as yet that the 
determinations of Hensen and Karsten are unserviceable. 
Owing to so little being known about their distribution, I have 
decided to ignore them for the present. 

The oceanic species may also be divided into three main 
groups : — 

(i) Arctic forms, corresponding to Cleve's Tricho-plankton and Arctic oceanic 
Chaeto-plankton. Most of them occur also in antarctic waters. species. 

Diatoms : Thalassiothrix longisshna, Coscinodiscus subbulliens, CJiceto- 
ceras criopJnlum, C. boreale, C. convolutum, C. atlanticum, C. decipiens, 
Rhizosolenia hebetata {seuiispina), Nitzschia seriata. 

Peridineae : Ceratimn arcticum, C. longipes, DinopJiysis gramdata. 

(2) Temperate- Atlantic forms, corresponding to Cleve's Styli-plankton Temperate 
and Tripos-plankton. The latter of these two designations comprises a oceanic 
small community of species, which are less exacting as regards salinity, *P^"^^- 
and are therefore produced in quantities along the coasts of North 
Europe. 

Diatoms : Rhizosolenia styliformis, R. acuminata, R. alata, Coscino- 
discus radiatus, C. centralis, C. stellaris, Chcetoceras densum, C. dichata, 
Corethron criophilum, Dactyliosolen antarcticus, Thalassiosira subtilis, 
Coscinosira cestrupi, Asteromphalus Jieptactis, Bacteriastrum delicatulu^n, 

B. elongatum. 

Peridineae : Ceratium tripos, C. bucephalum, C. azoricum, C. niacroceros, 

C. interjuedium, C. lamellicorne, C. reticulatum, C. fusus, C. furca, 

C. lineatuni, Dinophysis acuta, D. hastata, D. hommiculus. 

Coccolithophoridae : Coccolithophora pelagica, PontospJicsra Jiuxleyi. 
Chlorophyceae : HalospJicsra viridis. 

(3) Tropical-Atlantic forms, corresponding to Cleve's Desmo-plankton, Tropical 
and comprising a series of species, especially peridineae and coccolitho- oceanic 
phorids. Cleve's guiding form is the blue-green alga Trichodesmium 
tJiiebaultii. The following are some of the commonest : — 

Diatoms : Coscinodiscus rex, Planktoniella sol, Gossleriella tropica (see 
Fig. 245), Rhizosolenia castracanei, Chcetoceras coarctatum, Asterolampra 
marylandica, A. rotula. 

Peridineae : species of Ceratium of all groups {prcelongum, cephalotum, 
gravidum, cajidelabrum, pennatum, extensuvi, palmatum, massiliense, 
carriense, and several others), species of Oxytoxuvi and Podolampas, 
Ceratocoiys horrida, species of Phalacroma, Dinophysis schiittii and 

D. uracantJia, species of Amphisoletiia and Ty-iposolenia, Ornithocercus 
magnificus, O. quadratus, O. steinii and O. splejididus, Pyrocystis 
noctiluca and P. fusiformis. 

Coccolithophoridae : Coccolithophora leptopora, species of Syracosphcera, 
Calciosolenia murrayi, Michaelsarsia elegans, and many others. 

The boundaries of the areas populated by these communities 
of species are as variable as the limits of distribution for the 



348 



DEPTHS OF THE OCEAN 



species themselves. Our investigations at different seasons, 
both in coastal waters and in the North Atlantic, have shown 
us that the flora of each locality is constantly changing. One 
species succeeds another as month follows month, and different 
societies predominate in the same locality at different seasons. 

Along the west coast of Norway, for instance, we find a 
flora during the winter, from December to February, scanty in 
numbers, but consisting of many species, and mainly composed 
of true Atlantic forms (Styli-plankton), which reach their northern- 
most limits in the dark months of the year. About March or 
April the temperature attains its minimum, and great quantities 





Fig. 245. 
a, PlanktoTiiella sol, and b, Gossleriella tropica, from the Atlantic. (Schiitt. ) 



of diatoms are then produced, which are mainly arctic. Some- 
times these are almost entirely neritic, and sometimes there is a 
considerable addition of oceanic species. As often as not it 
is the species of Thalassiosira and Coscinodiscus which first 
appear, and then comes Chcetoceras, C. debile being usually the 
form found on the west coast, C. constiHctum preferring the 
Skagerrack. In May the predominant form is generally 
Leptocylindrus daniciis. We next get a period in June when 
the prevailing forms are oceanic, Ceratimn longipes at that time 
attaining its maximum development and characterising the 
flora. In August the warmth-loving peridineae begin to be 
more and more numerous, Ceratuim fusus, C. furca, and 
C. tripos being then much in evidence, and continuing to increase 
until October. Finally, in November we get a comparatively 



PELAGIC PLANT LIFE 349 

large amount of southern neritic species (Didymus-plankton), 
made up to a great extent of forms of distinctly foreign origin. 
As the dark months of winter approach, however, their numbers 
rapidly decline. 

In the open sea, too, our investigations appear to indicate Flora of the 
that the southern forms reach farthest north in the autumn, say °pensea. 
about November, while during the months of spring, from 
April to May, northern forms extend very far south. We have 
not as yet made investigations at different seasons in the tropical 
parts of the Atlantic ; consequently we cannot say whether there 
is an annual cycle of plant-development in a region where the 
conditions of existence seem to vary so little. It would be an 
excellent thing if researches of this nature could be undertaken. 

Supposing that the ocean -currents do exercise a direct Ocean- 
influence upon the character of the plankton in the tropics, it is J^hrpSnkton 
fair to imagine that it must be in the direction of periodicity. 
Lohmann has put forward the suggestion that the changes in 
pelagic animal life near the coasts of South Europe are connected 
with a cyclic movement of the water-masses. When these 
reach their northernmost point the conditions of existence will 
affect the organisms, so that the water-masses that pass through 
this region in the winter are likely to have a different fauna 
from that of the water passing through in summer. Elsewhere 
it is very difficult to tell what changes in the plankton are 
due to the direct influence of ocean-currents, and what changes 
are the result of altered conditions of existence partly due 
to ocean -currents and partly to other causes. It has often 
been observed, not only by Cleve and Hensen, but also 
during previous researches made by the " Michael Sars " and 
during the "Challenger" and " Valdivia " Expeditions, that the 
plankton changes its character the moment one passes the 
boundary between two currents. Thus an examination of the 
plankton may serve as a check on purely hydrographical 
investigations, which aim at ascertaining the boundaries of 
currents by means of observations of their temperatures and 
salinities. Perhaps the best guiding forms are the species of 
Ceratiwn, and strangely enough it is very often the species 
that systematically are the nearest related, which replace each 
other as we pass from one area to another. Many of them 
are so closely related that it is only for the sake of con- 
venience that we regard them as distinct species, and there 
is always the possibility that they may be able to pass directly 
from one form into the other, even if we cannot actually prove 



350 



DEPTHS OF THE OCEAN 



that they do so. There is a series of closely related species, 
for instance, grouped round Ceratiuvi macroceros. Ceratium 
arcticum is the farthest outpost in the direction of the polar 
sea, and shows the greatest variation. Its three horns are 
extremely divergent ; the centre one, which points forward, 
is slightly bent, and so also are the other two. Near the 
southern limit of the species there are more and more instances, 
in a series of transition forms, where the two posterior horns 
bend forward, till we get to Ceratium longipes, the characteristic 
form of the Norwegian Sea and North Sea during the first half 




Fig. 246. — Species of Ceratium belonging to the type of C. macroceros, 
northern species. 

a, C. arcticum; b, C. longipes ; c, C. macroceros ; d, C. infermediitm (-J-). (Jorgensen.) 

of summer. In this case, the posterior horns are bent quite 
forward, so that their extremities are parallel with the frontal 
horn. In the Gulf Stream we get C. intei'-niedium, which has a 
straight frontal horn, like the other members of this type, and 
all three of its horns are much longer and more slender than 
those of the two northern species. At the eastern limit, where 
fresh water from the Baltic and the coasts of North Europe 
reduces the salinity, and where, too, the high summer temperatures 
diminish the viscosity of the surface-layers, there is a species 
with an even better suspension-apparatus, namely C. macroceros 
(see Fig. 246). Its frontal horn is particularly long and thin, 
and the posterior horns first bend a little backwards, and then 



PELAGIC PLANT LIFE 



351 



sweep round to the front, sometimes in a direction parallel to 
the frontal horn, and sometimes with a moderate amount of 
divergence. We have already mentioned that C. ardicum and 
C. longipes belong to the Tricho-plankton and that C. inter- 
medium and C. macrocej^os are Styli-plankton. We have finally 
a whole series of variations belonging to the tropical Desmo- 
plankton, namely C. vultur, C. paviliardii, C. trickoceros, and 
C. tenue, which we reproduce from Jorgensen's excellent mono- 
graph (see Fig. ^^ ^, 
247), and many 
others. They 
illustrate the dif- 
ferent tendencies 
to variation. In 
similar fashion 
there are series of 
variations which 
group themselves 
round the other 
main types of the 
genus. 

Guiding forms 
like these are of 
very great assist- 
ance in defining 
the boundaries of 
adjacent currents 
which have a 
different biological 
character. But 
we need to exer- 
cise the utmost 
care in drawing 
conclusions as to 
the origin of ocean-currents from the composition of their 
pelagic flora, and it must not by any means be taken for 
granted that areas where the same species occur are neces- 
sarily united by a continuous stream connection. We have 
repeatedly made discoveries which go to indicate that most 
plankton-species of any consequence are to be found scattered 
about here and there outside their proper domain, so that 
these stray individuals might easily originate an abundant 
flora whenever conditions of existence became favourable. 




Fig. 247.— Species of Ceratium belonging to the type 
of c. macroceros, tropical species. 

a, C. paviliardii (\*-) ; b, C. trickoceros (-\4) ; c, C. vultur, var. 
Japonica (\*-) ; d, C. tenue, var. buceros {-\^). (Jorgensen. ) 



352 DEPTHS OF THE OCEAN 

Cleve, who looked upon the dispersal of organisms by currents 
as the chief factor in affecting the character of the plankton, 
was at first of opinion that he could fix the north-western 
boundaries of the Gulf Stream by noting the distribution of 
Rhizosolenia styliformis, the guiding form in his Styli-plankton. 
But he, too, found that its area of distribution extends northwards 
in the course of spring and summer, and that the swarms of 
Rhizosolenia actually outdistanced the speed of the current. 
The wider distribution of the algae was evidently, therefore, due 
not alone to the increased volume of the current, but also to a 
rapid propagation produced by summer warmth outside the 
influence of the current, the algae apparently having been already 
present in this area in small quantities. 

I may further instance the close agreement between oceanic 
species in arctic and antarctic waters. Thalassiothrix longissima 
and Rhizosolenia semispiiia [hebetata) are the two most character- 
istic forms among algae along both the polar boundaries of the 
Atlantic, though they have also been found in small quantities 
at various localities in the tropics. I personally came across them 
on several occasions during the "Michael Sars " Expedition, 
and it requires, in my opinion, no special theories to account 
for this " bipolarity." There is quite sufficient connection 
between the two oceans to enable a few germs which are 
exceptionally tenacious of life to pass from the one to the other, 
and this would amply explain the agreement. Characteristically 
enough there is no similar agreement between arctic and 
antarctic waters when we come to the neritic forms, and this is 
probably because they are less adapted to travel over such 
immense distances. It may be, too, that their tendency to evolve 
resting-spores is an obstacle to long passive wanderings. 

As a means of determinino^ the direction and velocity of 
currents pelagic algae will be found of very little use. Their 
continued existence during the progress of the current must 
always depend upon their persistence in reproduction, and this 
again is dependent upon conditions of existence and competition 
with other species. It is not mere coincidence that the 
microscopic flora of the warm Atlantic extends farthest north 
during the dark winter months, when no other species are much 
inclined to develop, and there is therefore no competition of 
any consequence, the character of the flora consequently 
remaining for a long time unaltered. Large animals, such as 
medusae and salpae, or the larvae of bottom-animals like Phoronis, 
will be found far better indicators of the currents. Ostenfeld 



PELAGIC PLANT LIFE 



353 



has, however, encountered one solitary case where plankton 
algae could be employed for this purpose. Biddulphia sinensis 
(Fig. 248), a neritic diatom from the coasts of the Indian Ocean, 
was met with in the North Sea for the first time in 1903, to 
begin with in the southern parts, and then gradually farther 
and farther north, until at last it was discovered on the west 
coast of Norway at Bergen. Its travelling rate corresponds 
to the values which have been otherwise obtained for the 
velocities of the current along the coasts of Denmark and 
Norway. Latterly, it has found a fixed distribution-centre in 
the north-eastern corner of the North Sea, whence it extends 

still farther northwards every 
autumn. The velocity of the 
current could hardly be deter- 
mined from the observations of 
these last few years, as there is 
always the possibility that this 
diatom has more than one 
centre of distribution, but its 
annual wanderings clearly in- 
dicate the direction of the 
current. 

A large quantity of plankton 
algae has been collected during 
the "Michael Sars " Expedi- 
tion along the whole route, and 
will contribute valuable infor- 
mation regarding the distribu- 
tion of the different species. We have been particularly 
successful in our study of the coccolithophoridae, owing to the 
improved methods we were able to adopt. I shall deal 
separately with their distribution in what follows, and at the 
same time give some particulars of their quantitative occur- 
rence. Part of the material is still incompletely examined. 
The difficult species of Peridinium in particular, and of a few 
other genera, will require a separate monograph for their special 
treatment ; we have secured immense numbers of these forms. 
In other respects our observations practically confirm the 
views regarding the distribution of species that we owe chiefly 
to Cleve. 

I shall now give a preliminary description of the character of 
the plankton along our route, founded upon an examination of 





Fig, 248. — Biddulphia sinensis (^ 
(Ostenfeld.) 



Phytoplank- 
ton collected 
during the 
" Michael 
Sars " Ex- 
pedition. 



354 DEPTHS OF THE OCEAN 

material from representative stations, and upon observations 
of the living organisms on board ship. 
The coast All our first stations about the middle of April, with the 

No'nh Europe, ^xception of Stations i and 5, that were close in to land 
(Stations i-io, and had a less abundant flora, had an extremely plentiful 
Aprfu^ diatom-plankton, such as we only get in the waters of North 

Europe during the spring. Our experiments with the closing- 
net, which, thanks to the fine calm weather, were made with 
the utmost exactitude at Stations 3 and 10, showed that by far 
the larger number were to be found between the surface and 
a depth of 100 metres, though even at a depth of 100 to 150 
metres there were still quite considerable quantities. The 
character of the flora was mainly northern, especially in the case 
of the oceanic species. Among the principal forms we got 
Rhizosolenia hebetata forma se7nispina and Nitzschia seriata. 
Neritic diatoms were also numerous, and some had resting- 
spores. They are of a distinctly southern character compared 
with the species which occur, for instance, along the coasts of the 
North Sea ; further, they belong to a local flora, which does not 
seem to have any direct connection with the North Sea. On 
the whole, these neritic diatoms are so small in their dimensions 
that they show signs of an "oceanic degeneration." 

Besides them, there was an addition of subtropical species, 
especially in the deeper layers, and especially at the southern- 
most stations, Nos. 9 and 10, consisting of both diatoms and 
peridinese, not in any great quantity, but still occurring regu- 
larly. These are the northernmost outposts of the Desmo- 
plankton, including such species as Planktoniella sol, Ceratmm 
gibberuni, Dinophysis schuttii, and D. uracantha} 

The coast Throughout the stretch of sea along the coasts of South 

Europe anT Europe and North Africa our investigations were carried 
North Africa, on Comparatively close to the coast, and the plankton was 
4i,Vi°srAprii- generally found to be poor both in quality and quantity as soon 
22nd May.) as we stood at all far out from the land. It was then 'composed 

^ As representing this area, I here give a list of species from Station 7, depth 0-20 metres : — 

Oceanic diatoms : ChcBtoceras decipietis, C. densum, C. convolutum, C. periivianum, 
C. atlatiticum, C. dichceta, Coscinodisctts centralis, C. margutatus, Euodia cuneiforniis, Thalassio- 
stra subtilis, Asteromphalus heptactis, Rhizosolenia alata. A', seinispitia, E. stolterfotkii, 
R. shrubsolei, R. acuminata, R. amputata, Dactyliosolen antarcticus, Nitzschia seriata, 
Thalassiothrix longissinia. 

Neritic diatoms : Chcetoceras diadema, C. schiittii, C. contortum, C. coronatum, C. scolo- 
pendra, Bacteriastrum varians, Eucampia zodiactis, Thalassiothrix nitzschioides, Cerataulina 
bergonii, Dattyliosolen tenuis, Thalassiosira decipiens, T. excentrica, T. tiordenskioldii. 

Peridineae : Ceratium tripos forma atlantica, C. lamellicorne forma compressa, C. azoricum, 
C. furca, C. arietinum, and several others. 

Coccolithophoridffi : Distephanus speculum, Coccolithopkora pelagica. 



PELAGIC PLANT LIFE 355 

of oceanic species, that we subsequently met with in the central 
parts of the ocean, though there was not more than a mere 
selection of the very commonest forms. It was here that we 
first became aware of the immense contrast between the scanty 
plant life and the teeming animal life. Sir John Murray and I 
examined the stomach contents of the salpee abounding in the 
Strait of Gibraltar, and could see that they lived almost entirely 
on small forms like coccolithophoridse and tiny peridinese, 
which were too diminutive for our silk nets to capture. 
Radiolaria, however, both Acanthometridae and colony-forming 
species, in symbiosis with brown flagellates, were present 
sometimes in such quantities that their assimilation of carbonic 
acid played no small part in proportion to that of the scanty 
plant plankton. Close in to the shore, on the other hand, there 
was abundance of plankton, and we got quantities of neritic 
diatoms off Lisbon, in the Strait of Gibraltar, and at several 
places on the coast of Morocco down to Cape Bojador. Different 
species predominated in the different samples, but Laiideria 
aimulata was the commonest form everywhere. 

No one accustomed to the plankton algae of northern waters, 
with their numerous dark-brown chromatophores, could fail 
to be struck by the fact that the species never had more 
than a few small chromatophores, and thus had a pale 
appearance. In the diatoms the strong light frequently had 
the effect of making the chromatophores group themselves in 
the centre of the cell, or in Lmtderia annulata at the terminal 
faces where the cells in the chain touch each other. This was 
invariably the case in plankton near the surface, though deeper 
down the position of the chromatophores might be normal.^ 

On this cruise we made acquaintance with the tropical The Central 
Atlantic plankton in all its abundance. For a northerner it ;A^tia'itic from 

V • • -11 r ' • 11 "^"^ Canaries 

was most tascmatmg to study the many strange forms, especially to the Azores, 
of peridineae. Every fresh batch disclosed species that were A^oresTo^he 
new or rare, or else remarkable stages of development. The Newfoundland 

1 The following list is from a sample pumped up from the surface, off the south coast of gg 28th May 
Portugal, on 24th April 1910 :— 29th Tune.)' 

Diatoms : Lauderia anmilata (the prevailing form, found with auxospores), Thalassiosira 
subtilis, T. gravida, Stephanopyxis turris, Paralia sulcata, Coscinodiscus concinnus, Lepto- 
cylindrus danicus, Rhizosolenia alata, R. shrubsolei, R. styliformis, R. stolterfothii, 
R. delicatula, R. robusta, Chatoceras densum, C. schiittii, C. didymu))i,C. curvisetum, C. decipiens, 
C.'lorenzianum, C. diversum, Eucanipia zodiacus, Hemiaulus hauckii, Biddtdphia mobiliensis, 
Bacteriastrujn varians, Nitzschia seriata. 

Peridineee : Ceratium lineatttm, C. macroceros, C. fusus, C. furca, C. candelabrum, species 
of Peridinium, Gonyaulax spinifera, Diplopsalis leiiticula, Dinophysis acuminata, D. rotundata, 
D. acuta; Coccolithophora pelagica. 



356 DEPTHS OF THE OCEAN 

multitude of species was surprising, though none of them was 
very numerously represented. Every day one might sit and 
examine some unique microscopical form, which might be lost 
only too easily, and consequently had to be drawn there and 
then. And whereas in the north there are large quantities of 
every species, so that it is easy to investigate them in all their 
stages of development and variation, this multiplicity of forms 
in the tropics renders it incomparably harder to find out what 
stages of development belong to the same species, or how the 
boundaries between the different species are to be fixed. 

The various stations did not differ much from one another, 
if we except Station 59, near Fayal in the Azores, where there 
were numbers of neritic diatoms, and Station 66, close to the 
Newfoundland Bank, where there was an addition of arctic 
forms. On the whole, the multiplicity of species increased as 
we went westwards. Possibly considerable differences may 
be revealed when the material has been completely treated, but 
all the species occur too sparsely in these samples to justify 
one in drawing conclusions from negative results.^ 

The Tropical Atlantic flora much resembles the plankton 
flora of the Indian Ocean observed by Karsten. In the Pacific 
there would seem, according to Kofoid, to be an even greater 
multiplicity of species, but I found several of the new species 
obtained by him during the "Albatross" Expedition, and it is 
probable that more and more of these rare Pacific species will 
gradually be found within Atlantic waters also. 

In conclusion, it should be stated that, as far as quantity 
is concerned, the smallest plankton organisms, Lohmann's 
Nanno-plankton, play a far more important role than the whole 
of the other species caught in our silk nets, which will be 
subsequently discussed in their proper order. 

^ To show the character of the flora I append a list of species found at Station 64, lat. 34° 
44' N. , long. 47° 52' W. , in a closing-net sample from a depth of 2CX) metres to the surface : — 

Diatoms : Coscinodiscus rex, C. Hneatus, Euodia cuneiformis, Planktoniella sol, Gosslenella 
tropica, Thalassiosira stibtilis, Asterolatnpra tnarylandica, Rhizosoleniacastracanei, R. acuminata, 
R. styliforinis, Bacteriastrum elongatuin, HemiaulKS sp., Chatoceras diclmta, C, tetrastichon, 
C. peruviaman, C. coarctattiiii, C.furca. 

Peridinese : Ceratium pentagonum, C. teres, C. candelabrum, C. gravidum, C. fusus, 
C. extensuin, C. pennattmi, C. gibberutn, C. buceros, C. platycorne, C. azoricum, C. ienue, 
C. pavillardi, C. karsteni, C. declinatuin, C. gracile, C. arietinum, C. macroceros, C. massiliense, 
C. arcuatum, C. ca}-riense, C. reticulatum, C. trichoceros, C. pahnatum, C. limidus, C. pulchellum, 
species of Peridinium, Diplopsalis lentictda, Blepharocysta splendor maris, Ceratocorys horrida, 
Goniodoma polyedricum, G. Jlvibriatum, Gonyatilax polygramma, G. joliffei, G. pcuifica, 
G. fragilis, G. mitra, Protoceratium retictdatum, Podolampas elegans, P. palmipes, P. bipes, 
Oxytoxum scolopax, 0. retictdatum, O. cristatum, O. milneri, O. tesselatum, Dinophysis 
uracantha, D. schiittii, D. schrdderi, PJialacrotna argus, P. doryphorum, P. cuneus, P. rudgei, 
Amphisolenia palmata, and another new species, Ornithocercus quadratus, O. magnificus, 
O. steinii, O. splendidus, Pyrocystis lunula, P. noctiluca, Hexasterias problematica. 

CyanophyccEe : Trichodesmium thiebauUi. 



PELAGIC PLANT LIFE 357 

The plankton of the cold water on the Newfoundland Bank The Nc 
was very poor in species, Ceratijim arcticum and Peridinmm g^^k^^ 



parallelum being the commonest forms. There were, besides, (Stations 70 

9, 3( 

loth July.) 



a few diatoms, such as Chcetoceras atlanticum, C. criophihim, 79, 30th June 



and Rhizosolenia seynispina, all well-known species in the 
Norwegian Sea. In the harbour of St. John's, on the other 
hand, we found the plankton quite abundant, consisting of 
northern forms, both neritic and oceanic : the species of Chce- 
toce7'as {decipiens, debile) predominated. 



to our 



ir northern section across the Atlantic contributed largely 
knowledge of the distribution of species, since it showed 



Atlantic 
section. 
(Stations 8i- 
92, I2th-24th 

July.) 




Fig. 2^().—Chmtoceras perpusillum (^f^). 

US that a great many tropical forms are still to be found in lat. 
45-50^ N. These particular waters had been very little studied 
previously, and it was extremely interesting to follow all this 
Atlantic flora on its passive journey northwards. On the whole, 
its character remains unchanged, though of course the number 
of species becomes considerably reduced. During the first half 
of the section, on the western side of the mid-Atlantic ridge, 
there were a few small degenerate neritic diatoms belonging to 
the species which occur in the Atlantic water-masses south of 
Iceland : namely Chcutoceras schiittii, C. laciniosimi, and others. 
It seems unquestionable that they are derived from the American 
coast, and follow the current as far as Iceland. At Station 85 I 
also came across a remarkable little ChcEtoceras, that Cleve found 
in 1897 ^^ ^^ Skagerrack and named ChcBtoceras perpusillum 



358 



DEPTHS OF THE OCEAN 



(Fig. 249), which had not been met with subsequently. The 
whole structure of this diatom shows that it, too, is most 
probably a neritic form, and it must therefore have a wider 
distribution than was commonly supposed.^ 

As we neared the coast banks of Europe we found the 
number of species growing distinctly less, though on the other 
hand the quantity of the plankton increased. 



The plants of the sea like those of the land build up all the 
organic substance which forms the chemical foundation of life. 
If we wish to know clearly when and how and under what 

^^^' conditions vigorous production takes place, or what prevents 

the development of an exuberant plant-life, we must first 
acquire the means of estimating the amount of vegetation in the 
different parts of the sea. 

Hensen. Hcnsen was the first to take up this problem, the solution 

of which depends on three assumptions: (i) it is absolutely 
essential to have apparatus that can capture all the organisms 
living in a specified quantity of water, (2) the plankton must 
be supposed to be uniformly distributed in the sea, so that the 
catch represents a reasonably extensive area ; and (3) a scientific 
examination of the catch must supply a really correct picture of 
the amount of plants and their capacity of production. 

Hensen'snet. The apparatus employed by Hensen and his assistants 

consisted of extremely fine straining-cloth, with meshes 0.04 to 
0.05 mm. in diameter. He made the mouth of his net small in 
proportion to the filtering silk surface, to ensure as far as 
possible the immediate filtering of all water that came in through 
the opening, his object in this being to ascertain approximately 
how much water was filtered, when the net was drawn through 
the sea for a calculated distance. Experiments showed that in 

^ As illustrating a haul on this section I append a list of the species found in the closing net 
at Station 8i (lat. 48° 2' N., long. 39° 55' W. ), from a depth of 50 metres to the surface : — 

Diatoms : Coscinodisciis excentrictis, Euodia c2ineifor»ns, Planktotiiella sol, Coscinosira 
(Estrtipi, Thalassiosira subtilis, Corethron C7-iophilum, Rhizosolenia styliformis, R. shrubsolei, 
R. fragillima, R. alata, R. semispina, Baderiastruni delicatulum, B. elongatum, Chatoceras 
atlanticum, C. boreale, C. mediterraneiim, C. peruvianum, C. criophilum, C. decipiens, 
C. contoftuiii, C. schiittii, C. curviseium, C. lacmiosum, C. furcellatum (a resting-spore), 
Thalassiothrix longissitna, T. nitzscktoides, Nitzschia seriata. 

Peridinese : Ceradum lineatu7n, C. candelabruvi, C. pe,7itagonum , C. gravidum, C. fusus, 
C. pennattim, C. tripos, C. azoricum, C. gibberum, C. plat y come, C. arcticiim, C. intermedium, 
C. macroceros, Protoceraiium reticnlatum, Peridinium oceanicum, P. depressum, P. divergens, 
P. conicum, P. ovatjim, P. tristylum,z.nA some others, Diplopsalis leiitictda, Pyrophactis horologium, 
Goniodotna polyedricm/i, Gonyaulax polygram ma, Podolampas elegaiis, P. palmipcs, Oxytoxum 
scolopax, O. diploconus, Ptychodiscus carinatus, Dinophysis acuta, D. schiittii, D. rotundata. 

Flagellates : Phceocystis poticheti. 

Silicoflagellates : Dictyocha fibtda. 

Chlorophycese : Halosphcera viridis. 

Cyanophycere : Trichodesmium thiebaulti. 



PELAGIC PLANT LIFE 359 

practise his net could not filter the whole of the water which 
ought to pass through ; it was possible, however, to work out a 
coefficient for each size of net, namely a fraction indicating 
what proportion of the total quantity of water had actually been 
filtered. Hensen trusted chiefly to vertical hauls, since he was 
anxious to know definitely the exact distance through which 
the net had passed. He lowered his apparatus open, but with 
a heavy weight attached, so that it went down end-first and 
therefore caught nothing until hauling in began. Initial investi- 
gations aimed at ascertaining the total quantity of plankton in 
the photic zone, and accordingly the net was drawn in one haul 
from a depth of 200 metres right up to the surface, or from the 
bottom to the surface in water shallower than 200 metres, the 
idea being to find out the quantity of plankton in a column of 
water of known depth i metre square. 

It is not, however, sufficient merely to compare the total 
quantity of plankton present in different localities ; it may be 
just as important to know what there is at different depths, not 
only because we have to consider the effect of light, let us 
say, upon plant production, but because there may be layers of 
water, such as we find especially in coastal areas, totally distinct 
in hydrographical characters, and with different conditions of 
existence. Hensen made vertical hauls from different depths, 
and had recourse to subtraction when estimating the plankton 
of the deeper layers, but since that time closing-nets have been 
introduced, and we are able now to get samples from any layer Petersen's 
we wish to study. C. G. J oh. Petersen constructed a closing- fp'^'Jft^,, 
apparatus to go with Hensen's vertical net, and Nansen also 
designed a vertical closing net which was invariably used by the Nansen's 
'' Michael Sars," and found to be handy and reliable. Provided ^i^^i^g"^^. 
only the bag be long enough in proportion to the opening, it 
will act successfully from a quantitative point of view, though 
we did not employ it much for this purpose, as we had better 
methods of our own for estimating quantity. Otto Pettersson Pettersson's 
obtained his estimates of quantity by attaching silk nets a^faching^nets 
to a large current-meter, which recorded the velocity of the to current- 
current, and thus indirectly supplied approximate figures de- "^^^^^' 
noting the amount of water filtered. A series of very interest- 
ing determinations, from samples secured in this way, has 
been described by Broch. Broch. 

The net-method was found unreliable as time went on. In 
the first place, it does not fairly represent the total quantity of 
plankton, since many of the smaller forms pass altogether, or to 



360 



DEPTHS OF THE OCEAN 



Lohmann's 
pump method 



a very great extent, through the meshes ; and, secondly, the 
meshes become gradually clogged with the slimy little algae, or 
animals, so that the coefficient of filtration does not remain con- 
stant. Even during the course of a single haul we occasionally 
noticed that everything worked well to begin with, but that the 
cloth became more and more stopped up, until at last filtration 
ceased entirely. In other words, it is sometimes impossible to 
tell how much water has been filtered, and consequently the 
catch is practically valueless from a quantitative point of view. 

An endeavour was made to overcome this last difficulty by 
filtering a quantity of water, previously measured, either through 
silk nets, or through an even less porous filter-material, such as 
taffeta, or hardened filter-paper, or sand, an additional advantage 
being that by this means the very smallest organisms could be 
retained. Water-samples were secured by water-bottles or by 
pumps. Lohmann, who did much to perfect the pump-method, 
was not only able to get his water-samples from any depth 
desired, but could obtain samples representing a column of 
water from the surface down to a specified level. The pump 
was made to work in connection with a long, flexible hose, the 
mouth of which was lowered as far down as considered necessary, 
and then drawn gradually up towards the surface as pumping 
proceeded. The pumped-up water thus represented propor- 
tionally the whole distance through which the hose passed 
before reaching the surface. These samples were afterwards 
filtered by Lohmann, and the results compared with catches 
obtained by vertical hauls with the silk nets. 

The methods of capture had thus been greatly improved, 
and it was possible to obtain the smallest organisms, but for 
practical reasons it was necessary to limit the quantity of water 
filtered on each occasion. This forced us to turn our attention 
to the second question, namely the regularity with which 
Distribution of organisms are distributed in the sea. Fortunately, the 
?!!!?™„?1^"^^ researches of Hensen and his assistants, as well as those of 
Lohmann and myself, have all gone to show that the distribu- 
tion of the pelagic plants, at any rate, is extremely regular. 
The samples from adjacent localities with similar life-conditions 
have yielded very concordant results. I do not consider it 
any exception to this statement that in tropical waters dense 
masses of Trichodesntium sometimes collect as water- bloom 
in certain areas and not in others, or that diatoms near 
the edge of the polar ice occur in more or less local swarms, 
for I consider it more than probable that these irregularities 



extremely 
regular 



PELAGIC PLANT LIFE 361 

arise because the conditions of existence vary in closely 
adjoining areas. Lohmann has found that at certain seasons 
10 to 15 c.c. of sea- water amply suffice to give a representative 
sample of the total plankton, but it is evident that only the 
commonest organisms floating in the sea in any locality do 
occur so densely and regularly that we can be sure of securing 
them, or even of catching enough for ascertaining their com- 
parative frequency, in a water-sample consisting of only a few 
litres of water or less. The more scattered or mobile the 
individuals are, the larger masses of water must we examine to 
get a knowledge of the quantity present in any locality. 

It follows, therefore, that we must abandon all thought of a No universal 
universal method. Fine silk nets give us complete collections "sUmatin^ 
of the larger Ceratia and diatoms, but are of no use for the quantity of 
smallest species, for which we are obliged to have recourse to p^^"^'°"- 
more delicate methods of filtration, and to the centrifuge. The 
larger forms, too, will be found in our silk nets in sufficient 
quantities, if they are at all abundant, but where they are 
scarcer than, say, fifty specimens to the litre, the centrifuge 
cannot be depended on. Besides amongst these larger organisms 
some species are so scanty that even a vertical haul with the 
big net yields insufficient material, so we have been compelled 
to adopt the special methods described in this volume. 

Various methods have been employed for estimating the 
quantity of plankton on the basis of catches made. We can Determina- 
allow the whole sample to sink to the bottom of a measuring tionsof 

, 1 . ^ . • 1 • 1 •! 1 volume and 

glass, and appraise its volume, or we can weigh it while the weight. 
organisms are saturated with water or spirit, or we can weigh 
the dry substance. Such determinations of volume and 
weight give us our first rough idea of the variations in the 
quantity of plankton, but there are many sources of error 
which it is unnecessary to discuss here. The worst fault is that 
measurements of this kind group into a whole the most diverse 
values, such as plants and animals, producers and consumers, 
one-celled organisms that are constantly reproducing themselves, 
and multicellular animals with a longer duration of life, or, again, 
organisms with slow and others with rapid metabolism. If we 
want to know a litde about the conditions of development of 
organisms, we must have a method of investigation that allows 
us to trace the growth and retrogradation of each of the different 
species by itself, and counting then becomes the only method counting 
possible, as Hensen has continually asserted. Counting is a necessary. 
method that requires much time, and also absolute accuracy in 



362 



DEPTHS OF THE OCEAN 



determining the species whose development we desire to trace ; 
consequently most of those who endeavour to work at these 
interesting questions will be forced to confine themselves to 
definite problems, and content themselves with tracing the 
growth of a limited number of species. No doubt a man like 
Lohmann may be able to know all the species within certain 
limits, and may actually calculate by counting what each of 
them contributes to the total plankton volume, but speaking 
generally a " uni- 
versal method " that 
will give us the total 
quantity of all the 
plants and animals 
of the sea in curves 
and tables is un- 
attainable. 

During the 
" Michael Sars " 
Expedition our 
quantitative investi- 
gations yielded really 
remarkable results. 
Lohmann had suc- 
ceeded by means of 
a centrifuge in de- 
termining the quan- 
tity of plankton in 
quite small samples 
of Baltic water, and 
we felt confident, 
therefore, that this 
excellent method 
ought also to prove 
serviceable in the 
open sea. We very soon found, however, that the algae there 
were too scarce for our little hand-centrifuge (Fig. 250) to be 
of much utility ; there was so little to be found at the bottom 
of the centrifuge glasses (Fig. 251) that we obtained a hope- 
lessly inadequate idea of the plant life, whereas in the 
stomachs of salpse we might, perhaps, get a quite abundant 
flora of small forms. Fortunately, we had taken with us a 
big centrifuge to be worked by steam (see Fig. 91, p. 105), 
and in its six glasses we could centrifuge at one time as much 




Fig. 250. — Lohmann's Hand-centrifuge. 



PELAGIC PLANT LIFE 



3^3 



as 1 200 c.c. of sea-water. It made 700 to 800 revolutions per 
minute, and after eight minutes the plants were all collected at 
the bottom of the glasses. Our next proceeding was to pour 
away the clear water, and after rinsing the deposit, to put it 

in a smaller glass with a tapering 
bottom, where it was subjected to 
the action of a small hand-centrifuge. 
In this way we collected all the con- 
tents of, say, 300 c.c. of sea-water in 
one drop, which we examined in a 
counting chamber beneath the micro- 
scope, and noted carefully each single 
organism. As a rule we had to 
centrifuge the whole 300 c.c, but, if 
the plankton was very abundant, 150 
c.c. or even 100 c.c. might suffice. 
Examination with the microscope is 
always more difficult when the or- 
ganisms in the counting chamber lie 
close together. 

These investigations were carried Smallest 
out all the way from the Canaries to Zo£m 
Newfoundland, and thence to the in the open 
Irish coast banks, and resulted in 
our discovering that the smallest 
organisms which pass right through 
the silk nets are far more abundant 
than the others in the open sea, 
while the larger diatoms and peridineae 
would appear to be so scanty that 
the total of all their species together 
only amounts to about ten per litre. 
Despite this fact, however, we found 
in the samples taken with our nets 
that there were at least fifty species 
Glasses of these larp-er forms at every station, 
SO that as far as species go the flora 
is exceedingly rich. 
We were also able in this way to determine the occurrence Amount of 
of algae at different depths. Samples from the surface, and §Jj-"Jejjf "^^ 
from 20, 50, 75, and 100 metres were taken regularly, and depths. 
we also examined samples now and then from still greater 
depths. We found, invariably, however, that the plant life 




Fig. 25 



. — Centrifuge 
AND Pipettes for use with 
Lohmann's hand-centrifuge. 



364 



DEPTHS OF THE OCEAN 



below 100 metres was extremely scanty. The maximum in 
the ocean nearly always lay at about 50 metres, which is 
what Lohmann also found in the case of the Mediterranean 
coccolithophoridse. At the surface there was less than down 
in the 20 to 50 metres zone, though the plankton nearly always 
approached its maximum value as soon as we reached a depth 
of 10 to 20 metres. At 75 metres the quantity diminished 
to about half of that found at 50 metres, and at 100 metres it 
had dwindled to at most a fifth. These were the values on our 
southern section. On the northern crossing the quantity of 
plankton fell away even more rapidly as we went deeper down ; 
at Station 92, where there was a slight admixture of coast- 
water near the surface, and the lighter surface layer was 
separated from the pure Atlantic water somewhere between 25 
and 40 metres, there were upwards of 250,000 plant cells per 
litre in the surface layer ; whereas at 50 metres the plankton 
was less abundant than at any of our previous stations, and only 
amounted to 2213 cells per litre. 

These results quite bear out the most valuable investigations 
so far made regarding the vertical distribution of algse in the 
ocean, namely Schimper's observations in the Antarctic during 
the " Valdivia" Expedition. He found that the entire produc- 
tion was practically limited to the uppermost 200 metres, that 
the bulk was to be found above 100 metres, and that the 
maximum lay between 20 and 80 metres, or to be more precise, 
between 40 and 60 metres. We were able to confirm this, after 
comparing the volume of the samples taken with nets on those 
few occasions when there was a sufficiently large quantity of 
plankton at our stations to make such volume-measurements of 
any real value. There was, however, a different vertical dis- 
tribution everywhere along the coasts where diatoms abounded, 
for then the exuberant plant production was limited to the 
surface layer, which was mixed with fresh water from the 
land. 

As illustrating our investigations at a station in the warmest 
part of the Atlantic, I give particulars of what I found at 
Station 64 (lat. 34° 44' N., long. 47" 52' W.) in water-samples 
from 50 metres (150 cc.) and 75 metres (300 c.c). The figures 
denote the number of individuals per litre. 



PELAGIC PLANT LIFE 



365 



Coccolithophoridae : — 

PontosphcEra huxleyi, Lohm. 
SyracosphcBra echinata, n.sp. 

,, spinosa, Lohm. . 

„ ampulla, n.sp. 

,, IcEvis, n.sp. 

„ blastula, n.sp. 

„ pulch7-a, Lohm. . 

„ robusta, Lohm. . 

Calyptrosph(e7-a oblonga, Lohm. 
Coccolithophora leptopora, Murr. and Blackm. 

,, pelagica, \Vallich 

„ wallichii, Lohm. 

,, lineata, n.sp. 

RhabdosphcEra styliger, Lohm. . 

„ daviger, Murr. and Blackm. 

DiscosphcBra fiibifer, Murr. and Blackm. 
Scyphosphcera apsteini, Lohm. . 
Calciosolenia murrayi, n.sp. 
Ophiaster for7nosiis, n.sp. 
Undetermined coccolithophoridfe ^ . 

Total coccolithophoridse . 



Pterospermataceai : — 

Pterosperma disci/liis, n.sp. 
Peridineae : — 

Protoditiium . 

Amphidiniuni gracile 

Oxytoxum scolopax . 
,, hjorti, n.sp. 

Di/iophysis, sp. 

Exuvicel/a, sp. 

Other peridineae 

Total peridineae 

Diatoms : — 

Nitzschia seriata 



sp. 



Rhizosolenia calcar avis . 
Thalassiothrix frauenfeldi 
Silicoflagellates : — 
Didyocha fibula 
Other plant-cells 

Total plant-cells 



Cells per 
50 m. 
300 
287 
193 

93 
147 

160 

80 

593 

33 

73 

7 

7 

33 

107 



3007 



57ii 



litre. 
75 m- 

173 
123 

33 

40 

83 

3 

100 

67 

370 

7 

53 



37 

7 

93 

23 

13 

7 

497 

[729 



853 


1007 


33 


37 


7 


3 




3 


7 






3 


300 


350 



1403 



7 


33 


14 


43 




7 


43 


93 


147 


377 



3708 



I have previously given a list from this station of the species 
found in a vertical haul with the silk net. The number of 



1 Mainly young stages, which could not be determined with certainty; to a great extent 
they belong no doubt to Coccolithophora leptopora. 



366 



DEPTHS OF THE OCEAN 



Plankton less 
abundant in 
the open sea 
than in coastal 
waters. 



species is very considerable, yet the total quantity of individuals 
is surprisingly small compared with what we might find, for 
instance, off the coasts of Europe. In the Skagerrack one 
often gets plant- cells in tens of thousands or even hundreds 
of thousands in every litre of sea-water from the upper layer, 
and, what is more, they are much larger and more nutritive 
than the stunted forms which make up the bulk of this ocean 
plankton. 

It cannot be denied that our investigations are as yet too 
incomplete to justify us in framing laws for plant production in 
the ocean. Still the great expeditions which have made 
researches in the open sea have given us a general conception 
of the conditions prevailing over wide stretches of water at 
certain seasons ; on the other hand, careful investigations of the 
variations in the plankton throughout the year have been 
carried out at a number of coast stations, while our international 
researches have resulted in a great deal of material being 
collected at all seasons from the North Sea and adjoining 
areas. Though these investigations have not all been devoted 
to studying quantity, they have nevertheless enabled us to 
form some idea of the annual variations. 

One thing at any rate we may learn even from this in- 
complete material. The development of the plankton is much 
more irregular than it would be if merely such simple factors as 
warmth and light controlled production. It is not in the 
warmest waters that the greatest amount of organic substance 
is to be found. On the contrary we get larger masses of plants 
in temperate seas than we have ever yet come across in 
tropical or subtropical areas,^ at any rate so far as the open 
ocean is concerned. Even when we come as far north as 
the coast of Norway we find that it is not in the hottest months 
of summer that the plankton attains its maximum, but in the 
early part of the spring or the end of autumn. Now it is 
certainly true that the quantity of vegetable matter present at 
any given moment is no direct measure of production. Ac- 
cording to the law of Van 't Hoff, metabolism always takes place 
quicker ceteris paribus at a high temperature than at a low 
temperature, and a plant-cell in the tropics may perhaps produce 
more organic matter than a similar cell would do in the North 
Sea in the same space of time. The small tropical plants may 

^ The "Challenger " met with diatoms in the Arafura Sea in as great abundance as in the 
Antarctic regions, but neritic in character (see lists of species in Summary of Results, 
Chall. Exp., pp. 515 and 733). 



PELAGIC PLANT LIFE 367 

pass more rapidly through their life-cycle, and their numbers may 
be more drawn upon by the abundant animal life ; consequently 
considerable additions to their apparent total may be necessary, 
if we wish to estimate properly the importance of plant life 
in the tropics, as compared with that in higher latitudes. We 
must remember, moreover, when dealing with observations 
made in coastal waters all the year round, that the different 
species have a natural periodicity that may be connected 
with unknown internal factors in their cycle of life, as well 
as with the influence of currents which at one time carry the 
surface - layers away from the coast and at another time 
towards it. All the same there are many irregularities which 
cannot be explained as being solely the result of the actual 
physical conditions of existence. Besides light and warmth we 
might perhaps be apt to think of salinity, which, in the course of 
its variations, influences both the density and the osmotic tension 
of the sea-water. Though we are aware that a low or greatly 
varying salinity is injurious to many pelagic organisms, there 
are others which thrive remarkably well and multiply exceed- 
ingly under such conditions, as for instance the diatom 
Skeletoneina costahmi and the peridinean Ceratiurn tripos forma 
subsalsa. Results, in fact, are often the reverse of what one 
might expect. The flora of brackish - water bays, which is 
poor in species, may develop into even greater masses than we 
find synchronously in the open sea, where no osmotic changes 
have disturbed the vital activity of the numerous species 
belonging to the community of oceanic algse. 

We cannot get away from the view, which was first con- Brandt. 
fidently put forward by Brandt, that certain indispensable 
nutritive substances occur so sparsely that, according to Liebig's Liebig's 
minimum law, they act as factors which limit production. ™™'"""^ ^^• 
Liebig found that the growth of plants on land depends on the 
amount of the requisite nutritive substances present, the deter- 
mining substance being the one of which at any moment there 
is least in proportion to the needs of the plant. As long as 
a particular nutritive substance occurs " in minimum," plant 
production will be proportionate to the available quantities of it, 
even though there be a superabundance of all other essentials. 

If this law is made to include all necessary conditions of life, 
it will be found to apply universally to all organisms both on land 
and in the sea, in which case that condition of existence, whether 
it be physical or chemical, which occurs " in minimum," will be the 
factor of limitation. We must remember, however, that produc- 



368 DEPTHS OF THE OCEAN chap. 

tion at a given moment need not necessarily be proportionate 
to the conditions of existence prevailing. There may be after- 
effects of a previous set of conditions. Indeed it is possible to 
point to places totally destitute of vegetation, owing to former 
unfavourable circumstances having destroyed all germs, while 
new germs have not yet found their way there. Still this is the 
only reservation we need to make, when asserting the universality 
of this natural law. 

The necessary nutritive substances which are most likely 
to occur "in minimum" in the sea are nitrogen, phosphoric 
acid, and, in the case of diatoms, silicic acid ; all others occur 
even to superfluity. Brandt in his works on metabolism 
in the sea discusses at some length the importance of nitrogen, 
phosphoric acid, and silicic acid, and his assistants at Kiel 
have carried out a number of tests to ascertain the extent 
to which these substances are present in sea- water. Not 
only the nitrogenous compounds (organic compounds, ammonia, 
and nitrates), but also phosphoric acid and silicic acid, occur in 
extremely minute quantities, so that it is particularly difficult 
to get accurate values representing them. We have therefore, 
unfortunately, no proper conception as yet of the way in which 
these substances vary in different parts of the sea. According 
Raben. to Rabcn's latest investigations the total quantity of combined 

nitrogen (ammonia, nitrates, and nitrites) in true North Sea 
water varies between o. no mg. and 0.314 mg. per litre, of 
which 0.047 to 0.124 mg. is saline ammonia, the whole being 
reckoned as free nitrogen. Even if we assume that the quantity 
of nitrogen in the Atlantic is considerably less, these values are 
high compared with the quantity of nitrogen to be found 
combined in the cells of the plankton -algs. It seems, 
therefore, hardly possible that the nitrogenous compounds are 
entirely consumed by thealgse. It is, however, quite conceivable 
that the variations in the total quantity of nitrogen, or in the 
quality of such compounds as are easiest to absorb, may hasten 
or retard the augmentation of the algse. The same is the case 
with silicic acid, which Raben found to vary between 0.30 mg. 
and 1.03 mg. per litre in thirty samples from the North Sea. 
The quantity of phosphoric acid, according to Raben's investi- 
gations, is as a rule below i mg. per litre, though it slightly 
exceeds the quantity of nitrogen. 

Brandt starts by discussing the occurrence of nitrogenous 
compounds in the sea. He calculates that large quantities of 
combined nitrogen are carried out from the land by the 



PELAGIC PLANT LIFE 369 

rivers, as organic nitrogenous compounds, ammoniacal salts, and 
nitrates. The result would be a constant increase, until at last 
the sea became poisoned, were it not that it is continually being 
absorbed by living organisms, or else being restored in some 
form or other to the atmosphere. We now know that there is 
very little combined nitrogen in the sea, so that it must evidently 
be used up as fast as it arrives. The consumers of nitrogen 
are first and foremost the seaweeds growing along the coasts, 
and the floating algae of the open sea, but besides them there 
are also bacteria, which exist in all sea-water, as shown by 
Fischer. Their competition with the algae for the nitro- Fischer. 
genous compounds is not of any great consequence, so long 
as they do not interfere with the circulation of nitrogen other- 
wise than by disintegrating organic compounds so as to form 
ammonia, or by binding ammonia and nitrates in their cells 
as albumen. 

From the bacteria-life of the soil, however, we are acquainted Nitrifying and 
with another kind of nitrogenous metamorphosis produced by bacterS?"^ 
bacteria. There are nitrifying species which oxidise ammonia 
into nitrites and nitrates, without requiring organic substance to 
enable them to live ; there are further whole series of other 
species which can reduce nitrites and nitrates, and give off 
nitrogen in a free state. Their action drives out of the natural 
circulation larger or smaller quantities of this valuable nutritive 
substance, scarce enough already, which all plants generally 
utilise to the uttermost. How great the loss is, as compared 
with the metamorphosis in other respects, and under what 
conditions it takes place, are questions that require our most 
careful attention before considering anything else. 

Baur, and others after him, succeeded in finding several Baur. 
kinds of these denitrifying bacteria in the sea, where they 
appeared to be widely distributed. It was found, too, that 
they produced free nitrogen with greater rapidity when the 
temperature was high (20° to 30° C.) than when it was low. 
Brandt, accordingly, put forward the hypothesis, that to the 
activity of these bacteria is due the fact that the abundance of 
plant life does not increase as we approach the tropics, but 
on the contrary very often decreases. This theory has now 
for some years been considered the only explanation of the 
irregular distribution of the plankton, but recent researches 
have shown that it is untenable. 

The denitrifying bacteria require organic substance for their 
existence. If they are to give off free nitrogen, they must have 

2 B 



370 DEPTHS OF THE OCEAN chap. 

nitrates or nitrites, though denitrification is as little a vital 
necessity for them as alcoholic fermentation is for the fermenta- 
tion fungi. Feeding them with sugar and ammoniacal salts will 
result in their multiplying to an unlimited number of generations, 
without exhibiting their power of denitrification. They can 
attack nitrates whenever met with, utilise their oxygen, and 
give off nitrogen, but denitrification is not of any particular 
importance, provided the bacteria find sufficient free oxygen in 
their surroundings. It is only when this fails that they attack 
nitrates to any great extent. Given the requisite quantity of 
oxygen they will enter the regular circulation, and no nitrogen 
worth mentioning will be produced even where denitrifying 
bacteria are living and multiplying. 

This is the case at any rate in the soil, where denitrification 
is of no importance, unless nitrates are brought into contact 
with considerable quantities of easily disintegrated organic 
substance. In the sea the quantity of organic substance is 
generally so small that a cubic centimetre of salt-water from the 
open sea rarely contains more than 50 to 100 living bacteria 
cells, while the nitrogenous compounds occur for the most part 
as ammonia or inorganic compounds, and not as nitrates or 
nitrites. It is more than likely that nitrates are not formed to 
any great extent in sea- water. Nitrifying bacteria are met 
with occasionally in the mud along the coasts, but they have 
not been proved to exist in the open sea ; in any case they 
have not the same importance there that they possess on land, 
where numbers of them are present in every single gram of 
cultivated earth. So it is probable that the small quantities of 
nitrates and nitrites in the sea-water are brought either from 
the land, or in a minor degree from the atmosphere as the 
result of electrical discharges. Most of the combined nitrogen 
of the sea occurs as organic compounds or as saline ammonia, 
neither of which can be reduced by denitrification. Supposing 
then that denitrification does play any noticeable part, it will 
only be in more or less enclosed bays and fjords, where 
there is a comparatively large amount of organic substance, 
a plentiful supply of nitrates from land, and so little circulation 
that there may be a lack of oxygen. In the open sea it is 
negligible. 
N.ithansohn. We must look for other conditions to explain the apparent 

irregularities in the distribution of the plankton. Nathansohn 
was the first to notice that vertical currents are bound to 
exercise considerable influence. If it be true that one or 



PELAGIC PLANT LIFE 371 

several of the necessary nutritive substances may be present in 
such small quantities as to act as factors that limit the develop- 
ment of the vegetation, then the more or less considerable 
exchange taking place between the illumined surface -layers 
and the vast water-masses of the deep is certain to produce a 
great effect. All the forms of animal life inhabiting the sea 
below 200 metres live solely upon organic substances which are 
due to plants in the surface layers ; that is to say, they either 
feed directly upon the plant-cells which sink downwards, or 
upon the inanimate remains or excrements of the animals living 
up above, or else upon other animals which, in their younger 
stages, have inhabited the surface-layers and fed on the plants 
they found there. A large proportion of the produce of the 
surface-layers must thus be continually descending into the 
deep sea, and these nutritive substances are therefore with- 
drawn from their regular circulation in the photic zone. Down 
in deep water, no doubt, the destructive metabolism of animals 
will set free these nutritive substances, so that eventually 
carbonic acid and ammonia will be produced ; still these gases 
can only regain the photic zone by very slow degrees if 
diffusion is their sole means of conveyance. If, however. Ascending 
whole masses of water are brought up from the deep sea to <^""e"^s- 
the surface, the nutritive substances contained in them will 
once more enter into circulation, and cause an abundant plant 
life to develop. Nathansohn has pointed out that marine areas 
where such ascending currents occur, and where the surface- 
layers are replaced by water from the deeper layers, are well 
known to be extremely prolific, not merely in plankton, but 
also in larger organisms. In anticyclonic systems like that 
of the Sargasso Sea, on the other hand, where, conformably 
to the laws of ocean-currents, the water-masses cannot ascend 
from the deep sea, but where the surface -layers sink down- 
wards, the plankton is much less plentiful than in any other 
similar area where investigations have been made. Our 
researches in the Atlantic during the summer of 19 10 have 
done a great deal to settle this question. I shall first of all, 
however, refer to a series of investigations which bring quite 
another light to bear upon the question, and show what 
difficulties we have to face. 

In 1907 Professor Nathansohn and I commenced to study Pelagic aigos 
the Christiania fjord, and subsequently I continued these in- f/oS"^*'''"'' 
vestigations alone. My previous observations had taught me 
that the pelagic algae in this fjord attain their maximum between 



372 DEPTHS OF THE OCEAN chap. 

March and May, and that they occur in rather smaller quantities 
from June to August. From September to October there is 
again a maximum, but from then onwards they decrease rapidly 
and reach their minimum between December and January. It 
is not surprising that the plankton is scanty during the dark 
period of the year, but the unmistakable secondary minimum 
in the summer months must be due to some special cause, 
which it should be possible to discover by studying carefully 
the whole year round the variations in quantity and the 
fluctuations in the outward conditions of existence. It struck 
me that the factors at work might be analogous to those which 
cause the differences in production met with in different regions 
of the great oceans. 
Method of To ascertain the quantity of plankton present we employed 

^uant?"ff'^^ the method introduced by Sedgwick and Rafter for drinking- 
piankton. water tests in North America, which has been described by 
Whipple. A litre of water is filtered through a fine grade of 
sand, and the algse that collect on its surface are rinsed off". 
To the rinsed-ofT water containing the algae, filtered water is 
added until the whole comes to exactly lo c.c. We then transfer 
I c.c. of this with a pipette to a counting-chamber 5 cm. 
long, 2 cm. broad, and i mm. high, which exactly holds it. For 
examination we use a microscope which magnifies to 40 or 50 
times the natural size. A thorough knowledge of the species 
is requisite to enable us to enumerate them correctly. When 
counting species represented by many individuals we require 
a micrometer, with a larger or smaller number of millimetre 
squares marked off by lines, placed in the eyepiece of the micro- 
scope. 

We soon found that our task was more difficult than we 
had at first imagined. The quantity of plankton fluctuated 
greatly in the course of short periods of time, yet the variations 
could not be ascribed directly to conditions of existence, since 
these remained fairly constant. The temperature in the surface- 
layers rose steadily during March to May from 1.5° C. to 6.3° C, 
the quantity of chlorine was about 16 per thousand, and according 
to Nathansohn the quantity of free ammonia in filtered samples 
of sea-water was between 0.0175 mg. and 0.031 mg. per litre, 
and of ammonia in organic combined form between 0.105 ^S- 
and 0.217 mg. per litre. Of nitrates and nitrites he only found 
infinitesimal quantities up to 0.009 ^ig-. set down as ammonia. 
Chcetoceras constrictum, one of the commonest diatoms in the 
spring plankton of the Christiania fjord, furnished the following 



PELAGIC PLANT LIFE 



Z7?, 



figures, denoting the number of living cells in every litre of 
surface-water near Drobak : — 



1907. 


27/111. 


■30/111. 


2/lV. 


9/n'. 


15/iv. 


20/iv. 


4/\'. 


6/v. 


l/VI. 


19/VI. 


ChcEtoceras 
constrictum 


20,850 


45=850 


12,750 


59.730 


760 


44,425 192,500 


95,480 


1280 






A quite satisfactory explanation presented itself, however, 
for the variations turned out to be closely connected with the 
direction of the winds and currents. The outflowing current 
in the surface-layers might reduce the quantity of plankton to 
a mere fraction of the normal amount in the course of a day 
or two, while the inflowing current might perhaps double the 
quantity in a few hours. The current exerts so great an 
influence because the abundant plant life is limited to a thin 
surface-layer which is sharply differentiated both in salinity and 
temperature from the water-masses below. On 28th March 
1907, for instance, the temperature from the surface down to 
20 metres was 2.6'^-3.6° C, and the quantity of chlorine worked 
out at 16.74-17.62 per thousand ; from 40 metres down to the 
bottom at 80 metres the temperature was 6.2^ C, and the 
quantity of chlorine was 18.73 P^^ thousand. The outflowing 
current carries the surface-layers with their algse out of the fjord, 
and the infertile deep water may be sucked up to perhaps 
5 metres below the surface. The inflowing current, on the 
other hand, heaps up the fertile surface-waters. We found, on 
examining the plankton at different depths, that the bulk of the 
plants was limited to a very thin surface layer, say 5 metres in 
depth, after the current had set outwards, whereas subsequent 
to the inflow of the current they were as abundant down to 
30 or 35 metres as at the surface. 

At a place like this it was difficult to trace any regular 
connection between the local conditions of existence and the 
development of plankton-algae, in view of the fact that currents 
caused variations of even greater extent than those actually due 
to^conditions of existence. We had therefore to conduct our 
investigations on other lines. Supposing it were possible to 
determine the rate of growth of the algae we should get a better 
measure of production, and probably also of the influence due 
to vital conditions, than variations in the total amount could 
give us. The number of individuals at any given moment 
depends not merely upon the rate at which production has 



374 DEPTHS OF THE OCEAN 

taken place, but also upon how many have perished or been 
carried away ; and the causes bringing about diminution, which 
we may perhaps term factors of loss, may vary without being 
in any way directly connected with the conditions of existence 
of the plankton. There is one genus, at any rate, whose rate 
of augmentation can be approximately determined. The 
species of Ceratmin only divide their cells at night, so that 
if we make our investigations early in the morning we can tell 
which cells have been divided during the night and which 
remain entire. In a sample of surface-water on loth September 
1907 we found 300 whole cells and 161 half cells of CeratitLvi 
tripos, the latter consisting of 79 anterior parts and 82 posterior 
parts. The number of cells, then, had in twenty-four hours 

increased from 300 -I = 380.5 on 9th September to 

300 -|- 161 =461 on loth September. The addition is accordingly 

= 80.5 individuals, and the percentage of the total amount 

10 1 1 100 X 80.5 
on 9tn September works out at — ^ ^ = 21.2 per cent. 

This was the plan we adopted for calculating the augmenta- 
tion of the species of Ceratimn at Drobak during the whole 
of their vegetation period in 1907, and we also recorded the 
average number per litre at different depths during the whole 
year.^ The following tables show our chief results : — 

^ Similar investigations in the case of Ceratiuni tripos were carefully carried out during 
1908-1909 by Apstein in the Baltic. The values he obtained for percentages of augmentation 
on the whole accord as nearly with mine as might be expected. 



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PELAGIC PLANT LIFE 



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3/6 DEPTHS OF THE OCEAN 

The figures in the tables clearly indicate that, though the 
rate of increase is highest in August, the number of cells of 
Ce^-atiiini in the fjord makes no great advance before October. 
Throughout the whole summer the number continues at about 
the same level, in spite of a comparatively rapid production. 
This affords a further indication that in the Christiania fjord 
variations in the current and other factors of loss exert a greater 
influence than the variations in the conditions of existence 
which affect rate of increase. 

The fact that we find in the Christiania fjord, and assuredly 
also in many other places along the coasts of North Europe, 
that the plankton is less abundant in the summer months than 
in spring, does not necessarily imply any unfavourable change 
in the conditions of existence due to summer. It may be caused 
by the melting of the snow in spring, and by the river water all 
through the summer driving the surface-water and its plant- 
life away from the coast, so that the production near land 
barely replaces the loss. In the autumn it would seem as 
if the prevalent sea-winds heap the surface -layers together 
along the coast, and thereby accumulate large quantities of 
plankton. 

What effect these movements of the surface-water have 
upon the occurrence of the plankton we are as yet unable to 
say definitely, but they must be taken into consideration. We 
were obliged, therefore, to abandon our original intention, 
which was to ascertain the importance of such conditions of 
existence as dissolved nutritive substances, and particularly 
nitrogenous compounds. 

I made a series of cultivation experiments, however, under 
experiments, conditions of existence resembling the natural conditions as 
nearly as possible. Stoppered glass bottles holding two and a 
half litres were kept just floating at the surface, by being filled 
with about two litres of sea-water ; the amount of plankton 
present was carefully checked in advance, and then one bottle 
was left in its original state, while in the other two small 
quantities of chloride of ammonium or calcium nitrate were 
placed. After an interval of 3 or 4 days the plankton in all the 
bottles was once more examined, and it was generally found 
that most of the species had augmented best when nitrogenous 
nutriment had been added. The addition had naturally to be 
made with the utmost care, since anything over 0.5 mg. per 
litre generally had a poisonous effect. The following table 
shows the result of one of these experiments : — 



Cultivation 



PELAGIC PLANT LIFE 

Number of Cells per Litre. 



Z11 



1 


Before experiment 
on 21/viii. 


Three Days Later (24/viii). 


In Original 
State. 


With addition of 0. 5 mg. 
NH4CI per litre. 


Ceratiinn tripos . 583 
„ fusus . 543 
„ furca . 155 

Prorocentrum micans , 1052 

Dinophysis acmiiinata 219 

„ rotundata 33 

Rhizosolenia alata . 157 
Cerataulina bergonii 2840 


640 
649 
149 

548 
107 

30 

232 
3381 


696 

833 
196 

1464 

226 

42 

345 
7214 



Experiments with pure cultures of different plankton- 
diatoms, made by Allen and Nelson at Plymouth, show that 
they do not thrive without a regular supply of nitrogenous 
compounds. The plan of working which they adopted may 
also be employed with advantage when we wish to ascertain 
what concentration of dissolved nitrogenous compounds induces 
the plankton-algae to augment most rapidly. This is the 
first thing to find out if we desire to know whether a want of 
dissolved nutritive substances is the limiting factor of production. 
It is quite possible that augmentation diminishes from lack of 
nitrogen long before the total amount of this essential has been 
fully consumed ; yet augmentation must not fall below a certain 
minimum if the species is to hold its own, because of the larger 
or smaller number of individuals that are constantly perishing. 
Questions like these can only be settled by experiment, so that 
the cultivation method of Allen and Nelson is bound to be of 
great assistance to us eventually. But in the meantime our 
comparative investigations over large areas of the sea are also 
of considerable value. 

I have already stated that plant life in the Christiania fjord 
was limited to a very thin surface-layer, which, owing to its 
lesser density, was differentiated from the deeper infertile 
water-masses, and this was practically the case along all 
the coasts where plankton-algse were plentiful. Out in the 
open sea, on the other hand, where there are not such 
marked differences in salinity, temperature, and density be- 



Allen and 

Nelson. 



Plankton 
extends 
deeper, but 
is less 

abundant, in 
the open sea 
than in 
coastal areas. 



378 DEPTHS OF THE OCEAN 

tween the surface water and the deep water, the pelagic 
algse extended deeper ; at 50 metres, for instance, the quantity 
was still near the maximum, and even as deep as 100 metres 
or more the number was considerable. This, at any rate, 
was what we found in the case of the diatoms that abounded at 
our first stations off the Irish coast-banks and in the Bay of 
Biscay, and this too was what Schimper discovered in the 
Antarctic. It is also a regular rule that plankton is far more 
plentiful along the coasts than in the open sea, and, judging 
from investigations hitherto made, the proportion between what 
is produced in a typical coastal area and what is developed in 
typical oceanic water-masses would be more accurately expressed 
by 100 : I than by 2:1. For this the best explanation which I 
can give is that the open sea generally suffers from a want of 
one or more nutritive substances required by the plants, for 
though these are brought down to the sea in comparatively 
large quantities by the rivers, they are almost entirely consumed 
by the plant life of the coastal areas. 

This is why the abundant plant life of the coastal seas is 
confined to the surface-layers, since the water-masses lying 
below remain separated, and consequently cut off from the 
plentiful supply of nutritive substances which regulate the 
augmentation of plants. But out in the open sea there is 
another important source of nutriment to be taken into account. 
Nathansohn has pointed out that pelagic animals are constantly 
taking nutritive matter down into deep water, and that for 
the time being it is accordingly withdrawn from the plants, 
even though the metabolism of the animals and the action 
of bacteria liberate it once more in inorganic form. These 
nutritive substances may rise to the surface-layers again by 
diffusion, but the process will require a long time. They may 
also accompany the ascending water-masses where off-shore 
winds bring about up-welling, in cyclonic current systems, and 
where the surface-layers, becoming chilled, sink and make 
Vertical room for warmer layers from below. Wherever vertical 

circulation takes place, and it is assisted in its action by storms 
and waves, the temperature and salinity will be extremely 
uniform from the surface down to a depth where the water- 
masses have such a high salinity that their greater density sets 
a limit to circulation. Conversely uniformity in temperature 
and salinity may be taken as a sign that vertical circulation has 
just taken place. This was the condition of affairs at our 
stations to the south-west of Ireland (see Fig. 252), where we 



circulation. 



PELAGIC PLANT LIFE 



79 



Stat. 4 a 

106 55-50 



found abundance of plankton in April 1910, algae being present 
in large quantities as deep down as they have been known to 
occur, that is to say as far down as sufficient light penetrates. 
We can appreciate the difference between these conditions and 
the conditions in coastal areas like the Christiania fjord, if we 
remember that the nutritive substances in the first case may rise 
up from the deep water, while in the second they are derived 
from the surface through the admixture of fresh water. 

Vertical circulation is regulated by differences in tempera- 
ture at the surface, due to summer and winter, which are 
sufficient to in- 
crease the density 
of the upper 
layers till it equals 
the density lower 
down, and if cir- 
culation is to have 
any effect in the 
open sea, the sur- 
face-layers must 
be able to sink to 
a depth of at least 
200 to 300 metres. 
The greater the 
difference in tem- ^^° 
perature between 
summer and win- 
ter, the more 
effective will ver- 
tical circulation 
generally be. 

Assuming, then, that our view is correct, namely that plant 
production in the sea is mainly regulated by the amount of 
dissolved nutritive substances, we must expect to find plankton 
produced in abundance in coastal areas to which large rivers 
convey nourishment from the land, and in oceanic areas where 
vertical circulation takes place on a large scale, or where 
ascending currents bring up the deeper water-masses. Where 
vertical circulation is the controlling influence, the greatest 
profusion will be at seasons when the temperature of the 
surface reaches its minimum ; that is to say, generally in 
winter, or in higher latitudes in the early months of spring. It 
would be possible to test the truth of this theory if we could 




Hydrographical Section off the Irish Coast 
(April 1910). 
Temperature and salinity nearly uniform from the surface down 
to a depth of 250 metres. 



38o DEPTHS OF THE OCEAN chap. 

carry out systematic quantitative plankton investigations all 
through the winter, in combination with hydrographical re- 
searches, in parts of the Atlantic like the sea round the Azores, 
where the plankton is known to be scanty during the summer, 
but where during the course of winter vertical circulation 
might be expected to create different conditions of existence. 
Whipple. In this connection it should be mentioned that the influence 

of vertical circulation upon the production of plankton-algse 
in fresh water has long been known to biologists. It has been 
pointed out by Whipple, who showed that the maxima of 
diatoms in particular coincide with the seasons when vertical 
circulation takes place, namely autumn and spring. And in 
the sea, too, it seems that diatoms, with their power of rapid 
augmentation, are the first to respond to improved conditions of 
nourishment. 

Which of the essential nutritive substances are the chief 
limiting factors in the sea, it is impossible to say as yet. Prob- 
ably, however, nitrogen is the most important, and next to it, 
perhaps, more especially in the case of diatoms, we may put 
silicic acid. Brandt and Nathansohn have both discussed 
the occurrence of these substances, but we need further and 
more conclusive information than what we now possess. 
Nathansohn has likewise considered the possibility of carbonic 
acid occurring "in minimum." This seems paradoxical, of 
course, since there are comparatively large quantities of it in 
sea-water. Still the greater part is combined in the form of 
carbonates, and only a very small portion is set free by dis- 
sociation at any given moment, so as to become available for 
the plants. How much there is in this form will depend on the 
alkalinity of the sea-water and on the temperature. When 
the free carbonic acid is used up by the plants, fresh quantities 
will gradually be absorbed from the atmosphere, though this 
may take place so slowly that there need not necessarily be any 
equilibrium between the carbonic acid tension in the atmosphere 
and at the surface of the sea. It is accordingly quite conceiv- 
able that the shortage may for a time be considerable enough 
to stop the algae from assimilating carbonic acid. When the 
temperature is high the quantity of free carbonic acid in the 
sea-water will ceteris paribus be less than when it is low, and 
this also may help to explain the relatively poor production in 
warm seas. Variations in the tension of carbonic acid, how- 
ever, have not as yet been sufficiently studied. 

The organic substances built up by pelagic algae unquestion- 



PELAGIC PLANT LIFE 381 

ably form the chief basis, and in the open sea practically the 

sole basis, of nutriment for all the pelagic animal life, as well 

as, through their pelagic forms, for the fauna of the sea-bottom. 

It is not, however, quite so certain that all the different algae 

are equally useful as food to the animals which live on plant 

stuffs. Brandt's chemical studies of plankton organisms have 

distinctly shown that nutritive value does not necessarily 

correspond to volume. Diatoms, with their long silicated 

setae, or with big bladder-shaped cells that merely enclose a 

thin layer of protoplasm along the inner side of the wall, have 

little nutritive value compared to the majority of the peridineae, 

in which most of the cell -chambers are full of protoplasm. 

The dry substance of diatoms, according to Brandt's analyses Chemical 

of plankton samples, chiefly ChcEtoceras, contains 10 to 11.5 per o? plankton 

cent albumen, 2.5 per cent fatty matter, 21.5 per cent carbo- samples. 

hydrates, and as much as 64.5 to 66 per cent ash, 50 to 58.5 

per cent of this last being silicic acid. Another sample, largely 

consisting of Ceratium tripos, had a totally different composition, 

the dry substance containing 13 per cent albumen, 1.3 to 1.5 

per cent fatty matter, 80.5 to 80.7 per cent carbohydrates 

(half of which was chitin), and not more than 5 per cent ash. 

We are still without systematic studies of the nutriment of 
plankton animals, and consequently do not know for certain 
whether some families of plants are preferred to others. The 
contents of the intestinal canals of salpse make it evident that ^ooAoi Saipa. 
these animals at any rate collect all the different small organisms 
to be found in their neighbourhood. In warmer waters the 
greater part of. their stomach-contents consists of coccolitho- 
phoridae and other tiny forms, but we find besides representatives 
of all the plankton-algae. Small peridineae, for instance, like 
Gonyaulax poly gramma, are seldom wanting. In fact, Stein, the 
well-known specialist on protozoa, who had no plankton-catches 
to aid him in his researches, got the best part of his material 
from the stomachs of salpae, and was thus able to write his valu- 
able initiatory monograph on peridineae. And this, too, was the 
plan adopted at first for studying diatoms, so that our knowledge 
of pelagic genera like Asteroinphalus and Asterolampra is largely 
due to the examination of the stomachs of salpae. During 
the cruise I invariably examined the stomach-contents of 
salpae, and obtained thereby plenty of small forms, coccolitho- 
phoridae especially, for comparison with the material in the 
centrifuge samples. As we approached the coast of Europe, 
however, the contents took on another character, for at Station 



382 



DEPTHS OF THE OCEAN 



Food of 

Appendicu- 

laria. 



Food of 
Copepods 



Proportion of 
plants and 
animals in 
the plankton. 



97 most of the forms were diatoms, and to a great extent con- 
sisted of Rhizosolenia alata. Generally speaking we discovered 
that salpse do not trouble to make any selection. Lohmann's 
studies of Appendicular ia have shown us t^t these animals get 
their nutriment by means of a filter apparatus, which allows only 
the minutest organisms, coccolithophoridse in particular, and 
small peridineae, to enter the digestive canal. 

The chief consumers of plants in the sea are undoubtedly 
copepods. Their conditions of nutriment, however, have so far 
been principally studied by means of their excrements, which sink 
down in the shape of small elongated lumps, and are often brought 
up in numbers by the silk nets. Still, in these excrementa all 
the softer components have been digested, and the shells that can 
be identified do not necessarily always belong to species which 
are an indispensable part of their nutriment. Undoubtedly the 
calcareous shields of coccolithophoridse occur too frequently for 
their presence to be ascribed to chance, indicating, moreover, 
that the digestive juices of copepods cannot have an acid 
reaction. In addition we very often meet with more or less 
bent and distorted coverings of peridineae, and in northern 
waters the excrements contain stiffer forms like the little 
Dinophysis gi'amilata in a practically unchanged condition. In 
localities where diatoms predominate, the excrements consist 
largely of bent and broken bits of species like Rhizosolenia 
semispina and R. alata. Even if Hensen's view be right 
that diatoms supply far less nutriment comparatively than the 
other classes of plants in the plankton, it is at any rate quite 
certain that the animals do feed on them, and especially when 
they are plentiful. In the Norwegian Sea I have several times 
observed that where diatoms abounded there might perhaps be 
only a few copepods and other plankton animals ; still the 
copepods were there, and In large numbers too, just below the 
diatom zone, and their excrements consisted to a great extent 
of the silicious coverings of diatoms. 

Hensen noticed that the plants in the sea are often 
so scanty that it is hard to understand how all the animals 
get enough nourishment, and this is even more difficult to 
comprehend when we consider that the plants have directly 
or indirectly to support every single animal from the surface 
right down to the bottom. In many cases, perhaps, the plants 
may be more abundant than a cursory examination would seem 
to indicate ; and the most diminutive forms, which are still 
practically unknown to us, undoubtedly exist in sufficiently 



PELAGIC PLANT LIFE 383 

large numbers to play a momentous part in the general economy. 
Still careful study distinctly reveals the fact that the plants 
of the sea are in striking disproportion to the animals. The 
most reliable results so far obtained are those due to Lohmann's 
researches in Kiel Bay. He studied the quantities of all the 
plankton organisms for a whole year with great thoroughness, and 
calculated the volume of the various groups in the plankton of the 
different water-masses at all seasons. To us his most interesting 
discovery is that the plants on an average made up 56 per cent 
and the animals 44 per cent of the total plankton. In the 
winter months the plants were easily outnumbered by the 
animals, and from December to February they formed scarcely a 
third of the total plankton. In the summer, on the other hand, 
they predominated, and made up sometimes even as much as 
three-quarters of the whole. Plants which are reproduced by 
division must necessarily decrease rapidly whenever vigorous 
augmentation ceases, if animals are constantly consuming 
numbers of them. 

The life-cycle of animals, with its growth-period in youth Life-cycle of 
and propagation in maturity, is more complicated than that of ^""^^^'^• 
plants, and gives them a better chance of withstanding unfavour- 
able conditions of existence. A lower temperature necessarily 
reduces their intensity of breathing, and thus diminishes their con- 
sumption of nourishment, and it may be also that they can go 
without feeding for a comparatively long time, during which they 
live upon reserve matter that they have accumulated at more 
favourable seasons. Damas made some interesting studies of 
the life-cycle of the larger copepods, and found that propagation 
may require a higher temperature than what is necessary for 
conserving vital energy, and that therefore these forms can 
delay their propagation until the conditions of existence become 
more favourable, so that the young animals may have the rich 
nutriment required for their growth. Calamis finmarchims, the 
commonest large copepod of the Norwegian Sea, abounds 
wherever the temperature is over 2° C, in both its half-grown 
and full-grown stages, but propagation does not begin till the 
temperature rises to 4" C, either owing to warmer water-masses 
arriving from the south, or to heating at the surface from the 
atmosphere. 

Lohmann has endeavoured to calculate the relation between Relation 
the augmentation of the algse and their consumption by animals production 
throughout the year in Kiel Bay. He assumes that there is a and consump 
daily accession of 2>'^ per cent to the volume of the algse, and '°" ° ^^^' 



384 DEPTHS OF THE OCEAN chap. 

that this can be consumed by the animals without harm to the 
plant aggregate. He further assumes that copepods and other 
multicellular animals require per day a quantity of nutriment 
equal to a tenth of their own volume, whereas protozoa need 
half their own volume. In view of what I have previously 
stated regarding the variations in the rate of production of 
Ceratiitm, I have no hesitation in declaring that the augmenta- 
tion of the algae varies within wide limits, and the same is 
undoubtedly also the case with the nutriment-requirements of 
the animals. Still I am quite ready to concede that Lohmann's 
assumptions may apply to the average conditions. The follow- 
ing table compiled by him, and showing values in cubic milli- 
metres of plankton per 100 litres of sea- water, will doubtless be 
of interest : — 



Organic 
matter in 
sea-water. 





Daily Augmentation 


Daily 


Surplus 




of Producers 


Nutriment-requirement 


or 




available for Nutriment. 


of Animals. 


Deficiency. 


August 


35 


6 


+ 29 


September 


27 


8 


+ 19 


October 


14 


5-5 


+ 8.5 


November . 


9 


4-5 


+ 4-5 


December . 


3-5 


2-5 


+ i.o 


January 


3 


1.8 


+ 1.2 


February . 


I 


1.8 


-0.8 


March 


3 


2.4 


-t-0.6 


April . 


13 


2.0 


+ 11 


May . 


14 


5-5 


+ 8.5 


June . 


20 


4.0 


+ 16 


July . . 


17 


4-5 


-f 12.5 


August 


16 


4-3 


-f 11.7 



According to this table the surplus plant substance is not 
large, and in February there was actually a deficiency. It is 
possible, too, that Lohmann's assumptions are on the optimistic 
side, and that he has put the production-capacity of the plants 
too high, and the nutriment requirements of the animals 
too low. 

Putter, after studying the quantities of oxygen consumed by 
different marine animals, both benthonic and pelagic, considers 
that the augmentation of the plant aggregate by no means 
suffices as nutriment for the animals. If his view is correct, there 
must, of course, be other sources of nutriment, both to replace 
the loss of organic substance which the animals incur by 



PELAGIC PLANT LIFE 385 

breathing, and also to supply building material for their growth 
and propagation. Putter has endeavoured to find out whether putter. 
organic matter dissolved in the sea-water does not provide this. 
He investigated its amount, and got surprisingly high values. 
Improved methods have enabled Raben to check his experi- 
ments ; in water from Kiel there were 10.9 to 13.9 milligrams, 
or on an average 12.25 milligrams, of organic combined carbon 
per litre of sea-water, and at a station in the Baltic 3 milligrams. 
These are really high values, if we compare them with the 
quantities of organic substance we are able to point to in the 
form of living organisms. Lohmann's studies show that the 
total amount of the organic combined carbon in the plankton at 
Laboe in Kiel Bay varied during the year between 12.7 mg. 
and 1 89.8 mg. per 1000 litres of sea- water. According to Raben's 
investigations at a place close by, the mean value of organic 
combined carbon in dissolved form is 12,250 mg. per 1000 litres, 
or in other words about sixty times as much. 

Too little is known, unfortunately, about the occurrence of 
organic matter, and there are many difficulties to be overcome 
before we can look for conclusive results. Perhaps the most 
discouraging thing is that even the best filters allow a good 
many organisms to pass through them. The water-samples 
to be examined ought possibly to be freed from all suspended 
insoluble matter by means of the centrifuge, but even this 
method will not always give entirely satisfactory results, since 
some of the algae (cyanophycese, Halosphcp.ra) are lighter than 
sea-water, while the nimbler animals will swim up from the 
bottom before one can separate the clear water from the 
deposit. Putter's hypothesis, however, certainly deserves to 
be further tested. If it be really true that in the salt-water of 
the open sea there is organic substance in sufficient quantities 
to be compared with what is combined in plants and animals, 
then this substance must be due to the production of plants. 
We will accordingly be forced to conclude that the pelagic 
algse distribute to their surroundings through their surface 
comparatively large quantities of organic substance, and that 
their production is thus in actual fact much more consider- 
able than we are led to believe, when we merely measure what 
they store up in their cells during growth and augmentation. 
Even if it seems strange biologically that they should evince 
such want of economy in regard to valuable nutritive matter, 
it would be unwise to reject the hypothesis, and the best plan 
is to await the results of continued investigations. Some 

2 c 



386 DEPTHS OF THE OCEAN chap, m 

biologists favour the theory and others oppose it ; some of 
them have pubHshed the results of special studies, particularly 
of the nutrition-processes of animals, all of which have been 
of service to the cause of science, though they have not 
succeeded in deciding this question. 

Lohmann and C. G. J. Petersen have maintained that 
organic detritus may be of intrinsic importance for the nutriment 
of animals, as well as plants, and they have demonstrated that 
organic detritus from the land is present in fairly large quantities 
in waters like the Baltic or off the coasts of Denmark. We 
have reason, therefore, to expect extremely interesting results 
from the work of the Danish biologists on organic detritus in 
the water and in the deposits at the bottom of the sea. But out 
in the open sea this detritus is only met with in inconsiderable 
quantities, as our centrifuge-samples showed us on board the 
" Michael Sars." I do not, of course, include inanimate organic 
substances, such as excrements or the empty chitin-coverings 
of copepods, which form a part of the circulation of nutritive 
substances through the pelagic organisms. Organic fragments, 
not actually derived from pelagic organisms, either do not occur 
at all in the open sea, or, if they do, are not worth taking into 
consideration. 

H. H. G. 



CHAPTER VII 

FISHES FROM THE SEA-BOTTOM 

Zoologists on both sides of the Atlantic have long been 
engaged in collecting facts regarding the occurrence of fishes 
and other organisms which inhabit the Northern Atlantic and 
adjacent waters. In recent times special expeditions have 
offered opportunities of collecting according to definite plans, 
and the American expeditions in the " Blake " and the 
"Albatross," and the European ones in the "Challenger," in 
the " Travailleur," the "Talisman," and the " Princesse Alice" 
have added essentially to our knowledge. As a consequence 
a very large amount of material has been accumulated, but as 
yet this material has not been utilised for the purpose of 
drawing up a general account of the distribution of the 
different animal-communities. 

Any attempt to review our knowledge, or to summarise the 
voluminous literature on this subject, would extend this book 
beyond all reasonable limits, and I shall therefore restrict 
myself to certain important and characteristic main lines in the 
distribution of Atlantic fishes and other animals, relying 
principally on the captures made during the cruises of the 
" Michael Sars." The material gathered during these cruises 
is so large that a representative view may now be obtained, 
and while confining myself to our own observations I hope to 
give some information of real value. My aim, then, will be to 
describe the geographical distribution of the fishes, as this 
group has been made the special object of our researches ; 
other groups of animals will be mentioned only in order to 
illustrate the surroundings and the animal-communities associ- 
ated with the different fishes. 

In dealing with animal geography one must always pre- 
suppose a knowledge of a vast number of animal forms. The 
animals inhabiting the depths of the sea are strange to all but 

387 



collected by 
the " Michael 
Sars." 



388 DEPTHS OF THE OCEAN chap. 

a few specialists, and are known only by Latin names, of 
which most zoologists even are ignorant. Nevertheless these 
names must be used if the reader desires to penetrate into the 
general laws which govern the distribution of animals in the 
ocean. In order to overcome this difficulty I commence this 
chapter with systematic lists recording the different species of 
fishes, and the details of their capture, accompanied by outline 
drawings of the most important species. By means of these 
lists the reader may easily obtain information as to what group 
in the system a certain fish belongs, and further details will be 
found in the literature of the subject.^ 
Bottom-fishes During the many cruises of the "Michael Sars" probably 

all the species of fish which live in the Norwegian Sea and 
the North Sea have been captured, but only the commonest 
species will be treated of here. Nearly all the fish caught 
during the Atlantic cruise in 19 10 will, however, be mentioned, 
or at all events as many as the present state of the work 
will permit. 

The following list includes all the forms captured by us in 
the Atlantic which, according to our experience, must be con- 
sidered as living mainly along the bottom. 



I. List of Fishes caught by the "Michael Sars" 

ALONG THE SeA-BoTTOM IN THE NoRTH ATLANTIC 

This list includes 138 different species belonging to almost all the 
most important groups of bottom-fishes. Thirty-two species belong 
to the order Plagiostomi, fishes with a cartilaginous skeleton, and 106 
to the order Teleostei, fishes with an ossified skeleton. 

The Elasmobranchii. — Our list includes of the order Plagiostomi 
the two sub-orders, Selachii (sharks) and Batoidei, with the family Raiidae 
(rays), besides the order Holocephali with the Chimaeridae. 

Seventeen species are sharks (Selachii), including the large Atlantic 
Notidamis, the small but numerous Scylliidas, which also go into the 
Norwegian Sea. Of the large group of the Spinacidae, Acanthias -vulgaris 
is caught by the nets of the fishermen in the North Sea ; it follows the 
herring shoals, and is therefore called dog-fish by the fishermen. 

The two genera CentropJiorus and Spinax include deep-sea fishes living 
on the slope. CentropJiorus is confined to the Atlantic only, and so is 
CentroscylliuDi ; Spinax niger is caught in the Norwegian fjords also. 
Two teeth of extinct species of sharks, CarcJiarodon and Oxyrhina, were 

' See, for instance, A. C. L. G. Giinther, An hitroduciion to the Study of Fishes, chap, 
xxi., Edinburgh, 1880 ; Francis Day, The Fishes of Great Britain, Edinburgh, 1880-84 ; 
Boulenger and Bridge, Fishes, in the Cambridge Natural History, 1904. The lists are arranged 
according to the system proposed by Boulenger. 



FISHES FROM THE SEA-BOTTOM 389 

found in deep water by the " Michael Sars," similar to those found in 
such great numbers by the "Challenger" in the Pacific, 

Twelve species are rays (Raiidae). Raia niicroocellata and R. miraletus 
are true Atlantic species, caught by the "Michael Sars" only south of 
the Canaries. The other species are caught also in the Norwegian 
Sea. 

Of the family Chimseridae, CJiimcEva monstrosa is recorded from the 
Norwegian Sea, from the extreme north of Norway, from the whole of 
the Atlantic down to the Cape of Good Hope, from Sumatra and Japan. 
C. viirabilis was discovered by the " Michael Sars " in 1902, south of 
the Faroe Islands, in deep water. Hariotta raleighana, in appearance a 
most remarkable deep-sea fish, was previously known from the Atlantic 
slope off the United States. 

The Teleostei are represented in our list by no less than eight 
sub-orders. 

The Malacopterygii include salmon-like fishes ; two species of the 
genus Argentina live near the continental edge or the deepest part of 
the coast-banks of the Norwegian Sea and the Atlantic. The family 
Alepocephalidae includes true deep-sea fishes, black in colour, known 
from the greatest depths of the ocean, but not recorded from the 
Norwegian Sea. They are salmon-like in form, and attain the dimen- 
sions of a small salmon. 

The Apodes, or eel-like fishes, include a great number of deep-sea 
fishes belonging to the family Synaphobranchidas. SynapJiobrancJius 
pinnatus is known from all the oceans of the world, and was caught 
in deep water by the " Michael Sars " at many stations. The family 
Mursenidae includes shore -fishes ; the splendid Murcena helena was 
caught off the African coast. 

The Haplomi and the Heteromi include true deep-sea fishes, the 
genera being BatJiysauriis, Bathypterois, the new genus BatJiyniicrops, 
Halosauropsis, and NotacantJnis. None of them are known from the 
Norwegian Sea, but some have a world-wide distribution, and have been 
caught at the very greatest depths where trawlings have been taken. 

The Catosteomi and Percesoces are only represented by one species 
each ; both coast-fishes. Centriscus scolopax is a brightly-coloured little 
coast-fish with a pipette-like rostrum. 

The Anacanthini are represented in our list by no less than 36 
different species, 19 of Macruridae, and 17 of Gadidae. These two 
families are very nearly related. The Macrurids include the most 
important and numerous bottom-fishes on the continental slopes and 
over the abysmal areas of the ocean. The Gadidae are the most numer- 
ous and economically the most important food-fishes in northern and 
subtropical waters. The Macruridae have representatives which live in 
very deep water only, others which are confined to certain geographical 
areas of the slope, and so on ; these will be treated in greater detail later. 
Of the Gadidae the genus Gadus has a number of species (for instance, 
the cod, the haddock, the whiting, the pollack, the saithe) which are 
characteristic of different parts of northern waters, while the genus 
Merluccius is the most important food-fish on subtropical coast-banks. 
The genera Molva (ling) and Brosviius (tusk) inhabit the deepest parts 



390 DEPTHS OF THE OCEAN 

of the coast-banks, and the genera Mora, Lepidion, and Halargyreiis the 
uppermost part of the continental slope. 

The Acanthopterygii.- — Fifty-one species belong to this very important 
and large group of highly developed fishes, most of which are true coast- 
bank fishes, only a few of them being known from the uppermost part 
of the slope. 

Most of these fishes, the Serranidae, Sciaenidae, Pristipomatids, 
Sparidae, Mullidae, Caproidae, Labridae, Scorpaenidae, Triglidae, Trachi- 
nidai, Uranoscopidae, and Callionymidae, are brightly-coloured fishes, with 
hard ossified scales and spines of moderate size, living in shallow water, 
or deeper, on the coast-banks, with a maximum distribution in warm 
subtropical waters. The northern limit of their distribution differs for 
different species, several extending even to the southern warmer parts of 
the bays and fjords of Scandinavia; other families, e.g. Cottidae and 
Blenniidae, have representatives in the Arctic {Triglops, Lumpenus). 
None of these families have, however, any economical importance in 
the Norwegian Sea or North Sea. 

The family Pleuronectidae, or flounders, includes very important 
food-fishes. The plaice, flounder, sole, dab, megrim, halibut, all belong 
to this family. Hippoglossus, Pleuronectes, and Zeugopterus are northern 
genera ; Solea is the most important genus in the Atlantic, Solea 
vulgaris being of importance also in the southern parts of the North Sea. 

The Scombriformes, to which belong the genera Trachurus or 
Caranx, Scomber, Thynnus, are mostly pelagic, but are also caught very 
near to the shore. The mackerel, the tunny, the horse-mackerel are 
all economic species of great importance. 



Class— PISCES 

Sub-Olass— ELASMOBRANOHII 

Order — PL AGIOSTOMI 
Sub-Order— SELACHII 

NOTIDANID^ 

Notidanus griseus, Cuv. (six-gilled shark), 1902, Faroe-Shetland channel (Fig. 
253)- 




Fig. 253. 
Notidanus griseus, Cuv. (After Bonaparte.) 



FISHES FROM THE SEA-BOTTOM 



391 



SCYLLIID^ 

Scyllium canicula, Cuv. (rough hound), 1910, Stations 3, 14, 20, 39. 

Pristiurus melanostomtis, Bonap. (black-mouthed dogfish), 1902, Faroe-Shetland 

channel; 19 10, Stations i, 21. 
Pristiurus murifius, Coll., 1902, Faroe-Shetland channel, 11 00 to 1300 metres. 

CARCHARIIDyE 

Mustelus vulgaris, Miill. and Henle (smooth hound). 19 10, Station 13. 

Lamnid^ 
Carcharodon, fossil tooth, 19 10, Station 48 (see Fig. 254). 
Oxyrhina, fossil tooth, 19 10, Station 48. 




Fig. 254. 
Carcharodon mrgalodon. Fossil Tooth. Station 48. (After Zittel. ) This figure shows a Car- 
charodon tooth from Tertiary deposits ; those dredged from the deep-sea deposits have never 
the base preserved (see Fig. 126, p. 156). 



Spinacid^ 
Cenirina salviani, Risso, 19 10, Station 13. 

Acanthias vulgaris, Risso (dog-fish), 1902, Faroe Bank, 390 metres; Faroe- 
Shetland channel; 1910, Stations i, 3, 20, 39 (see Fig. 255). 




Fig. 255. 

Acanthias vulgaris, Risso. (After Smitt. 



192 



DEPTHS OF THE OCEAN 



Centrophorus crepidater, Boc. and Cap., 1902, Faroe Bank, 750 metres. 
Cetitrophorus squamosus, Gmel., 1902, Faroe Bank, 390 to 750 metres (see Fig 
256). 




Fig. 256. 

Centrophorus squamosiis, Gmel. (After Jensen. ) 

CeJitrophoriis ca/cei/s, Lowe, 1902, Faroe Bank, 750 metres. 
Centrophorus coelokpis, Boc. and Cap., 1902, Faroe Bank, 750 metres. 
Spinax niger, Bonap., 1902, Faroe Bank, 426 metres; 1910, Station 21. 
Spinax (Etmopterus) prificeps, Coll., 1902, Faroe-Shetland channel and Faroe 

Bank. 
Centroscyllium fabricii (Reinh.), 1902, Faroe-Shetland channel and Faroe Bank. 

RhINID/E 

Rhiiia squatina, Dumeril, 1910, Station 39. 



Sub-Order— BATOIDEI 

Raiid^e 
Ram clavata, L. (thornback ray), 1902, Faroe Bank, 130 metres; 1910, Stations 
I, 3, 13, 14, 20, 39 (see Fig. 257). 




Fig. 257. 
Eaia clavata, L. (After Smitt. ) 

Raia punctata, Risso, 1910, Stations 37, 38,^39. 
Rata mkroocellata, Montagu, 1910, Station 37. 



FISHES FROM THE SEA-BOTTOM 



393 



Raia alba, Lacep., 1910, Station 37. 
Raia miraletus, L., 1910, Station 39. 
RaiafyllcB, Ltk., 19 10, Stations 25, 95. 
Raia circularis, Couch, 19 10, Stations 3, 13, 



;9 (see Fig. 258). 




Fig. 258. 
Raia circularise Couch. (After Smitt. ) 

Raia batis, L. (skate), 1902, Faroe Bank, 130 metres; Faroe-Shetland channel. 

Raia vomer, Fries, 1902, Faroe Bank, 750 metres ; 19 10, Station 3. 

Raia /lidrosiensis, Coll., 19 10, Station 4. 

Raia fullonica, L., 1902, Faroe Bank, 390 metres; 1910, Station 21. 

MyliobatidtE 
Myliobatis aqiiila, Cuv. (whip-ray), 1910, Station 36. 



Order— HOLOCEPHALI 

Chimverid^ 
Chimcvra monstrosa, L., 1902, Faroe Bank, 435 metres; 1910, Station 21. 
Chimcera mirabilis, Coll., 1902, Faroe-Shetland channel; 1910, Station 4 (see 
Fig. 259). 




Fig. 259. 

Chimcera mirabilis. Coll. Nat. size, 76 cm. 



394 DEPTHS OF THE OCEAN 

Hariotta ra/eigha?ia, G. and B., 1910, Stations 35, loi (see Fig. 260). 




Fig. 260. 
Hariotta 7-aleighana, G. and B. (After Goode and Bean. 



Sub-Class— TELEOSTOMI 

Order— TELEOSTEI 

Sub-Order— MALACOPTERYGII 

Salmonid^ 



Argentina sihts, Nilss., 1910, Station 39 {see Fig. 261). 
Argentifia sphyrcena, L., 19 10, Stations i, 3. 




Fig. 261. 

Argentina stilts, Nilss. (After Sniitt. ) 



Alepocephalid^ 



Alepocephalus giardi, Koehl., 1902, Faroe-Shetland cliannel ; Faroe Bank, 750 
to 840 metres (see Fig. 262). 




Fig. 262. 
Alepocephaliis giardi, Koehl. (After Collett. ) 



Bathytroctes rosfmtus, Giinth., 19 10, Stations 29, 56. 

Conocara macroptera, Vaill. (G. and B.), 1910, Station 25 (.see Fig. 263). 



FISHES FROM THE SEA-BOTTOM 



395 




Fig. 263. 
Coiiocara 7nacroptera, Vaill. Nat. size, 20 cm. 



Sub-Order— APODES 

SYNAPHOBRANCHIDiE 



Synaphobi-anchus pintiatus, Gron., 1902, Faroe-Shetland channel; Faroe Bank, 

750 metres; 1910, Stations 4, 24, 41, 53, 88, 95, loi (see Fig. 264). 
Histiobranchus sp., 19 10, Station 




Fig. 264. 

Synaphobranchus pinnaiits, Gronov. Nat. size, 31 cm. 



MUR/ENID.^ 

Miirana helena, L., 1910, Station 38 (see Fig. 265). 




Fig. 265. 
Miircena helena, L. Nat. size, 102 cm. 



396 



DEPTHS OF THE OCEAN 



Sub-Order— HAPLOMI 

SCOPELID^ 

Bafhysaiirus ferox, Giinth., 1910, Stations 25, 35, 53, 95 (see Fig. 103, a). 

Bathypterois longipes, Giinth., 1910, Station 53. 

Bathypterois dtibius, VailL, 1910, Stations 23, 41 (see Fig. 266). 




Fig. 266. 
Bathypterois diibiiis, VailL Nat. size, 17 cm. 

Benthosaurus grallator, G. and B., 19 10, Station 53. 
Bathymicrops regis, n.g., n.sp., 1910, Station 48 (see Fig. 305). 

Sub- Order— HETEROMI 

Halosaurid^ 
Halosaiiropsis macrochir, Giinth. (Coll.), 1910, Stations 35, 53, 88, 95 (see Fig. 
103, b). 

NOTACANTHID^ 

Notacanthus bojiapartii, Risso, 1902, Faroe-Shetland channel; Faroe Bank, 840 

metres (see Fig. 267). 
Polyacanthonotus sp., 1910, Stations 53, 95. 



® 





Fig. 267. 
Notacatithus botiapartii, Risso. (After Goode and Bean. ) 

Sub-Order— CATOSTEOMI 

Centriscid^ 
Centriscus scolopax, L., 19 10, Station 39 (see Fig. 268). 



FISHES FROM THE SEA-BOTTOM 



397 




Fig. 268. 
Centi-iscjis scolopax, L. Nut. size, 16 cm. 

Sub-Order— PERCESOCES 

Atherinid^ 
Atherina p7-eshyter, Cuv. and Val., 19 10, Station 36. 

Sub-Order— ANACANTHINI 

Macrurid^ 
Trachyrhynclms trachyrhynchus^ Giinth., 1910, Stations 4, 23. 
Trachyi-hyiichiis mtirrayi, Giinth., 1902, Faroe-Shetland channel ; Faroe Bank, 
840 metres (see Fig. 269). 




Fig. 269. 

Trachyrhynchits miirrayi, Giinth. (After Giinther. ) 



Macrurus {Cxlorhynchus) talismani, Collett, 1902, Faroe Shetland channel 

1910, Stations 4, 24, 41. 
Macrurus {Ca'Iorhynchus) ca'lorhyiichus, Risso and Bonap., 19 10, Station 21. 
Macrurus sclerorhynchus, Val., 1910, Stations 25, 41, 88, 95, loi. 
Macrunis cequalis, Giinth., 1902, Faroe Bank, 750 metres; 1910, Stations 4, 23, 

25> 35> 41 (see Fig. 270). 
Macrurus zaniophorus, Vaill., 1910, Stations 4, 41. 
Macrurtis guntheri, Vaill., 1902, Faroe-Shetland channel. 
Macrurus {Coryphee noides) rupestris, Gunn, 1902, Faroe - Shetland channel 

Faroe Bank, 750 to 840 metres. 



DEPTHS OF THE OCEAN 




Fig. 270. 
Macrurus aqualis, Giinth. Nat. size, 23 cm. 

Macriirus {Coryphcenoides) asperrimus, Vaill., 19 10, Station 41. 
Macrurus {Cetotiurus) globiceps, Vaill., 19 10, Station 41 (see Fig. 271). 




Fig. 271. 
Macrurus (Cetonurus) globkeps, Vaill. 



(After Vaillaiit. ) 



Macrurus {Chalinura) bj-evibarbis, G. and B., 19 10, Station 10. 
Macrurus {Chalinurci) murrayi, Giinth., 1910, Stations 25, 95. 
Macrurics {Chalinura) swtulus, G. and B., 1910, Station 53. 
Macrurus {Ma/acocephalus) lewis, Lowe, 1910, Station 21. 
Macrurus {Ne?}iatomirus) armatus, Hect., 19 10, Stations 10, 35, 53, 
Fig. 272). 



(see 




P'iG. 272. 

Macrurus [Neviatonurus] armatus, Hect. (After Giinther.) 



FISHES FROM THE SEA-BOTTOM 

Bathygadus lo?tgifilis, G. and B., 1910, Stations 23, 24, 41 (see Fig. 273). 
Bathygadus melanobranchus, Vaill., 19 10, Stations 23, 41. 



;99 




Fig. 273. 
Bathygadus longijilis, G. and B. (After Brauer. ) 

Gadid.® 
Gadits ca/larias, L. (cod), 1910, Rockall (see Fig. 274). 




Fig. 274. 

Gadus callarias, L. (.\fter Sniitt. ) 



Gadus ceglefimis, L. (haddock), 1902, Faroe Bank, 130 metres; 1910, Station 3. 
Gadus merlangus, L. (whiting), 19 10, Station 14. 
Gadus luscHS, L. (bib), 19 10, Station 14. 
Gadus esmarki, Nilss., 1910, Station i. 
Gadus poutassou, Risso, 19 10, Stations i, 3. 
Gadiculus argenteus, Guichenot, 1910, Stations 3, 21, 96. 

Merluccius vulgaris, Flem. (hake), 1910, Stations i, 3, 14, 20, 21, 2)^, 39 (see 
Fig. 275). 




Fig. 275. 
Merluccius vulgaris, Fleni. (After Smitt.) 



400 DEPTHS OF THE OCEAN 

Phycis l)k?tntoides, Briinn, 1910, Stations i, 3, 21 (see Fig. 276). 




Phycis ble 



Fig. 276. 
ides, Briinn. (After Smitt. ) 



Molva jnolva, L. (ling), 1902, Faroe-Shetland channel; Faroe Bank, 350 to 
440 nietres (see Fig. 277). 




Fig. 277. 

Molva molva, L. (After Smitt. ) 



Molva byroelange, Walb., 1902, Faroe Bank, 840 metres. 

Molva elongata, Risso, 19 10, Station 21. 

Brosmius brosine, Ascan (tusk), 1902, Faroe-Shetland channel ; Faroe Bank, 

550 to 440 metres. 
Mora mora, Risso, 1902, Faroe Bank, 750 metres; 1910, Stations 4, 23, 41 (see 

Fig. 278). 




Fig. 278. 
Mora mora, Risso. Nat. size, 45 cm. 

Antimora viola, G. and B., 1910, Stations 4, 95, loi (see Fig. 279). 
Lepidion eques, Giinth., 1902, Faroe-Shedand channel; Faroe Bank, 750 metres; 
1 910, Station 4 (see Fig. 280). 



FISHES FROM THE SEA-BOTTOM 



401 



Halargyreus affinis, Coll., 1902, Faroe-Shetland channel ; Faroe Bank, 750 
metres (see Fig. 281). 




Fig. 279. 
Antimora viola, G. and B. (After Giinther. ) 




Fig. 280. 
Lepidion eqites, Glinth. (After Giinther. ) 




Fig. 281. 

Halai-gy reus affi fits, Coll. (After Collett.) 



Sub-Order— ACANTHOPTERYGII 

Division— PERCIFORMES 

Berycid^e 

Hoplostethus mediterraneum, Cuv. and Val., 1910, Stations 4, 21 (see Fig. 282). 

2 D 



402 



DEPTHS OF THE OCEAN 




Fig. 282. 
Hoplostethus mediterraneum, Cuv. and Val. (After Goode and Bean. 



ACROPOMATIDyE 

Epig07itis tekscopiis, Risso, 1902, Faroe Bank, 750 metres. 

Serranid.^ 
Serramis cabrilla, Cuv. and Val., 19 10, Station 37 (see Fig. 283). 




Fig. 283. 
Serranus cabrilla, Cuv. and Val. Nat. size, 21 cm. 



SCI^NID^ 

SdcBna aquila^ Risso, 1910, Station 36 (see Fig. 284). 
Ufnbrina roiichus^ Val., 1910, Station 36. 



FISHES FROM THE SEA-BOTTOM 




Fu;. 284. 
Sciceiia aquila, Risso. (After Smitt. ) 



Pristipomatid/e 

Pristipoma bennettii, Lowe, 19 10, Station 36. 

Diagramma i7iediterra)ieum, Guichenot, 1910, Canary Islands. 

Sparid^ (Sea-Breams) 

Dejitex vulgaris, Cuv. and Val., 19 10, Canary Islands (see Fig. 285). 
Dentex macrophthalmus, Cuv. and Val., 19 10, Stations 20, 38, 39. 
Dentex Jtiaroccatms, Cuv. and Val., 19 10, Stations 20, 37 (see Fig. 48, a). 




Fio. 285. 
Dentex -i'lilgaris, Cuv. and Val. (After Cuvier and Valenciennes.) (The teeth, after Day.) 

Cantharus Htieatus, Montagu (White), 1910, Canary Islands, Station 37. 

Box vulgaris, Cuv. and Val, 1910, Station 36. 

Sargus rondeletii, Cuv. and Val., 1910, Canary Islands. 

Sargus annularis, Cuv. and Val., 1910, Station 36 (see Fig. 286). 

Chrysophrys aurata, Cuv. and Val., 1910, Canary Islands. 

Pagrus vulgaris, Cuv. and Val, 1910, Canary Islands, Stations 38, 39 (see Fig. 

287). 
Pagellus centrodontus, Cuv. and Val., 1910, Stations 13, 20 (see Fig. 288). 
Pagellus acar7ie, Cuv. and Val., 19 10, Station 20. 



404 



DEPTHS OF THE OCEAN 




Fig. 286. 
Sargi/s annularis, Cuv. and Val. (After Cuvier and Valenciennes.) 




Fig. 287. 
Pagriis vulgaris, Cuv. and Val. Nat. size, 50 cm. 




Fig. 288. 
Pagellus cenfrodoufus, Cuv. and Val. (After Smitt. ) 



MULLID/E 

Muilus surtmtktus, L. (red mullet), 19 10, Stations 20, 37, 39 (see Fig. 289). 



FISHES FROM THE SEA-BOTTOM 405 




Fig. 289. 
Mullus siininiletiis, L. Nat. size, 29 cm. 

Caproid/e 
Capros aper, Lacep., 19 10, Stations i, 3, 20, 39 (see Fig. 290). 




Fig. 290. 
Capros ape)-, Lac^p. Nat. size, 9. 3 cm. 



Labrid^ 
Coris Ji/lis, L., 1910, Station 37 (see Fig. 291). 




Fig. 291. 
Coris Julis, L. Nat. size, 18 cm. 



4o6 



DEPTHS OF THE OCEAN 



Division— SCOMBRIFORMES 

CARANGIDit: 

Caranx trachurus, L. (horse-mackerel), 1910, Stations i, 3, 14, 20, 36, 39 (see 

Fig. 292). 
Temnodon saltator, Cuv. and Val., 19 10, Station 36. 




Fig. 292. 
Cara?ix i?-achuri/s, L. Nat. size, 1 1 cm. 




Fig. 293. 
Zeusfaber, L. Nat. size, 26 cm. 



FISHES FROM THE SEA-BOTTOM 407 

Trichiurid^ 
Lepidopiis caudatus^^w^hx., 1910, Station 43 (Gomera). 

Division -ZEORHOMBI 

ZeiD/E 
Zeusfal/er, L. (dory), 19 10, Stations i, 20 (see Fig. 293). 

Pleuronectid^e 
Hippoglossus vulgaris, Flem. (halibut), 1902, Faroe-Shetland channel ; Faroe 
Bank, 130 to 450 metres (see Fig. 294). 




Fig. 294. 

Hippoglossus vulgaris, Flem. (After Smitt. ) 

Pleuronecies /imanda, L., 1902, Faroe Bank, 130 metres. 
Arnoglossus laterna, Walb., 19 10, Station 3. 
Arnoglossus lophotes, Giinth., 19 10, Stations 3, 37, 38. 
Ar?ioglossus gro/wiafini, Bonap., 19 10, Station 38. 

Zeugopterus niegastoma, Donov. (megrim), 1902, Faroe Bank, 130 metres; 191c, 
Stations i, 3, 96 (see Fig. 295). 




Fig. 295. 

Zeugopterus mtgasioma, Donov. (After Smitt.) 



4o8 



DEPTHS OF THE OCEAN 



Zeugopterus boscii, Risso, 19 lo, Station 21. 

Solea vulgaris, Quensel (common sole), 1910, Stations 20, 38 (see Fig. 296). 




Fig. 296. 
Solea vitlgaris, Quensel. (After Cunningham. ) 



Soka lufea, Bonap., 1910, Stations 36, 38. 
Solea variegafa, Flem., 1910, Station 3. 



Division— SCLEROPAREI 
SCORP/ENID^ 

Sebastes dactylopterus, Nilss., 1910, Station 21 (see Fig. 297). 
Scorpcena scrofa, L., 1910, Stations 37, 38 (see Fig. 298). 




Fig. 297. 
Sebasfes dactylopterits, Nilss. ( After Moreau. ) 



Scorpcena ustulata, Lowe, 19 10, Stations 37, 39, 
Scorpana cristtilata, G. and B., 19 10, Station 4. 



FISHES FROM THE SEA-BOTTOM 



409 




Fig. 298. 
ScorpcEna scrofa, L. Nat. size, 48 cm. 



Triglid^ (Gurnards) 

Trigla pini, Bl., 19 10, Stations 3, 20. 

Trigla hiriindo, Bl., 1910, Station 20. 

Trigla gurnardiis, L., 1910, Stations i, 3. 

Trigla cuculus, BL, 19 10, Station 20. 

Trigla fyra, L., 1910, Stations 3, 20 (see Fig. 299). 

Trigla obscnra, L., 19 10, Station 38. 




Fig. 299. 
Trigla lyra, L. (After Day. ) 



Lepidotrigla aspera, Cuv. and Val. (Giinth.), 1910, Stations 20, 39. 
Peristedion cataphractiim, Cuv. and Val., 19 10, Stations 20, 39 (see Fig. 300). 



4IO 



DEPTHS OF THE OCEAN 




Fig. 300. 
Peristedion cataphractum, Cuv. and Val. Nat. size, 30 cm. 

Division— JUGULARES 
Trachinid.^ (Weevers) 

Trachiiius draco, L., 19 10, Station 38. 

Trachinus vipera, Cuv. and Val., 1910, Station 14 (see Fig. 301). 




Fig. 301. 
Trachinus vipera, Cuv. and Val. (After Cuvier. ) 

■ Uranoscopid^ 
Uranoscopus scaher, L., 19 10, Station 37. 

Callionymid^ 
Callionymiis maculatus, Bonap., 19 10, Station 3. 

ZOARCID/E 

Lycodes ferrcB novce, Coll. (?), 19 10, Station 70 (see Fig. 302). 




Fig. 302. 

Lycodes terrce ?iovcs. Coll. (?) Xat. size, 11 cm. 



FISHES FROM THE SEA-BOTTOM 411 

Sub-Order— PEDICULATI 

LOPHIID^ 

Lophhis piscatorius, L., 1910, Station 3 (see Fig. 303). 




Fig. 303. 
Lophins piscatorins, L. (After Smitt. ) 

Malthid^e 
Dibranchus hystrix, Garm., 19 10, Station 70. 



Sub-Order— PLECTOGNATHI 

Tetrodontid^ 
Tetrodon speiigleri^ Bl., 19 10, Station 37 (see Fig. 304). 




Fig. 304. 
Tctrodon spengleri, Bl. (After \'alenciennes. ) 



412 DEPTHS OF THE OCEAN 

2. The Geographical Distribution of Bottom-Fishes 
IN the North Atlantic 

The Fishes of the Abyssal Plain ^ 

In Chapter IV. the areas of the ocean-floor at different 
depths are given, the percentages being as follows : — 



reas shallower than loo 


fathoms 


= 7-o%. 


„ between loo and 500 




= 5.6 %, or 1.4 % per 100 fathoms 


„ „ 500 „ 1000 




= 3.0 %, or 0.6 % „ 100 


„ „ 1000 ,, 2000 




= 19-3 %, or 1-9 % .> 100 


„ „ 2000 „ 3000 




= 58.4 %, or 5.8 % „ 100 


„ deeper than 3000 




= 6.7 %. 



About two-thirds of the sea-floor is thus covered by more 
than 2000 fathoms (or 3600 metres) of water, forming an abyssal 
plain 90J millions of square English miles in extent, or nearly 
half the surface of the earth. 

What organisms inhabit this abyssal plain ? When studying 
the literature of deep-sea expeditions, we must remember that 
all the hauls hitherto made in the abyssal area have been effected 
by means of trawls or dredges, which function not only while 
being towed along the bottom, but also while being lowered 
and raised, filtering the immense column of water from bottom 
to surface. Therefore only organisms like worms, molluscs, 
holothurians, starfishes, corals, and all sessile forms may safely 
be considered as having been captured at the bottom. In the 
case of crustaceans and fishes, however, it may be doubted 
whether they were really caught at the bottom or in intermediate 
waters. Lists recording the catches of deep-sea expeditions at 
great depths cannot therefore be accepted as representing the 
animal-life on the ocean-floor, for in such lists we often find 
forms which are now known to live quite close to the surface. 
Although we have now a much more precise idea of the vertical 
distribution of pelagic fishes than was previously possible, some 
surprising facts are occasionally brought to light. Thus, as 
mentioned in Chapter HI., the "Michael Sars " at Station 48, 
between the Canaries and the Azores, brought up an Alepo- 
cephalus in the large trawl towed at the bottom in 5000 metres, 
just as these fishes have been captured by most deep-sea 
expeditions ; on the trawl-rope a small tow-net was fixed in 

^ The mean sphere level, which lies at a depth of about 1700 fathoms, has hitherto been 
regarded as the depth at which the abyssal plain of the ocean commences, but it will be seen 
that Dr. Hjort places this depth at 2000 fathoms. — J. M. 



FISHES FROM THE SEA-BOTTOM 413 

such a way that it was towed about 1000 metres above the 
bottom, and in this net an Alepocephalus was also captured. 

Such facts warn us against hasty conclusions. Many fishes 
may, like the fishes in the Norwegian Sea (Gadidse, Sebasies), 
occur in midwater above considerable depths as well as on the 
coastal banks and the continental slopes. A single record of 
a species from intermediate waters does not necessarily entitle 
us to consider the species as entirely pelagic. As in most 
biological questions, we have to judge from the available 
evidence, and, in dealing with the captures of fishes by deep- 
sea expeditions ^ in depths exceeding 2000 fathoms {3600 metres), 
I have endeavoured to eliminate all those species which are 
apparently pelagic, having been frequently captured at inter- 
mediate depths. In this way I have attempted to ascertain Fishes from 
how many species and individuals have really been captured on d^pth°"ovTr^" 
the bottom of the abyssal plain of the oceans, and the result is 2000 fathoms. 
given in the following table, which comprises 35 individuals 
belonging to 2 1 species in all : — 

^ The excellent lists given by Brauer in his Report on the Deep- Sea Fishes of the 
" Valdivia " Expedition, the list by Vaillant in his Report of the French deep-sea expeditions, 
Carman's Report of the "Albatross" expeditions, Goode and Bean's Oceanic Ichthyology, 
and Murray's splendid Summary of the "Challenger" Expedition, have greatly facilitated 
this task. 



[Table 



414 DEPTHS OF THE OCEAN chap 

Bottom-Fish taken at Depths exceeding 2000 Fathoms (3600 metres). 







Greatest 


Number 




Species. 


Taken by. 


Depth 
(Metres). 


of Indi- 
viduals. 


Locality. Other Localities. 


ALEPOCEPHALID/E. 












Aleposomus copei 


"Albatross" 


5317 


I 


East of North 
America 












/'Between the Morocco, the 


Alepocephalus rostratus . 


"Talisman" 


3655 




J Azores and : Azores, the 


Bathytrodes attritus 


"Talisman" 


3655 




1 France | Canaries,Medi- 
\^ terranean. 


SCOPELID^. 








■ 


Bathysaurus mollis . 


"Challenger" 


4360 


I 


Mid- Pacific 1 


5) 


" Talisman" 


3655 




Cape Verdes ; 


Bathypterois longipes 


"Challenger" 


4844 




East of South 

America 
Mid-Pacific 


„ longicaudata 


"Challenger" 


3761 




Ipnops murrayi 


"Challenger" 


3931 




North of Celebes i Brazil, Tristan 
' da Cunha. 


Halosaurid/e. 










Halosaurus rostratus 


"Challenger" 


5027 




Mid -Atlantic 


Macrurid^. 










Macrurus sclerorhynchtis . 


"Talisman" 


3655 




Cape Verdes Whole eastern 
slope of North 
Atlantic. 


,, liocephalus 


"Challenger" 


3747 




Japan, Mid- 
Pacific 
South and Mid- 




„ armatus . 


"Challenger" 


4432 














Pacific, New 












Zealand 




„ Sis-as 


"Talisman " 


4200 




Between the 
Azores 'and 
France 




, , filicaiida . 


"Challenger" 


4843 




East and West of 
South America, 
Antarctic 




ZOARCID/E. 












Neobythites crassus . 


"Talisman" 


4255 




Between the 
Azores and 
France 




Mixonus laticeps . 


"Challenger" 


4570 




Mid-Atlantic 




Lycodes albus . 


"Talisman" 


3975 




Between the | 










Azores and 












France 




Bassozetus tania 


"Challenger" 


4570 




Mid-Atlantic 




Typhlonus nasus 


"Challenger" 


4460 


~ 


North of Australia | 










and Celebes 




Alcockia rest rat a 


"Challenger" 


3888 




North of Celebes 




Synaphobranchid^. 












Htstiobratichus infernalis 


"Albatross" 


4062 




East of North 












America 


,, bathybhis . 
Number of species . 21 


"Challenger" 


3749 




Mid-Pacific Japan. 




35 







It is doubtful whether ail these came from the bottom. 
Thus the three Alepocephalidae, the six Scopelidse, the one 



FISHES FROM THE SEA-BOTTOM 415 

Halosaurus, and the two Synaphobranchidse may be suspected of 
pelagic habitat. Less doubt may be entertained about the 15 
Macruridae and the 8 Zoarcidae, and the probability is that these 
(some 20 individuals) constitute the total result of the attempts 
of all the deep-sea expeditions to capture bottom-fish on the 
abyssal plain beyond the 2000-fathoms line. Most of these 
fishes were taken by the "Challenger" in 57 hauls with the 
dredge or trawl in depths exceeding 2000 fathoms. In these 
hauls 22 individuals were captured, and the French expeditions 
caught 1 1 bottom-fish in eight hauls, giving an average of i 
fish to two hauls. 

The 35 individual fishes enumerated belong to 21 species, 
15 genera, and 6 families. On the average not even two 
individuals of each species have been captured. The genus 
Macrurus preponderates, 15 of the 35 individuals belonging to 
this genus, and of deep-sea fishes the Macruridae may most 
safely be regarded as bottom-dwellers. The impression of Scantiness of 
scantiness conveyed by these facts, only one or two individuals greTdepOis.^ 
of each species of fish being known from the immense area of 
the abyssal plain, agrees with the scarcity of the lower orders 
in the same barren region. A perusal of the "Challenger" 
Reports astonishes us by the fact that large numbers of species 
of lower animals are known only from a single locality, and 
often from one solitary specimen. 

These facts suggest that the bottom-fishes of the abyssal 
region are very local in their occurrence, but, considering the 
small number of individuals recorded, it seems risky to come to 
that conclusion, as the want of material for comparison tends to 
weaken our power of discriminating between the species. In 
certain problems of geographical distribution, the question may 
be vital whether two individual fishes caught in widely separated 
parts of the world are to be referred to one species or not. 
The systematic study of these deep-sea species leaves a strong wide dis- 
impression that many of them differ very slightly from one Jj^^p!^"^ °^ 
another. Thus, for instance, my collaborator, Mr. E. Koefoed, forms. 
and myself have not been able to convince ourselves that there 
is any specific difference between the two species, Macrurus 
armatus and M. gigas, mentioned in the above table, and this 
circumstance alone leads to far-reaching conclusions, M. armatus 
having been caught in the Pacific and M. gigas in the North 
Atlantic (see Fig. 308). 

The collections of the " Michael Sars " throw much new 
light on these questions. In the following table I give the 



4i6 



DEPTHS OF THE OCEAN 



distribution of the most important forms taken in the abyssal 
plain and the bordering intermediate zone. The localities of 
special importance are the Southern Ocean for Halosauropsis 
macrochir, and the Pacific for Macrurus armalus. 



Species. 


Localities where Captured. 


By the " Michael 
Sars." 


By other Expeditions. 


Hariotta raleighana . 
Bathypterois lotigipes . 
Halosauropsis macro- 
chir 

Macrui'us cequalis 
„ siinulus 

„ brevibarbis 

„ armatus 

globiceps . 
Synaphobranchus pin- 
natus 


Stations. 

35, loi 

41, 53 

35, 53, 88, 95 

25, 35, 41 
53,88 

10, 88 

10, 35, 53, 88 

41, 88 
24, 41, 53, 88, 

95, loi 


Off the east coast of North America. 

Off the east coast of South America. 

Between South Africa and Kerguelen, 
off east coast of North America, 
Gibraltar, Morocco, the Azores. 

From Faroe Islands to Cape Verdes. 

Off the east coast of North America, 
Denmark Straits. 

Off the east coast of North America, 
Denmark Straits. 

Pacific. 

Bay of Biscay to the Azores. 

Japan, Philippines, Arabian Sea, off 
east coast of North America, Faroe 
Islands to Cape Verdes, off Brazil. 



Besides these we caught at Station 48 an Alepocephalus and 
the new form Bathymic7'ops regis (see Fig. 305), which may both 
be pelagic. 

Excepting the Hai'iotta, which has only been taken at some- 
what lesser depths (Station 35, 2603 metres), all these species 




Fig. 305. 
Bat hyfiticrops regis, n.g. , n.sp. Nat. size, ii cm. 

belong to the genera recorded by previous expeditions from 
the abyssal plain. Of the nine species, three \Halosa2iropsis 
mac7^ockir, Macrurus armatus, and Synaphobranchtis pinnatus) 
have previously been taken in other oceans. Of special interest 
is the fact that M. armatus has been found in so many new 



FISHES FROM THE SEA-BOTTOM 



417 



localities, and this species is now known to have the widest 
distribution on the abyssal plain, and on this only. Another 




Fig. 306. 

Macrurus {Liomtrus) Jilicaiida, Giinth. (After Giinther. ) 




Fic. 307. 
Hariotta ralcighana, G. and B. Xat. size, 30 cm. 




Fig. 30S. 

Chart showing the localities where Macrurus armatus % and M. Jilicauda have been taken. 

Temperatures in Centigrade. 

species, M. jilicauda, also shares this wide distribution (see 
Fig. 306, and Chart, Fig. 308). 

Highly interesting also is the fact that no less than four of 
these deep-sea forms, viz. Hariotta raleighana (see Fig. 307), 

2 E 



4i8 



DEPTHS OF THE OCEAN 



Species found 
on both sides 
of the North 
Atlantic. 



Abyssal forms 
have a con- 
siderable 
vertical 
distribution. 



"Challenger' 
hauls in the 
deep water 
of the North 
Atlantic. 



Bathypterois longipes, Macrti^nis simulus, and Macrtcnis brevibar- 
bis, are now known from both sides of the Atlantic. The three 
last-mentioned species were also caught near the Azores, and we 
must therefore conclude that their habitat stretches right across 
the Atlantic. Macrurus csqualis was previously known only 
from the eastern side, Macrurus globiceps also from the Azores, 
and during the cruise of the " Michael Sars " it was taken a 
little north of the latter locality (Station 88). If the above 
table is compared with the list of " Michael Sars" stations, it 
will be noticed that these fishes from the abyssal region have 
a considerable vertical distribution, occurring also on the 
continental slopes. 

Sir John Murray has, in his excellent "Summary," given 
lists recording all the different animals captured at each of the 
" Challenger " stations, and in a final chapter he endeavours to 
lay down some of the most important laws governing the distri- 
bution of animals in the ocean. At twenty-five stations where 
the depth exceeded 2500 fathoms the "Challenger" took with 
dredge and trawl 600 individual animals of all kinds ; this gives 
24 individuals per haul. Now, firstly, many of these were 
pelagic (most of the crustaceans and some of the fishes), and 
secondly, many of them were very small (hydroids, bryozoa). 
As examples I give a list of the bottom-forms (protozoa 
excluded) obtained at some of the "Challenger" stations 
between the Canaries and the West Indies. 

Station 5. Depth, 2740 fathoms. Three living mussels {Leda, Limopsis, Area), 

and some dead shells. 
„ 13. Depth, 1900 fathoms. Some bryozoa and brachiopods (10 Tere- 

bratiila). 
„ 14. Depth, 1950 fathoms. Some bryozoa. 
„ 16. Depth, 2435 fathoms. Sharks' teeth {Oxyrhina, Lamna\ valves of 

Scalpellum, 2 mussels {Area). 
„ 20. Depth, 2975 fathoms. Dredge came up half full of clay, containing 

half a dozen tubes of serpulids, some of these with the worms 

living. 
,, 61. Depth, 2850 fathoms. Trawl captured some ophiuridte (6^////^^/)7^//rt'), 

2 holothurians, 7 Sealpellum. 
„ 63. Depth, 2750 fathoms. Trawl captured some fragments of worms, 3 

Scalpelhim, i fish {Halosaiirus rostratus). 



This list is representative of most deep-sea hauls, and their 
uniform poverty is only broken by rare exceptions, as in a note- 
worthy haul taken by the " Challenger " in the Pacific, between 
Japan and Hawaii, at Station 244, in 2900 fathoms, which 
gave :— 



FISHES FROM THE SEA-BOTTOM 419 

I sponge, I antipatharian, 6 actinians, 2 corals, i hydroid colony, 2 crinoids, 
3 starfish, i sea-urchin, 5 holothurians, many worms, 7 or 8 mussels, and a 
brachiopod. 

This is, as far as I have been able to ascertain, the richest 
haul in depths exceeding 2000 fathoms on record, but never- 
theless the impression created by the results of the many deep- 
sea hauls of the " Challenger " is that animal life is poorly 
developed in the abyssal region. 

During the cruise of the "Michael Sars " I therefore con- "Michael 
sidered it an interesting object to ascertain if our large otter i^^Jhe^er'* 
trawl could catch more, and possibly larger, animals on the water of the 
abyssal plain. As stated in Chapter HI., technical success Atlantic. 
attended our attempts at great depths, and the catches were 
certainly somewhat larger than those previously taken in the 
North Atlantic, but nevertheless they were very poor, as shown 
by the following list :^ 

Station 10. Bay of Biscay, 2567 fathoms (4700 metres). Trawl dragged for 
five hours gave : Some sponges, 3 actinians, some holothurians 
{Elpidia), 2 starfish {FrugeUa, Dorigona), a few worms, ascidians, 
and bryozoa, i gasteropod, and 2 fishes, presumably bottom-fish : 
Macrurus armatus (Hector), i individual 70 cm. in length, and 
M. brevibarbis (G. and B.), i individual 25 cm. in length. 

Same Station. Duration of haul, 3J hours. Cod-end full of ooze, and in the meshes 
3 ophiurids [Ophiopkura, Ophioglypha, Ophiocte?t}) ; washing the 
ooze produced 4 actinians (one of them growing on a hermit 
crab), I holothurian {Elpidia), worms in clay tubes, and some 
gasteropods. 

Station 48. Between the Canaries and the Azores, over 5000 metres. Duration of 
haul, 4I hours. Trawl contained a large quantity of ooze, the 
washing of which produced : 30 pieces of pumice-stone, i shell of 
Argonaufa, i ear-bone of a whale, 2 sharks' teeth {Carcharodon 
and Oxyrhina), 10 large shells of pteropods {Cavolifiia), 1 umbel- 
\\i\ax\dix\ {Utnbellula gihitheri), i sertularian, 2 holothurians {Lcet- 
■mogone violacea, Elpidia sp.). Besides these there were 3 pelagic 
fishes {Malacosteus indicus, Argyropekciis sp., and a Leptocepha- 
lus), and 3 fishes which may be surmised to have lived at the 
bottom {Alepocephalus, a new genus related to Ipnops : Bathy- 
microps regis, see Fig. 305, and a specimen not yet determined). 

These hauls of the "Michael Sars" thus entirely confirm 
the idea of the poverty of the abyssal plain, a confirmation 
especially valuable on account of the size of the trawl employed 
and the technical success attending its use in great depths. 
The proof afforded by these results of the " Michael Sars," like 
that from all other expeditions, suffers from the inherent weak- 
ness attached to all negative proofs. The barrenness of the 
abyssal plain may be only apparent, owing to imperfections in 



420 DEPTHS OF THE OCEAN 

the methods of capture, the technical difficulties of operating 
dredges and trawls at great depths being of considerable 
moment, but I do not attach great importance to this, because 
the same appliances, when used in deep water on the continental 
slope, gave large catches. 

If we fix the boundary of the abyssal plain at the 2000- 
fathoms line, we may consider the area between the 2000- 
and 1500-fathoms lines as an intermediate zone between the 
abyssal plain and the continental slope. In this zone the 
"Challenger" made 25 hauls with trawls and dredges, with the 
result that three times as many fishes per haul, and twice as 
many invertebrates, were captured as on the abyssal plain. The 
"Michael Sars " made 3 hauls with the trawl in such depths, 
which, compared with our results from the abyssal plain, are 
very interesting, and invite inspection of their details : — 

Station 35. South of the Canaries, 1424 fathoms (2603 metres). Trawl dragged 
two hours. Result of haul : Many silicious sponges (including 
Hyalonetfia), hundreds of holothurians, large prawns {Benthesicymus, 
n.sp.), 18 bottom-fish (9 Macrurids, i Bathysmirus, 2 Halosau- 
ropsis, 5 Alepocephalus, i Hariotta). 

„ 53. South of the Azores, 1430 to 1570 fathoms (2615 to 2865 metres). 
Trawl dragged three or four hours. Result of haul : 2 large and 
many small sponges, 3 mussels, 5 cirripeds {Sca/pellum), 30 large 
prawns {Aristeopsis), 15 hermit crabs, 5 Pentacheles, i large white 
decapod {Mutiidopsis, n.sp.), 500 holothurians, 39 bottom-fishes, 
(17 Macruriis, 5 Halosauropsis, 2 Benthosmirus, 2 Bathysaurus, 
2 Bathypterois, 6 Alepocephalus, 5 Synaphobranchus). 

„ 88. North of the Azores, 1700 fathoms (3120 metres). Result of haul : 
a great number of holothurians, sea-urchins, starfish, ophiurids, 
some crustaceans {^Polycheles, Mti?ndopsis, Farapagurus), 2 1 bottom- 
fishes (17 Macrurus, i Bathysaurus^ 3 Histiobranchus\ 

These hauls plainly show that the appliances of the " Michael 
Sars" were excellently suited for the capture of bottom organisms, 
fish as well as invertebrates. Indeed in one single haul (Station 
53) we caught nearly as many individual bottom-fishes as the 
" Challenger " captured in its twenty-five hauls in depths between 
1 500 and 2000 fathoms. I think we are justified in concluding 
that the vast difference between our captures on the abyssal plain 
and these three hauls in 2600 to 3200 metres represents an 
actual difference in the abundance of animal life in the two 
regions. The fauna of the abyssal plain must be very poor 
compared with the more abundant life met with, at all events 
in the Atlantic, in depths of about 3000 metres and less, where 
the fauna is infinitely richer in number of species as well as in 
number of individuals. Perhaps the most striking contrast is 



FISHES FROM THE SEA-BOTTOM 421 

obtained when we consider the enormous difference in the 
number of animals brought up by the trawl from the two regions 
in question. 

The Fishes of the Continental Slopes 

The angle of the slopes rising from the abyssal plain 
towards the coast varies in different parts of the globe, being 
in some places steeper than in others. The percentages of the 
ocean-floor given on p. 132 show that the steepest angle 
occurs between 500 and 1000 fathoms, while the slope between 
1000 and 2000 fathoms is much steeper than in the upper 100 
fathoms. Between the shore-line and the loo-fathoms line the 
angle of the slope is low, and this area is regarded as a special 
region, generally termed the coast -plateau, or the continental 
shelf or platform (see Fig. 144, p. 198). The fishermen's term 
for this section of the sea-bottom is " the banks," and the narrow 
intermediate belt between the coast-plateau and the continental 
slope is by the fishermen termed " the edge." 

One of the objects of the " Michael Sars" Expedition was 
to make a number of trawlings on the continental slopes of the 
Atlantic in different latitudes, in order to study the fish-fauna at 
different depths and under varying conditions. We succeeded "Michael 
in making quite a number of good hauls, and, taken together onThe*^^"^^ 
with the captures of other expeditions (especially those of the continental 
French deep-sea expeditions), they give a good representation ^^°p^' 
of the different fish-faunas. Our stations along the slope may 
be divided into three groups : — 

1. West of Great Britain (including some hauls from 
localities south of the Faroe Islands in the year 1902). 

2. Spanish Bay, west of Morocco. 

3. South of the Canaries. 

First of all, we will consider the number of fishes caught in 
these hauls at different depths, as recorded in the following 
table, and next we will investigate the vertical and horizontal 
distribution of the species : — 



[Table 



422 



DEPTHS OF THE OCEAN 



West of Great Britain. 


Spanish Bay, west of 
Morocco. 


South of the Canaries. 


Station. 


Depth 
(metres). 


Number 

of 
Fishes. 


Station. 


Depth 
(metres). 


Number 

of 
Fishes. 


Station. 


Depth 

(metres). 


Number 

of 
Fishes. 


I 

3 
Faroe slope 

4 
Faroe slope 

95 

lOI 


146 
184 
831 
923 
1060 
1073 
1797 
1853 


308 
332 
300 
332 
76 
127 
82 
90 


20 
21 

23 

24 

25 


141 

... 

535 

1215 
1615 

2055 


161 
117 

77 
32 
29 


39 

41 
35 


280 

1365 
2603 


about 300 

about 80 
18 



The French deep-sea expeditions made in all 106 hauls at 
different depths down to 5000 metres, mostly in the same part 
of the Atlantic examined by the " Michael Sars," the fishing 
results being very interesting : — 



4 hauls between 


and 


100 


metres 


gave 


224 


fishes, 


or 


56 


per 


haul 


9 


, 100 




200 


,, 




323 






36 






6 


, 200 




500 


„ 




1275 






212 






28 


500 




1000 


„ 




1044 






37 






29 


, 1000 




2000 


„ 




905 






31 






20 


, 2000 




2900 


„ 




115 






6 






4 


2995 




4000 


„ 




61 






IS 






6 


„ 4000 




5000 


„ 




10 






2 







Both these tables show clearly that the number of bottom- 
fish decreases from land towards the abyssal plain. This 
decrease is, however, far from uniform. Even down to 500 
fathoms the "Michael Sars" obtained just as many fishes as 
on the bank, viz. about 300 fishes in one haul, and these were 
not small. At the same time the trawl was also crammed with 
other animals. In depths greater than 500 or 600 fathoms we 
no longer obtained anything like that number, but even down 
to 1000 fathoms (1853 metres) we still got as many as 90 fishes 
in one haul. Beyond 1000 fathoms fishes seem rapidly to 
decrease in number, for neither the " Michael Sars " nor the 
French expeditions got more than a score, or exceptionally 
nearly two score of fishes in depths exceeding 1000 fathoms. 
The richest haul of fishes known from a great depth is one 
taken by the "Michael Sars" at Station 53, in 2865 metres, 
viz. 39 fishes, of which some were large. 



FISHES FROM THE SEA-BOTTOM 



423 



If we now consider what species of fish we obtain in our 
trawlings along the continental slopes, we immediately recognise 
different strata, each characterised by its peculiar fish-community. 
It will be of interest to define the extent of these communities 
by means of the species found most abundantly at different 
depths, though there are no sharp limits between them, as it is 
difficult to find even two kinds of fish (or other animals) having 
in every respect the same distribution. It is thus obvious that 
on the borders of the different communities recognised by us, 
we shall find species belonging to neighbouring communities. 

We have already mentioned that the " Michael Sars " 
caught some of the abyssal species along the continental slopes, 
and the French deep-sea expeditions also gathered similar 
information. We may then first consider the bathymetrical Bathymetricai 
range of some of these peculiar bottom -fish living at the seali^shes?^^^' 
greatest depths : — 

Bathymetrical Range. 
Macriirus sckrorhynchus . . . from 540 to 3655 metres. 
„ talismani, 

globiceps . 
Ahpocephalus rosiratus . 
Halosauropsis macrochir . 
Synaphobranchus pinnatus ^ 

We see here a group of species which may occur in very 
deep water as well as along the continental slope ; the upper 
limit seems to be about 800 or 900 metres (about 450 fathoms), 
although stray individuals have been caught in somewhat 
shallower water. 

The main body of the fishes peculiar to the continental slopes 
consists, however, of other species, which have not been captured 
in the abyssal plain, though they have a wide distribution, like 
the denizens of the abyssal plain, and resemble them also in 
shape. Such are the following : — 



460 , 


, 2220 


"39 , 


, 2995 


«3o > 


, 3655 


1183 , 


> 2995 


201 , 


, 3250 





Bathymetrical Range. 


Macrunis cequalis . . . . 


from 460 to 1319 metres. 


„ zaniophorus .... 


„ 830 „ 1590 


Bathygadus melanobranchus 


,, 830 „ 1590 ,, 


„ longifilis .... 


„ 1374 „ 1635 „ 


Mora mora 


„ 614 „ 1367 


Lepidion lepidion ..... 


„ 631 „ 1097 „ 


Chimcera monstrosa .... 


„ 535 >» 1257 


Different species of Centrophorus (sharks) 


„ 1230 „ 1853 „ 



^ The fact that this form has been taken within such wide limits must, in my opinion, give 
rise to the suspicion that it may really be caught in midwater ; perhaps it never actually occurs 
in the abyssal area. 



424 DEPTHS OF THE OCEAN chap. 

These appear to be representatives of the fauna peculiar to 
the steepest part of the slope, from 700 to 1500 metres (400 to 
800 fathoms). 

The " Michael Sars " captured on the Atlantic slope, in 
depths between 800 and 2600 metres, over 1200 fishes, the 
relative abundance of the different forms being as follows : — 

569 fishes, or about 47 per cent, belonged to Macruridse. 

393 „ 33 ., ,, Gdid\<l2d{Mora,Anti?nora, Lepidio?i, 

Halargyreus). 
66 ,, 6 ,, ,, Alepocephalid^. 

47 „ 4 ,, „ Sharks {Cefttrophortts, Chimcera, 

Etmopterus). 

The remaining 10 per cent consisted offish represented by 
only a few individuals (Notacantktcs, rays, and others). 

In about 400 to 500 fathoms (700 to 900 metres) we meet 
with forms having their lower limit in this region, which live in 
greatest abundance at 200 to 300 fathoms. As instances may be 
mentioned : — 

Bathymetrical Range. 
Sebastes dactylopterus . . . from 75 to 975 metres. 

Motella macrophthalma . . . „ 146 ,, 987 „ 

Hoplostethus mediterranettm . . „ 140 ,, 1435 ,, 

In about 300 to 350 fathoms (550 to 650 metres) we meet 
with real representatives of the fauna of the coast banks. The 
following are some of these species, found in deep water by the 
French expeditions, with their bathymetrical range : — 

Bathymetrical Range. 
Merluccius vulgaris (hake) . . from 65 to 640 metres. 

Gadici/lus argenieiis . . . ,, 411 „ 550 „ 

Zeugopferus megastoma . . . „ 60 ,, 560 ,, 
Dentex macrophthalmus . . . „ i2o„46o „ 

In these depths we thus find in the same hauls representa- 
tives of two entirely different faunas, and we must therefore 
consider this region as an intermediate belt. 

Before attempting to describe the fauna of the coast banks, I 
wish to discuss some questions of general importance arising 
from the examination of animal life on the continental slopes. 

In his report on the deep-sea fishes of the " Valdivia " 
Expedition, Brauer gives a very able and interesting review of 
the general laws governing the geographical distribution of 
these fish, particularly the Macruridae. While the genus 
Macruriis is found in all the oceans, he considers most of the 
species to be local. Of 116 species of Macruridae he has so far 



FISHES FROM THE SEA-BOTTOM 425 

only found one (^M. parallelus) which is common to the Indian, 
Atlantic, and Pacific Oceans. All the 19 species taken at the 
Sandwich Islands are known only from that locality. Some 
species, like M. ar77iatus and M. filicmtda, have a wide distribu- 
tion, but these are exceptions from the rule. Thus, in his 
opinion, there are no species common to both sides of the Atlantic. 
The only exceptions then known i^M. siimtlus, M. goodei, 
M. berglax, and M. rupestris) are explained by him as being due 
to these species following the cold Labrador current from their 
normal habitat, the eastern side of the ocean. 

Brauer attempts to explain the peculiar distribution of the 
Macruridae. He considers that the Macruridse have originated 
from coast-fishes, and only commenced to migrate towards the 
abyssal region after a great variety of coast-forms had been 
developed. ** The fact," he observes, "that only a few species 
have penetrated into the abyssal plain, while the main body of 
the species still remains on the slope, tends to show that in 
most cases the migration towards the abyssal plain is still going 
on, that it is very slow, and that it has not yet reached the 
borders of the abyss ; or else it indicates that the abyssal plain 
tends to limit further distribution, acting as an almost in- 
surmountable obstacle." 

We have seen that all the deep-sea expeditions, prior to the 
"Michael Sars," captured only 35 individual "bottom-fishes," 
and that these belonged to twenty-one species. Our present 
knowledge must therefore be very imperfect. We have not yet 
learnt to fish to perfection at 2000 or 3000 fathoms, and we 
have as yet made too few fishing experiments at such depths. 
The short cruise of the "Michael Sars" in the Atlantic has 
essentially altered Brauer's ideas of the distribution of deep-sea 
fishes, and it appears desirable to give the interesting question 
raised by him a fresh trial, in view of the large amount of 
information which we now possess regarding the migrations 
of many fishes. When, for instance, we find the cod of the 
Norwegian Sea at one season spawning near the coasts of 
Norway, at another season migrating to Spitzbergen, or to 
the slopes of the coast - plateau, we must conclude that 
fishes may undertake horizontal as well as vertical migrations 
of enormous extent in a short space of time. Seeing that 
Macrurus sclero^'-JiyncJms has the enormous bathymetrical range 
of from 540 to 3655 metres, we can hardly suppose that the dis- 
tribution of deep-sea fishes down the slope and on the abyssal 
plain could have been prevented by "lack of time." We have 



426 



DEPTHS OF THE OCEAN 



every reason to believe that the physical conditions in these 
depths have been essentially the same at least for thousands of 
years. 

We possess, of course, no information as to the time required 
for the distribution of a species into oceanic depths. In shallow 
waters we know quite well that new physical conditions may 
permit a species to migrate into new areas and to multiply 
enormously in a short space of time (as an instance may be 
mentioned the immigration of cod into the Liimfjord after 
the North Sea broke through at Thyboroen). At all events it 
seems reasonable, first of all, to look for factors in operation at 
the present day, the influence of which may be investigated, 
before we fall back on the hypothetical conditions prevailing in 
a previous geological period. 

In his " Challenger " Summary, Sir John Murray has 
attempted an explanation of the quantitative distribution of 
organisms in different depths, which not only throws much 
light on these important geographical questions, but also possesses 
the great advantage of containing in itself a whole programme 
of future research. He found that many deep-sea animals — the 
hydroids, for example — had developed special apparatus for 
catching the minute shells and particles of food that fall from the 
surface waters, and the holothurians and other echinoderms — 
the most abundant of deep-sea animals — had their intestines 
always crammed with the surface layers of the deposit on which 
they were captured, either Blue mud, Diatom ooze, Globigerina 
ooze, Pteropod ooze, or Red clay. 

We have seen in Chapter IV. that marine deposits may be 
separated into two main groups : terrigenous deposits and 
pelagic deposits, the former occurring in deep and shallow 
water around all continents and islands within an average 
distance of one hundred or two hundred miles from the coast, 
and the latter occurring in the deeper water towards the central 
parts of the great ocean basins. 

It is a well-known fact that the detrital matter which is 
carried into the sea by rivers is rapidly deposited on meeting 
salt water, but in shallow water, where currents and wave-action 
produce their maximum effect, these fine detrital matters are not 
allowed to settle on the bottom, but are moved along till they 
reach the lower limit of wave-action. In enclosed seas this may 
be at a depth of only a few fathoms, but along coasts facing the 
great oceans the waves are so long and so high that to a depth 
of several hundred fathoms minute particles of sand may be dis- 



FISHES FROM THE SEA-BOTTOM 427 

turbed, as, for instance, off the north of Scotland. Murray has 
termed the Hmit of wave-action the mud-lme, and the average 
depth in the open ocean at which mud commences to be laid 
down he places at about 100 fathoms. 

Beyond the mud-line the physical conditions become more 
and more uniform, and for a few hundred fathoms below this 
limit animal life is exceedingly abundant. This region, accord- 
ing to Murray, is the "great feeding ground" of the ocean, 
especially around continental shores ; the organic particles from 
the continents and from the shallow waters there slowly come to 
rest on the bottom and supply food to the wealth of crustaceous 
forms which are captured in such situations (Calantis, Bzickcsta, 
PasiphcEa, Crangon, Calocaris, Pandahcs, Hippolyte, Pagitmis, 
Amphipoda, Isopoda, and Mysida). 

The surface layers of the organic deposits which are Decreasing 
situated in moderate depths towards the central parts of the food"on°pro- 
ocean basins (Diatom ooze, Globigerina ooze, Pteropod ooze), ceedinginto 
yield an abundance of food for benthonic animals, but all '^^^p^'^^"- 
investigations go to show that where the organic oozes pass 
with increasing depth into Red clay, the quantity of food for 
bottom-living animals rapidly diminishes, and the number of 
animals captured on Red clay bottoms likewise diminishes very 
greatly. The poorest hauls during the whole of the " Challenger " 
Expedition were those taken in the stretches through the 
central Pacific from Japan to Valparaiso, and Alexander Agassiz's 
investigations on board the "Albatross" gave similar results. 
He calls the central South Pacific a "barren region." 

This short statement will make it obvious, that the condi- 
tions of life offered to organisms may vary greatly in different 
depths. Murray's theory on the importance of the deposits to Relation 
the distribution of animal life is of special value, because it df^^rent kinds 
opens up to science the possibility of finding certain definable of deposits 
reasons for the differences observed in the specific composition, Hvfng^on^""^ 
and in the abundance, of animal life from place to place. them. 

This study has, however, been somewhat neglected as far as 
the oceans are concerned. Most of the deep-sea expeditions 
have been so absorbed in faunistic research, that the problems of 
the economy of the ocean have been very little attended to, 
and the strong interest taken in theoretical plankton-research 
peculiar to recent times has drawn attention away from the 
bottom-life of the ocean and the importance of the deposits as 
food for the bottom fauna, but Lohmann and C. G. J. Petersen 
have recently turned attention again to Murray's point of view. 



42; 



DEPTHS OF THE OCEAN 



During his plankton work in the Liimfjord, Petersen 
arrived at the conclusion that the plankton played a very 
unimportant part in the food of bottom-animals (as, for instance, 
the oyster). He commenced therefore to study the finely 
granular mass found in the gut of the bottom animals. He 
discovered that the uppermost layer of mud on the fjord bottom, 
2 or 3 mm. in thickness, consisted of detritus containing minute 
remains of organisms, mainly of decayed plants from the 
littoral region, and that only this upper layer of the mud has 
any nutritive value, the deeper blue-black layer not occurring 
in the gut of the bottom animals. Starting from these re- 
searches, Petersen studied the organic (nutritive) constituents 
of the mud, especially of the upper layer, and investigated the 
abundance of bottom-animals over different kinds of deposits. 
For this purpose he constructed an apparatus (see Chapter X.) 
for cutting away from the sea-bottom a square foot of its 
surface. When this large "bottom sample" is sifted the 
animals contained in the mud can be counted, and by com- 
paring the quantities of mud-eating animals thus found per 
square foot of bottom, the yielding power of different areas 
may be estimated, much on the same principle as the productive 
value of agricultural land is estimated. 

The "Michael Sars " had, during the Atlantic cruise, some 
of Petersen's apparatus on board, but owing to difficulties in 
using them in deep water, we did not succeed in obtaining 
material of any value, a fact all the more regrettable, as there 
is no doubt that Petersen's method gives far more exact results 
as regards the quantities of certain animals living on the bottom 
in shallow water than hauls with dredges and trawls. Neverthe- 
less, the material at hand may be used to illustrate the question. 
The most stringent quantitative science is in the first stages of 
a new study satisfied to dispense with the demand for absolute 
exactness, and contents itself with relative values — in other 
words, with a comparison between different localities. 

Sir John Murray long ago attempted to compare the number 
of animals taken in the dredge or trawl on different deposits, 
based on the results of the " Challenger " Expedition, and I 
reproduce some of his figures f^pm the second volume of the 
" Challenger " Summary : — 



[Table 



FISHES FROM THE SEA-BOTTOM 



429 





Specimens per Haul. 


Trawlings. 


Dredgings. 


On Red Clay- 
In the Atlantic .... 
„ Pacific .... 
„ Southern Ocean . 

On Globigerina Ooze — 

In the Atlantic .... 
„ Pacific .... 
„ Southern Ocean . 

On Terrigeftous Deposits — 

In the Atlantic .... 
Pacific .... 
„ Magellan Strait . 
„ Southern Ocean . 


40.0 
20.3 
50.0 

21. 1 

56.5 
96.7 

108.5 

71.4 

lOO.O 


4.2 

5-2 

7.0 
5-0 

55-3 
59-0 

93-0 



These figures plainly show that animal life was found most 
abundantly on terrigenous deposits, though the Globigerina 
ooze was also, especially in the Southern Ocean, very rich in 
organisms. 

At the two deepest stations of the " Michael Sars " (Station 
10, 4700 metres, and Station 48, over 5000 metres) the trawl 
was dragged for hours along the bottom, and brought up great 
quantities of ooze, which on being sifted yielded only a few 
holothurians (one individual at Station 10 and two at Station 
48). Of other mud-eating animals we found none at Station 
48; and at Station 10, in two hauls, a gasteropod, two ophiurids, 
and a few worms. 

These hauls are comparable with those made by the 
"Challenger" between the Canaries and the West Indies (see 
p. 418), in depths between 2000 and 3000 fathoms. 

Different conditions are encountered on the slopes in 
shallower water, the slopes of both continents and submarine 
ridges. From the " Michael Sars " journal the following results "Michael 
of trawlings on the continental slope west of the British Islands frawiin son 

may be quoted : - • the continental 

Station loi, 1853 metres (about 1000 fathoms). Besides 90 fishes, great wesTof 
numbers of invertebrates, mainly echinoderms, ophiurids and starfish being Britain, 
especially abundant. 

Station 95, 1797 metres (981 fathoms). Besides 82 fishes, 300 holothurians, 
800 ophiurids, starfish, Fhormoso/fia, etc. 



430 



DEPTHS OF THE OCEAN 



Station 4, 923 metres (547 fathoms). Besides 332 fishes, quantities of star- 
fish, sea-urchins {Brissopsis, Fhormoso?na), etc. 

South of the Faroe Islands, 831 metres (460 fathoms). Besides 300 fishes, 
large numbers of invertebrates. 

In Chapter IV. Sir John Murray has stated that the bottom- 
samples collected during the cruise of the " Michael Sars " show- 
that Globigerinaooze approaches nearer to the coasts of the British 
Islands than was previously supposed, having been found at 
Station 4, 547 fathoms; Station 93, 688 fathoms; Station 95, 
981 fathoms; Station 98, 742 fathoms; and Station 100, 835 
fathoms. 

While the fishes of the continental shelf all live on terrigenous 
deposits, like Blue mud, the " MichaeliSars " results prove that 
in the eastern Atlantic, at any rate, most of the fauna of the 
continental slope live on Globigerina ooze. Circumstances may 
be quite different on other slopes, as, for instance, the Atlantic 
slope off the United States, or off Newfoundland, where terri- 
genous deposits seem to have a much wider distribution. But 
the very important question of the limits between the terrigenous 
and the pelagic deposits requires further careful study by means 
of series of hauls with the trawl and series of samples of the 
deposits from shallow water down the slope to the abyssal plain. 

The results given above show in any case that . the 
Globigerina ooze in depths of 550 to 1000 fathoms may be a 
rich ground for animal life, since we got such good hauls at 
the stations quoted, and this is corroborated by the hauls taken 
on this type of deposit in deeper water, far from continental 
land, as at Stations 53 and 88. 

At Station 53, south of the Azores, 2615 to 2865 metres 
(1430 to 1570 fathoms), the trawl captured in one haul, besides 
39 fishes, about 500 holothurians, and abundance of different 
crustaceans, actinians, etc. 

At Station 88, in 3120 metres (about 1700 fathoms), the 
trawl brought up a wealth of animals, especially sea-urchins, 
starfish, ophiurids, holothurians, etc. 

We thus see that it is not terrigenous deposits alone wJiich 
harbour an abundant bottom fauna ; in fact, on true pelagic 
deposits, like Globigerina ooze, we may have the conditions 
necessary for abundant life. The percentage of carbonate of 
lime gives no indication of the suitability of the conditions for 
animal life, for the terrigenous deposits with abundant fauna, as 
well as the barren Red clay, both contain very little calcium 
carbonate. The important item is the organic stcbstance con- 



tion of fish. 



FISHES FROM THE SEA-BOTTOM 431 

tained in the deposits, which fertilises the surface layers of the importance 
Blue mud as well as of the Globigerina ooze. maufr^?n^he 

Petersen has shown that only the uppermost layer of the deposits. 
mud contains organic detritus, but the quantity of organic 
substance deposited is not always the most important factor. 
Where the water is in motion at the bottom, a fine cloud of influence of 
organic matter is swept along, and in such localities the mud- ^^H'^^^l ^^ 
eaters thrive in great quantities. The fishermen have for a the distribu 
long time profited by this fact, for they do not seek those places ' ^""^ 
(as in pits and channels on the bottom) where mud is laid 
down, but choose rather the spots where the bottom is covered 
with coarser particles, and where the finest mud cannot settle. 
In these places the fish find most food, and the fishermen most 
fish. 

Perhaps conditions like these prevail on the eastern Atlantic 
slope, as, according to the current-measurements of the 
" Michael Sars," considerable currents extend down to great 
depths. All such conditions call for further examination, 
especially in the open ocean, and it may be affirmed that studies 
of this kind will be essential for an understanding of the 
quantity of life along the bottom. 

Returning to the question of the geographical distribution of 
different species of fish, we may now examine some of the 
conditions which influence that distribution, according to the 
present state of our knowledge. 

We have seen that the species Macrttrus arniatus is known 
from the abyssal plain in the Pacific as well as in the Antarctic 
and Atlantic Oceans. The chart (Fig. 308) indicates the 
localities of capture and also the temperature, and shows at a 
glance that, notwithstanding the immense geographical range of 
this species, it is taken only where the range of temperature 
is very small (1° to 3^ C). The species is not local ; it is not 
limited by distance, but by certain physical conditions, which in 
this case prevail over an immense geographical area. 

Temperatures in abyssal depths are, as we have seen in 
Chapter V., on the whole very uniform. It is therefore interest- 
ing to note that it is especially the abyssal forms that are known 
from wide areas ; thus, for instance, Macrurtis filicatida, known 
from the Pacific and Antarctic, has a bathymetrical range from 
2515 to 4843 metres. Macrnrns parallelus, known from New 
Zealand, Japan, Ceylon, South-west Africa, ranges down to 1300 
metres. Halosauropsis 7nacrochir, known from the Southern 



Distribution 
of different 
species of fish. 



432 DEPTHS OF THE OCEAN 

Ocean, between South Africa and Kerguelen, and from the 
" Michael Sars " Stations 35, 53, 88, and 95, was taken down to 
2995 metres. 

As regards the North Atlantic in particular, the distribution 
of the deep-sea fauna and the hydrographical conditions show in 
many instances a marked and interesting correspondence. The 
rule just discussed holds good also in this ocean : the deepest 
living forms have a wide distribution. Thus three forms 
[Macrtirits brevibarbis, M. simulus, and Hariotta raleighana), 
previously known from the American side of the Atlantic, were 
found by us on the eastern side, as well as on the ridge in Mid- 
Atlantic. These forms were only taken at the deepest stations. 

In Fig. 99, p. 115, a section is given from Newfoundland 
to Ireland, showing the vertical distribution of salinities and 
temperatures, and we see from this that on the eastern side 
of the Atlantic high temperatures go far deeper than on the 
western side, where the isotherms take an upward turn along 
the slope. In intermediate depths, for instance between 500 
and 800 fathoms, it is therefore much colder on the western side, 
while at depths of 1000 to 2000 fathoms similar temperature 
conditions prevail on both sides. Special interest thus attaches 
to the fact that representatives of the deepest living forms were 
found on both sides of the ocean, while the faunae of the slopes 
in 500 to 800 fathoms are, on the whole, distinct. From this 
latter rule exceptions may be noted, some forms being also at 
these depths common to both sides, like Antimora viola, found 
first on the eastern side by the " Michael Sars," Macrurus 
7'upestris, and M. ccElo^'hynchus ; these forms, however, appear 
to be allied to the fauna of the coast banks, and they can hardly 
be counted among the forms characteristic of the intermediate 
depths on the slopes. 

Among the Macruridse the following species may perhaps be 
considered as characteristic of the two sides of the North 
Atlantic : — 

Western Side. Eastern Side. 

Macrurus carminatus. Macrurus zaniophorus. 

„ bairdii. „ cEqualis. 

„ goodei. „ sclerorhynchus. 

„ sulcatus. Bathygadus melanobra/ichus. 

„ longifilis. 

Fishes from We will here only discuss the fauna of the eastern side, 

the eSern° where trawHngs as well as hydrographical investigations were 
Atlantic. made by the " Michael Sars." The most important fish caught 



FISHES FROM THE SEA-BOTTOM 



433 



are recorded in the following table, arranged according to the 
three series of trawlings taken: (i) west of the British Isles, 
(2) west of Morocco, and (3) south of the Canaries : — 



West of the British Isles. 


West of Morocco. 


South of the Canaries. 


South of Faroe Islands, 
831 metres. 

73 Lepidion eqiies. 

94 Halargyn-etis affinis. 


Station 21, 535 metres. 
Merhiccius, Gadiculus ar- 
genteus, Molva, Phycis, 
Zeugopterus boscii, Sebastes 
dactylopterus, Chimcera vion- 
strosa, Spinax niger, Hoplos- 
tethus mediterraneum. 
20 Macrurus, mostly hevis and 
ccelorhynchus. 


Station 39 B, 2S0 metres. 

400 to 500 fishes, mostly 
Sparidre. 


74 Macrurits mostly rupestris 
and (vqiialis. 

I Trachyrhynchtis niurrayi. 

I Alepoccphalus giardi. 
15 Notacantlms bonapartii. 

I Synaphobranchus pinnatus. 


Station 41, 1365 metres. 
4 Mora mora. 

18 Macrurus {talismani, sclero- 
rkynckus, zaniophorus, 
aqualis, asperrimus ; 


Centrophorus, Chinntra 
mirabilis, and several 
others. 


Station 23, 1215 metres. 
36 Mora mora. 

II Macrurus, mostly aqualis 
and Bathygadus longifilis. 
5 Alepocepkalus. 
3 Halosaurus. 
I Bathypterois. 
3 Synaphobranckus pinnatus. 


Batky gadus melano- 
branckus). 
6 Alepocepkalus. 
12 Bathypterois. 


Station 4, 923 metres. 


15 Sytiaphobranckus pinnatus. 


I A)itinio)a viola. 
70 Mora mora. 
31 Lepidion eques. 
200 Macriirus, mostly talismani, 
aqualis, zaniophoriis. 
16 Trachyrhynchus. 

9 Alepocepkalus giardi. 

I Halosauriis. 

3 Hoplostethus mediterraneutn. 

3 Siorptma cristtilata. 

3 Synaphobranchus pinnatus. 

8 Chinuera mirabilis. 

I Rata nidrosicnsis. 


Station 35, 2603 metres. 
6 Macrurus [armatus and 
ceqtcalis). 


Station 24, 161 5 metres. 

12 Macrurus, mostly talisniajii, 

Bafkygadus longifilis. 
12 Alepocepkalus. 
3 Synaphobranckus pi)inatus. 


5 Alepocepkalus. 
2 Halosauropsis. 
I Hariotta raleighana. 


Station 25 B, 2055 metres. 
9 Macrurus {sclerorkynckus 

and tcqualis). 
16 Alepocepkalus. 
I Bathysaurus. 
I RaiafyllcE. 




Station 95, 1797 metres. 
16 Atttimora viola. 
36 Macrurus, mostly sclero- 
rhynchus, murrayi. 

5 Alepocepkalus. 

2 Bathysaurus. 

3 Notacantkus. 

2 Synaphobranchus pinnatus. 
2 Kaiafylhe. 




Station ioi, 1853 metres. 
16 Antimora viola. 
66 Macrurus, mostly sclero- 
rhynchus. 

3 Alepocepkalus. 

3 Synaphobranchus pinnatus. 

2 Hariotta raleighana. 





From this list we see that the fish fauna of the slope is very 
uniform all the way from the Faroe Islands to south of the 
Canaries ; no less than six species are common to the northern 

2 F 



434 DEPTHS OF THE OCEAN 

and southern series. The hydrographical conditions prevailing 
along the east side of the Atlantic at these depths are well seen 
in the chart for 500 fathoms (see Fig. 202, p. 296), which shows 
that the temperature at 500 fathoms to the south of the Faroe 
Islands is above 7.0° C, and south of the Canaries, 8.0° C. 
Only outside of the Mediterranean do we find a higher tempera- 
ture. On the western side of the Atlantic the temperature at 
the same depth is only 4.0" C. These facts seem to me to 
throw much new light on the geographical distribution of the 
deep-sea fauna. 

The conditions in the deep basin of the Norwegian Sea, which 
has been described in Chapter IV., are no less interesting. In 
the little chart (Fig. 309) the contour-lines for 600 and 2000 
metres are shown. The 2000 metres isobath encloses the 
abyssal plain of the Norwegian Sea, the central parts of which 
are covered by 3000 and 3500 metres of water. The area 
between the 2000 and the 600 metres isobaths shows the region 
of the slopes, which are steep all the way from Spitzbergen to 
the Wyville Thomson Ridge, a deep channel (the Faroe- 
Shetland channel) running from the deep basin right down to 
the ridge. The hydrographical conditions in the Norwegian 
Sea are indicated in the vertical section (Fig. 310), which runs 
through the points a, b, <;, from the east coast of Greenland 
across Jan Mayen to Vesteraalen in Norway. In this section 
the "Atlantic water," with a salinity above 35 per thousand, is 
shaded, and is seen to be limited to the eastern side, the 
depth of the layer not exceeding 600 to 700 metres (or 350 
to 400 fathoms). All the water to the west, and beneath this 
" Atlantic water," is quite cold, most of it below 0° C, the 
abyssal plain itself being covered by water having a temperature 
below — 1° C. 

The fauna of this cold deep basin has been extensively 
studied during the Norwegian expeditions on board the 
" Voringen " and the "Michael Sars," during the Danish 
expeditions on board the " Ingolf" and the " Thor," and also by 
Swedish and French expeditions (Duke of Orleans, etc.). On 
the chart (Fig. 309) small circles denote localities where 
Norwegian expeditions have employed dredges or trawls, the 
captures everywhere being remarkably poor in species. 

The abyssal plain and the slopes of the Norwegian Sea do 
not show a single species in common with the Atlantic. While 
in the Atlantic the genus Macrurus plays an important part in 



FISHES FROM TH^: SEA-BOTTOM 



435 



the fauna of the abyssal area, not one species of this genus 
has been found in the cold water of the Norwegian Sea, where 
the genus Lycodes (of the family Zoarcidae) predominates. But 
Lycodes is not limited to the Norwegian Sea, being represented in 




Fig. 309. — -The Norwegian Sea. 

Continuous line-— 600 metres. Broken line =2000 metres. 

Section through a, b, c, shown in Fig. 310. 

the abyssal depths as well as on the slopes of the Atlantic, though 
no species has been found common to the Atlantic and the 
Norwegian Sea. To the Danish scientist Adolf Jensen we owe 
our knowledge regarding this interesting biological fact. 



436 



DEPTHS OF THE OCEAN 



The principal "cold-water" fish of the deep Norwegian Sea 
belong to the following species : — 

ZoARCiD/E — Lycodes mitrcB/m, L. flagellicauda, L. fn'gidus, L. palHdus, 
L. similis, L. eudipleurostictus, L. seminudus. 
OPHiDUDiE — Rhodichthys reglna. 

Li PAR I D^ — Careproctus reinhardi, Paraliparis bathybii. 
CoTTiD^ — Cottunculus microps, C. stibspinosus. 
Sharks — Sonmiosus inicrocephalus (the Greenland shark). 
Rays — Raia hyperborea. 

Excepting the Greenland shark these species have been 




Fig. 310. — Section across the Norwegian Sea from Greenland to Norway in 
Position shown in Fig. 309. (Drawn by Helland-Hansen.) 

taken in cold water only, below 0° C, and mostly in small 
numbers, though occasionally they are more numerous. 

Thus a haul made by the " Michael Sars " to the north of 
the Faroe Islands, in 975 fathoms, with a trawl similar to the 
one used in the Atlantic, gave in two hours : 34 Paraliparis 
bathybii, i Rhodichthys regina, and 17 Lycodes. East of 
Iceland, in 467 fathoms, where the temperature was -0.6° 
C, the Danish research steamer "Thor," on a line of 225 
hooks, obtained 4 Raia hyperborea, i Greenland shark, and 20 
black halibuts (Hippoglossiis hippoglossoides) ; the latter two 
species are not, however, exclusively cold-water fish. 



FISHES FROM THE SEA-BOTTOM 437 

Previously all these fishes of the Norwegian Sea were 
generally believed to live only along the bottom, but, as 
mentioned in Chapter HI., the "Michael Sars " in May 191 1 
obtained in a pelagic haul in the cold layers of the Norwegian 
Sea a specimen of Paraliparis bathybii. In the cold water 
layer there are thus fishes which at least occasionally occur in 
midwater. 

On the coast banks off Greenland, Jan Mayen, and the Arctic 
most northerly coasts of Spitzbergen dwells a genuine Arctic Juia ofThe^'' 
fauna. Of these shallow cold-water species the following are Norwegian 
most important : Icebis kamatics, Triglops pingelii, Ltwipenus 
niactilatits, L. viedius, and L. lampetriformis, besides Gadtis 
saida (the polar cod). 

On the east and south side of the Norwegian Sea, from 
Spitzbergen along the coast of Norway and the North Sea 
banks, and also at Iceland, the cold water does not occur on the 
slopes in depths less than 600 or 700 metres, and the change 
from the cold water to "Atlantic water" is very marked. The 
deep-sea fauna and the fauna of the coast banks are for this 
reason much more sharply separated than in the Atlantic. At 
most seasons the limit is determined by the vertical distribution 
of the Atlantic water, and this limit may oscillate according to 
changes in the current, though this point has not yet been 
thoroughly examined. 

The fishing experiments of the " Michael Sars " have some- 
times in a very striking way shown how sharp the limit is 
between the two faunce. In June 1902, for instance, a long line 
of 1200 fathoms was shot on the northern slope of the North 
Sea bank towards the deep water, one end of the line being in 
217 fathoms, where the temperature was 6° C, and the other end 
in 300 fathoms, where the temperature was — 0.2° C. In the cold 
water we obtained cold-water fish {Raia hype^'borea), while near 
the upper end of the line (in warmer water) the fish belonged to 
the coast bank species [Sebastes, Macrurus fabricii). Rata 
hyperborea has been taken from North Spitzbergen down to the 
slope of the North Sea plateau ; Macrurus fabricii is known 
from the Bay of Biscay, from the ocean off the east coast^of 
North America, and from other localities. 

The Fishes of the Coast-banks 

The " Michael Sars " has now had the opportunity of 
investigating the coast-banks from Spitsbergen to a little south 



438 DEPTHS OF THE OCEAN 

of the Canaries, a stretch of more than 40 degrees, or 2400 miles, 
A survey of the animal life on this long stretch of sea-floor is 
very interesting. As the temperature gradually falls toward the 
north the fauna changes. Some species are hardy, and are dis- 
tributed over a greater part of the area ; others can only live 
under more uniform conditions, and therefore have a more 
limited area of distribution. 

Zoological oceanography has long recognised this, and 
zoological literature contains much information regarding the 
distribution of animals within our area of investigation. I will 
mention only one example, for which purpose I choose the 
excellent survey of the mollusca of Arctic Norway by G. O. 
Sars, recording the geographical distribution of 1 74 species of 
lamellibranchs and 366 species of gasteropods. 

Of the 174 lamellibranchs no less than 128 or 74 per cent 
were known also from Great Britain ; 119 or 70 per cent from 
the Mediterranean, and 56 or 32 per cent from boreal North 
America. 

Of 366 gasteropods found in Norway, 225 or 62 per cent 
were also known from Great Britain ; 133 or 36 per cent from 
the Mediterranean, and ']^ or 23 per cent from the coasts of 
boreal North America. A great many species of molluscs have 
been taken in the Mediterranean as well as in Norway, and 
quite a number of forms are common to the faunae of Norway 
and of North America. 

Examining the conditions in various parts of the coast of 
Norway, we see that the Mediterranean species rapidly decrease 
in number as we go north from western Norway, for instance, 
from the latitude of Bergen towards the North Cape. While 
119 lamellibranchs and 133 gasteropods are common to the 
Mediterranean and Southern Norway, Northern Norway and the 
Mediterranean have only 49 lamellibranchs (28 per cent) and 35 
gasteropods {10 per cent) in common. Also south of the 
Mediterranean we find a similar decrease in the number of 
species common to both areas ; thus only 5 species of lamelli- 
branchs and 4 species of gasteropods are common to Madeira 
and Northern Norway. 

1^ A thorough understanding of the distribution of different 
animals, or of the different animal-communities, is, however, not 
obtainable by m.eans of records of this kind, for it makes a 
world of difference whether a few specimens of a species have 
been found in a certain locality or whether it lives there in 
great quantities. A complete knowledge of the distribution of 



FISHES FROM THE SEA-BOTTOM 



439 



a species would be based on material containing information 
as to how many individuals of the species live in different 
sections of the area, and a complete knowledge of an animal- 
community would be to have information as to the exact 
relative occurrence of the animals. 

In regard to no species, however, does our present knowledge 
comply with this ideal demand. As regards the fishes we have 




Fir,. ^11. — Steam-Trawlers laid up in Grimsby during Engineers' Lock-out. 



most information on the species of economic importance, for In 
recent years many fishing experiments have been made with the 
object of ascertaining what quantities of fish occur in different 
waters. In co-operation with the International Council for the Fishery 
study of the sea, the fishery statistics of several countries have ^^^^'^^^^^ 
also been so far improved, that the quantities of fish landed are 
now separated in regard to species and areas where caught. 
The quantities landed are certainly not on the whole repre- 



440 DEPTHS OF THE OCEAN chap, vn 

sentative of the quantities living in the sea. For instance, it is 
clear that the intensity of fishing is not only determined by the 
abundance of fish, the prices and the distances to fish markets 
being (among others) very important points. But notwith- 
standing these drawbacks, we possess at the present time hardly 
any better means of judging of the abundance of fish in different 
areas than the information regarding the capture of edible fish 
contained in the fishery statistics of recent years. An enormous 
fleet of modern fishing steamers (see Fig. 311) is now dis- 
tributed from Cape Kanin, at the mouth of the White Sea, 
down to Morocco, that is to say, over the area investigated by 
the " Michael Sars." 

From the statistics published by Dr. Kyle of the Inter- 
national Bureau for the Study of the Sea, we have compiled 
two tables recording the capture of bottom-fish in 1906. One 
(Table A) shows the catch of each species in each fishing area 
expressed in percentages of the quantity of the species landed 
from all areas ; the other (Table B) shows the catch of each 
species expressed in percentages of the aggregate quantity 
landed from each area. The tables deal with nearly a million 
tons of fish of all kinds from all waters, the quantities varying 
greatly in different areas. First of all is the North Sea with 
nearly 400,000 tons, or nearly 40 per cent of the total quantity ; 
then comes the coast of Norway, north of Stat, with 28 per cent, 
Iceland with 18 per cent, the Faroe Islands with 4 per cent, the 
region north-west of the British Isles with 5 per cent, the Bay 
of Biscay, Portugal, and Morocco with less than ^ per cent 
each. Among the different bottom-fish the cod plays the most 
important part with no less than 44 per cent, next comes the 
haddock with 25 per cent, plaice with 6|- per cent, saithe with 
3|- per cent, ling 3 per cent, and hake with a little above 
2 per cent, of the total quantity. 

Considering now the abundance of each species in each of 
the nine areas recognised by the fishery statistics, we first 
observe that most of the species have their maximum abundance 
in the North Sea. This applies principally to the haddock, 
the whiting, the species of Bot/ms, the plaice, the lemon sole, 
and the dab. The intensity of the fishing in the North Sea 
is, of course, to some extent responsible for this. But never- 
theless we find several exceptions. Thus the Norway haddock 
(Sebastes), the cod, the saithe, and the tusk are taken in the 
greatest quantities off the coast of Norway, the halibut at 
Iceland. On the other hand, we find in regard to dog-fish. 





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CHAP. VII FISHES FROM THE SEA-BOTTOM 443 

bream (Pagelhts), pollack, hake, megrim i^Zetigopte^^us), and 
conger-eel, that the greatest quantities are taken south-west of 
the British Isles in the Atlantic. 

We can thus distinguish northern species which are mainly Northern and 
taken north of the North Sea and in the North Sea, and ;°^'^^^';^^ ^j^^ 
southern species, which are chiefly derived from the Atlantic, easteni 
notwithstanding the fact that comparatively little fishing is '^^^^"*^'^- 
carried on in this area. The percentages of each species in the 
aggregate quantities landed from each area confirm these facts. 

In the area between the mouth of the White Sea and the 
west coast of the British Isles we find the cod constituting at 
least 20 per cent of all the fish caught, on the coast of Norway 
even 81 per cent, at Iceland 60 per cent, and at the Faroe Islands 
48 per cent. South-west of the British Isles the quantity of 
cod dwindles to 4|- per cent, and farther south it disappears. 
The haddock also constitutes a large proportion of the quantities 
landed from the area between the White Sea and the north- 
west of the British Isles (excepting off Norway, where the 
bottom is unsuitable for haddock-fishing) ; in the North Sea even 
45 per cent of all the fish caught are haddock. The quantities 
of this fish also dwindle and finally disappear south-west of 
the British Isles. The same applies to plaice, halibut, ling, and 
tusk. 

The percentages of southern fish, on the other hand, increase 
west of the British Isles. The hake [Alerhiccius) practically 
does not occur north of the North Sea, where it constitutes 
only about J per cent of the total quantity ; south-west of the 
British Isles it reaches 32 per cent, in the Bay of Biscay even 
65 per cent, and all the way southward it constitutes at least 
30 per cent of the total quantity. Similar conditions apply to 
the pollack, sole, sea-bream [Pagelhts), the monk or angler, the 
gurnards, and others. 

On the coast banks of the western side of the Atlantic we Northern and 
meet with similar groups of northern and southern forms, JpedeT^n the 
the change between these groups occurring about the New western 
England states. We give some instances of quantities of fish 
landed in the New England states, the middle Atlantic states, 
and the south Atlantic states, taken from the fishery statistics 
for the year 1906, the figures signifying tons : — 



[Table 



444 



DEPTHS OF THE OCEAN 





Northern States. 


Middle States. 


Southern States. 


Cod . . . 


40,000 


1,400 




Haddock 






21,000 


200 




Saithe . 






7,900 


50 




Flounder 






2,150 


1,400 


350 


Halibut 






5.500 






Hake . 






15,000 


200 




Mullet . 








150 


18,500 


Sci^nidas 






3>3oo 


11,400 


4,300 


Sparidse 






30 




6,100 



Influence of 
temperature 



fishes. 



The northern forms — cod, haddock, saithe, flounder, and 
hahbut — disappear along the coast of the southern states, as does 
also the hake. On the other hand mullet, ScisenidEe, and 
Sparidae, i.e. the southern forms, increase as we go south, just as 
they do on the eastern side from the Bay of Biscay towards the 
coast of Morocco. 

If, with these facts in mind, we look at the chart (Fig. 312) 
,.,. recording: the temperature at a depth of 100 metres (about 50 

conditions on p ,11, -ii 1 r 1 1 tm • 

distribution of fathoms), we shall be astonished at the tact that the distribution 
of different species curiously coincides with certain temperatures. 
The southern limit of northern boreal species everywhere 
coincides with the isotherm for lo^ C. On the west side this 
isotherm just reaches the border between the northern and 
middle states of North America, while on the east side, on the 
coast of Ireland, this isotherm just separates the two areas 
termed respectively areas north-west and south-west of the 
British Islands. 

The areas of the northern species correspond on both sides 
of the ocean to the area between 2° and 10" C, the maximum 
frequency of the species occurring between 6^ and 8° C. These 
latter temperatures are found on the Newfoundland banks, on 
the southern and western banks of Iceland, in the North Sea, 
and along the entire coast of Norway. The uniformity of the 
fauna peculiar to all these localities compares well with the 
uniform conditions of temperature. South of the 10° isotherm 
we have on both sides of the ocean belts with temperatures 
between 10' and 18° C. ; that on the west side ranges from 
Cape Cod to Florida, and that on the east side from Iceland to 
south of the Canaries. 

A peculiar feature is that all the isotherms on the west side 
are quite close together, the water layers being squeezed 



FISHES FROM THE SEA-BOTTOM 



445 



between the oceanic sub-tropical waters from the south and the 
arctic Labrador current from the north. All changes in 
temperature are therefore on the western side very sharp. On 
the eastern side the layers are spread out fan-wise, and as a 
consequence we may at a depth of lOO metres find the same 
temperature prevailing from north to south over wide areas, as, 




Fig. 312. — Distribution of Temperature in the North Atlantic at a Depth of 
100 metres. (Drawn by Helland- Hansen.) 



for instance, along the coast of Norway from the North Sea to 
the North Cape. 

We may now discuss the distribution of the southern and 
northern species. 

Comparing the percentages of the different species noted in The southern 
the quantities landed from different geographical areas (see ^p^"^^- 



446 DEPTHS OF THE OCEAN chap, vn 

Table B), we observe that northern (boreal) forms decrease 
enormously to the west of the British Isles, We may say that 
there is a sharp southern limit to the distribution of these 
species west of the Channel ; the cod, saithe, tusk, and halibut 
here quite cease to play any part in the captures. 

The northern limit for the southern forms is essentially 
different. Of the species recorded in the systematic list of 
bottom-fish captured by the " Michael Sars " in the Atlantic, 63 
species were previously known from the Mediterranean, and are 
found there in abundance. Of these only a few are genuine 
southern forms; 10 species have their northern limit on the coast 
of France, 19 on the coasts of the British Isles, and 23 occur 
in varying numbers even on the coasts of Scandinavia. As we 
shall show in Chapter X., this wide range of certain species is 
probably due to the fact that the water- layers in the North 
Atlantic run north, and transport especially the young stages of 
certain southern species, which may as a consequence pass their 
youth very far from the localities where they were born. This 
is why the boreal fish-fauna is more or less mixed up with 
southern forms, especially in the southern part of the boreal 
region, for instance in the southern North Sea, in the areas 
west of the British Isles, in the Kattegat, and along the coast of 
the Skagerrack, in which localities high summer temperatures 
prevail in the upper layers. 

To the south-west of the British Isles, from the Bay of Biscay 
towards Morocco, we enter the real area of the southern fauna. 
This is shown by the table containing the fishery statistics, as 
well as by the record of the captures made by the " Michael Sars " 
in the Atlantic. In the following list the captures made during 
the cruise down to about 500 metres, or 300 fathoms, are 
recorded and arranged in three groups : (i) West of the British 
Isles, (2) West of Morocco, and (3) South of the Canaries. 



[Table 



Fishes from the Atlantic Coast Banks. 


West of British Isles. 


West of Morocco. 


South of Canary Islands. 


Off Faroe Islands, 
130 metres (trawl and long-line). 
2 Gadus aglefimis. 
1 2 Hippoglossus vulgaris. 
6 Plettronectes limanda. 
I Zetigopterus niegastoma. 
I Raia clavata. 
9 Raia bat is. 


Off the Coast of Portugal, 

Stations 13-14, 70-80 metres, 

(trawl and line). 

8 Gadus merlangus. 
36 ,, luscus. 
22 Merluccius vulgaris. 

I Pagellus centrodontus. 

I Caranx track urns. 

3 Trachinus viper a. 

I Mustelus vulgaris. 

I Scyllium canicula. 

I Centrina salviani. 

I /"a/a clavata. 

I j?a/« circularis. 


Station 36, 10 metres. 
5 Merluccius vulgaris. 

1 .SW^a /z^/^a. 

Many Sargus annularis. 
Many Pristipoma beniiettii. 

2 Sciczna aquila. 

2 Umbrina ronchus. 

2 .5(?.r vulgaris. 
32 Atherina. 
77 Caranx trachurus. 

I Temnodon saltator. 
73 Clupea pilchardus. 

I , , «/^ja. 
26 Engraulis encrasicholits. 

I Myliohatis aquila. 


Station i, 146 metres. 
2 Gadus esviarkii. 
2 ,, poutassoH. 
2 Phycis blennioides. 
20 Merluccius vulgaris. 


4 Zetigopterus niegastoma. 


Station 20, 141 metres. 
52 Merluccius vulgaris. 
I ^o/cja vulgaris. 

7 Pagellus centrodontus. 
1 , , acarne. 

3 Dentex maroccanns. 

5 ,, niacrophthalinus. 
1 1 Mullus surmuletus. 

8 Caranx trachitrus. 

4 Zeus faber. 
30 Capros aper. 

1 Trigla hiriindo. 
16 ,, /j'ra. 

3 , , cuculus. 

2 , , //;;/. 

20 Lepidotrigla aspera. 
I Peristedion cataphractum. 

4 Acanthias vulgaris. 

6 Scyllium canicula. 
I ^a/a clavata. 


184 Caranx trachwus. 

I Zeusfaber. 
52 Capros apcr. 
18 Trigla guniardus. 

5 Argentina sphyncna. 
20 Acanthias vulgaris. 

I Pristiurus melanostonius. 

7 /'a/a clavata. 


Station 37, 39 metres. 
I Artioglossus lophotes. 

1 Dentex maroccatius. 

2 Cant'harus lineatus. 

3 Serranus cabrilla. 
I Coris julis. 

1 Mullus surmuletus. 

2 ScorpcEna scrofa. 

2 ,, ustulata. 

1 Uranoscopus scaber. 

2 Tetrodon spengleri. 
2 Raia punctata. 

2 ,, microocellata. 
I „ a/^a. 


Station 3, 184 metres. 
I Gadus czglefinus. 
8 , , poutassou. 
40 Gadiculus argenteus. 
5 Merluccius vulgaris. 

1 Phycis bleiinioides. 

170 Zeugopterus megastoiiia. 

2 Arnoglossus latema. 

2 ,, lophotes. 

3 vSi^/^a variegata. 

2 Caranx track icr us. 


Station 38, 77 metres. 
2 .S^/fa vulgaris. 
2 „ /i^/^a. 
2 Arnoglossus lophotes. 
I ,, grohmanni. 
I Pagrus vulgaris. 

1 Dentex macrophthalmus. 

2 Trigla ohscura. 

I Scorpicna scrofa. 
I Trachinus draco. 
I Lophius piscatorius. 

1 Miimna helena. 

2 i?a«'a punctata. 


2 Capros aper. 
12 Trigla gurnardus. 
29 ,, /j'ra:. 

I ,, //wz. 

5 Callionymus maculatus. 

4 Lophius piscatorius. 

4 Argentina sphyncna. 
8 Acanthias vulgaris. 

5 Scylliuii! canicula. 


Station 21, 535 metres. 
14 Gadiculus argenteus. 

8 Merluccius vulgaris. 
12 Phycis blennioides. 

1 Molva elongata. 

9 Malacocephalus lisvis. 

9 Ca-lorhynchus calorhynchus. 

2 Macrurunger. 

6 Zeugopterus boscii. 

10 .Se bastes dactylopterus. 

30 Hoplostethus mediterraneum. 
2 Chimcera monstrosa. 

1 1 P7-istiurus melanostonius. 
2 Spinax niger. 

I RaiafuUonica. 


25 /'«;« clavata. 
I , , vomer. 
I , , ciirularis. 


Station 39 B, 280 metres. 
10 Merluccius vulgaris. 
I Pagrus vulgaris. 
250 Dentex macrophthalmus. 

1 Mullus surmuletus. 

2 Caranx trachurus. 
I Capros aper. 

Many Centriscus scolopax. 

I Trigla lyra. 
]\Iany Lepidotrigla aspera. 

I Peristedion cataphractum. 

I Scorpcena ustulata. 

5 Argentina silus. 

5 Acanthias vulgaris. 

1 Scyllium canicula. 

2 Rhina squatifta. 
20 /v'az'a miraletus. 

I , , clavata. 
4 ,, punctata. 
I , , circularis. 


Off Faroe Islands, 
442 metres (long-line). 
8 J/(?/z'a ;«^/z;rt. 
40 Brosmius brosme. 
2 Hippoglossus vulgaris. 

2 ChimcEra inonstrosa. 

40 Pristiurus melanostonius. 
I Spinax niger. 

3 Ceiitrophorus 'squamosus. 



448 DEPTHS OF THE OCEAN chap. 

In the lists from the stations west of the British Isles we find 
the northern forms : haddock, halibut, and tusk, but also forms 
which never occur in the Norwegian Sea or the North Sea, 
such as Capros aper and Centrophorus squamosus. The hake 
(Merhiccitcs), the gurnard (Trigld), and southern flatfish 
\Arnoglossus lophotes, A. laterna) also occur. 

To the west of Morocco the hake and the southern cod 
{Gadus luscus), besides a few whiting, are the only representa- 
tives of the cod family. Here we find no less than five 
species of gurnards in one haul, mullets (Midlus surmiiletzis) , 
and Sparidse [Pagellus centrodontus, Dentex maroccanus, and 
D. macrophthalmus). In the deep haul in 535 metres we 
observe the southern ling [Molva elongatd), Sebastes dactylop- 
terus, and different Macruridse, along with Merliicmis (hake), 
and Gadiculus argenteus. 

To the south of the Canaries the acanthopterygian fish 
decidedly predominate. We find Sparidse {Dentex, Pagrus, 
Sargiis, Box, Serranus, Scorpcsna, Mullus, Trachinus, Trigia). 
There are also soles [Solea, Arnoglossus), hake, and anglers. 
In shallow water we also meet with the young of different 
herrings, such as pilchards, Clupea alosa, and anchovy. 

Thus the three series of hauls show the changes encountered 
in the fauna, from the mingled community of boreal and 
southern forms west of the British Isles to the entirely southern 
fauna on the west coast of Africa. 

These records also serve to illustrate the catches of fishing 
vessels on the European and African banks of the Atlantic. 
As is well known, the trawling industry was developed in the 
North Sea. When it was carried farther south along the Bay 
of Biscay, along the coast of Portugal, and along the coast of 
Morocco, the hake and the sole were first and foremost the main 
objects of capture. These two species are still of first import- 
ance to the trawlers. From Table B, page 442, we learn 
that in the Bay of Biscay the hake constitutes 65 per cent, and 
farther south 36 per cent, of all the fish caught. The valuable 
sole constitutes no less than 16 per cent of the weight of all 
the fish caught in the most southerly areas. The rays play an 
important part (in the Bay of Biscay 15 per cent, farther south 
2 1 per cent), but also the acanthopterygians (Pagel/ns, Mullus, 
Dentex, etc.) are of great importance. I have obtained some 
information on their catches off the Moroccan coast-banks from 
trawlers, who tell me that the hake constitutes two-thirds of the 
catch. The acanthopterygians very often make up one-fourth. 



FISHES FROM THE SEA-BOTTOM 



449 



and farther south, near the Canaries, off Agadir, they may 
even amount to two-thirds of the total catch. Soles are also 
numerous. South of the Canaries we saw during our cruise 
(see Chapter HI.) a considerable handline fishery for acanthop- 
terygian fish {Dentex, Diagranwia, etc.) carried out on hard 
stony and gravelly bottom. The trawl cannot be worked there, 
where the acanthopterygians were present in enormous shoals, 
outnumbering all other species. We had there a fauna entirely 
different from the boreal fauna, lacking all the northern forms. 

All the way from western Ireland to the coast banks of 
Morocco, fishing is carried on down to deep water, at least to 
300 fathoms (500 to 600 metres). West of Ireland the trawlers 
in April capture two kinds of ling (Molva violva and M. eiongata), 
hake and breams (Pagelhis), down to 300 fathoms, and west of 
Morocco they get large hake down to 200 or 300 fathoms. Fish- 
ing thus goes on as deep as the fauna of the coast banks extends. 

As we have seen already, the Macruridae peculiar to the 
fauna of the slopes, commence at about 500 or 600 metres. 
Will this fauna of the slopes, particularly the Macruridae, Mora, 
etc., ever be the object of a fishing industry.^* This question 
is important, and the possibility of such an industry cannot 
a priori be denied. If we consider that the " Michael Sars " in 
one haul, with a comparatively small trawl, at Station 4 took over 
300 fishes, some of which, as for instance the Mora, seemed just as 
fit for the market as the tusk, it does not seem improbable that 
improved technical appliances may render fishing profitable 
even down to 500 fathoms and more. 

It is very interesting to note, as shown in the following 
table, that the temperature in 300 fathoms (the limit of the 
coast fish) is 10° C. — a temperature which we have previously 
referred to as marking the southern limit of the northern forms 
to the west of Ireland, where the southern forms commenced to 
increase in abundance : — 



Depth limit 
of fishing on 
Atlantic slope. 



Depths in Fathoms. 


Station 43, 
South of the Canaries. 


Station 93, 
West of Ireland. 


50 


16.8° 


10.8° 


100 


15-7° 


10.4 


200 


I3-I 


10.3 


250 


11.7° 


10.2 


300 




lO.O 


350 


9-5° 




400 




9.2 



2 G 



450 DEPTHS OF THE OCEAN 

Vertically as well as horizontally the fauna termed by me the 
southern one appears to exist within the same limits of tempera- 
ture. The different species appear to be at liberty to move 
within these limits and to be independent of depth. Thus 
there are many observations showing that the southern species 
occur in deeper water on the Atlantic slope than they do in 
the North Sea. This is easy to understand, because in the 
North Sea only the shallow upper layers are affected by high 
summer temperatures. Nevertheless the records of such species 
from deeper water available from the results of the "Michael 
Sars " and other expeditions are quite surprising. Thus the 
French deep-sea expeditions found : — 



Solea vulgaris 


in 235 metres. 


Solea variegata 
Arnoglossits grohmanni 
Gobius 7ninutns 


„ 306 „ 
„ 175 » 
„ 118 „ 


Callionymus lyra 
Trachhius draco 


>, 175 ,, 



Lophius piscatorius hoXw^tQn 2 1() 3.nd 668 „ 

Merluccius vulgaris ,, 99 „ 640 „ 

Motella tricirrhata „ 112 „ 640 „ 

Phycis albidus „ 40 „ 460 „ 

These instances are quite sufficient to show that in the 
southern part of our area the fishes tend to migrate vertically 
within considerable bathymetrical ranges. Evidently tempera- 
ture here plays a dominant part, and perhaps also other factors 
come into play, above all the deeper penetration of light in 
southern waters. 

The Northern We have previously seen that the northern species in North 

(boreal) European waters rano^e from the Barents Sea in the north to 

west of the British Isles in the south. But within this wide area 
we meet with many variations in detail, even though the fish 
fauna of the whole area in a broad sense may be said to be 
homogeneous. Thus some species belong mainly to the most 
northerly part of the area, while others are taken in quantities 
worth mentioning only in the far south of the region. The 
abundance of a species does not alone depend on latitude or 
conditions of temperature, but the extent of the area of bottom 
suitable to the species is also of great importance. 

An analysis of this question cannot, however, be restricted to 
a search for the geographical limits of the species. As regards 
the northern forms, information as to their bathymetrical dis- 
tribution is very important. The English fishery statistics 



FISHES FROM THE SEA-BOTTOM 



451 



recording the catches of trawlers in the North Sea contain the 
most ample details on the vertical distribution of certain northern 
species. Within this area information has been gathered Fishes taken 
separately for certain smaller areas, the limits of which coincide depthJ'in"the 
with isobaths of the North Sea. Thus one area comprises all North Sea. 
the banks between the coast and the 20 metres line, i.e. all the 
coast banks and the Dogger Bank ; another area occupies the 
space between the 20 and the 40 metres lines, etc. In the 
following table we have reproduced a record of the occurrence 
of the principal food fishes at different depths compiled from 
these statistics, the figures indicating the percentage of each 
kind of fish landed from each of the seven areas : — 

Percentages of Fish taken at Different Depths in the North Sea 





















Over 






Species. 


0-20 


20-40 


40-60 


60-80 


80-100 


IC0-200 








metres. 


metres. 


metres. 


metres. 


metres. 


metres. 


metres. 


I 


Dogfish 


Acanthias vulgaris . 


16.3 


64.0 


II. 


3-5 


5-2 






2 


Skates and Rays 


RaiidK .... 


3-2 


36.8 


319 


10.4 


8.8 


8.5 


0.2 


3 


Monks 


Lophius piscatorhis . 


o.S 


17-3 


20.7 


28.6 


15-2 


17-5 


0.3 


4 


Gurnards . 


Trigla sp. . . . 


0.7 


25.1 


31.0 


18. 1 


10.9 


14.0 


O.I 


5 


Catfish 


Anarrhicas hipus . 




7-7 


26.1 


39-1 


15.2 


II. 8 


O.I 


6 


Cod, large . 


Gadus callarias 


0.7 


19.9 


2g.g 


28.7 


12.4 


8.3 


0.2 


7 


,, medium 


,, ,, . . 


I.O 


41.8 


29.4 


13-3 


8.9 


5-5 




8 


,, small . 


,, ,, . . 


0.6 


36.1 


259 


31-7 


3-9 


1.9 




9 


Coalfish 


,, virens . 




3-9 


6.1 


19.7 


21.6 


48.4 


0.3 


10 


Haddock, large . 


,, aglefinus 


0.4 


18.6 


SO. 2 


20.6 


5.6 


4.8 




II 


,, medium 


,, ,, . . 


O.I 


19.9 


27.2 


17.2 


21.5 


13-6 


0-3 


12 


,, small . 


,, ,, . . 




8.6 


16.6 


25-2 


19.6 


29.9 


0.3 


13 


Pollack 


,, pollachius 




12.0 


31-7 


14.2 


17.9 


23.6 


0.6 


14 


Whiting . 


,, merlangiis . 


0.3 


29.2 


40.3 


9-3 


7-4 


13-4 


0.1 


15 


Hake, large 


Merhtccius vulgaris 


O.I 


5-7 


15-3 


4-7 


4.1 


68.3 


1-7 


16 


,, medium . 


jj J) 




iS-4 


26.3 


4.6 


5.0 


46.2 


2.3 


17 


,, small 






26.5 


3^-4 


2-5 


4.2 


30.7 


47 


18 


Ling . 


Molva molva . 




5-6 


14.9 


25-3 


20.3 


33-S 


0.3 


19 


Tusk . 


Brosinius brosme 






0.4 


7-9 


7.9 


82.5 


1-3 


20 


Soles, large 


Solea vulgaris 


6.4 


64.3 


27.8 


1-3 








21 


,, medium . 


,, ,, . . 


5-2 


Si.o 


43-6 


0.3 








22 


,, small 


,, ,, . . 


8-5 


S6.7 


35-4 


0.2 








23 


Brill . 


Bothus rhombus 


3-3 


63.2 


32-7 


0.6 


0.1 






24 


Turbot 


,, maximus 


2.6 


40.0 


48.2 


5.6 


1.6 


1.4 




25 


Plaice, large 


Pleuronectes platessa 


0.6 


48.5 


42.8 


6.3 


1-3 


0.3 




26 


,, medium . 


,, ,, . . 


2.8 


49-8 


43-3 


2.9 


1.0 






27 


,, small 


,, ,, . . 


13-9 


59-5 


25.8 


0.3 


0.2 






28 


Lemon soles 


,, viicroccphalus 


0.4 


317 


18.2 


32-9 


12.4 


4.3 




29 


Flounders . 


,, flesus . 


7-1 


67.2 


24.7 


0.9 


0.2 






30 


Dabs . 


,, limanda 


3-4 


81.7 


5-5 


6.7 


2.7 


0.2 




31 


Witches . 


, , cynoglossus . 




0-5 


1.4 


12.3 


21.2 


64.2 


0.4 


32 


Halibut . . 


Hippoglossus vulgaris 


0.1 


2.4 


7-3 


24.7 


33 -o 


32.5 


0.2 


33 


Megrims . 


Zeugopterus me gas to ma , 






0.8 


3-3 


8.1 


87.2 


0.7 


34 


Conger eels 


Conger vulgaris 


0.6 


37-8 


SO. 8 


7-5 


1-7 


1-7 





On the shallow banks between the shore and a depth 
of 40 metres (about 20 fathoms) the flat-fish — sole, brill, plaice, 



452 



DEPTHS OF THE OCEAN 



flounder, and dab — are the most characteristic, but young stages 
of cod, rays, and dog-fish (Acantkias) also occur plentifully. 

In medium depths, from 40 to 100 metres (25 to 50 fathoms), 
the gadidae — haddock, large cod, pollack, and whiting — pre- 
dominate, but we also meet with flat-fish, turbot, lemon sole 
{P/eiironectes microcep/ialiis), and young halibut, and with some 
southern forms : hake, gurnards, anglers, and conger eels. 

Below 100 metres (50 fathoms) we meet with the saithe, 
ling, tusk (see Fig. 313), large hake, besides witch, megrim, and 
large halibut. 




Fig. 313.— The "Michael Saks fishing Ling and Tusk in the deep part of 
THE North Sea. 

Different physical conditions accompany these characteristic 
differences in the distribution of the fish ; for instance, the 
depths from o to 40 metres are the ones mainly influenced by 
summer temperatures ; on the shallow coast banks and on the 
Dogger Bank the temperature at the bottom rises to at least 
12° C. in the summer season. The sole may thus find here 
temperatures similar to those off the Atlantic coast of Europe, 
though in somewhat shallower water. Below 40 metres the 
summer temperature is not much higher than the temperature 
during winter, viz. between 6° and 7" C. 

The species inhabiting the deeper areas of the plateau 
extend out towards the deep basin of the Norwegian Sea until 



FISHES FROM THE SEA-BOTTOM 453 

the cold bottom water with a temperature below o'' C. is reached, 
where they are gradually replaced by the cold water fauna pre- 
viously described. 

The same laws which regulate the distribution of different 
species in the North Sea apply also in the main to other boreal 
waters where these species live. Scientific fishing experiments, 
and above all the mass of information gathered from the fishing 
industry, have in recent years vastly contributed to our know- 
ledge on these points. If on the basis of this knowledge we 
want to compare the actual conditions in different boreal waters, 
we must compare areas of corresponding depth. In this way 
we may possibly form an idea as to the part played by the 
extent of the sea-bottom, and by physical conditions, in regard 
to the distribution of our northern species. Some examples 
may illustrate this point. 

In the North Sea the shallow banks in depths less than 40 
metres cover large areas, while off the coast of Norway there 
are hardly any such banks, the coast sloping steeply into 
greater depths. Shallow banks occur off the south and west 
coast of Iceland, and far north and east in the Barents Sea, 
as well as round Cape Kanin. Of the fish inhabiting the 
shallow areas of the North Sea, only the plaice and the cod 
occur in great quantities on these northern banks of Iceland and 
Cape Kanin. Sole, brill, and other flat-fish might also find suit- 
able conditions of depth here, but the temperature is too low. 
Off the coast of Norway none of these fiat-fish, neither the 
plaice nor the sole, occur abundantly. Thus we plainly see 
the important parts played by depth as well as by temperature 
in respect of the occurrence of various species. 

While the haddock in the North Sea constitutes nearly half 
of the total weight of bottom-fish landed, the same species 
constitutes only 3 per cent off the coast of Norway. This is 
not because Norway is too far to the north, nor because the 
temperature of the water is too low, since at Iceland and in the 
Barents Sea, where conditions are similar, haddock amounts to 
20 per cent of the catch, but because off the coast of Norway 
there are no great areas of suitable depth and with the soft 
bottom preferred by the haddock. On the contrary we here 
meet with great areas of "cod-bottom" (sand, stones, shingle, 
or rocks overgrown with kelp), and therefore the cod makes up 
over 80 per cent of all the bottom-fish taken off northern 
Norway. 

Thus the extent of the area, and the captures made therein. 



454 



DEPTHS OF THE OCEAN 



of the North 
Atlantic 



Food-fishes are closely correlated. If we know the area where a vessel 
Sfferen't parts hshes, we Can predict the nature of the catch, and on the other 
hand we may judge of the extent and nature of the area from a 
knowledge of the fish caught in that area. This fact may be 
illustrated by the following table giving the quantities of 
important food-fish in millions of kilograms landed from 
different areas of the North Atlantic : — 





Cod. 


Haddock. 


Plaice. 


Halibut. 


Hake. 


White Sea, Barents Sea. 

Norway, north of Stat . 

Iceland .... 

Faroe Islands 

North Sea . 

Atlantic coast of Europe 

Total . 


3 

221 

io6 

i8 

73 

9 


2 

8 

37 

II 

174 

II 


lO 

i 

45 1 

3 2 


2 

I 


o 
o 
o 
o 

2 
20 


43° 


243 


88 


14 


22 



Boreal fishes 
on the slope 
of the 
Norwegian 
Sea. 



According to this table the North Sea proves to be the 
richest of all in plaice and haddock, just as it includes the 
greatest area of shallow sandbanks and fiats with muddy bottom. 
The sea of Norway is richest in cod, just as it represents the 
greatest stretch of rocky coast with temperatures between 6° 
and 8° C. 

Below lOO metres (50 fathoms) and down to 300 fathoms, 
we find on the northern slope of the North Sea plateau the 
following species to be the most important : saithe, ling, tusk, 
and halibut (see Fig. 314). During the summer we also find the 
cod in such depths, especially to the north of Lofoten, and on 
the slopes from the Faroe Islands to Lofoten. A little higher up 
on the bank these species are mingled with large hake, witch 
iyPleuronectes cyjtoglossus), and megrim iyZeugopterus megastonia). 
Lower down on the slope below 200 metres we find Norway 
haddock [Scbastes), blue ling, black halibut (Hippogiossus 
hippoglossoides), Macrurus fabricii, Argentina sihis, and Green- 
land sharks. This latter group of species has been found during 
the Norwegian fishery investigations along the " edge " of the 
continental platform all the way from Spitzbergen and Bear 
Island along the coasts of Norway, the North Sea plateau, the 
Faroe Islands, and along the Faroe-Iceland ridge. 

If we follow the 600 metres line in the chart (Fig. 309) from 
Spitsbergen and round the southern part of the Norwegian Sea 



FISHES FROM THE SEA-BOTTOM 455 

to Iceland, we shall at the same time trace the limit between 
the cold-water fauna of the deep basin and the boreal fauna of 
the slope of the coast plateau. Within this boreal region we 
may discern different areas of distribution. The ling, for 
instance, is caught off the coast of Norway in abundance as far 
north as Lofoten ; north of Lofoten, between the Faroe Islands 
and Iceland, and at Iceland, the ling is only poorly represented, 



A. i 


■■■■ / 


B^/ /^ 


m< 






rr 


1 




W^^l^k 


>. 






ii 




1 




Fig. 314.— The "Michael Sars" fishing Halibut on the Slope. 

while the cod there plays an important part in the "edge" 
fishery during the summer. Large halibut, from 50 to 1 50 kilos 
in weight, on the other hand, occur on the slope from west of 
Bear Island, round the North Sea plateau, the Faroe Islands, 
and on to Iceland. The Norway haddock has a similar distribu- 
tion to that of the large halibut. 

The fauna of the eastern and southern slopes of the 
Norwegian Sea thus proves to be very uniform for a distance of 



456 



DEPTHS OF THE OCEAN 



1 200 or 1500 miles, in accordance with the uniformity of the 
physical conditions. As we have previously seen, uniform 
physical conditions of a different character are met with along 
the slopes of the Atlantic from the Wyville Thomson Ridge down 
to south of the Canaries, the forms peculiar to this region being 
entirely different to those inhabiting the slopes of the Norwegian 
Sea. 

J. H. 




CHAPTER VIII 

INVERTEBRATE BOTTOM FAUNA OF THE NORWEGIAN SEA 
AND NORTH ATLANTIC 

The topography of the Norwegian Sea has been briefly noticed 
in Chapter IV. and the hydrography in Chapter V. 

The distribution of forms in the Norwegian Sea agrees 
with the hydrographical conditions, and we can distinguish two 
great regions, the boreal and the arctic, each of which has its 
own appropriate fauna. All those parts of the ocean-floor Boreal region 
covered by Gulf Stream water or by coast-water make up the jlJ^'^w j^n 
boreal region, while the arctic region is covered by water with Sea. 
polar characteristics. The temperature and salinity in boreal 
areas vary greatly in the different water-layers, and are much 
affected by the seasons. What chiefly distinguishes the boreal 
region from the arctic region is the higher temperature, which 
never falls below o C, and over large areas never sinks below 
6° C. The uppermost water-layer may form an exception, for the 
temperature may occasionally at the very surface and for a com- 
paratively short time fall below o' C. High summer temper- 
atures are characteristic of the upper water-layers, and exercise 
a considerable effect upon the fauna. The boreal region of the 
Norwegian Sea includes the North Sea with the Skagerrack and 
Kattegat, the Norwegian coast plateau as far as the North 
Cape, the coast plateau of the Faroe Islands, and the south and 
west coasts of Iceland. 

In the arctic region the temperature and salinity are much Arctic region 
more uniform than in the boreal region : the temperature is jfor^^gian 
usually below o° C, though in summer the actual surface may Sea. 
show higher temperatures under the influence of the sun, but 
the sun's heat does not penetrate so deeply as in the boreal 
region ; the salinity varies greatly at the surface, but at the 
depth of a few metres it is rarely less than -t^o per thousand. 
The arctic region comprises the coast plateaus of Greenland 

457 



458 DEPTHS OF THE OCEAN 

north of Denmark Strait, Spitsbergen, Franz -Josef Land, 
Novaya Zemlya, the coast between the White Sea and the 
Kara Sea, as well as the plateau of Jan Mayen and the 
deep central basin of the Norwegian Sea, 

In addition to these purely boreal and purely arctic areas 
there are transitional areas, designated boreo - arctic, which 
may be found wherever boreal and arctic water-masses meet 
Such areas occupy more or less extensive tracts, and exercise 
a distinct influence upon the distribution of the fauna. The 
temperature is not so high as in the boreal region, except 
perhaps at the surface, varying between o" C. and 3° or 4 C, 
though in the shallower parts a far higher temperature is found 
in summer, due to the heat of the sun, and as a result there 
are certain boreal littoral forms that occur also in the boreo- 
arctic region. 

The following are boreo-arctic areas : the south - western 
portion of the Barents Sea, from the East Finmark and Murman 
coasts to the White Sea, where a branch of the Gulf Stream, 
flowing eastwards, is gradually blended with arctic water ; the 
north and east coasts of Iceland, where branches of the Gulf 
Stream unite with the East Iceland Polar Stream^ ; the Iceland- 
Faroe ridge, where the East Iceland Polar Stream meets the 
Gulf Stream ; the Wyville Thomson Ridge, over which the Gulf 
Stream passes into the Norwegian Sea, where a mixture of 
the two waters undoubtedly takes place, but this boreo-arctic 
area is of small importance compared to the others ; and the 
continental slope on the eastern side of the Norwegian Sea, 
where there is a narrow area of mixture between Atlantic 
water and arctic water, resulting in temperatures slightly higher 
than o" C. A weak branch of the Gulf Stream flows along the 
west coast of Spitsbergen, giving rise to a very limited boreo- 
arctic belt, though, generally speaking, the west side of 
Spitsbergen must be considered purely arctic. The shallower 
parts of the coastal waters, as well as the inner portions of the 
fjords, from Lofoten to the North Cape, are boreo-arctic. 

North The topographical conditions in the North Atlantic are 

Atlantic, rnych like those of the Norwegian Sea, but the hydrographical 

conditions are dissimilar. On the eastern side the coast banks 

of both Europe and North-West Africa are bathed by much 

warmer water than those of corresponding parts of the Nor- 

' I ought to state, however, that owing to the influence of the East Iceland Polar Stream 
the north-eastern coast must perhaps be considered a purely arctic area. 



INVERTEBRATE BOTTOM FAUNA 459 

wegian Sea, and the littoral fauna naturally accords with its 
surroundings. This is true also of the archibenthal area (that 
is to say, the steep continental slopes) and the abyssal region. 
The temperature at 1000 metres may be as high as 6' or 8' C, 
and 2^ or 3° C. at still greater depths. Here, again, the fauna 
conforms to its surroundings. In addition to the vast central 
abyssal plain, the boreal region of the Atlantic includes the 
coast plateaus off Europe and North -West Africa, and the 
southern slopes of the ridges extending from the Shetlands to 
Greenland, that is to say, practically the whole of the eastern 
portion of the Atlantic. Arctic currents, on the contrary, 
prevail in the western portion of the Atlantic, and cause 
hydrographical, and therefore faunal, dissimilarities at different 
parts of the coast. In the coastal areas south of Cape Cod 
(about lat. 42" N.) we find Gulf Stream water and a character- 
istic warm-water fauna ; but north of Cape Cod we meet with 
an icy polar current descending from higher latitudes, so that the 
stretch of coast from Cape Cod to the north of Newfoundland 
must be looked upon as boreo-arctic. More genuinely arctic 
conditions prevail off the coasts of Labrador and Greenland. 

Boreal Region of the Norwegian Sea 

The boreal coastal area may be divided into three vertical The coastal 
zones, distinguished by different physical, topographical, and bo*rea°iVeg1on 
biological conditions. The uppermost is the littoral zone, which of the 
extends from the shore down to a depth of 'X)'^ or 40 metres — sea."^^^'^" 
that is to say, almost as far down as there are sea-weeds. The 
physical and topographical conditions characterising the littoral 
zone are : periodic changes in temperature and salinity (the 
temperature of the water being directly affected by that of the 
air), strong light, and a great variety in the materials at the 
bottom, such as loose stones, solid rock, sand with or without 
coarse or fine fragments of different kinds of shells, mud, 
and " mixed mud " — that is to say, sand, mud, and stones all 
mixed together. Here we find the whole vegetation collected, 
consisting of fucoids, green and red algae, Laniinaria, and 
Zostera, all of which, as a rule, form big interdependent com- 
munities that are very often arranged in belts. 

The lower limit of the sttblittoral zone on the west coast 
of the Scandinavian peninsula may be put at about 150 
metres. It differs from the preceding in being without 
vegetation, as well as in having more uniformity in the bottom- 



46o DEPTHS OF THE OCEAN 

deposits, higher and more constant salinities, and less pro- 
nounced differences in temperature. The bottom consists 
either of solid rock or sandy clay, or else of a rather coarse 
mixture of shells and sand, which is often found on the slopes 
of rocky portions in particular, together with large stones 
and pebbles. On the other hand, we do not get the fine 
mixture of shells and sand which is so characteristic of the 
littoral zone out among the skerries. The lower limit of this 
zone practically coincides with the lower limit of the coastal 
water, the salinity of which is lower than that of the Atlantic 
water lying beneath it.^ The temperature does not vary more 
than a few degrees in the different seasons, being lowest during 
the summer in the deeper portions, but it is, for part of the year 
at any rate, higher than that of the Atlantic water. 

Below the sublittoral zone we come to another zone, dis- 
tinguished by more uniform and more constant topographical 
and physical conditions, which we may call the continental 
deep-sea zone (ranging from 150 to 1000 metres or more). The 
bottom consists mainly of rock or a fine mud, which may 
perhaps be mixed with a little sand in the uppermost portions. 
In its upper parts, near the borders of the sublittoral zone, 
temperatures and salinities vary to a slight extent, but in the 
deeper parts both are constant, the salinity being 35 per 
thousand or a little over, and the temperature between 6° and 
7^ C. all the year round. 

We propose to discuss the coastal area of the boreal region 
under three headings: (i) the islands of the Norwegian west 
coast, where the littoral zone alone is represented ; (2) the 
fjords, where all the zones are represented ; and (3) other 
northern boreal areas. 

(i) Islands of the Norwegian West Coast i^' Skj(:(^rgaard''\ — 
We may divide the littoral zone among the islands of the Nor- 
wegian west coast into different areas. There is first a low-tide 
area, subject to changes of tide, and accordingly dry for certain 
portions of the twenty-four hours. Here we can distinguish 
three " facies" with different bottom-conditions, namely (i) rocky, 
either bare rock or very scantily overgrown ; (2) a fucoid belt ; 
and (3) sand. Each of these has, as a rule, several forms pecu- 
liar to it, though unquestionably a good many species of the 
littoral fauna are common to all. The dissimilarity in the com- 

' It must, however, be stated that the Hmits between the coastal water and Atlantic water 
vary with the seasons. 



INVERTEBRATE BOTTOM FAUNA 



461 



position of the fauna of the different " facies " depends to a great 
extent on the structure of the animal-forms, inasmuch as some 
forms must have a vegetable or hard solid foundation, while 
others require loose material. Littoral gasteropods, as a rule, 
require a solid foundation, and they are therefore generally absent 
from the sandy bottom ; but there are certain burrowing forms 
which can only live where the bottom is incoherent. Other 
forms, again, like the crab, are able to live on nearly every 
kind of bottom. 




Fig. 315. 
Balaiius ba/anoidcs, L. 

Below the low-tide area, with its fucus vegetation, we find 
on hard bottom a Laminaria belt beginning immediately below 
the fucoid belt, and always covered by water.^ We find also a 
Zostera belt, hard bottom, and sandy bottom. 

On the bare or scantily overgrown rocks near high-water Low-tide 
mark we find a white belt of barnacles {^Balamis balanoides, see ^'^'^^• 
Fig. 315); when examined at high tide we notice these little 
creatures extending and contracting their lash-like limbs to set 

^ Only at very low ebb-tides and in certain places do we find certain species of Lamiuaria 
also laid bare. 



462 DEPTHS OF THE OCEAN chap. 

the water in more rapid motion, and so bring nourishment to 

their mouths inside their shells, but when exposed at ebb-tide the 

shells are closed and 
the animals remain 
concealed within 
them. Immediately 
below the barnacle- 
belt we frequently 
find a belt consist- 
ing of dense masses 
of mussels {Mytilus 
edit lis, see Fig. 3 1 6), 
though the individ- 
uals in such locali- 
ties never attain 
any considerable 
size. On the rocks 
we find everywhere 

four species of gasteropods, which are very characteristic of this 

area, namely, the limpet {Patella vulgafa, 

see Fig. 317), two periwinkles {Littorina 




Fig. 316. 

Mytilus edulis, L. 






Fig. 317. 
Patella vulgata, L. a. From the side ; 



from beneath. 



Fig. 318. 
Littorina littorea, L. 



littorea, see Fig. 318, and L. rudis), and the purple snail 
(Purpura lapillus, see Fig. 319), this last being 
often plentiful in the barnacle -belt, where it 
feeds on these crustaceans. These forms live 
chiefly on the naked rock, but, except the limpets, 
also often on the algae in the tidal area. But 
when the belt of fucoids is exposed at ebb- 
tide, especially in sheltered places where a 
good current runs, we see that the algae, the 
species of Fucus in particular, have their special 
Fig. 319. fauna, consisting chiefly of attached forms. 

Purpura iapiiius,\.. -j^j^^ majority of them are hydroids, the com- 
monest species being Dynamena puniila (see Fig. 320), 




INVERTEBRATE BOTTOM FAUNA 



463 



Laomcdea flex2wsa, and Clava squamata (see Fig. 321). There 
are several bryozoans ^ here too, and the fucoids are often densely 
thronged by small white spiral-shaped tube-worms [Spirorbis). 
Amongst the un- 
attached forms as- 
sociated with the 
algae I may mention : 
Littorina obtusata, 
which keeps mostly 
to little bays shel- 
tered from the action 
of the waves ; L. 
littorea, which is very 
common ; and our 
smallest shelled snail 
Skene a planorbis, 
which is met with in 
favoured spots under 
stones and upon algae 
of different species. 

More local in 
their occurrence, 
though generally numerous 
of Actiniae 




Fig. 320. 
Dynamena pmnila, L. (After Hincks. 



where found, are certain species 
the red Actinia equina (see Fig. 322), the yellow 
or brownish MetiHdiuvi dianthus (see Fig. 
323), and Urticina crassicornis being the 
commonest forms. The first of these is 
generally found in quiet bays where the 
shore is covered with large stones and 
pebbles, the individuals being sometimes 
attached to these and sometimes to cracks 
in the rock. As this species produces its 
young fully developed, and the newly-born 
actiniae are able to attach themselves easily, 
it is frequently met with in fairly large 
colonies. 

Another remarkable mode of propaga- 
tion, namely schizogony, is to be seen in Metridium diantJms 
in its younger stages. From the foot-disc of the animal small 
pieces unwind and form new organs, such as new tentacles, new 
mouth, etc. In this way colonies are formed, which may be 
widely distributed over the rock or the roots of the laminaria. 

^ Chiefly Alcyonidiuin hirsiitum, Fliistrella hispida, Bowerbankia i?/ibricata. 




Fig. 321. 

Clava squamata, Miill. 
(After Hincks.) 



464 



DEPTHS OF THE OCEAN 



The fully developed individuals of Metriduuu are usually found 
in places where there is a strong current. 

Off the coasts of Scandinavia the sandy bottom of the 
low-tide area is not so extensive as along other coasts of the 
North Sea, but it is interesting to note that the fauna inhabiting 
this region is much the same everywhere, and that burrowing 
forms predominate. There is first the sandgaper i^lMya 




Fig. 322. 
Actinia equina, L. 



arenaiHa), and then the cockle [Cardmm ediile, see Fig. 324), 
and also different species of Tapes, though these are not so 
universally distributed. The lugworm [Arenicola piscatorum, 
see Fig. 325) is another burrowing form, and its presence can 
easily be detected by little heaps of string-like excrements. 

In addition to these forms, which are adapted for life in 
the low-tide area at those parts of the coast where the ebb-tide 
recedes a long way, we also get the common shore crab 
{Carcimis moeiias), often to be found under fucus that has been 
left exposed. This is the case also with the common starfish 
[Asterias itibens), and occasionally, too, with the common 



INVERTEBRATE BOTTOM FAUNA 



465 



sea-urchin {Echinus esaUentus), the hermit crab' {Pagiirus 
bernkardiis), and a few other forms. Their occurrence is, 
however, really due to their being surprised by the receding 
of the tide, and they are not, strictly speaking, adapted to a 
life in this area. 

There are some forms characteristic of the low-tide area 




Fig. 323. 

Metridiitm diaiifkus. VA\. (After Andres. ) '~ 

which cannot be regarded as belonging solely to any particular 
facies. Perhaps the commonest are the sandhoppers (Gam- 
marids), which have a wonderful knack of hiding themselves 
quickly in holes and cracks, when the stone or other object, 
under which hundreds may be sheltering, is removed. One 
of the most abundant is Orckestia littorea, which, although a 
true marine form, is able to exist for a long time out of the 
water. I have found quantities of them during summer living 

2 H 



466 



DEPTHS OF THE OCEAN 



perfectly happily with true land-animals, such 
as centipedes and woodlice, in places that 
were very rarely covered by the sea, so that 
they had to depend upon the slight moisture 
retained beneath the stones ; individuals 
found living under these conditions on being 




Fig. 324. 
Cardiiim cdule, L. 



transferred directly to sea-water showed not 
the least sign of being inconvenienced by 
the sudden change. Another equally com- 
mon sandhopper ( Gaminartis locusta, see Fig. 




Fig. 326. 
Gammarus locusta, L. (After Bate and \\'estvvood. ) 

326) is also a littoral form, but it never quits 
the sea for any length of time. 



Unexposed 
area. 



Laminaria 
belt. 



In the unexposed portion of the littoral 
zone of the skerries we may distinguish four 
"facies": (i) Laminaria belt, (2) Zostera 
belt, {3) hard bottom, and (4) sand. 

The Laminaria belt begins immediately 
below the fucoids, and alone the west coast of 



Fig. 325. 
Arenicola piscatorum, L. 



INVERTEBRATE BOTTOM FAUNA 



467 



Norway there are three common species : Laniinaria hyperborea, 
L. digitata, and L. saccharina. The first of these occurs in 
great thickets in open bays or places where the play of the 
waves is felt, whereas the other two grow in more sheltered 
localities. The fauna varies accordingly. On the stalks of 



Lanimaria hyperborea we 
chiefly hydroids, bryozoans, 




^et numbers of attached forms, 
synascidians (see Fig. 327), and 
calcareous sponges. Halichondria 
panicea, one of the few siliceous 
sponges of the littoral zone, also 



Fig. 327. 

Synascidian : Polycycli/sficscus, 

Huitfeldt Kaas. 




Fig. 328. 
Obelia ge7iiculata, L. (After Hincks. ) 



frequently forms a thick covering over long pieces of the stalks. 
On the blades of the laminaria two forms are very common, 
namely the bryozoan Membranipora nievibranacea, which makes 
a white covering over large portions, and the little hydroid 
Obelia genicidata (see Fig. 328). An unattached form, the 
gasteropod belonging to the Patellid family [Nacel/a pelhicida), 
is very conspicu- 
ous, owing to its 
handsome blue- 
striped shell, and 
lives exclusively 
on the laminaria. 

Besides the fig. 329. 

I 1 c Caprella linearis, L. 

attached lorms, 

that often completely cover the lower parts of the laminaria, 
there are unattached species in great abundance existing upon 
or among them. The best way of observing them is to shake 
a thickly overgrown laminaria stalk, placed in a large glass of 
sea-water, when we may perceive swarms of amphipods, worms,^ 
tiny mussels and snails, little starfishes, and other creatures. 
The most noticeable of the amphipods are the elongated and 
strangely built caprellids, of which Caprella linearis (see Fig. 329) 

^ A species of Nicolca is common. 




468 DEPTHS OF THE OCEAN 

is the commonest. With their prehensile claws they climb 
about among the hydroids and red algae, hooking themselves 
on by their hind limbs, swaying to and fro for a time, and then 
catching hold of another branch with their front claws and 
climbing farther. In fairly sheltered localities we often get 
among the branches of the hydroids and algse little tube- 
shaped dwellings constructed out of various materials and 
inhabited by different species of amphipods,^ and here, too, 
we meet with some kinds of pycnogonids.^ Beautifully coloured 
,.y, nudibranchs (usu- 

^"^^; ''^^'^"-' " ~^ ally species of 

V^T y^olis, and especi- 

^■^^^^^^^ ^ . s ^jj^ yEolis inifo- 

* branc hialis, see 

Fig. 330- Fig. 330) crawl 

^olis rufobranclualis, Johnst. (After Alder and Hancock.) slowlv aboUt and 

feed like the pycnogonids upon the hydroids ; certain kinds of 
nudibranchs (especially some species of Doris, see Fig. 331, 
Polycera, etc.) occur chiefly in the winter. Animal groups 
that are very numerously represented in the algse -vegeta- 
tion of the littoral zone, though they must be very carefully 
searched for, are rhabdocoelous turbellaria and several species 
of Halacarids. There are, in addition, quantities of the young 
of Myfilus, asterids, 
etc. Among the 

" roots " of the lamin- 



aria we frequently get 
Nereis, Ophiopholis 
aculeata, and borer 
mussels [Saxicava). 

I n contradistinction ^^^.^ tuberculata, Cm^'V^ftJ; Alder and Hancock. ) 

to Laniinaria hyper- 

borea, which prefers the most exposed situations, where there 
are waves or strong currents, as well as hard bottom to which 
to attach itself, we find the eelgrass [Zostera marina) in 
enclosed sheltered localities (pools, estuaries, etc.) and upon 
soft muddy bottom. The fauna of the eelgrass is not nearly 
so rich in species as that of the laminaria, still there are several 
characteristic forms living mainly, and perhaps exclusively, in 
its vicinity. There is, for instance, a small whitish semi-trans- 

^ Especially species of the family Podoceridre, characterised by the extremely hairy antennte. 
- N'yniplioi brevirostre, Phoxichilhihtin fentoi-aii(ni, Phoxichilns spinosus, etc. 




INVERTEBRATE BOTTOM FAUNA 469 

parent snail [Rissoa), which may often be found in enormous 
quantities ; often also there are great numbers of another snail 
(Akei^a biillatd), and in the mud, even where there is no zostera 
vegetation, we frequently find species of Philine. A species 
of attached ascidian {Ciona intestmalis, see Fig. 332), which, 
however, is also found on laminaria, especially when growing 
in sheltered or rather deep places, is one of the most prominent 
animal forms of the eelgrass. Hydroids and synascidians are 
also occasionally met with. Swim- 
ming amongst the blades of the -^ ;, (?»',** 
eelgrass we further find various crus- 
taceans, of which two species of 
prawns [Pandalics animlicornis and 
Palcumoii) are the most noticeable. 
They are not limited to the eelgrass, 
however, but occur also in places 
where zostera does not grow. The 
list of forms to be found here is 
far from exhausted, for I have men- 
tioned only some of the chief ones. 
The zostera belt is not of so much 
importance along the Atlantic and 
North Sea coasts of Scandinavia, as 
it covers a very limited area in com- 
parison with the other subdivisions of 
the littoral zone, and it is negligible 
indeed, when compared with the im- 
mense tracts in the Kattegat which 
are literally overgrown with this plant. ^--^^i 

Such in general is a picture of the 
fauna to be found in the algat and ^. ^.^^'•^^";. , 

111 Ciona mtestinalis, L,. 

zostera vegetation of the strand-belt; (After Aider and Hancock. ) 
though it must be understood that 

when speaking of this fauna as associated with the plants I 
do not imply that these animal -forms can exist only upon 
them. This is only exceptionally the case. The relation- 
ship between them depends on the fact that, as a rule, the 
algse afford an excellent foundation for the attached forms, 
which find favourable conditions of nourishment wherever 
the alg^e flourish. For we must remember that these attached 
forms are obliged to obtain their nourishment from such 
organisms as chance to come within their reach, and since 
currents and waves furnish the necessary assistance, we 



470 



DEPTHS OF THE OCEAN 



generally find the most abundant animal life among the algse 
in localities where wave-action is most effective. Most of the 
non-attached forms are in no way directly dependent upon the 
algae-vegetation. 

It will be evident that attachment to fucus and laminaria 
is not biologically essential, if we bear in mind that the same 
animal forms which attach themselves to these plants occur 
also on rocks and stones. The vegetation merely increases 
the area available for the attached forms. Nor is any particular 
plant essential for any particular species of animal. No doubt 

on the Norwegian west coast 
Laomedea flexuosa and Clava 
sqiianiata nearly always attach 
themselves to Ascophylhmi, while 
Obelia o-eniculata and some others 
prefer laminaria, but this is chiefly 
owing to the tides. On the 
Skagerrack coasts, where tides 
are inconsiderable and irregular, 
we find even in the fucus belt 
forms like Coryne (see Fig. '^ZZ)> 
Tubularia, and Obelia geniculata, 
though on the west coast of Nor- 
way they grow only among the 
laminaria and at a lower depth. 
These forms cannot stand exposure 
for any length of time, and they are 
therefore not to be found in places 
where the ebb regularly goes back 
a long way. The forms met with 
in the tidal area cannot, however, be in any way dependent 
upon the ebb-tide for their existence, seeing that they occur 
numerously also on the coasts of the Skagerrack, where tides 
are scarcely felt. Instances of this are furnished by Clava, 
Campanularia Jlexuosa, and Dynamena pumila, but the fact that 
these forms are able to withstand exposure for considerable 
periods of time makes it possible for them to occupy a far 
more extensive area than would otherwise be the case. 

So far as the structure of their organs is concerned, the 
unattached forms in the algae-fauna are particularly well 
equipped for gripping, climbing, or creeping about among the 
hydroids and the red bushy alg^e that usually grow in quantities 
upon the laminaria. The crustaceans (caprellids and amphipods) 




Fif5. 33. 

Coryiic pusilla, Gaertn. 



(After Hincks.) 



INVERTEBRATE BOTTOM FAUNA 471 

have extremely bent legs and claws, the naked snails have their 
flexible foot-discs and the planarians their rhabdites, so that 
these creatures furnish excellent examples of adaptability to 
external conditions. A bodily structure of this kind is necessary 
for these forms, or when exposed to the action of the waves 
or currents they would run the risk of being torn from the 
objects to which they cling. 

The marine algse are known to be rather particular about 
the localities they select. Some species grow high up on the 




Fig. 334. 
Asterias glacialis, L. (After Ludwig. ) , 

rocks so as to be covered only at high tide, while others choose 
the lowest limit of ebb-tide ; some prefer sunlight, while others 
thrive only away from it ; some grow best amidst the waves and 
breakers, while others need sheltered places. This is, to some 
extent, true also of the animal forms of the upper littoral zone, 
many of which prefer the open parts of the coast, while others 
live in sheltered localities, and others again where the currents 
are strong. The three bryozoans Alcyonidiuni, Flustrella, and 
Bowerbankia, for instance, seem to prefer shelter and a good 
current, whereas Membranipora pilosa flourishes best in the 
laminaria belt, in exposed places where Laminaria hyperborea 



472 



DEPTHS OF THE OCEAN 



grows. Litto7'ina littorea and L. obtusata again are found in 
greatest abundance wherever there is shelter, while Nacella 
pelliicida generally lives on the blades of Laminaria hyperborea. 
In the sheltered haunts of Lmnmaria saccharina and L. 
digitata, particularly on the first named, we find the brittle-star 
OpJiiothrix fragilis, while the localities with L. hyperborea have 
evidently no attractions for it ; the blades of L. saccharina, too, 
are much patronised by the bryozoan Aetea. Asterias glacialis 
(see Fig. 334) also prefers sheltered localities. Why there 
should be these apparently capricious affections is as yet un- 
known, but it may be that in undisturbed waters there are 
higher temperatures during the summer, and that consequently 
various influences are brought to bear upon the organisms at 
one stage or another of their 
lives. 

The most typical localities 
of this kind are met with as 
portion of the a rul.e in sounds amongst the 
skerries, where there is a more 
or less strong current, which 
carries away the finer particles 
of mud that would otherwise 
settle, and leaves only large 
fragments of shells and similar 
debris. On the hard bottom 
there are usually numbers of 
both attached and unattached 
forms, chiefly consisting of bryo- 
zoans, hydroids, especially the 

genus Ttibitlaria, and ascidians. The coral Alcyoniiim digitatiim 
too is often plentiful,^ generally attached to large empty mussel 
shells or stones. The empty mussel shells are also patronised 
by big colonies of the serpulid Pomatoceros triqueter, which 
however is just as much at home on the rocks up to the very 
shore. There are, besides, Anoinia ephippittm, Chiton cinereus, 
Tectura virginea, Buccimun nndatiwi, and several others, some 
sedentary, and others, like the chitons and Tectiira, able to 
move about from one place to another ; as well as Mytilus 
77todiolus, though this mussel is far more plentiful inside the 
fjords, and Gonactinia prolifera. 




Fig. 335. 
OphiopJiolis aculeaia, L. 



^ This form may even be found up to hiw-tide mark, where there are strong currents, as for 
instance in narrow shallow sounds. 



INVERTEBRATE BOTTOM FAUNA 



47; 



Several echinoderms occur numerously wherever there are 
currents. There are quantities of the brittle-stars : Op/iiop/iolis 
aciileata (see Fig. 335), Ophiocoma nigra, and Ophiura albida. 
Two species of sea-urchins that live on the hard bottom in the 
littoral zone are very common among the skerries on the west 
coast of Norway, namely Echiims esculentiis and Strongylocen- 
trotiis drdbackiensis. On the other hand, Echinus acittiis and 
Parcchinus miliaris^ have a different local distribution, to which 
I shall allude later. All four species 

may be found up to low tide mark. _ t 1%^ 

This is true also of the big dark- 
brown holothurian Cuciimaj^ia fron- 
dosa (see Fig. 336), large numbers of 
which live on the hard bottom among 
the skerries, and in the outer parts 
of the fjords, especially where there is 
a strong current. They fasten them- 
selves to the rock by means of their 
suckers, and often have their tentacles 
stretched out in order to capture pe- 
lagic organisms, which are afterwards 
licked off, the animal sticking one 
tentacle at a time into its mouth. 

Together with the above forms 
we find a mussel, Lima hians, which 
is very characteristic of these localities. 
It is of interest biologically, because 
it lives within a nest constructed with 
the assistance of its byssus out of 
bits of empty mollusc shells, frag- 
ments of echinids or serpulids, and 
similar materials ; in fact, no loose 
substances appear to come amiss. 

Two starfishes are always present, namely Asterias rubens 
and A. miilleri. There are other species as well, of course, 
such as worms and serpulids, but they cannot be called particu- 
larly characteristic. 

Here, too, the lobster {Homartts vidgaris) is equally at home, 
and may be met with under rocks and stones, occasionally 
venturing on to sandy bottom. It is distributed throughout the 
whole littoral zone from a depth of about one metre downwards, 
a certain proportion of individuals migrating vertically, descend- 

^ In a few localities all these species may be found together. 




Fig. 336. 
Cucumaria frondosa. Gun. 



474 



DEPTHS OF THE OCEAN 



ing- to greater depths in winter. The spawning females usually 
repair to shallow places in the summer, the higher temperatures 
being better suited to the development of the eggs and larvae. 

Several of the strange mask crabs {Hyas, see Fig. 2)2)7 > 
Stenorhyncktis, Inachus) also inhabit the littoral zone, chiefly 
where the bottom is overgrown with algae, bryozoans, and 
hydroids, being rarely met with upon sandy bottom. They 
are supplied with small hooks on the carapace and extremities, 
by which they attach to themselves the algae or animal-colonies 
around them. These crabs are extremely sluggish and inactive, 
and they derive an advantage from this remarkable habit, since 
they are difficult 
todistinguish from 
their surround- 
ings, and conse- 
quently they can 
conceal them- 
selves from their 
prey as well as 
from their ene- V 



The bottom 
here chiefly con- 
sists of what has 
been called shell- 
sand, made up Hyas arar,eus, L. 

entirely of shell- 
fragments of molluscs, echinoderms, balanids and other creatures ; 
it is usual to make a distinction between the coarse and the fine 
shell-sand. This detritus is practically only met with in the 
littoral zone of the skerries, and is undoubtedly due to the action 
of the waves and breakers. Burrowing forms, for the most part 
mussels, spatangids, clypeastrids, and worms, predominate. 
The lancelet {Ampkioxtis) also makes this its principal home. 
The loose formation is burrowed into quite easily, and a 
lancelet can work its way down in the course of a few seconds.^ 
We must also include the sand-eels i^Am.modytes) amongst the 
vertebrate forms that burrow in this sandy bottom, though they 
are somewhat local in their occurrence. 




Fig. 337. 



' This form burrows in a curving direction beneath the surface of the sand, finally pro- 
truding its head very slightly a short distance from where it went in, and remaining stationary 
in this position. 



INVERTEBRATE BOTTOM FAUNA 475 

Several families of burrowing mussels inhabit the shell-sand, 
the most important being Veneridse, Tellinidse, Astartidae, 
Cardiidse, and Solenidee. The most characteristic species 
are Venus casina, V. fasciata, Timoclea ovata, the species of 
Tellina and Psainmobia, Nicaitia banksi, Solen ensis and 
Cardiiivi fasciatuin. The common cockle, Cardhmi edule, on 
the other hand, never occurs here. Solen ensis is generally so 
deeply embedded that an ordinary dredge brings up merely 
fragments instead of the whole animal. The small species of 
Lunatia belonging to the gasteropod family Naticidse, and par- 
ticularly Lunatia intermedia, also burrow some distance down, as 
they feed on little mussels, boring through their thin shells to get 
at the animals within. Antalis entalis is often common here. 

Spatangids are represented by Echinocardium fiavescens (see 
Fig. 338), the commonest of 
all, Spatangits purpureus, and 
Echinocyainus pusillus, the last 
named being the only clypeastrid 
in northern seas. Except perhaps 
Spatangus piupuretis, they are 
not confined to the shell-sand of 
the skerries, but may be found 
also in the clay of the sublittoral 
zone. All of them burrow deeply. 
Another deep-burrowing form is fig. 338. 

// / / / • 1 • U ■ 1- Echinocardiiini fiavescens, O. F. Miill. 

Asti'opeden irregularis, which ■' 

also lives in the clay bottom of both the skerries and fjords. 
This creature has conical legs (without suckers) particularly 
well adapted for digging, though they compel it to procure its 
food in a different way from Asterias riibens, which preys on 
large mussels by placing its foot-suckers on their shells and 
pulling the valves apart till the muscles relax and the shell is 
opened, whereas Astropecten swallows whole little worms, 
mussels, the young of Echinocardium, and other small animals. 

The worms are chiefly those belonging to the genera 
Glycera and Nepktkys, and the family Ophelidse {Ophelia lima- 
cina and Travisia forbesi). They live down in the sand, where 
they make long passages that are kept open by having the 
walls lined with a film of slime. 

All these animals are variously equipped for living buried 
in the sand, which naturally forms a splendid protection against 
their enemies. The burrowing mussels are provided with two 
more or less elongated movable siphons, the openings of which 




476 



DEPTHS OF THE OCEAN 



are always raised above the level of the sea-floor, the one being 
for supplying food and water, and the other for voiding excre- 
ments. The Spatangids get their nourishment down in the 
sand by means of their remarkably shaped mouth-feet, and 
through the rapid vibrations of the spines, some of which are 
specially adapted for the purpose, they keep the water circulat- 
ing in the holes where they lie, and so obtain oxygen for breath- 
ing. Astropecten has a row of small spines along its arms, which 
vibrate in similar fashion, and cause a circulation of water round 
its body. The tubes of the worms are almost invariably directly 
connected by an opening with the level of the sea-floor. 

Among the higher crustaceans inhabiting the sandy bottom 

we get one or two 
species of swimming 
crabs {^Portumts, see 
Fig- .339)- They har- 
monise in colour with 
the variations in the 
colour of the bottom, 
and are thus enabled 
to escape notice when 
motionless. Their 

name is derived from 
the terminal joint of 
the fifth pair of swim- 
merets, which is ex- 
panded and paddle- 
shaped, so that they are able to swim upwards. During the 
cruises of the " Michael Sars " in the North Sea one of these 
swimming crabs {Porttnuis depiLrator^ was found hanging in 
the drift-net, and numbers of young crabs of the same species 
were captured in the plankton net. These forms must, 
nevertheless, be regarded as genuine bottom animals ; I have 
observed that they can even burrow down into the sand for 
a short time, but never remain there long. 

One of the most characteristic forms of the littoral zone is 
the common edible crab. Cancer pagiirus, which is not so 
particular as the lobster regarding the nature of the bottom, 
being as much at home on sand as on rocks. Cancer pagiiriLS 
goes farther up the fjords than the lobster does, but they both 
are undoubtedly littoral animals, occasionally found close up to 
low-tide mark, and occurring exceptionally below the lower 
limit of the littoral zone. 




Fig. 339. 
Portiaius depurator, L. 



After Bell. ) 



INVERTEBRATE BOTTOM FAUNA 477 

(2) The Fjords. — We have seen that the fauna of the Littoral zone. 
Httoral zone among the skerries, especially in the tidal area and 
laminaria belt, is abundant both in species and individuals. 
There is a diminution, however, as we penetrate farther into 
the fjords. In the tidal area of the inner fjords, and at greater 
depths also, we miss the limpet and the purple snail, while the 
hydroids to be found on the fucus in the skerries become less 
and less abundant, until even Dyna77iena piunila disappears/ 
This change in the fauna is mainly due to the decrease in 
salinity, since the surface of the inner fjords, for a great part of 
the year at any rate, is occupied by a layer of less saline water 
in which these forms cannot thrive. Far up the fjords, however, 
in the tidal area, we get the barnacle, the mussel Mytiliis, and the 
black periwinkle, which seem to be less affected by a difference 
in salinity, though even they require a certain percentage of salt, 
since they disappear, for instance, from the tidal area in the more 
enclosed parts of the fjords, where, owing to the great accession 
of fresh water, the salinity is particularly low. The mussel and 
black periwinkle, it is true, may sometimes occur even here 
also, but only in fairly deep water. We also find the horse 
mussel in the fjords. The great thickets of Laniinaria hyper- 
borea, which are so characteristic of the skerries, are absent 
from the inner fjords, and so are most of the forms associated 
with them. In their place, however, we get Laminaria digitata 
and L. sacckarina, but in comparatively small quantities. 

The difference between the inner fjords and the skerries is 
not so marked when we descend to greater depths, since a 
good many forms are equally at home in both. Some of the 
littoral fauna, like the lancelet, appear to avoid the fjords 
altogether.^ Two forms, which rarely ascend far up the fjords 
of West Norway, are the lobster and the common edible crab ; 
but the common shore crab {Carcimts moenas) penetrates to 
their inmost recesses. The big black sea-slug i^Cucumaria 
frondosa) is another form which abounds among the skerries 
and in the outer parts of the fjords, but very exceptionally 
penetrates far in. No doubt their absence is due to the feeble 
currents, or the greater or less accessions of fresh water 
prevailing in the fjords — local conditions that are bound to 
affect the distribution of the fauna. 

The distribution of the two sea-urchins Echinus escnlcnttts 

1 It is interesting to note that Dynamena piimila is also found in the estuary of the Elbe as 
far up as Cuxhaven. 

^ The reason for this may perhaps be that the lancelet requires pure sand or shell-sand to 
live in, while the bottom of the fjords generally consists of mud. 



478 DEPTHS OF THE OCEAN 

and Echimts acutus (forma flemingi) is curious. The former is 
very common out among the skerries, while E. aczUus confines 
itself to a few localities, but on ascending the fjords E. escidentiLs 
becomes scarcer, and descends to greater depths, whereas 
E. acutus occurs in the greatest abundance. A similar distribu- 
tion characterises the sea-urchins Pai^echinus miliaris and 
Strongylocentrotus drobacJiiensis, which much resemble one 
another in outward appearance, and are both exceedingly 
plentiful in their different localities. Strongylocentrotus lives in 
the more open estuaries and bays of the skerries, whereas 
Parechinus miliaris keeps to sheltered waters, and especially to 
pools. For instance, in a pool south of Bergen (the Inderoe 
Poll) I found Pai'echimis miliaris literally in thousands, but there 
was not a single specimen of Strongylocentrotus ; in the neigh- 
bourhood of Bergen again I collected from another pool of a 
rather less typical character, sixty-three specimens oi Pai^echinus, 
and only three specimens of Strongylocentrottis. This difference 
has not been explained, though most probably the cause is to be 
found in the difference in temperature. Pools contain water 
of a much higher temperature than the sea outside, and most 
likely Pai^eckinus miliaris requires for its reproduction warmer 
water than Stro7igylocentrotus. It is interesting to note that, 
according to Petersen, there is the same diversity between these 
two forms in the Kattegat. 

The foregoing is not meant to be even an approximately 
complete account of the forms inhabiting the skerries and the 
fjords, my sole object having been to show that the dissimilarity 
in physical conditions (temperature, salinity, etc.) and in the 
nature of the bottom, between the skerries and the inner parts 
of the fjords, determines the difference in their biological 
conditions. 

Those areas of the littoral zone which have been called 
Pools, pools, or "polls" (see p. 225), are salt water basins connected 
with the sea outside by a shallow channel. The pools vary in 
depth, the deepest not exceeding 30 metres. One feature 
which they all have in common is that their channels to the sea 
are far shallower than their basins. The surface is always 
covered by a layer of more or less fresh water derived from the 
land, having a lower temperature than the salt-water layer 
underneath. About i^ or 2 metres below the surface the 
temperature in some summers may rise to 30° C. or even more, 
while that of the surface-layer does not rise above 18° or 20° C, 



INVERTEBRATE BOTTOM FAUNA 479 

though the conditions vary in different years. Below 2 metres 
the summer temperature decreases as we approach the bottom, 
but late in autumn and in winter the temperature is highest at 
the bottom. 

In the intermediate warm salt water layers we get a fauna 
abounding in individuals that form a distinctive feature of the 
pools. There is, first of all, the oyster, Ostrea edtdis, which 
finds its principal home here, and there are also quantities of 
Pecten operailaris attached to the rocks all round. The 
ascidian fauna is represented by several species, which are all 
exceedingly plentiful, the commonest being Ascidia vientttla, 
Ascidiella aspersa, Ciona intestinalis, and Clavellina lepadiformis} 
The most abundant of the bryozoans is Aetea, while a species 
of Botigainvillia appears to be the commonest hydroid. The 
principal sea - anemones are Metridium diantJms, Urticina 
crassicornis, and a species of Sagartia. Parechinus miliaris is 
the only echinoid, but it occurs in great numbers. Ostrea, 
Pecten, and Pai'ecJiinus indicate the decidedly southern 
character of the fauna, and it may not be out of place to 
mention that among the plankton forms we get a copepod 
{Paracartia grani) belonging to a genus not met with again till 
we reach the west coast of Africa. 

In addition to the forms having a southern distribution and 
of southern origin, however, we find eurythermal and euryhaline 
forms. Asterias rubens, Carcinus i?icenas, and Mytilits edzilis 
are nearly always present, the last named in particular being in 
great abundance, frequently attached to the lines stretched 
across the oyster-pools for carrying the bundles of twigs or the 
baskets to which the oyster spat attaches itself. Mingled with 
this assemblage of mussels, ascidians, etc., we get enormous 
quantities of smaller animal forms, the crustacean family Tanaidae 
being invariably represented. 

Among the forms described as characteristic of the littoral vertical 
zone, there are very few that do not occur in all its depths, that fije^iuorar °^ 
is to say, only a few forms are restricted to the actual strand- fauna. 
belt. These few, however, include most of the forms that 
characterise the tidal area." No doubt even these may 
occasionally be met with at a depth of a few fathoms, but 

1 In enclosed places, though not actually in pools, Corclla paralldogya»ima is also common. 

- For instance, Patella vulgata, Piu-pura lapillus, Littorlna littorea, L. rudis, and L. obtiisata ; 
besides Balanus balanoides, Mytilus edulis, Oixhestia littorea, Campaiiiilaria flexiiosa, Clava 
squatjiafa. Actinia equina, Alcyoniditwi hirsutum ; and among the burrowing species Alya 
arenaria, Carditim edtile, and Arenicola piscatornm. 



48o DEPTHS OF THE OCEAN chap. 

the tidal area is their proper home. On the other hand, 
those forms which have been described as passing their 
hves in the vicinity of low-water mark are not limited to 
this situation, but may be met with throughout the whole 
littoral zone, sometimes on sand, sometimes on rock, and 
sometimes impartially on either hard or soft bottom. Further- 
more, on the coasts of Norway the majority of the forms which 
characterise the littoral zone either never, or only to an 
inconsiderable extent, pass below its lower limit, though there 
are some that go down to perhaps about lOO metres, and a very 
few that descend to greater depths. But forms which on the 
Norwegian west coast are exclusively littoral, may be met 
with in deeper water in other northern areas, as I shall show 
later on. 

It would hardly be possible in a short account like this to 
give even an approximately complete description of the fauna 
along the coasts in the sublittoral zone, seeing that this is the 
abode of most coastal species living below the littoral zone. As 
a rule, the soft bottom is of a different character from that in 
the deepest parts of the fjords. Instead of viscous gray clay or 
mud, a coarser clay, more sandy in character, covers the Hoor 
in the medium depths of the sublittoral zone, which in the case 
of the fjords is near the sides or on submarine banks. Where 
there are plateaus sloping gradually down from the sides we 
also get rocks and stones and bits of shells, and there is thus 
accommodation for forms that naturally live on hard bottom. 
We often get, for instance, quantities of brachiopods and 
bryozoans, as well as a certain number of hydroids, ascidians, 
etc. Generally speaking, the character of the bottom here is 
more favourable to animal life than in the deep water, for while 
the mud harbours chiefly burrowing mussels, for instance, the 
medium depths accommodate, in addition, a large number of 
creeping snails, 

A good many forms which occur in the continental deep- 
sea zone ascend to the sublittoral, and some even as high as 
the littoral ^ zone. Still for most of them we may put the upper 
limit of distribution at lOO to 200 metres. Probably, however, 
their vertical distribution is affected to some extent by the 
variations in the vertical distribution of the Atlantic water, 
which may be higher or lower according to the different seasons 

1 For instance, Paguriis ptibcscens, Ophiopholis aculeata, and Terebellides siromi. 



INVERTEBRATE BOTTOM FAUNA 481 

of the year.^ Other sublittoral species again are plentiful every- 
where throughout the whole sublittoral zone, but rarely descend 
below its lower limit, so that we find at a depth of 100 to 200 
metres a mixed fauna, consisting partly of forms that have here 
reached their upper or lower limit of vertical distribution, and 
partly of forms which find here the most favourable conditions 
of life. The sublittoral zone accordingly ranks first in number 
of species. 

The continental deep-sea zone for all practical purposes The 
coincides with the deeper parts of the fjords, whereas out among deep"efz^one 
the skerries, with their comparatively shallow water, we either 
do not find it at all or else meet with it merely in very limited 
areas. A feature of the fjords is their very great depth, usually 
increasing as we proceed inwards, and in their deepest parts, so 
far as the nature of the bottom and the physical character of 
the water are concerned, we get what are practically Atlantic 
conditions. 

In the fjords the greatest depth is met with along the 
middle and in the innermost portions, and may be put on an 
average at 400 to 800 metres." The sides of the fjords descend 
in some places practically perpendicularly into deep water, in 
other places forming more or less extensive submarine plateaus 
and terraces. At various depths, especially in the seaward 
portions, there are cross ridges, which frequently consist of hard 
bottom. The material covering the floor in deep water is 
almost invariably a soft, viscous, grayish clay or mud. It is 
the animal life existing upon and in this mud which I shall now 
describe. 

The mud-fauna of the deeper parts of the fjords resembles the 
sand-fauna in the littoral zone, inasmuch as it consists mainly of 
burrowing forms, or at any rate of forms which to some extent 
burrow into the mud to obtain their nourishment. When we 
sift the mud brought up by the trawl or dredge, we obtain a 
number of curious little bodies (round, star-shaped, rod-like, 
conical, etc.), composed of sand or particles of mud. These 
creatures are rhizopods (foraminifera). By putting out 
extremely fine thread-like prolongations of their protoplasm 
through one or more openings in their covering, they attract to 
themselves small organic particles in the mud which furnish 

^ Thus Helland-Hansen has fixed the summer limit along the coasts at 75 metres, and the 
winter limit at 150 metres. 

'■^ In some fjords, such as the Sogne and Hardanger fjords, the depth is in places 1000 metres 
or more. 

2 I 



482 DEPTHS OF THE OCEAN 

them with nourishment — an operation that under favourable 
circumstances can actually be observed/ Of larger forms, the 
numbers of which render them characteristic of these depths, two 
sea-slugs deserve mention : a red one {Stichopus treimilus, see 
Fig. 340), and a gray one i^Mesotlnuna intestmalis). They belong, 
however, to a division different from the sea-slugs found in the 
littoral zone, the distinction consisting inte7' alia in a different 
structure of the tentacles. 

Other characteristic forms are: the brittle star AvipJiiura norvegica, 
the sea-slugs Cuciiuiaria Jiispida and BatJiyplotes ticardi. Of higher 
crustaceans we have the genus Munida, with the two species M. rugosa 
and M. tenuimana, of which the latter in particular is to be met with in 
the deepest parts of the fjords, and the prawn PontopJiilus norvegicus. 
The mussels come next to the rhizopods in number of species, the forms 




Fig. 340. 
Stichopus tremulus, Gunn. Reduced. (After O. F. Mtiller. ) 

most frequently found being Malletia obtusa, Portlandia hidda, P. tenuis, 
and P.frigida, Abra longicallis and A. nitida, Kelhella miliaris, Axinus 
flexuosus and A. ferruginosus, Ntccula tiimidula, and the species of 
Necera. Scaphopods include three characteristic forms, namely Antalis 
striolata, Siplwnentalis tetragona, and Cadulus aubfusifonnis, which last 
becomes more abundant as the depth increases. Worms are represented 
by the families Maldanidae and Terebellidse, of which latter Terebellides 
stromi is very common, and there are also Luvibrinereis fragilis, Nephthys, 
Aricia, etc. 

The coelenterates are represented on the mud of the deeper parts of 
the fjords by the group of pennatuhds or sea-pens, a kind of unattached 
coral animal. The commonest forms are Kophobeknmoii stellifeTum (see 
Fig. 341) and Fiiniculina quadrangiilaris, though they are not so regularly 
or abundantly distributed as the two sea-slugs already referred to, which 
are found practically everywhere. Two species of sea -anemones 
{Actinostola callosa and Bolocera tiiedicB) - are also universally distributed, 

1 The following are a few forms which are characteristic owing to their numbers and size : 
the globular Saccammitia spluzrica, the rod-like ramifying Rhabdatnmma abyssoruin, and the star- 
shaped Astrorhiza m-enaria, the test of which consists of particles of sand, the rod-like non- 
ramifying Bathysiphon fdifo7-mis, etc. In addition there are other large forms of which I may 
mention the species of Cristellaria, the shells of which are calcareous and consist of several cells. 

- Both these forms are found in the deep parts of the fjords, but I am not certain whether 
they live on the mud or on the patches of harder bottom which occur here and there. 



INVERTEBRATE BOTTOM FAUNA 



483 




:%^i 



and so is the sponge TJienea inuricata (see Fig. 342), which adheres to 
the mud by means of long outgrowths, and the worm-like gephyrean 
Sipunculiis priapuloides. 

Thus the majority of the mud-fauna in the deep parts of 
the fjords, owing to the nature of the bottom, 
consists of unattached animal forms, most of 
the sponges, corals, hydroids,^ bryozoans, 
ascidians (including the unattached molgulids), 
and brachiopods being absent ; in other words, 
the nature of the bottom gives the fauna its 
character. Still even here it is possible for 
certain attached forms to occur normally, and 
very often abundantly. There are frequently 
great quantities of the little mussel [Area 
pectiuiciLloides), which fastens itself by its 
byssus-filaments sometimes to the larger for- 
aminifera, sometimes to slag from steamers, 
or any other hard substances which it happens 
to come across in the mud. There are also 
numbers of the white semi-transparent Peden 
abyssorimi, which occurs, according to Sars, 
also in the deepest parts of the Christiania 
fjord, where it attaches itself to rotten bits 
of sea- weed. 

I shall now turn to the faunal conditions 
in the fjords where there is hard rocky 
bottom, i.e. the more or less steep sides of 
the fjords and the submarine ridges or emin- 
ences. These latter are sometimes isolated 
raised portions of the floor surrounded on 
all sides by softer bottom, and sometimes 
spurs running out from the walls of the fjord. 
The slopes of the ridges and eminences are 
frequently covered with coarse sand and 
stones, as are also the sides of the fjords 
where not too steep. In many cases, how- 
ever, the walls go down so steeply that no 
loose deposits occur till we reach. a depth of 
several hundred metres. 

The fauna here is quite different from that on the muddy 
bottom, consisting mostly of attached forms of various groups, 

^ Only a little form {Perigoniimis abyssi) is common here, attached to mussel shells, 
■especially those of Nticula tuviidula. 



Fig. 341. 
Kophobelevinonstelliferum, 
O. F. Miill. (After 
Asbjornsen. ) 



484 



DEPTHS OF THE OCEAN 



especially sponges, coelenterates, bryozoans, brachiopods, and 
tube - worms, with a few unattached forms, of which the 
crustaceans are the most important. Most of the species of 
attached forms belong to the sponges, coelenterates, and 
bryozoans, though the brachiopods and tube - worms exceed 
the others in number of individuals. The sponges are nearly 




Fig. 342. 
Thejiea muricata. Bowerbank. 



all silicious, whereas in the littoral zone they are chiefly 
calcareous. The principal coelenterates are attached coral 
animals, especially gorgonians,^ alcyonarians, and hydroids. 
We commonly get, for instance, one or two species of alcyonaria 
of the genus Paraspongodes, the larger specimens of which 
resemble cauliflowers ; in the same way we find Alcyonium 

1 Paramuricea placomtis, Primnoa lepadifera. In the same localities we also find two sea- 
anemones {Phellia abyssicola and Bolocera ttiedia:), of which the latter also occurs on muddy 
bottom in the deep parts of the fjords (see p. 482). 



INVERTEBRATE BOTTOM FAUNA 485 

digitattun, belonging to the same group, upon hard bottom in the 
Httoral zone. We must also include among the alcyonaria the 
sea-tree, Paragorgia ai'borea (see Fig. 343), which is taller than 
a man and has many branches. Of true corals we may mention 
Lophohelia prolifcra and AinpJiihelia raviea, though the coral 
fauna is not regularly distributed over the hard bottom, but is 
more or less local ; still 
there are often numbers 
of individuals where 
hard bottom does occur. 
Several species of hy- 
droids, such as Lafoea 
ditmosa, Sertularella 
gayi, ' etc., are very 
common ; and of the 
bryozoans, Retepora 
beaniana, easily recog- 
nisable owing to its 
trellis-like structure, is 
both widely distributed 
and plentiful. So, too, 
are the brachiopods, 
Terebratulina capiit- 
serpentis and Wald- 
heiuiia a^anmin, and 
the two tube - worms, 
Placostegus tridentahis, 
the tube of which divides 
into three tooth - like 
processes, and Serpiila 
verinicularis (see Fig. 
344). Both these worms, 
it may be added, have 
calcareous tubes, in 
contradistinction to the „ ^ , J^^' ^^^: , . 

Branch of Paragorgia arborea, L. 

tube-worms of the mud 

which inhabit tubes of mud or sand. There is, besides, a species 
of barnacle ( Verruca strmni) on the stones, which is frequently 
nearly as abundant as Balamis balanoides in the tidal area. 

It would take too long to give a full description of the 
unattached fauna associated with the hard bottom. I will 
therefore merely point out that some free forms occur only 
upon the attached forms, and seem accordingly to be dependent 




486 DEPTHS OF THE OCEAN 

upon them. The most noticeable of these is medusa's head 
{Gorgonocepkalus linckii, see Fig, 345), a brittle-star with ex- 
tremely branching arms that lives upon the larger gorgonians 
and sea-trees. A crustacean, GalatJiodes tridentatus, appears 
also to be intimately connected with the corals, and large 
quantities are occasionally found upon them. As for the 
remaining higher forms of crustaceans the fauna consists chiefly 

of prawns, though they are 
, >• different from the ones in 

the littoral zone,^ but other 

groups are not entirely 

wanting.- 

The large mussel, Lima 
excavata, is extremely character- 
istic of the rocky bottom, attach- 
ing itself by means of its fine 
silky byssus-filaments. We may 
further mention a sea-slug {Psolus 
sqiiajiiatus, see Fig. 346), easily 
recognisable owing to its abruptly 
truncated disc with suctorial feet, 
by which it adheres to stones, 
shells, etc. ; a crinoid {^Antedon 
petasus) occurring locally, though 
often in abundance, especially 
where there are sponges ; several 
star -fishes, Pentagonaster granu- 
laris, Porania pulvillus^ Hippa- 
sterias phrygiana {plana), which 
last seems to prefer places where 
the hard bottom is covered with 
coarse sand ; a brittle - star 
{Ophiopliolis aculeata) ; molluscs, 
as, for instance, species of Pecten ; 
ascidians, particularly of the family 
Styelidae ; sea-spiders {NyuipJion strdmi\ etc. At considerable depths 
there is also the remarkable starfish Brisinga endecacnemos. Some of 
these are exclusively deep-sea forms, and rarely leave the deeper 
parts of this zone. Munida te7iuiniana, BatJijplotes tizardi, Brisinga 
endecacnemos, and Lima excavata do not occur in depths less than 300 
or 400 metres. 

(3) Other Northern Boreal Coastal Areas. — There are 
several areas where the littoral zone has been but little studied, 

^ Pandalus pj-opinquus, P. brevirostris, Hippolyte polan's, and H. securifrons. 

- Thus a hermit-crab {Pagurus ptibescetts), which occurs, too, in the littoral zone, is quite 
common, and so are Munida rugosa, which also inhabits soft bottom, and the stone-crab 
{Lithodes maja). 




Fig. 344- 
Serpula verinicttlaris, Mtil 



INVERTEBRATE BOTTOM FAUNA 487 

and the information received from Iceland and the Faroe 
Islands is not as yet sufficiently comprehensive to enable one 
to speak with confidence regarding the composition of the 
littoral fauna there. In Iceland, however, if we may judge 
from our knowledge of the hydroid fauna in the boreal coast 
areas, the conditions are very similar to those on the Scan- 
dinavian coasts, and the same is true also of the North Sea 
coasts of Britain. 

If we compare the North Sea coasts with the Skagerrack 
coasts of Scandinavia we find many points of resemblance, the 
littoral fauna for the 
most part living under 
similar natural con- 
ditions in both areas. 
The tides of the 
Skagerrack, however, 
are inconsiderable and 
irregular, and in conse- 
quence forms, which 
on the North Sea 
coasts belong to the 
low-tide area, can un- 
doubtedly live here in 
shallow water and on 
thesame kind of bottom, 
but they are not left 
regularly exposed by 
the ebb. A good 
instance of this may be 
seen in the case of the 
hydroids Clava squa- 
mata and Laomedea flexuosa, which are quite common on the 
fucoids in spite of the fact that the ebb-tide only on rare 
occasions leaves them exposed. On the other hand, certain 
species, which are not met with in the low-tide area of the 
North Sea, and consequently do not patronise the fucus there, 
attach themselves to these algae on the Skagerrack coasts. It 
is evident from this that it is not the actual foundation but 
the natural conditions and the ability to adapt themselves to 
these conditions which determine the distribution of the animals 
in the strand-belt. 

Although the littoral faunas of these two coastal areas bear 
a very strong resemblance to each other, there are yet 




Fig. 345. 
Gorgonoccplialiis linckii, M. and T. 



^'ar. Reduced. 



488 



DEPTHS OF THE OCEAN 



some differences between them. Thus several forms that 
abound on the west coast of Norway are absent from the 
Skagerrack coast, if we may judge from my observations at 
Risor in Norway compared with the researches of Theel at 
Kristineberg in Bohuslan.^ For instance, Cuctunaria froiidosa, 
a littoral echinoderm common on the North Sea coast, has 
not been met with in the Skagerrack, and Ophiocoma nigj^a is 
very rarely found in the latter area. Echiims acutiis occurs in 
enormous quantities on the North Sea coast, but is extremely 




Fig. 346. 
Psoitis squamatus, Koren. 



rare on the Skagerrack coast, while the mussel, Lima kians, 
has not been met with on the Bohuslan coast of Sweden, 
though in certain localities of the Norwegian west coast it is 
one of the most characteristic forms of the littoral fauna. On 
the other hand, the Skagerrack coast is the home of certain 
littoral forms which occur but rarely on the coast of the North 
Sea. Thus on the west coast of Norway Echmocardium 
cor datum is seldom found, and then only in a few special 
localities, whereas in Bohuslan it seems to be one of the 

^ Theel, " Om utvecklingen af Sveriges zoologiska hafsstation Kristineberg och om djurlifvet 
i angrjinsande haf och fjordar," Arkiv. f. Zoologie, Bd. iv., 1907. 



INVERTEBRATE BOTTOM FAUNA 489 

commonest forms. Ophhtra ciliaris, too, is far more plentiful 
in the Skagerrack, and the gasteropod, Nassa reticidata, occurs 
in quantities in the littoral zone of the Skagerrack, but is 
comparatively rare on the North Sea coast. 

I have noticed also a difference between the fauna which 
patronises Laminaria hyperborea and the fauna associated with 
the two other species oi Laminaria. It is only the first named 
with its stiff thick stalks which is densely crowded with attached 
forms, whereas the comparatively thin pliant stalks of the other 
two are either entirely neglected or only made use of to an 
inconsiderable extent, with the result that there are nearly 
always far more individuals in the L. hyperborea belt than in 
either of the other two laminaria communities. 

I have already stated that the natural conditions prevailing 
on the different coasts affect the character of the fauna much 
more in the littoral zone than at greater depths. Where, for 
instance, there is nothing in the way of foundation for attached 
forms, we must expect to find a fauna more suited to another 
kind of environment. Thus on many North Sea coasts, where 
the long shallow shores consist merely of sand, like the "vader" 
of Schleswig and Holland, upon which the waves do not break 
with any violence, there are immense stretches where practically 
the sole inhabitants are the lug-worm [Arenicola), a tunnelling 
amphipod [Corophium grossipes), and one or two other forms. 
In such sandy stretches the fauna differs entirely from that 
found along rocky coasts, and only occasionally do we get 
attached forms where piles, stone quays, or other suitable 
foundations happen to occur. The animal life differs again on 
the sandy Danish coasts, which are unprotected by a line of 
outer islands, and are therefore exposed to the full force of the 
breakers, where the constant disturbance produced by the waves 
upon the sandy bottom is distinctly unfavourable to plant and 
animal life ; consequently the upper littoral zone on such coasts 
rarely harbours many forms. On the other hand, at slightly 
greater depths, and in fjords or similar enclosed areas, we get 
the conditions requisite for the development of Zostera vege- 
tation with its special fauna. We may see how much the 
topography of the bottom affects the development of animal life 
by studying the conditions on the Kattegat coast of Denmark ; 
wherever reefs, overgrown by algae, occur amidst the eelgrass, 
we may be certain of finding a fauna consisting of chitons, snails, 
bryozoans, and hydroid polyps. 

The littoral fauna in the southern portion of the North Sea 



490 DEPTHS OF THE OCEAN chap. 

comprises quite a number of shallow-water forms that are 
otherwise foreign to northern regions — Mediterranean immi- 
grants which make occasional visits or have effected a 
permanent lodgment in comparatively limited tracts. Some of 
them I shall refer to later on, when dealing with the shallower 
portions of the North Sea. Their presence may be ascribed to 
hydrographical conditions, and in no way depends upon the 
topography of the bottom. To some extent the English 
Channel acts as a boundary between two littoral faunal areas, a 
fairly large number of Mediterranean forms living in the 
Channel but not venturing into the North Sea ; while on the 
other hand several northern forms do not enter the Channel, 
these last being especially forms of Arctic origin. Many or 
probably most of the species are common to both areas, since the 
majority of the boreal species of the North Sea were originally 
immigrants from southern waters. 

So far as the coasts of the boreal region are concerned the 
sublittoral zone does not vary much, though certain species from 
the continental deep-sea zone, which ascend to the sublittoral 
zone along the North Sea and Atlantic coasts of Scandinavia, are 
absent from large portions of the Skagerrack and Kattegat as well 
as from other coasts of the North Sea. They would seem to be 
forms whose distribution follows the Gulf Stream, and are there- 
fore found mainly along the eastern coasts of the North Sea 
and Atlantic. They include the holothurian Psohis sq2ianiatus, 
the asterid Pentagonaster granularis, the gephyrean Bonelha 
viridis, the brachiopod Waldheimia cranium, and some mussels. 
Munida rugosa, which is one of the most characteristic decapods 
belonging to the sublittoral and deep-sea zones is, according to 
Theel, seldom met with on the Bohuslan coast of Sweden ; the 
true corals and gorgonids of the deep-sea fauna, which else- 
where patronise the sublittoral zone, are much restricted in 
their distribution throughout the Skagerrack and wide tracts of 
the North Sea, and seem to be absent from the fjords of the 
Bohuslan coast. Certain forms, which along the coasts are 
chiefly sublittoral in their distribution, occur sometimes quite 
commonly in one area, whereas in another area they may be 
scarce or even entirely absent. For instance, on the Swedish 
and Norwegian coasts of the Skagerrack the spatangid 
Brissopsis lyrifera is generally met with in the sublittoral 
zone, but on the west or North Sea coast of Norway it is 
comparatively rare. The converse is the case with the 



INVERTEBRATE BOTTOM FAUNA 491 

spatangid Schisasier fragi/is, y^h'ich is plentiful in the North 
Sea, but not found in the Skagerrack/ 

We propose now to discuss the fauna of the continental 
plateaus within the boreal region, dealing firstly with depths less 
than 100 metres, "-^ and secondly with depths greater than 100 
metres. 

I. Continental Plateaus covered by less than 100 Metres (?/ The southern 
Water. — In the portion of the North Sea to the south of ^"^'^J^J'/JJg 
the Dogger Bank, where the waters are shallow and the North Sea. 
summer temperature is high, there are southern forms unknown 
farther north, though this exclusively southern element in the 
fauna is very inconsiderable compared with the remaining 
boreal forms, some of which are more abundantly developed 
than in more northerly latitudes. During the cruise of the 
" Michael Sars " in 1904, I was able to carry out investigations 
with the dredge at a series of stations from the Danish coast 
to Scotland, in lat. 56° to 58° N. in depths between 14 and 100 
metres, an area not previously systematically examined. 

The floor of the North Sea is for the most part covered with 
soft materials (sand, sandy mud, and clay), with areas of stony 
bottom in places, though even here the rocks and stones are 
nearly always mixed with softer materials. In some localities 
the soft materials contain masses of empty shells, which are 
invaluable to the animal life, acting as a foundation for the 
hydroids, bryozoans, and other attached forms. This mixed 
bottom supports a greater variety of forms than the soft bottom, 
offering suitable conditions to unattached forms, whether they 
burrow or not, as well as to attached forms. 

The abundance of echinoderms characterises to a great extent 
the fauna of the North Sea. Among the star-fishes Asterias 
rubens occurs at all depths and upon every kind of bottom, 
though it seems less partial to soft clay bottom at considerable 
depths. Astropecten irregularis is met with everywhere, and the 
sea-mice Echinocardium and Spatangus purpureus ^ are equally 
common. Ophiura ciliaris (see Fig. 347) may be described as 
the brittle-star of the North Sea, for we found well-developed 
specimens everywhere on mixed bottom down to a depth of about 
100 metres, and at temperatures varying from 7° to 12° C, but 

1 The continental deep-sea zone not being represented, or only in very limited tracts, in the 
coastal areas of the Skagerrack, Kattegat, western and southern North Sea, a good many forms 
characteristic of that zone are absent here. 

- As the type for this area we take the southern and central parts of the North Sea, those 
parts being the best explored. 

•' In a trawling at 96 metres we found 500 specimens of the last named. 



492 DEPTHS OF THE OCEAN 

not on soft clay bottom ; all the individuals from stations in the 
open North Sea at considerable depths were very much lighter 
in colour and much larger than those taken along the Norwegian 
and British coasts. A good idea of the enormous quantities in 
which this form sometimes occurs was afforded by a haul with 
the dredge off Aberdeen, in 25 metres of water (temperature 
10.26° C), where they must have literally covered the bottom, 
and the same remark applies to the west coast of Jutland. In 
some localities we met with numbers of Brissopsis lyrifera, 
which prefers as a rule clay bottom in deep water at a tem- 




FiG. 347- 
Ophiura ciUaris, L. Reduced. 

perature of 6° or 8^ C, though occasionally specimens may be 
found on sand. Everywhere, throughout the whole area 
examined, there were the two brittle-stars Ophiopholis aculeata 
and Ophiothrix fragilis, as well as the starfish Liddia sarsi, 
which are numerous here and there, but cannot be called 
characteristic forms. More local, though plentiful in places, 
were sea-slugs {Cucumaria elongatd), which were met with at 
two stations, together with Brissopsis, on muddy bottom in 
about 50 metres, at a temperature of approximately 8° C.^ 

^ Of other echinoderms found at a few stations, in smaller quantities, I may mention Ophiura 
albida (only at one or two stations in the neighbourhood of the Danish coast and one station off 
Aberdeen in 25 metres) and O. sarsi, Aniphiiira filiformis {chiajeil), Ophioden sericeum (many 
young-stages in young-fish trawl east of Aberdeen in 62 metres, temperature 8'4° C, and also 
from the Norwegian depression), Asterias 7iiiillcri, Solaster papposus (only from the edge of the 



INVERTEBRATE BOTTOM FAUNA 493 

Special mention must be made of specimens of our common 
sea-urchin Echimis esculentiis from two stations in the North 
Sea: two specimens from ']'] metres, temperature 7.1° C, and 
eight specimens from 96 metres, temperature 6.15° C. The 
species generally varies very little, and individuals from our 
littoral zone scarcely differ at all. Normally the shell is high 
and of a reddish colour, while the spines are violet. The ten 
specimens from the North Sea, however, all differed from the 
typical form, having a flattened shape and varying considerably 
in colour. The shell itself shows variations from the typical 
red hue to a chocolate brown, and the spines assume every 
intermediate shade from the most beautiful vermilion (like what 
we find in E. elegans) to pure green. Many specimens have 
in consequence an outward resemblance to Strongylocentrotus 
or Echimis miliaris. Mortensen has described from the 
North Sea (40 fathoms) two specimens of flattened shape with 
unusually long bright red spines (like those of E. elegans). 
Norman tells of a variety from deep water near the Shetlands 
that had very fine spines and an exceptionally high shell, and 
Sars has described a similar variety from the Great Edge. 

These facts appear to justify the conclusion that, whereas in 
shallow water and along the coasts the species is of a fairly 
constant type as regards both shape and colour, it has a marked 
tendency to variation at greater depths, although the normal, 
or almost normal, form is to be found also in deeper water, as 
on the Faroe banks. The deeper portions of the North Sea 
in particular appear to produce very striking variations. 

Of shell-bearing snails there are two forms which characterise 
the area investigated, namely Nephmea antiqiia and Sipho 
gracilis, both species being met with everywhere from Denmark 
to the Scottish coast, and sometimes in great numbers.^ 
Judging by our investigations Nephinea extends into shallower 
water than Sipho, though both species exist plentifully side by 
side at considerable depths. One biological peculiarity worth 
recording was that every individual of Sipho in the haul referred 
to had a sea-anemone {Chondi^actinia digitata) on its shell, and 
at other stations, too, they were found living together in 
symbiosis. These sea-anemones were likewise found on the 

Norwegian depression, from the Danish coast, and east of Aberdeen in 62 metres), Eckmaster 
sangumolenius, Sti'ongylocentrotus drobachiensis (only from the Danish coast, one specimen with 
Stylifer tiirtoni on its shell), Echinus esculent us var., Echinocyamus pusillus (only east of 
Aberdeen in 62 metres), Cucwnaria lactea. 

^ We secured 130 specimens of Neptunea and 375 of Sipho at one haul from a depth of 96 
metres (temperature 6.15° C. ). 



494 DEPTHS OF THE OCEAN 

shells of Neptunea, and on several specimens of this large snail 
two other large actinians {Urticina crassicornis and Met7ndm7n 
dianthus) had attached themselves. Our common whelk 
[Buccininn iindatum, see Fig. 348) occurred over the whole area 
down to a depth of 100 metres, as a rule along with the two 
snails referred to, though never in such great abundance.^ 

Nudibranchs yielded, with one or two exceptions, only a 
very few specimens, and this was particularly the case with 
Tritonia, Doris, and Doto. At certain stations, however, re- 
markably enough from muddy bottom where there were no 
hydroids, the young -fish trawl brought up quantities of 

yEolis, which had 

i \^' ^ ' most probably located 

J #. themselves upon 

I Virgiilaria and Alcy- 

, Ij- oniiun, although their 

'^ \^?. usual home is among 

'^Wr- hydroids. Chceto- 

dei'ma, a worm -like 

.::.Z,^'^'h form belonging to the 

y " ^ /-' "-^^ molluscs, was repre- 

^' ^ ^ .%.^ sented by only a few 

^^ '*!/ ^^'-'.V.i* specimens (depth 47 

^"'1^*»^ -^^ to 80 metres, tempera- 

' ' / * ture f to 8" C.) ; 

^' cuttle-fishes by some 

Fig. 348. specimens of Lolio^o 

Buccinuin imdatinn, L. r i ■ • 

joroesi at one station 
(depth 38 metres, temperature 10° C), and a little Sepiola from 
94 metres. The almost complete absence of species of Chiton, 

^ Of more or less regularly distributed mollusc-forms we may further mention : Pecten 
opercidaris (large), Mytilus modiolus (from a depth of 96 metres about 70 specimens were taken, 
averaging 11 or 12 cm. in length and often with Urticina attached), Modiolaria nigra, Cardium 
echinatnin, Cyprina islandica, Venus gallina, Mactra elliptica (very numerous off the coast of 
Jutland, 14 metres, temperature 12.5° C), Solen ensis, Cultellus pelhtcidus, Aporrhais 
pes-pelecani, Antalis entalis. At some stations we came across Niictda tenuis, Leda tninuta, 
Kellia suborbicularis, Coj-btda gibba, Dosinia lincta, Cylichna cylindracea, all on mud in about 50 
metres and at a temperature of 8° C. Astarte sidcata was extremely numerous at one station 
(depth 86 metres, temperature 8.4° C), but otherwise very scattered. Aho Nicania banksi, 
Peclunculus glycimei'is, Mactra stidtoriim, Psatnmobia ferroensis, Panopcea norvegica (large 
specimen, 80 mm. long, 55 mm. high), Saxicava arctica, Pholas crispata (in pieces of timber on the 
bottom, depth 32 metres, temperature 10.9° C), Abra sp., Montacuta (on Spatangus), Philine sp., 
Velutina hcvigata, Lunatia intermedia (in enormous quantities at Jammer Bay off the coast of 
Jutland, 14 metres, together with Mactra elliptica, on which latter, judging from the many 
shells with holes bored in them, it feeds), Lunatia montagui, Natica catena (strings of eggs were 
found in large quantities on the north slope of the Dogger Bank, though the animal itself was 
rarely captured), Boi-eofusus berniciensis, Scalaria trevelyana, Volutopsis norvegica (only at one 
station, depth 96 metres, temperature 6.15° C, though in fairly large quantities— about 30 
specimens). 



INVERTEBRATE BOTTOM FAUNA 495 

notwithstanding the apparently suitable bottom of stones and 
shells, is very remarkable, a few specimens of Lepidopleztriis 
{Chiton) cinereiLS at one station (57 metres, temperature 7.9'" C.) 
being all that we met with. 

The bottom of the North Sea abounds, as already stated, 
in empty shells, particularly of mussels. The commonest forms 
are Cardium echinatinn, Cyprina islandica, Venus gallina, 
Dosinia lincta, Mactra, Psanwiobia ferroensis, So/en, etc., all 
of which were likewise taken alive. Lucina borealis, on the 
other hand, though shells were met with here and there at a 
depth of 38 to 98 metres, sometimes even in fairly large 
quantities, was not captured alive out in the North Sea by 
us, and the "Pomerania" Expedition obtained only empty 
shells on the Dogger Bank ; it is not included by Heincke 
amongst the molluscs of Heligoland, but we do find it along 
the coasts of Britain and in the Skagerrack. Empty shells of 
Alya truncata forma typica were also found in two localities, 
one at a depth of 14 metres off the north-west coast of Jutland, 
and the other midway between Jutland and Scotland at a depth 
of 68 metres. 

The higher crustacean fauna is comparatively poor in species, 
most of them being restricted in distribution and few in numbers. 
The hermit crabs Pagm^us bernkardns and P. p2ibescens are 
exceptions, as they are pretty generally distributed over the 
whole area, though only the first named is met with in shallow 
water, at or below 40 metres ; at greater depths both species 
occur, as in some other areas of the North Sea. Of crabs Hyas 
coarctattts is common in both deep and shallow water, whereas 
Portunus depiLrator (or holsatics^) and P. pusillus are more 
limited in their distribution, and occur mainly in the lesser 
depths. Other forms are more local, though frequently met 
with in considerable numbers, like the little Porcellana longi- 
cornis ; as a contribution to its biology I may mention that we 
found large numbers at two stations (depth 32 metres and 42 
metres, temperature 10.9° C. and 8.7° C), where in one case 
it had crept into the holes made by the borer-mussel (Pholas 
crispata) in sunken pieces of timber and in the other it occu- 
pied cavities in the large clotted lumps of sand constituting the 
colonies of the tube-worm Sabella^Ha alveolata. At greater 
depths it was absent, Porcellana being to a great extent a 
littoral form.^ 

^ We also found two other crabs in shallow water west of Jutland (32 metres) : the ordinary 
edible crab {Cancer pagiirus) and Hyas araneus. Single specimens of two species of Ebalea 



496 



DEPTHS OF THE OCEAN 



The stone crab {Lithodes maja, see Fig. 349) was met with 
only in the deeper parts where the temperature was lower (^j 
metres and 96 metres, temperature 7.1' C. and 6.15° C), as in 
the deep parts of the Norwegian tjords. The whole central 
portion of the North Sea proved remarkably poor in shrimps 
(caridids) though the few species present were frequently in 
considerable numbers.^ 

The ordinary wide-meshed appliances (trawls and dredges) 
undoubtedly give a good idea of the larger bottom-forms 
composing the fauna, but are less satisfactory when the fauna 
consists mainly of small crustaceans, for which we found the 
young-fish trawl extremely useful, as by its means we secured 




the large numbers of young crangonids already referred to, 
besides quantities of lower forms of crustaceans, especially 
amphipods, cumaceans, etc., and larvae of higher crustaceans, 
particularly hermit crabs. Even these, however, occur locally, 



{E. cranchi and E. tuberosd) were obtained at depths from 47 metres to 86 metres, with 
temperatures of 8° to 8.4° C. W^e also obtained specimens of the crabs Inachiis dorsettensis 
and Stenorhynchtis rostraius, and a single specimen of Atelecydus septemdetitattis was taken 
in the neighbourhood of the Scottish coast in 62 metres at a teinperature of 8.4" C. At one 
station on the coast of Jutland (32 metres, temperature 10.9° C.) the crab Corjsles cassivelamis 
was common, but it was quite absent in the central portions. Galathea dispersa and G. inter- 
media were got at some stations. 

^ We found, for instance, numerous specimens of a little crangoriid {Ckeraphilus nanus) at 
a depth of 78 metres, temperature 7° C, a number of individuals belonging to a form related to 
the common shrimp, Crangon alhnanni, and Pandalus anmdicornis. At a station near the 
Scottish coast, that is to say in the western portion of the North Sea, at a depth of 86 metres, 
temperature 8.4" C, we found in addition to small specimens of the two last-mentioned forms, 
of which Crangon was in myriads, several specimens of another shrimp {Hippolyte secitrifrons), 
which is also met with on the eastern side, but not at corresponding depths in the central 
portion. 



INVERTEBRATE BOTTOM FAUNA 



497 



being extremely numerous in certain localities and absent in 
others ; no doubt the currents at the bottom are responsible for 
this, seeing that the depth and temperature are in themselves 
entirely favourable. These enormous quantities of small 
crustaceans must have an appreciable influence upon the shoals 
of fishes, and in particular upon the young fishes, and this I have 
been able to confirm by direct observation. On the northern 
slope of the Dogger Bank we captured a number of young 
whitings and flounders with the trawl at a depth of 38 metres 
(temperature 10^ C), and their stomachs at first sight seemed 
to contain only sand, but closer 
investigation revealed small amphi- 
pods (sand- hoppers) which thus 
formed their principal nourishment, 
the sand being swallowed simul- 
taneously with them ; the stomachs 
of the larger fishes generally con- 
tained hermit crabs and swimming 
crabs (Portunus). The caprellids 
seemed to be especially associated 



with a bottom overgrown with 




Fig. 350. 
Macrocliymm pomum, M. Sars. 



hydroids, and were found only 
exceptionally where hydroids were 
absent.^ 

The central portion of the 
North Sea is poorly supplied with 
pycnogonids (sea- spiders), there 
being only one widely distributed 
form [Pyaiogonum littorale), and 
it was only found in deep water (80 to 100 metres) at low 
temperatures (6°-7° C), where I sometimes found it, as 
described by Sars, clinging to large sea-anemones [Urticina 
crassicornis and Metridium diantkus), into the skin of which 
it bores its proboscis for sucking ; a solitary specimen of 
Nyniphon stromi was the only other pycnogonid found in deep 
water. 

The ascidians (sea-squirts) are also poorly represented ; the 
monascidians (simple sea-squirts) were not very conspicuous any- 
where in the area examined, but we got large and well-developed 
specimens of Ciona intestinalis in about 80 metres (tempera- 

1 The commonest is Caprella linearis (it seems difficult to discover any invariable difference 
between this species and C. septenirionalis), but stray specimens occur o{ Proto pedata, mainly 
found along the edge of the Norwegian depression, at a depth of about lOO metres, and one 
individual o{ Protella phasma was captured at 77 metres, temperature 7.33° C. 

2 K 



498 



DEPTHS OF THE OCEAN 



ture about 7' C), whereas along the Norwegian coasts it is 
chiefly found in quite shallow water, where it attains its fullest 
development. Asciciiella virginea and Styela loveni were 
fairly widely distributed. A large globular compound ascidian 
{Mac7'oclinum pomiun, see Fig. 350), although very local, was at 
times very plentiful. 

The attached fauna, which, properly speaking, includes the 
sea-squirts, is mainly represented by three groups : sponges, 
hydroids, and bryozoans, the two last forming occasionally 
regular little forests. On the northern slope of the Dogger 
Bank (depth 'i^'^ metres, temperature 10° C.) there were con- 
siderable quantities of large bush-like colonies of two species 
of bryozoans (Fhtstra securi/rons, see Fig. 351, and Alcyonidium 

gelatinosiim\ which, ^'whFlustra 
foliacea, are the most character- 
istic of the North Sea bryo- 
zoans ; they vary in relative 
abundance, but on the Great 
Fisher Bank Flustra foliacea 
appears to be the predominant 
form. Small bryozoans, some- 
times occurring in large quan- 
tities, are found growing on the 
bigger species or on other 
substances. 

Hydroids are distributed 
over the whole area examined 
wherever the bottom is suit- 
able, especially where it is covered with empty shells or 
stones. They sometimes form " communities," but are as 
a rule scattered about here and there. Tuhilaria larynx is 
occasionally met with in enormous quantities, and there 
are sometimes "communities" of Tlmjaria thuja (see Fig. 
352), Hydrallmannia falcata, Campamilaria longisshua, and 
C. verhcillata. The species of Dicoryne and Hydractinia are 
very often found on shells inhabited by hermit crabs. ^ The 
hydroids in the central portion of the North Sea differ to a 
certain extent from those found in the northern portion or 
on the other plateaus. Tkujaria and Hydrallmannia are, how- 
ever, common to both areas. 

Among coelenterates there are really only two forms, if we 




Fig. 351. 

Flustra sectirifrons , Pallas. 



' Dicoryne conferta, Hydractinia echinata ; other species commonly found in the North Sea 
are Campanidaria johnstoni, Plumularia pinnata, Lafoea diimosa. 



INVERTEBRATE BOTTOM FAUNA 499 




Fig. 352. 
Thujaria thuja, L. (After Hincks. ) 



500 DEPTHS OF THE OCEAN 

except the sea - anemones already referred to/ which are 
universally distributed over the central portion of the North 
Sea, namely dead-men's fingers {Alcyonmin digitatuni) and the 
sea-pen Virgidaria mirabilis. The former generally consists 
of irregularly shaped ramifying masses attached by the base to 
other substances, but in the area examined by the " Michael 
Sars " during 1904, in depths between 2)^ and 96 metres, 
temperature 10° to 6.15° C, there was an interesting variation 
in its relation to its foundation. An annelid [Sabel/a pavonid), 
commonly met with here, inhabits an upright muddy tube 
attached at the lower end. The whole length of this tube was 
covered by the dead-men's fingers, which in some instances grew 
out from the lower end of the tube into the usual irregularly 
ramifying masses. This symbiosis was no fortuitous occurrence, 
but was invariable throughout the whole of the central portion 
of the North Sea where these two forms are everywhere to be 
found." On the coasts of Scotland and Jutland, on the other 
hand, Alcyoniwn occurred in its ordinary form. The common 
Virgularia mirabilis, found at depths of 50 to 100 metres, 
with a temperature of 7°-8° C, was the only sea-pen met with 
in the area examined, but we obtained a fairly large number 
of individuals. 

Sponges constitute a group of attached forms abounding 
in individuals, though remarkably poor in species ; they cannot 
be said to be regularly distributed, but are more or less local. 
On the north side of the Great Fisher Bank in particular 
we got enormous quantities of a ramifying whitish form 
[Halickojidria panicea van bibitla)} The different variations of 
Ficulina {^Siiberites) fiats are, however, the most prevalent. 
The commonest of these variations, where the sponge grows 
round shells and gives shelter to the hermit crab Pagiiriis 
pubescens, are comparatively scarce in the central portion of 
the North Sea, and we came across them at only one or two 
stations, but in the more northern parts of the North Sea 
plateau they were plentiful. Another variety, attached to 
empty shells of the sea-tooth [Anfa/is entalis) which as a rule 
shelter the gephyrean Phascolosoma strovibi, was abundant at 

^ Urttcina crassicornis, Metridiuin dia>it/uis, chiefly found on large shells of Mytihis modiolus 
and NepUinea, Boloccra tuedia and Chondradinia digitata on shells of Neptunea and Sipho ; at 
one or two stations (depth about lOO metres, temperature slightly over 6° C. ) we got Zoatithns. 

^ Several of these overgrown tubes were empty, which looks as if the worm benefited least 
by the symbiosis. 

^ Thanks to information kindly sent me by Professor Plate, Berlin, I can add H. panicea 
forma typica as being common on the Great P'isher Bank ; this form was also abundant on the 
northern slope of the Dogger Bank. 



INVERTEBRATE BOTTOM FAUNA 



501 



several stations, for instance on the northern slope of the Dogger 
Bank (38 metres) and north-west of the Great Fisher Bank 
{']'] metres). 

The Httle tube - worm Filigrana implexa, whose slender 
white irregular tubes are associated in trellis - work colonies, 
was met with over a large portion of the area examined, but 
only in the deeper parts. Another common form is Tkeieptts 
circi7tnaius, whose sinuous, parchment-like tube, covered with 
fragments of shells, grains of sand, etc., is attached to foreign 
substances such as empty 
mussel - shells, Flustra, etc. 
The annelid Aphrodite acu- 
leata is characteristic of the 
North Sea, but is as a rule 
limited to the deeper parts 
with soft or "mixed" bot- 
tom, though nowhere found 
in any great quantity. I 
have already stated that 
Sabella pavonia is common,^ 
and, speaking generally, we 
may say that as far as worms 
are concerned the central 
portion of the North Sea 
does not differ typically from 
the boreal portion of the Nor- 
wegian Sea. 

One peculiarity of the 
deeper parts of the central 
North Sea is that on soft 
bottom there is an absence 
of the foraminifera so plenti- 
ful in the Norwegian fjords 

very minutely the contents of the fine sieves through 
bottom-material was passed. 

It has been mentioned that in the southernmost portion of 
the North Sea, off the coasts of Belgium, Holland, and south- 
eastern England, there are many forms of southern origin, 
which are absent in more northerly latitudes ; some of them, 
however, find their way farther north than the others, though 
all keep to shallow waters with high temperatures. ^' ' ' 




Fig. 353- 
Cory5tescassivelanus,Wo\\l. ,5 Reduced. (After Bell.) 

this I can assert after examining 
which the 



This is, for 



1 On deep soft bottom we found representatives of the MaldanidK, as well as Eiimenia 
crassa, Trophom'a glauca, Lnmbrinereis, and N'ephthys, which we also find on the coasts. 



502 DEPTHS OF THE OCEAN 

instance, the case with the crab Corystes cassivelanus (see Fig. 
353), the mussel Mactra stultorum, the shelled snail Natica 
catena, and the tube-worm Sabellaria alveolata, all of which were 
found west of Jutland to the north of lat. 56' N. The last 
mentioned was met with at only one station (depth 41 metres, 
temperature 8.7" C), but in large quantities and big colonies; 
while the other three were taken in shallow water (less than 
40 metres) with the highest temperatures observed during the 
cruise (10° to 12^ C). The characteristic ribbon-like egg-clusters 
of Natica were found as far out as the northern slopes of the 
Dogger Bank, where the animal itself had been previously 
captured. According to Professor Plate both Natica catena and 
Mactra stultorum occur on the Great Fisher Bank, which shows 
that these forms do sometimes leave the coast region. On the 
other hand, Corystes seems exclusively to follow the coasts of 
Britain and Denmark, since we did not capture it with our 
trawl on the Dogger Bank, though depths and temperatures 
appeared to be favourable, and it has not been recorded at any 
great distance from the coast. These forms are found along 
the shores of Britain, and penetrate into the northern part of 
the Kattegat, but, if we except Mactra stultoru7n, they do not 
reach the coast of southern Norway. 

Our knowledge regarding the faunal character of the North 
Sea may be briefly recapitulated as follows : In the southern- 
most portion, at depths down to 40 or 50 metres, where the 
water-layers in summer attain a temperature of 13°-! 5' C, but 
in winter are cooled down to 4 or 5 C, the fauna consists 
partly of northern elements capable of adapting themselves to 
variations of temperature, and partly of a special southern 
contingent that has wandered in through the English Channel 
and requires high temperatures for at any rate part of the year. 
Most of these latter forms are limited to the southernmost 
portion, though a few follow the coasts towards the north, 
penetrating on the east side even to the Skagerrack, and on the 
west side to the coasts of Northumberland or perhaps still 
farther, but avoiding the deeper parts of the central area. The 
northernmost portion of the plateau, where the depths exceed 
100 metres, but where, notwithstanding, the waters are warmer 
than in the central parts, is characterised in similar fashion, as 
we shall presently show, partly by special southern deep-water 
forms that have wandered in past Shetland and only very rarely 
get as far as the coast of Norway or the Skagerrack, and partly 
by forms which may either have arrived originally from the 



INVERTEBRATE BOTTOM FAUNA 503 

south, or else are true natives, nowadays at any rate widely dis- 
tributed throughout the northern seas. Most of the forms met 
with in the central portion are also to be found along the 
coasts, but numbers of forms frequenting the coasts, especially 
shallow-water forms, do not inhabit the plateaus. 

We have not at present sufficient information to describe in 
detail other plateaus in depths less than 100 metres. The 
" Michael Sars " occupied two stations in 50 to 100 metres, off 
south-eastern and south-western Norway, where the fauna did 
not appear to differ from that in the outer part of the fjords and 
in the island belt. Certain forms (for instance Balanoglossus, 
taken off Risor on the south-east coast) have, however, not 
been taken in the western fjords nor in the central North Sea, 
but they have been recorded from the west coast of Sweden 
(Bohuslan). At the localities mentioned we were able to 
observe the remarkable fact that certain forms (for instance 
Echinus esculentus, Asterias rudens, Ophiothrix fragilis) occur 
in comparatively deep water, while in the fjords and island 
belts they generally occur in the littoral zone only. 

The investigations of C. G. J. Petersen in the Skagerrack 
show, as far as we can judge from his short statements, a marked 
similarity to the conditions prevailing in the North Sea. At 
present it is impossible to enter into a detailed account, and we 
can only state that along with the similarity there are certain 
discrepancies : thus, for instance, the pennatulid Pennatula 
phosphorea has not been captured by the " Michael Sars " in the 
central North Sea, but it is frequent on the Norwegian North 
Sea plateau and in the Kattegat. 

2. Continental Plateaus covered by more than iog Metres of 
Water. — The different lands bounding the Norwegian Sea and 
North Sea form the emerged portions of larger or smaller 
submarine plateaus. The bottom on these plateaus varies con- 
siderably, though, generally speaking, it may be described as a 
mixture of stones and rock together with fine or coarse sand ; 
only exceptionally, and in the deeper portions, is it composed of 
mud. The character of the bottom renders investigations 
extremely difficult, and the fauna is therefore not so well known 
as that of the fjords. Where the bottom is covered with 
softer material the fauna resembles that of the fjords. This 
is particularly the case in the Norwegian depression or gut, Norwegian 
running parallel to the Norwegian coast from the latitude of ^^^p^^s^^""- 
Stat to the Skagerrack. The depth in the middle averages 



504 DEPTHS OF THE OCEAN chap. 

approximately 300 or 400 metres, till we come to the inner 
portion of the Skagerrack where it increases to about 700 
metres. The bottom consists of soft mud throughout, except 
for a long narrow strip of stones and rock that penetrates its 
north-eastern portion. On the one side the depression is 
bounded by the Norwegian coast-plateau, which is here only a 
few miles wide, and on the other side by the plateaus of the 
North Sea and Skagerrack. 

During the cruise of the " Michael Sars " in 1902 investiga- 
tions were made with the trawl and dredge in its northern 
portion, the principal forms found being as follows : — 

Echinoderms : SticJiopus tremiihis (in quantities), Bathyplotes tizardi^ 
Cucinnaria hispida, MyriotrocJms vitreus, A mphiura norvegica, Ophioscolex 
glacialis, OpJiiura sarsi, Aster onyx loveni (on Funiculind), ScJiizaster 
fragilis, Bj'issopsis lyrifera, Spatangus rascJii, Psilaster andromeda, 
Pontaster tenuispiniis. 

Crustaceans : PontopJiilus norvegicus, Pandalus bonnieri. 

Ascidians : Ascidia obliqua. 

Molluscs : Abra longuallis, Malletia obtusa, Portlandia lucida, 
Axiniis flexuosus, Pecten septeinradiatus, Sipho islandicus, Scaphatider 
punctostriatus, Antalis agzlis, SipJionentalis tetragona, Caduliis 
subftcsiforni is. ^ 

Worms : Lumbrinereis fragilis, LcEtinonice filicornis, Aricia sp., 
Terebellides str'dmi. 

Gephyreans : Sipunadus priapuloides. 

Ccelenterates : Bolocera ttiedzce, Actinostola callosa, KopJwbelemnon 
stelliferuiii^ Fiinicidina quadrangularis , UlocyatJius arcticiis. 

Sponges : Thenea muricata. 

Also the foraminifera AstrorJiiza and RJiabdamniina, though these 
are not numerous. 

These animal forms make it tolerably certain that the fauna 
in the Norwegian depression is practically identical with the 
Atlantic fauna in the boreal region of the Scandinavian 
peninsula, and closely resembles the fauna of the western 
fjords of Norway. Petersen's researches have revealed 
similar conditions in the deepest portion of the Skagerrack. 
But along with the fjord forms, which exceed the others in 
numbers, there is a fauna in the Norwegian depression composed 
of forms seldom or never occurring among the skerries and in the 
fjords, but having their home on the plateaus of the open sea.'^ 

^ On the other hand, Mesothuria intestinalisYiz.'i not been found by the "Michael Sars" 
nor by other Norwegian and Danish Expeditions. 

^ This species was found by the Norwegian North Atlantic Expedition. 

3 To this fauna I assign the following forms : — Echinoderms : Spatangus raschi, Pontaster 
tenuispimis •■, Molluscs: Sipho islandicus, Antalis agilis ; Crustaceans: Pandalus bonnieri; 
Coelenterates : Ulocyathus {Flabelliim) arcticus. 



INVERTEBRATE BOTTOM FAUNA 505 

In the depression these are all common enough to be regarded 
as an essential part of the fauna. Spatangus rascki, for 
instance, appears never to approach the coasts or to enter the 
fjords, but keeps to the deeper parts of the plateaus where it 
takes the place oi Spatangus pttrpuretts ; it has also been found 
by the " Michael Sars " on the continental slopes south of the 
Faroe Islands. Pontaster te^iiiispimts only exceptionally enters 
the fjords of West Norway to the south of Stat, though it is 
found now and then in the Trondhjem fjord, and during the 
cruise of the " Michael Sars " in 1902 it was found at the mouth 
of the Sulenfjord near Aalesund.^ Antalis agilis and Pandalus 
bonnieri are only met with occasionally in the fjords,^ and 
Ulocyatlms arcticus belongs to the forms which do not enter 
our more southerly enclosed fjords, but may be met with in the 
more open northern fjords as far as the North Cape ; it has 
also been found, according to Norman, on the Shetland 
plateau. 

All or most of the forms enumerated as belonging to both 
the fjords and the plateaus, as well as those which chiefly or 
exclusively belong to the plateaus, may be met with as far north 
as Lofoten, and probably extend to the North Cape. The 
Norwegian North Atlantic Expedition came across many of 
the forms that inhabit the Norwegian depression and fjords in 
deep muddy hollows on the plateau north of Stat, and some of 
the forms occur on muddy bottom upon the outer slopes of the 
continental edge wherever the temperature is above 0° C. 

One peculiarity of the Norwegian depression still remains to 
be mentioned, namely that a deep trench extends along the north- 
eastern side to about the latitude of the Sogne fjord, approxi- 
mately 400 metres deep, where experiments with lines revealed 
a true hard-bottom fauna of corals (Paragorgia, PrijJinoa) and 
sponges ; the "Michael Sars" found this to be the case in several 
places in the trench.^ It is strange that this deeper portion is not 
full of mud like the adjoining shallower parts, since usually we 
find a reversed state of things, hard bottom rising up out of the 

^ Pontaster tenuispimis is found in two variations of colour, namely a rather pale form of 
weak structure, which belongs exclusively to the warm area, and a deep-red form much more 
stoutly built, which as a rule seems to belong to cold areas, though reddish individuals of weak 
structure occur also in warmer waters. 

'^ A good many individuals of Pandahis bonnieri, which used to be regarded as rare, have 
lately been found in the Norwegian depression and in the fjords north of Stat. It is of 
interest to state that the Danish research vessel "Thor" has found large quantities off 
South Iceland. It has also been discovered in the fjords near Bergen during certain years in 
varying quantities. 

* Large well -developed colonies oi Lophohelia prolifera were found on the plateau near Stat> 
together with other forms that are characteristic of such localities. 



5o6 DEPTHS OF THE OCEAN 

surrounding mud, and we can only conclude that the bottom 
here must be scoured by the action of currents. 

Some very interesting discoveries were made by the 
"Michael Sars " in 1904 in a southern part of the depression 
between lat. 58° and 59^" N., at a depth of 292 metres, the 
temperature being 5.83° C, where the young-fish trawl brought 
up a quantity of amphipods, cumacea, Euchcsta norvegica, 
etc. Among these forms there were two that were particularly 
noticeable, namely Epimeria loricata, of which there were 
many specimens, full-grown as well as young, and Acanthozone 
cuspidata, of which there was one young specimen. Both these 
species were hitherto only known to exist in more northern 
latitudes, the former not having been met with to the south of 
the Malangen fjord, and the latter not south of the Trondhjem 
fjord, where several other arctic forms have their southern 
limit. ^ 

The faunal conditions on hard bottom and on sand at the 
upper part of the Norwegian depression, from about 100 metres 
down to considerable depths, are very like those in the Nor- 
wegian fjords, but differ in many respects from those of the 
central parts of the North Sea. The sponges resemble those 
taken on hard bottom in the deep parts of the fjords. Among the 
hydroids there was S er hilar e lla gay i, a form that is absent from 
the central portion of the North Sea, but is one of the com- 
monest deep-water hydroids of the fjords. Crangon alhtanni 
and Pa7idalus aftmilicornis again were represented only by young 
individuals in the central portion, whereas at the edge of the 
depression our appliances brought up numbers of full-grown 
specimens. Other forms that we failed to find in the central 
area, but which occurred on the edge of the Norwegian 
depression, were : Hippasterias plana, Solaster endeca and 
S. papposus, Antedon sp., Psoitis squamahis, Nymphon stromi (of 
which we secured only one solitary specimen in the central 
portion, in spite of repeated trawlings and dredgings, though 
quite common on the edge of the depression), Crania anomala 
(common), Porella (characteristic of hard bottom in the fjords), 
as well as one or two other bryozoans, Scaphander punctostriatus, 

^ The following are a few of the other forms taken at the same time, showing that the boreal 
fjord and plateau forms occurred together ; several of them are met with in the arctic region, 
and may perhaps be of arctic origin : — Amphipods : Epimeria cornigera, Pardalisca abyssi (in 
quantities), Lilljeborgia Jissicornis, Khachotropis (two or three species). Cumacea : Eiidorella 
emarginata, Canipylaspis verrucosa and C. horrida, Hemilamprops cristata. Isopods : Apseudes 
spinosus, Munnopsis typica, Rocinela dammoniensis. Decapod crustaceans : Pontophilus 
norvegicus, Pandalus bonnieri, Hippolyte polaris, Bythocans siinplicirostris, Caridion gordoni. 
Molluscs : Rossia sp., Torrellia vestita, Portlandia tenuis, Pecten hoskynsi, Cardium jnininnun. 
Echinoderms : Ophioscolex glacialis, Aniedon tenella. Worms : Filigrana implexa (in quantities). 



INVERTEBRATE BOTTOM FAUNA 507 

etc. It must, however, be clearly borne in mind that there were 
many forms common to both areas, — partly those which belong 
to the entire boreal region, and partly those which are ex- 
clusively or nearly always found on the plateaus. 

As already stated, the bottom on the plateaus rarely, and Fauna of the 
as a rule only in deep hollows, consists of soft mud, being for 
the most part coarse or fine sand, sandy mud, stones, and rocks. 
The stony bottom usually predominates near the outer limits of 
the plateaus, or continental edge. Investigations by Rasch in 
1844 and by Sars in 1871 made it clear that large round stones 
and pebbles are to be met with on the Great Edge to the west 
of Aalesund at a depth of about 200 metres, and the " Michael 
Sars " also found round stones and pebbles there, as well as on 



continental 
edge. 




Fig. 354. 
Dorocidaris papillata, Leske. Reduced. (After Diiben and Koren. ) 

the rather less sharply defined edge of the Faroe plateau ; in 
the latter locality the dredge brought up from a depth of about 
400 metres a mass of loose round stones. 

The character of the fauna on the edges of the boreal 
plateaus, judging from what we have found on the Faroe and 
the Norwegian plateaus, is fairly uniform. Owing to the nature 
of the bottom we meet with attached forms, particularly sponges 
(for instance Oceanapia robusta), hydroids, corals, brachiopods, 
and bryozoans, together with a number of unattached forms, 
of which the echinoderms are the most characteristic. Among 
brachiopods we get Crania anotnala, Terebratulina caput- 
serpentis, Waldheimia cranitwi, and W. septaia, the last of 
which inhabits the plateaus of the open sea and never or 
only exceptionally enters the fjords. The same is the case 
with several echinoderms: Dorocidaris papillata (see Fig. 354), 



5o8 DEPTHS OF THE OCEAN 

for instance, easily recognisable owing to its long thick spines, 
is one of the most characteristic forms of the plateaus and 
especially of the edges, but hitherto not found within the 
fjords ; a characteristic brittle-star, Gorgonocephalus lamarcki, 
is also a plateau form, represented within the fjords by 
Gorgonocephalus linckii. One species of Echmus {E. acutiis 
forma norvegiciis) is often found in quantities, and far exceeds 
the fjord form in size. There are also the following brittle-stars, 
some of which are found in large quantities : Ophiacantha 
abyssicola and O. bidentata, Opkiactis abyssicola, all three of 
which are pure coast forms that do not go far up the fjords,^ 
Ophiophol