INTRODUCTION 1 1 



arrived at. The work has been materially forwarded 

 by the vast strides in mechanism of every kind which the 

 last few decades has seen. Drift bottles and other appar- 

 atus serve to track the rate and direction of ocean currents, 

 deep-sea thermometers now give accurate temperature 

 readings, whilst a bewildering diversity of nets allow little 

 that is plant or animal to escape scientific notice. The 

 vast floating populace of microscopic organisms known as 

 plankton is now measured by a device not unlike a large 

 camera film. A gauze ribbon is steadily unwound, whilst 

 being towed behind the survey ship, all creatures adhering 

 to the gauze being automatically preserved as the exposed 

 ribbon winds itself upon a drum. By this means the precise 

 nature and quantity of the plankton over a wide area is 

 accurately ascertained. 



The survey ship may use a score of nets attached at 

 intervals to a tow-rope which descends perhaps to a 

 depth of several miles. Yet another device — the " grab " 

 — extracts samples of the sea-floor from any depth required. 

 The contents of fish stomachs are also now largely relied 

 upon to give an idea of the forms of life existing in many 

 situations beyond the reach of either grab or deep-sea 

 trawl net. 



Finally the last few years have produced that astonishing 

 device the bathysphere — a huge steel observation chamber 

 which can be let down from a specially equipped ship to 

 a depth of half a mile and from which the scientist armed 

 with a search-light looks out upon the world undreamed 

 of by the early naturalist. 



To the layman much of the work that exercises our 

 marine biologists may seem of purely scientific interest 



