12 THE OCEAN 



the past twelve years an International Com- 

 mission has been engaged in the scientific 

 exploration and study of the North Sea and 

 Norwegian Sea. In addition marine labora- 

 tories have been established in many parts 

 of the world for the purpose of carrying on 

 the systematic examination of the ocean and 

 its inhabitants. The general result has been 

 that all the methods and instruments used 

 in deep-sea work have been much improved. 

 It is impossible in this little book to follow all 

 the developments that have taken place in this 

 direction, but a short statement concerning 

 the methods and instruments now generally 

 in use may be instructive and interesting. 



Methods and Instruments. — In making obser- 

 vations at the surface of the sea all the ordinary 

 methods and instruments in use among 

 meteorologists and physicists are available, 

 but whenever we commence to explore the 

 deeper waters of the ocean other methods 

 must be adopted and other instruments 

 invented. While functioning beneath the 

 surface the instruments are removed from 

 direct observation, and various contrivances 

 must be used to control their action. The 

 difficulties which have to be overcome add 

 very greatly to the interest of all deep-sea 

 investigations. Thermometers for deep-sea 

 work must be protected from pressure on the 



