GENERAL INTRODUCTION 



It 



sea dredging is a lengthy business, the dredge taking many 

 hours to be lowered and hauled through the enormous 

 depths. They were not disappointed ; living animals 

 were present at the greatest depths ; and an added excite- 

 ment arose, every haul brought up strange and beautiful 

 organisms that man had never yet set eyes on. 



The time was now deemed ready for a great expedition 

 to explore all the oceans of the world, to study animal and 



Fig. 3.— H.M.S. Challenger. 



plant life and the chemical and physical conditions under 

 which they existed. Accordingly in 1872 Her Majesty's 

 Government commissioned the famous research ship, 

 H.M.S. Challenger, under command of Captain Nares, 

 carrying on board some of the most noted men of science 

 of the day, headed by Sir Wyville Thomson. This ship 

 (Fig. 3) sailed the oceans for three years, travelling in 

 that time 69,000 miles. Soundings were made the world 

 over, temperatures noted, and samples of water taken 

 from all depths ; samples of the sea floor were obtained ; 



