IV. 



Chemistry and Physics in the " Challenger 



Report. 



ALTHOUGH the interest of zoologists in the "Challenger" 

 Expedition and its results, as embodied in the fifty volumes of 

 Report, chiefly centres upon the zoological section and its revelations 

 of life in the great oceans, yet it should not be forgotten that the 

 unique services rendered by the Expedition to oceanography, in its 

 chemical and physical aspects, are not only valuable in themselves, 

 but have a profound bearing on marine zoology. The fundamental 

 conditions of an animal's existence are expressible as physical data : 

 what is the average temperature of its habitat, and to what range of 

 temperature is it subjected ? how much oxygen can it have ? how 

 much sunlight ? and, in the case of marine organisms, the amount of 

 salinity and pressure may become questions of importance. All these 

 questions are for the physicist and the chemist to answer, and to him 

 must the naturalist apply if he would render a full account of marine 

 life, especially in the consideration of such general questions as the 

 distribution of species and the like. 



On board the " Challenger " the chief physical work was the 

 determination of the specific gravity of samples of water collected 

 from the surface every day ; from the bottom at sounding-stations by 

 means of a shp bottle attached to the line; and, wherever practicable, 

 from intermediate depths of 25, 50, 100, 200, 300, 400, and 800 fathoms 

 from the surface. A characteristic feature of the Expedition's work 

 was the determination of the temperature of these water samples in 

 situ, as was also the collection of samples from various depths all over 

 the great oceans. 



The chemical work of the ship-laboratory consisted in extracting 

 the gases from, and determining the carbonic acid in, as many 

 samples as possible. Besides this, a very large number of samples 

 of sea-water from the surface, the bottom, and intermediate depths 

 were carefully stored in glass bottles for more detailed examination at 

 home. This was the daily programme for some three and a half 



