240 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



ports of the officers who will have it in charge a correct 

 appreciation of its practical usefuhiess can be based. 



WORK ACCOMPLISHED BY THE CHALLENGER. 



The thoroughness of the equipment of the Challenger^ the 

 abilities of the several officers and assistants, and the favor- 

 able circumstances generally combined to render this expedi- 

 tion one of the most fortunate and successful of any on rec- 

 ord. Indeed, it may well be considered as marking an epoch 

 in the scientific history of the world. 



The first important advance made by the Challenger on 

 our previous knowledge of the deep seas was in the discovery 

 of a vast extent of red clay on the floor of the ocean at pro- 

 found depths, and the comparative absence of life there. 

 This extends far into the South Atlantic, merging into gray 

 ooze to the north, w^hile to the south a remarkable deposit of 

 silicious matter covers the Antarctic Sea floor. The small 

 amount of carbonate of lime and large amount of alumina 

 and oxide of iron contained in it render its formation ex- 

 tremely difficult to understand. An important deduction is 

 made that while this formation is going on to an immense 

 extent, with but little trace of organic life in the depths be- 

 low, the sea above teems with a variety of animal forms, 

 thus having an exact analogy in well-known terrestrial strata. 

 The cause of the absence of organic remains, as suggested 

 by Professor Thomson, lies in the large amount of carbonic- 

 acid gas held in suspension by the sea at great depths, which 

 acts as a solvent on the carbonate of lime, leaving only the 

 decomposed residuum to increase the thickness of the sea 

 bottom. 



Another result of the Challenger'' 8 work has been to estab- 

 lish as general principles what was only known to exist in 

 isolated instances, namely, the universal lowering of the tem- 

 perature of the great seas with increasing depth. 



Previous expeditions have shown that the fauna of the 

 deep seas contained species, genera, and groups which ex- 

 isted during past ages, many of them being forms known only 

 as fossils, thus surviving the various alterations that accom- 

 panied the geological periods. Numerous additional illustra- 

 tions were found in connection with the expedition of the Chal- 

 lenger^ which will doubtless in due time be brought forward. 



