144 LIGHT SCIENCE FOR LEISURE HOURS. 



who saw it and remembered through what mysterious 

 depths it had twice passed ; its breaking away almost 

 from the very hands of those who sought to draw it on 

 board; and the successful renewal of the attempt to 

 recover the cable, all these things were heard of as 

 one listens to a half-incredible tale. Yet when that 

 work was accomplished deep-sea dredging had already 

 been some time a science, and many things had been 

 achieved by its professors which presented, in reality, 

 greater practical difficulties than the recovery of the 

 Atlantic Cable. 



Kecently, however, deep-sea researches have been 

 carried on with results which are even more sensational, 

 so to speak, than the grappling feat which so surprised 

 us. Seas so deep that many of the loftiest summits of 

 the Alps might be completely buried beneath them 

 have been explored. Dredges weighing with their load 

 of mud nearly half a ton have been hauled up without 

 a hitch from depths of some 14,000 feet. But not merely 

 has comparatively rough work of this sort been achieved, 

 but by a variety of ingenious contrivances men of 

 science have been able to measure the temperature of 

 the sea at depths where the pressure is so enormous as 

 to be equivalent to a weight of more than 430 tons on 

 every square foot of surface. 



The results of these researches are even more re- 

 markable and surprising, however, than the means by 

 which they have been obtained. Sir Charles Lyell has 

 fairly spoken of them as so astonishing * that they have 

 to the geologist almost a revolutionary character.' Let 

 us consider a few of them. 



