DREDGING. 



CHAPTEK LVI. 



SMDfllNG IN MODEUN TIMK8 — WHAT IT HAS TAOQHT US— DKKP SEA SOUN DINGS— FIRST 

 ATTEMPTS — IMPLEMENTS USED FOR IT — THE CHANCE FOR INVENTORS. 



In modern times we have learned a great deal more of the 

 ocean than the ancients knew, from dredging. By this means 

 we have become acquainted not only with the outline of the 

 bottom, but have also become acquainted with the temperature 

 of deep seas, with the varied forms of animal and vegetable 

 life which are present there, and have come to know, with far 

 greater certainty and completeness than ever before, the part 

 which the ocean has played and is still playing in the pre- 

 paration of the land. 



By sounding, the ancients, of course, knew the depths of the 

 shallow waters along their coasts. It would be the most 

 natural thing for a sailor to tie a stone to a string, and let it 

 down into the water, when he wanted to know whether it was 

 deep enough to float his vessel, and the same means would 



also be used to discover whether there were any sunken rocks 



71G 



