62 



THE OPAL SEA 



The deep- 

 sea record 

 not com- 

 plete. 



Ocean 

 transpar- 

 ency. 



Seeing with 

 the unaided 

 eye. 



supposed to be very old. Then, again, the deep- 

 sea record is by no means complete. It is 

 largely the tale of the Challenger dredge. 

 That was a beginning not a finality. 



And, of course, there is no seeing into the 

 great depths, no gaining of ocular proof. If 

 the water were clear — ^yes; but it is not. The 

 particles of dust, salt, and minute sea life that 

 float in it check and bend back the rays of 

 light, at least the rays familiar to us in the 

 sun's spectrum; and what we see and know of 

 ocean transparency is merely the illuminated 

 surface, a hundred fathoms of the upper 

 crystal. 



It is said that in the clear waters of the polar 

 regions the unaided eye can see seventy fath- 

 oms down — a statement that seems very ques- 

 tionable and yet may be true, though certain 

 experiments, made by sinking white disks in 

 the water and noting the point of their disap- 

 pearance, have not resulted so favorably. All 

 depends necessarily upon the clarity of the 

 water. That at the poles seems a trifle clearer 

 than that at the tropics. And yet it is aston- 

 ishing what depths may be sounded with the 

 eye in such a salt sea as the Mediterranean. 

 Looking down into it from the prow of a 

 yacht, the beams of the sun can be seen, hun- 



