/. LIGHT IN THE OCEAN. 389 



after its having been lowered deep into the sea, 

 marking several inches lower than before it was 

 sent down. At the depth of 20 fathoms, 20 

 cubic inches of sea-water only occupy the space 

 of 19 at the surface. 



In its profound depths, the ocean is darker 

 than the darkest night. No twinkling of the 

 stars gives variety to the dark expanse over 

 head ; and not even the brilliance of the noon- 

 day sun can enliven these gloomy regions. 

 Silent and black, it might be conceived to be 

 the abode of eternal night. It has been a ques-. 

 tion how deep it is possible for daylight to 

 penetrate into the waters. In the clear regions 

 of the tropics, where however the utmost bril- 

 liancy of natural light is attained, the bottom 

 of the ocean, at a depth of many fathoms, may 

 be distinctly seen, and navigators state that the 

 zoophytes and marine plants may be very clearly 

 beheld, and that they appear most delusively 

 near to the surface. Shells are visible in parts 

 of the Arctic Ocean at a depth of 80 fathoms. 

 In the seas around the West India Islands the 

 bottom is distinctly perceptible at 30 fathoms. 

 Ordinarily, about 700 feet appears to be the 

 extent to which light penetrates into the 

 ocean. 



The colour of the ocean has engaged much 

 attention, although not in some instances with 



