CORAL REEFS 49 



low tide ; as barrier reefs far out at sea, such as the 

 Great Barrier Reef, which, at a distance of from 15 

 to 100 miles from land, skirts almost the whole north- 

 eastern coast of the Australian continent ; and lastly, 

 as atolls or island-rings in the open ocean. 



In the parts of Indian seas that are surveyed by 

 the Investigator only fringing reefs and atolls are met 

 with ; the former in those parts of the Andaman Sea 

 and Bay of Bengal where the water is not too turbid 

 with river-borne sediment, the latter in the Laccadive 

 and Maldive Archipelago ; but the series of coral banks 

 which flank the western shore of the Andamans may 

 perhaps represent a discontinuous barrier reef. 



The most perfect depths at which to observe a 

 living coral-reef in these seas are from 3 to 10 fathoms, 

 according to the amount of daylight at the time. One 

 cannot make out much detail, even when the sea is 

 quite calm, by merely looking down over the boat's 

 side unless one has a water-glass. This is a wooden 

 funnel, with a window of good plate-glass in the broad 

 end and a pair of handles about halfway up. Taking 

 a good grasp of the handles, you run the funnel over- 

 board, push the window end well below water, and 

 put your eyes to the narrow end, and then a perfect 

 picture of the bottom is before you, free from all the 

 distortions caused by ripples and surface reflection, 

 and free from glare. 



And what a picture it is to a man who comes from 



D 



