NORMAL FORM OF THE BARRIER, 



333 



From an examination of our charts, it would 

 appear that the normal condition of this long mass 

 of reefs is, that the outer barrier should be narrow, 

 rising precipitously from a great depth, and running 

 more or less nearly in a straight line, and that inside 

 this outer barrier there should be a clear space about 

 20 fathoms deep and several miles wide, between which 

 space and the land should be another body of reefs. 



Diagram to represent an imaginary section of the Great Barrier reef. 

 The proportions are enormously distorted, the perpendicular scale being 

 fifteen or twenty times greater than the horizontal one. 



a Sea outside the barrier, generally unfathomable. 



b. The actual barrier. 



c. Clear channel inside the barrier, generally about 15 or 20 fathoms deep. 



d. The inner reefs. 



e. Shoal channel between the inner reefs and the shore. 



F. The great buttress^of calcareous rock, formed of coral and the detritus of corals and 



shells. 



G. The main land, formed of granites and other similar^rocks. 



The most remarkable deviations from this con- 

 dition are in the spaces between Cape Melville 

 and Lizard Island, and at the back of Wreck 

 Bay and Raine's Islet. Now in each of these 

 cases there are islands of granite or other rocks 

 advanced from the main land, and thus causing 

 an original irregularity in the depth of water, as it 

 would be independent of the coral reef. This is 



