NORMAL IORM 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 he a clear space about 

 SO 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 tin* barrier, generally unfa I burnable, 

 ft. The actual barrier. 



r. ('tear ctmniii't irisidp the barrier, pem-rally nbimt 15 or 40 fathoms iieeji. 

 d. The inner reefk. 



«. Shoal channel between the inner ni ts and the thore. 



F. The great ItttfewCaf calcareous rock, formed of coral and Ibe detritus of corali and 

 shells. 



(;. The main IiikI, formed of granites and other similar roots. 



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 



