366 AUSTRALIA : 



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 twenty fathoms deep and 

 several miles wide, between which space and the land should be 

 another body of reefs. Vol. i. p. 332. 



Thus there may be said to be two channels connected with 

 the Great Barrier Reef; the Inner one having an average 

 width of about thirty miles, though narrowed by subordinate 

 reefs on the land side; the navigable part of it varying in 

 depth from ten to thirty fathoms, safe in being thoroughly 

 sheltered from the storm of the ocean without, and affording 

 good anchorage wherever the channel is narrow or intricate. 

 The Outer passage, on the other hand, though giving a wider 

 route for navigation, has a profound depth of sea without 

 the possibility of anchorage ; so that under no circumstances 

 in which a vessel is placed can refuge be had, unless she is 

 able to make her way through one of the openings in the 

 Great Barrier, and thus to find access to the sheltered sea 

 within. In this general description will be seen the objects 

 and value of the survey now completed; which, by ascer- 

 taining the openings of easiest access, and of width and 

 depth best suited to navigation, and by fixing beacons to 

 mark and distinguish them, gives great increase of safety 

 and facility to ships traversing these seas. The probable 

 number of these openings or transverse channels we do not 

 find anywhere denoted. In truth, it would be difficult to 

 enumerate them, seeing that they vary from mere fissures 

 in the reef to passages several miles in width. The good 

 ship-channels alone have value, and these seem to be com- 

 paratively rare. 



But the objects of this survey would not have been fully 

 attained, without a thorough examination also of that 

 northern portion of the Great Barrier reef which stretches 

 well-nigh across Torres Strait ; and intercepts, though in a 



