io8 THE GREAT BARRIER REEF. 



which composes the greater part of the beach in the same position become consolidated ? Per- 

 manent springs containing carbonate of lime are, of course, improbable in so small a heap of low 

 sand as the islet is composed of. Either, then, the stratification and consolidation is the result of 

 a gradual deposition beneath the level of low water, in which case a movement of elevation must 

 have taken place, which in so small a spot seems a difficult and gratuitous hypothesis ; or else 

 the present structure must have been produced in the interior of a mass of loose sand by the in- 

 filtration of sea or rain water, or some other cause of which we are ignorant. I say in the interior, 

 for had it been on the outside, what was to defend it from the wash of the sea that is now breaking 

 down the hard solid rock, and shifting and washing backwards and forwards the loose sand of 

 which the present beach is composed? After the interior of such a mass of sand had been con- 

 solidated, the loose exterior may have been washed away and the solid rock exposed. The 

 speculation concerning the structure of this little island may seem a very unimportant circumstance 

 even to the geologist; but it is not so, as this same rock is found along every beach and on every 

 island among the coral-reefs of Australia, and I believe in other parts of the world also." 



The geological data and speculations connected therewith, embodied in Mr. Jukes' diary, 

 herein reproduced in extciiso, receive further notice in a later page of this chapter. Whether 

 or not Mr. Jukes' description of a living coral-reef, as " a half-drowned mass of dirty brown 

 sandstone, in which a few stunted corals had taken root," is actually as universally applicable 

 as the associated context would seem to impl}^ is a subject which may be left to the decision 

 of the reader already familiar with the photographic reef illustrations in this volume. To 

 the majority of voyagers and explorers, however, who cannot pick and choose the most favour- 

 able times and tides for landing on them, the earliest, and it may be the most frequently 

 renewed, acquaintanceships with coral-reefs and banks are equally productive of disappointment. 

 Many a veteran fisherman, indeed, who has been connected for the greater portion of his life with 

 the Barrier Beche-de-mer and pearl-shell fishing industries, and to whom copies of the original 

 photographs were submitted, was unacquainted with reefs laid bare, and exposing their coral 

 groves and thickets to the extent portrayed in many of the accompanying plates. 



Immediately north of the Capricorn Islands group, the wide entrance passage to the Inner 

 Route, known as the Capricorn Channel, intervenes. This gap, which may be designated the 

 chief entrance to the Inner Route from the south, is no less than sixty miles wide, and carries 

 soundings of from thirty to over sevent}' fathoms that gradually shelve in from the open ocean. 

 The outer boundary of this channel is represented by the Swain reefs, an archipelago of several 

 hundred tidally-exposed reefs, very similar in character to Westari reef of the Capricorn group, 

 which jut out oceanwards, forming part and parcel of the Barrier to a distance of one hundred , 

 and fifty miles east of the mainland. With the exception of two insignificant sand patches 

 known as Bell Cay and Hixson Cay, this entire reef system is submerged at high water. 



A brief account of the aspect of one of the reefs belonging to Swain's group, on which 



