386 AUSTRALIA : 



coral, as the lower portions of the mass subside. Sectional 

 sketches would better illustrate these points ; but even without 

 such aid, we think there will be no difficulty in conceiving 

 them. The same views may further be applied to the other 

 peculiarities of these formations, the precipitous descent to 

 vast depths on the outer side of the reef the isles within 

 the channel, forming residual points of the old continent 

 the fringing reefs the openings into the channels or 

 lagoons, &c. 



We have spoken of this as a bold hypothesis ; and it will 

 not appear less so when we look at the magnitudes, both of 

 space and time, which are involved in such interpretation of 

 the facts. The extent it is needful to assign to some of the 

 areas of subsidence may well alarm an imagination not ac- 

 customed to deal with these subj ects. Spaces of many hundred 

 thousand square miles exist in the ocean, occupied by coral 

 isles of such description as to admit of no other valid ex- 

 planation than the sinking of the bottom of the sea over this 

 extent. The length of the Australian barrier reef, 1,200 

 miles, proves that at least an equivalent line of coast has 

 been subsiding since its formation began. The same infer- 

 ence extends to the great island of New Caledonia, in relation 

 to the reef half encircling it. Mr. Darwin has delineated 

 these several areas, as far as at present known, in a map 

 prefixed to his work ; adding to its value by designating also 

 the areas of upheaval in the -same oceans, and the sites of 

 active volcanoes, interpreting by their proximity some of the 

 remarkable phenomena in question. For both these great 

 events the subsidence and upheaval of the solid crust of 

 the globe are familiar to the speculations of modern 

 geology, and variously attested in different parts of the globe 

 by facts which, though recent in discovery, are unequivocal 

 in the inferences they afford. The magnitude of these move- 

 ments and changes may seem inconsistent with our ephemeral 



