BY W. G. WOOLNOUGH. 473 



fully discussed in my former paper, and the mechanism of 

 separation, namely faulting, was there suggested. In this paper 

 it is shown that some faulting, at all events, has occurred. 



I am therefore compelled to respectfully differ from Dr. 

 Guppy* in his general conclusions as to the origin of Vanua 

 Levu. He believes that the second island of the group is 

 essentially an oceanic island, built up from great ocean depths, 

 and that it has never formed part of a great continental mass. 

 Its axis is parallel to the second line of faulting I have suggested 

 for Viti Levu, and the whole of the structure lines of the group 

 strongly suggest that the archipelago is essentially a unit built 

 upon the axes which I have postulated for the main island. 



The absence of granitic or slaty rocks on Vanua Levu may 

 possibly be explained by the fact that its rivers, not being so 

 powerful as those of Viti Levu (I do not speak here from personal 

 experience) have not as yet succeeded in reaching and laying 

 bare the basement rocks. 



With his reading of the later portions of the geographical 

 history, I am in agreement, particularly as regards the general 

 upward movement of the land. No student of Island geology 

 can fail to be indebted to his painstaking labours for many 

 valuable suggestions, even if he cannot share with him all his 

 conclusions. 



In conclusion 1 beg to again point out that a most fascinating 

 field for study lies almost at our doors. The work is of interest 

 and importance to the biogeographer as much as to the geologist, 

 and I sincerely hope that Australian men of science will not 

 rest till the secrets of this wonderful land have been completely 

 laid bare. 



Postscript {added 16th August, 1907). — I have lately received 

 from the Rev. — Lelean, of Nailaga, a suite of specimens illus- 

 trating the gravels of the Ba River. They contain no 

 trace of granite rocks, so that the older series cannot outcrop 

 extensively in the area drained by that river. 



* "Observations of a Naturalist in the Pacific." London. 



