124 



LOED HOWE ISLAND. 



any great width of ocean, wliile tlie Australian birds arc mostly such as fly 

 well, and might easily have emigrated to the island. This sufEciently explains 

 why, although the great majority of its birds are Australian, yet naturalists 

 consider this group of islands to belong really to the New Zealand 

 zoological district." 



I thin];:, on the whole, therefore, there is reason to believe that Lord Howe 

 Island originally formed a portion of the Now Zealand volcanic area, and 

 certainly dates back to the Pleiocene period, perhaps further ; but of this we 

 have no definite proof at present, although the diabasic basalts, accordino- to 

 Mr. Edgeworth David, may bo Palaeozoic, at any rate they are probably 

 Pre-Tertiary. On, the other hand his conclusion that all the non-diabasic 

 basalts are not earlier than Tertiary will tend to support the hypothesis 

 suggested here. 



Evidence lias been adduced to show that Lord Howe formerly consisted of 

 three or more but little separated islands, aiid, assuming the Coral-sand rods: 

 to be of asolian origin, that it was not until after its accumulation that any 

 further depression took place ; but these minor changes did not to any great 

 extent alter its configuration from what we now see it, beyond rounding the 

 general contour and deepening the gullies. The separation of portions of 

 its surface one from the other probably conveyed to the mind of Mr. E. S. 

 Hill the expression that, " at one time, it appears to have been a chain of 

 atolls, linked together by the coral insects."* There is not the faintest trace 

 whatever of any condition of things, so far as my own observations went 

 which could be likened to that of an atoll ; nor did any evidence of sub- 

 mergeance other than the facts derived from a study of the Coral-sand 

 rock present themselves to our notice. 



A very important statement, however, has been made by Mt. Fitzgerald. 

 When speakingt of the Coral-sand rock he mentions that '' it even seems to 

 cap the tops of the mountain." This appeared to me so improbable that I com- 

 municated with that gentleman, who very kindly replied as follows :J — " The 

 first time I went to Howe's Island I did not succeed in reaching the top of 

 the mountain, but was informed that it was composed of the same kind of 

 rock as the low parts of the island (coral), and as it appears to be flat from 

 below, I thought it might be the case ; but on my second visit I found that 

 the top was not flat but deeply furrowed, and showing no coral or coral-rock. 

 I refer to Moimt Grower, but have no doubt that Lidgbird is exactly the same." 



The supposition that Lord Howe, as we now know it, was composed of a 

 few small islets is based on the fact that it w-ould require a depression of but 

 comparatively few feet to return it to this condition. This granted, we have 

 but to imagine a slight upheaval, and circumstances favourable for the 

 accumulation of the Coral-sand rock would at once exist. It is possible that 

 this may have resulted to some extent from the destruction of pre-existino- 

 fringing reefs, bearing in mind the formation of the calcareous deposit at 

 Norfolk Island, described by Carne. The destruction of a coral shore 

 invariably gives rise to calcareous sand such as we have now before us. 

 Pinally, the presence of nuUipores, which play so conspicuous a part in the 

 construction of some reefs, such, for instance, as Keeling Island, must not 

 be overlooked. " There," says Darwin, " the nulliporc bed has a thickness 

 of two or three feet, and a breadth of twenty feet. "§ 



When first I examined this deposit in situ, 1 regarded it as of aqueous 

 deposition ; but after due consideration of all the facts for and ao-ainst I 



* Hill'g Lord Howe Island, loo. cit. p. 54. 



X Letter, dated May 26, 1888. 



§Dana, Corals and Coral Islands, 1872 (Engl. Edit.), p. 137, 



t Hill's Lord Howe Island, loo. cit. p. 44. 



