18t6.] CLARKE ON THE GEOLOGY OF THE ISLAND OF LAFU. 61 



4. On the Geology of the Island o/'Lafu, one of the Loyalty Group, 

 east of New Caledonia in the Southern Pacific, By the Rev. 

 W. B. Clarke, M.A., F.G.S. 



On the eastern side of New Caledonia, and within sight of that 

 island, occur two groups, known on the charts as the Loyalty and 

 Britannia Islands. The former group has been generally represented 

 to consist of two, but has been recently found by Mr. T, B. Simpson 

 to consist of eight islands, of which Lafu, sometimes called Dafoo, 

 at the eastern, and Emingina at the western extremity, are the 

 largest. iVTr. Simpson's opinion is, that the original discoverer saw 

 but one, but that he visited part of its south-western coast where an 

 east and west bay, seven or eight miles wide at the entrance, and 

 from ten to twelve fathoms deep in places, but in the middle more 

 than ninety fathoms deep, is fringed with a narrow coral reef, and 

 has the appearance of dividing the island into two. 



Of the other islands or islets, one is about eighteen miles north of 

 Emingina, the northern end of which is in 21^ '26' S. and 167° 44' E., 

 and the rest are intermediate between it and Lafu. 



The present purpose is to offer some remarks on the geological 

 features of one island of the Loyalty group, viz. Lafu. It may be 

 quoted as an example of an elevated coral island, and is selected 

 because it exhibits more strikingly than the rest of the two groups, 

 which are of similar construction, the distinctive proofs of that phae- 

 nomenon. 



The circumference of Lafu is about ninety miles ; its base is sur- 

 rounded by a narrow fringing reef or shelf, upon which the depth 

 gradually increases for about a quarter of a mile, and then plunges 

 sheer down, out of the reach of soundings. The whole island is , 

 composed of dead coral, which in patches on the summit is bare,^ 

 but which is generally covered by a scanty soil of decomposed ma- 

 terials in which is rooted a very luxuriant vegetation. 



The average height of the above ocean is about 120 feet, but on , 

 the eastern side, which is the most abrupt, there are points 250 feet « 

 high. On the western side the headlands are all remarkably simi-,s 

 lar in height and outline, each being crested with a summit highei?.^ 

 than the neighbouring surface, and crowned with pines of similar; 

 character to the Araucaria excelsa. 



At the lower part of the island are found blocks of recent cal- 

 careous rock, similar to those seen on various parts of the great 

 coral reefs; consisting of recent Cardia and other shells, whole and 

 in fragments, cemented by a paste or powder derived from triturated 

 shells, and having the aspect of chalk and solid limestone. Stalac- 

 tites and stalagmites are also frequent in the hollows below the head- 

 lands. These probably result from the action of the sea spray and 

 atmospheric water combined with evaporation. So rapid are these 

 agencies in certain localities, that I have seen sandstone walls in 

 New South Wales coated by patches of calcareous matter, which is 

 the product of moisture and evaporation acting on the fragments of 

 sea shells employed in the cement of the buildings ; and many such 



