362 Transactions. 



Australasian Association for the Advancement of Science, for research on 

 the alkaline rocks of Australasia. 



Letters written previously to the Governor, M. Leon Geraud, received 

 replies which assured me of every assistance in the project of ascending 

 the Papenoo Valley, which was said to be " herisee de difficultes " and " il 

 n'existe pas de sentier bien trace et on doit se frayer soimeme son chemin." 



On my arrival in the colony M. Geraud kindly gave me a letter to the 

 chief of the Village Papenoo, situated at the mouth of the River Tuoru, 

 and he promptly furnished us with the necessary guides. It was extremely 

 fortunate that one of these, Teaeo by name, had accompanied M. Seurat 

 when he made his geological collections in the valley. This enabled me to 

 find his localities with the utmost certainty and with the least loss of time. 



The entrance to the Papenoo Valley is about 300 metres wide, and its 

 sides rise precipitously to a height of 100 metres at first, but they ascend 

 gradually towards the interior of the island. Its floor is covered with 

 gravels, in which boulders of plutonic rocks of some variety are quite common. 

 These vary from pure white types to dark theralites, many of which 

 contain conspicuous crystals of hornblende and augite. Mixed with these 

 there is a great variety of basalts, and a few of tinguaite and monchiquitc. 



The river maintains a wide floor as far as Tiamii (see map of valley), 

 about 9 kilometres from its mouth. Here the Tamanu tributary branches 

 off from it. This stream drains the east and north of Orofena, the highest 

 peak of the island. In its gravels there were no boulders of plutonic rock. 

 Above this point the Papenoo Valley narrows rapidly, and in many places 

 flows over the native rock. 



Close to Tiamii an area of plutonic rock is indicated by Seurat. The 

 guide Teaeo showed me a large boulder in the forest, which he said was the 

 outcrop discovered by Seurat. It was clearly a transported boulder, and 

 I could find no outcrop of plutonic rock near it, though basalt occurred 

 in situ 100 metres farther up the stream. 



The same was found to be true at the mouth of the Navenave and Pihoi, 

 other localities where plutonic rocks had been reported in situ by Seurat. 

 In both of these places large boulders of plutonic rocks were to be seen 

 in number, but no rock other than basaltic breccia could be found in place. 

 From a point a little beyond the mouth of the Pihoi our track led some 

 distance above the bed of the Tuoru across the small stream Teti. Here 

 again the only plutonic material that was found consisted of large boulders 

 evidently water-borne. The bed of the Tuoru was not seen near this place, 

 so I am not able to say whether the plutonic occurrence recorded by Seurat 

 at this place is correct, though, as far as appearances went, it appeared 

 unlikely that it was so. 



Shortly above the junction with the Teti the Tuoru forks into the Maroto 

 and the Tahinu. My guide (Teaeo) asserted that Seurat went no farther 

 than the junction with the Teti. j Lacroix, however, states that Seurat 

 went for some distance along the bed of the Maroto, and found that the 

 plutonic boulders soon disappeared, and that the upper part of the valley 

 is constituted entirely of basalt. There must be some mistake here, for 

 at the junction of the Tahinu and Maroto there is nothing but volcanic rock 

 in sit", while a little farther up the Maroto plutonic rock is to be seen forming 

 the bed of the stream, and it continues to form its banks for some distance. 



It thus appears that in all but one of the localities where Seurat is stated 

 to have found plutonic rock in situ I was unable to find any, and this one 

 I was not able to visit. 



