282 Transactions. 



The only place that I was able to visit was the Bay of Putoa, on the 

 south-east side. At the head of this bay is the village of Afareaitu, one of 

 the early missionary settlements — -where, in fact, the first printing-press in 

 the South Sea Islands was installed, in the year 1817. 



A narrow strip of flat land separates the hills from the beach. This is 

 formed mainly of the gravel brought down by the two small streams from 

 the pinnacled mountains a little more than a mile distant. The gravel- 

 flat extends a little distance back into the valleys, which appear to have 

 been formed when the land stood at a higher level. The rock at the lower 

 end of the spurs is a basalt, which, though generally fine-grained, contains 

 relatively large crystals of olivine. The stones in the bed of the small 

 stream are, however, phonolite of a trachytoid nature, and they evidently 

 come from lava-flows at relatively high levels. High up on the hills are 

 to be seen outcrops of massive lava-flows with the same colour and the 

 abrupt appearance that is so characteristic of the phonolitic rocks in 

 Raiatea and Huaheine. When seen in thin section this rock is found to 

 be composed of small microlites of feldspar. Between these there can occa- 

 sionally be seen a few minute crystals of nepheline, though in much smaller 

 quantity than in the corresponding rock from Huaheine.* Aegerine augite 

 is quite plentiful, and it has an extinction-angle of 40°. A good deal of 

 magnetite is present. 



The island of Rurutu, one of the Tubuai group of islands included in 

 the French possessions in the Pacific Ocean, lies in latitude 22° 27' S. and 

 151° 21' W. longitude. It is six miles long and three miles long, and rises 

 in a sharp peak to an elevation of 1,300 ft. The island was discovered by 

 Cook in 1769, and Tupia, who was then a passenger in Cook's ship, called 

 it Ohiteroa. It is, however, noticeable that in Tupia's map of the South 

 Sea Islands published in Forster's " Observations made during a Voyage 

 round the World " Rurutu is the name given to an island placed in 

 a group including Rimatarra and Reevavai, which are obviously 

 intended for the islands now known as Rimatara and Raivavae. This 

 group is, however, in his map placed to the north-West of Tahiti, whereas 

 it actually lies some three hundred miles to the south of that island. 

 Rurutu seems to be the name that is almost universally used for this island, 

 and, seeing that it is the name used by Tupia himself for the island in his 

 map, it appears to be probable that he mistook this island for some other 

 when it was first sighted. 



The reef that surrounds the island is almost in touch with the shore, 

 and it is not penetrated by any good passages. So far as the geology of 

 Rurutu is concerned, the only statement that I can find is that of Ellis, 

 who says that there is limestone on the island, and that garnets have been 

 found there. 



I am indebted to Mr. Fred. Hildreth, of Gowgonda Lake, Ontario, 

 Canada, for specimens of rock from this island, and for much information 

 in regard to it. On the eastern side of the island there is a good deal of 

 calcareous conglomerate with much included volcanic rock. This forma- 

 tion rises to a level of 300 ft., and has a highly irregular surface. Above 

 this levej the surface of the ground consists of highly coloured clays, 

 obviously derived from the decomposition of basic volcanic rock. This is 

 apparently a coarse-grained doleritic rock, which in hand-specimens appears 



* Marshall : " Alkaline Rocks of the Cook and Society Islands," Trans. Aust. Assoc. 

 Adv. Sci., vol. 13, 1912, p. 198. 



