10 ME. J. S. GAEDINEE Olf THE GEOLOGY OP EOTTJMA. [Feb. iSqS^ 



winds, but with JST.W. winds the storms are of long duration and 

 very dense. Hurricanes, with heavy rain, occur about every three 

 years. The total annual rainfall is estimated by residents, from 

 known Pijian statistics, at from 150 to 250 inches. 



No perennial streams flow except on Uea, where there are two. 

 Deep channels have been cut by the rain, however, on Sororoa and 

 Sol Kopi. In the regions of volcanic rock there are no signs of 

 watercourses, but two streams flow perennially out of this rock 

 between tide-marks at Lopta and ISToatau. Towards the middle of 

 this part of the island is an extensive watershed with no visible 

 escape to the sea; possibly these two streams are fed from a 

 reservoir filled by this. 



Eound the island is no current, except a drift, caused by and 

 varying with the wind. The 100-fathom line follows the contour 

 everywhere very regularly, but extends considerably to the north- 

 east and south-west along the lines of Hoflewa and Uea. 



YI. Conclusion. 



Erom the foregoing evidence I am inclined to think that Rotuma 

 was first formed of a kind of basaltic rock, such as is found in 

 Kugoi now. This rock I believe to have extended along the whole 

 island as it now runs, but to have been broken up by that great 

 eruption, or series of eruptions, which formed the central U-shaped 

 range of hills of the eastern end. By this eruption I believe that this 

 same basaltic rock was in places loosely piled up, and then, by dis- 

 integration and admixture with lava, formed the hills and islands of 

 volcanic ash. The last stage is the washing away of these, and the 

 formation of the coral-reef and the beach-sand flats. 



YII. Appendix. 



Notes on the Rocks collected hy Mr. Stanley Gaedinek. 

 By Heney Woods, Esq., M.A., F.G.S. 



1. Olivine-Dolerite from Kugoi. 



This is a light-greyish, moderately coarse-grained dolerite, con- 

 taining much felspar. The rock is quite fresh, and consists of 

 plagioclase-felspar, augite, olivine, magnetite, and apatite. Two 

 generations of felspar are very distinct — the crystals belonging to 

 the earlier showing good contours. It is probable that this is an 

 intrusive rock. 



2. Basalts from Tarasua Pointy Mafiri Cave^ and 

 ■ An Hnfhuf. 



These are very vesicular basalts, black or grey in colour. The 

 specimen from Tarasua Point was found by Dr. W. Pollard to 

 contain 48*86 per cent, of silica ; the rock is dark in colour and 



