Abstract

I. Iintroduction.

Nothing of a detailed character has, so far as I am aware, been published on the geology of Rotuma. J. D. Dana mentions it as a high island with encircling reefs in ‘Corals and Coral Islands.’ Darwin, in ‘The Structure and Distribution of Coral Reefs,’ says that it possesses a fringing-reef only, and that it has an extinct volcano.

My notes were made in the months of September to December, 1896, which I spent on the island; I am indebted to Capt. Field and the officers of H.M.S. Penguin for their kindness, which enabled me to visit the island. I am further greatly indebted to Mr. J. E. Marr for his kindly advice and for reading through the accompanying paper, and also to Mr. H. Woods, who has examined the rocks which I obtained.

II. Topography.

The island of Rotuma is situated in lat. 12° 30' S. and long. ]77° 1' E. ; it is thus about 260 miles almost due north of the Yasawas, the nearest islands in the Fijian group. According to the Challenger's charts it lies in a general depth of 2000 fathoms, on a plateau which includes the Fijian, Tongan, Samoan, and Ellice Islands. The soundings of H.M.S. Penguin: 2438, 2715 fathoms, etc. in 1896, show that the Ellice Islands must be removed, while the most recently published chart of Samoa to Fiji shows that the former is separated from all neighbouring groups by a depth of at least 2200 fathoms.

Thus there is