This island, which is the most southerly of the group, is rectangular in plan, one mile by three-quarters. High cliffs bound the south, east and west sides. The northern slopes descend gradually to the sea, where they terminate in cliffs about 30 feet high. The highest point is on the east side of the island, and is about 1,000 feet above sea level. It is connected by a low featured col to the high land to the south-west. To the west, that is, towards the interior of the island, there is a depressed area which now has a small pond in it. It is probable that this was once the crater from which the lavas issued. [Illustration: NIGHTINGALE IS] _Geology_ One day only was available for work on this island, and orders were that the supposed guano deposits which were reported at the north side were to be examined. These deposits are of no economic value, and an analysis is here appended. _Certificate of Analysis._ Ogston and Moore, Analytical Chemists, 89 Aldgate, London. July 28, 1922. _Guano from Nightingale Island._ Moisture 72.12 Organic matter and ammonia salts 24.70 Phosphoric acid _nil_ Lime _nil_ Magnesia, alkalies, etc. 1.60 Silicious matter 1.58 ------ 100.00 ====== _Guano from Cave on Middle Island._ Moisture 17.00 Organic matter and ammonia salts 15.15 Phosphoric acid 3.85 Lime 5.10 Magnesia, alkalies, etc. 10.20 Silicious matter 48.70 ------ 100.00 ====== The rocks, however, appeared to be in general of a trachytic nature. MIDDLE ISLAND _Topography_ Middle Island lies less than half a mile to the north of Nightingale. It is in plan about a quarter of a mile square, and rises to a height of about 200 feet. It is flat-topped, with minor depressions. _Geology_ There have been questions asked as to the origin of Middle Island, and to the writer, who had this in mind when visiting the island, the following were the reasons for its existence.