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The islands of the southern Cook and Austral groups in the South Pacific exhibit astonishing differences in geology and topography, even between closely adjacent islands of similar ages. Some are sea-level atolls, others have low fringes of Pleistocene raised reefs, and others substantial rims of elevated mid-Tertiary limestones, locally known as makatea. On some islands the relief of the makatea is subdued, but on others it is dominated by eroded volcanics, sea-level swamps, and vertical limestone walls. Sixty years ago there was great controversy over whether the makatea of Rurutu represented a reef-growth or an erosional topography. Using insights from Mangaia in the southern Cooks we argue that the makatea relief of Rurutu is of erosional origin, and we identify why the Paparai Valley - seen as a key area in the old arguments, even though none of the protagonists had seen it - holds a key to the great inter-island differ- ences which exist in makatea topography in this part of the Pacific.

Tongatapu, like Tahiti, was visited by many early European navigators and was one of the first of the South Pacific islands to be charted in any detail. Though it was discovered (and named Amsterdam Island) by Tasman in January 1643 (Sharp 1968, 152-158), the first comments on the sand cays of the surrounding reefs were made by Cook during his second voyage, with the Resolution and Adventure, in October 1773. On this occasion Cook spent less than a week at Tongatapu, anchored in the northwest, and commented that "it would have taken up more time than I could spare to have surveyed these parts Minutely as there are a number of small Islots and reefs of rocks extending to the NE even further than we could see" (1961, 261). His naturalists, the Forsters, did not describe the cays, though Georg Forster remarked on the emersion of reef limestones on Tongatapu and its similarity to the continuing emergence of the land in Scandinavia (1777, I, 453). Cook returned on his last voyage in 1777, with the Resolution and Discovery, and stayed for a month. He anchored near modern Nuku'alofa and landed on Pangaimotu and possibly other islands (1967, 124-125, 155, 890). He charted the area but gave no description of the cays.

Rarotonga and Aitutaki form the summits of separate volcanic masses rising from depths of 4000 m, at which depth the cones are 45-55 km in diameter (Summerhayes and Kibblewh 1966, 1967).The lower slopes of the cones average 15-25 increasing to 30 in the upper 750 m and becoming very steep the surface reef is approached. The Mauke-Aitutaki line of islands is thought to be of early Tertiary age: the surface volcanics are much eroded, with a subdued topography, or are capped with limestones (Wood, 1967; Wood and Hay, 1970). On Rarotonga, where the relief is much stronger (maximum altitude 640 m), radiometric ages of 2.3-2.8 million years date the 1 as Pliocene (Tarling, 1967). Mangaia, with a cap of Oligoce Miocene limestones, must be much older (Marshall, 1927). Evi dence from the deep-sea drilling programme indicates that th ocean floor in the area of the southern Cooks is Paleogene (22.5-65 million years) in age (Winterer, 1973), thus provid a maximum age for the islands. It is probable that the gross history of the Cooks resembles that of other, better-known reef-capped Pacific volcanic cones known to have been initia in the early Tertiary.

Fais (Tromelin) is an elevated coral island, surrounded by interrupted cliffs 15-20 meters high, lying some 140 miles east of Yap Island, at latitude 9'46' N, longitude 140'31' E in the western Caroline Islands. It has an area of 2.8 square km, and has a population of about 300 people, Micronesians, speaking a dialect of the Ulithi-Woleai tongue. As with many such raised coral islands, valuable calcium phosphate deposits occur on Fais, the greater portion of which was removed and exported during the period of Japanese rule (1914-1945).

Rangiroa is the largest atoll in the Tuamotu Archipelago, and since the institution of a regular air service, the most accessible; yet in common with other Tuamotuan atolls it has rarely been visited by scientists and is barely mentioned in the literature. Dana (1849) published brief notes following the Wilkes Expedition; but the only full account is that by Agassiz (1903). Agassiz's descriptions are, however, verbose and imprecise, and marred by misinterpretations of major atoll features. In the study of Tuamotuan atolls, a major reference point is provided by the reports of the 1952 Pacific Science Board Expedition to Raroia Atoll, led by N. D. Newell. Major reports resulting from this expedition are those of Newel1 (1953, 1956) on geology and geomorphology; Doty and others (1954), Doty and Morrison (1954), and blorrison (1954) on plant and animal systematics and ecology; Harry (1953) on ichthyology; and Danielsson (1954, 1956) on culture and econoinic life. More recently, Ranson (1962 and earlier papers) has published accounts ofllikueru and other atolls, and detailed work has been carried out in connection with the French weapons tests at Mururoa at the eastern end of the archipelago (Lalou and others 1966, Chauveau and others 1967)