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SCIENCE. 



[N. S. Vol. XI. No. 269. 



deyelopment in the Lau G-roup of the Fijis 

 or the Paumotus. The first island of the 

 Tongas we visited, Eua, is perhaps the most 

 interesting of the islands composed of ter- 

 tiary elevated coralliferous limestone I 

 have visited. From Dana's account of it, 

 evidently given at second hand, I expected 

 to find an island somewhat like Viti Levu 

 on a very much smaller scale. But as we 

 steamed up to it from the east there could 

 be no mistaking the magnificent face of 

 nearly vertical limestone clififs forming the 

 whole eastern face of the island, and at 

 points rising to over a thousand feet in 

 height. At all projecting points lines of 

 terraces were plainly marked ; at the 

 northern point three could be followed, 

 and at the southern extremity five, with 

 perhaps traces of a sixth. 



Upon rounding the southern extremity 

 of the island we could see that the island 

 was composed of two ridges, running north, 

 separated by a deep valley, the western 

 ridge being much lower than the eastern, 

 not rising to a greater height than a little 

 over 500 feet. The western ridge is also 

 composed of limestone, and at the head- 

 lands we could trace three terraces. There 

 is a narrow shore-platform along the 

 western face, at many points of which 

 there are blow-holes where the sea throws 

 up spray to a considerable height, but these 

 blow-holes are best seen off Cook Point, 

 the southern extremity of Tonga-Tabu. 



As we steamed along the western face of 

 Eua Island, we could see the ridges of the 

 eastern side rising above the crests of the 

 lower ridge, its slopes indicating a valley of 

 considerable size. We anchored at English 

 Roads, opposite the outlet of the drainage of 

 the interior basin where a small river has 

 cut its way through a depression in the 

 shore terrace. On landing we followed the 

 crest of the western ridge for a few miles 

 and could see the whole valley forming the 

 basin of the island lying between the two 



ridges, at our feet ; the slopes leading to 

 the bottom are quite gentle, and the valley 

 dips very gradually northward back of the 

 outlet, on the western shore. Nothing 

 could show more clearly that such an island 

 was not an elevated atoll, but a plateau 

 which has been eroded and denuded for a 

 long period of time by atmospheric and 

 other agencies, and in which a deep basin- 

 shaped valley with gentle slopes has been 

 gouged out— a plateau similar to that of 

 Tonga-Tabu Island and of Vavau, but of 

 greater height and less extent. 



To the westward of the Tonga Islands is 

 a line of volcanic islands extending nearly 

 200 miles from Honga Hapai to Fanualai, 

 some of which have been active very re- 

 cently. Falcon Island disappeared in 1898 

 and Lette is still active. This line of vol- 

 canoes runs at a distance of from 15 to 20 

 miles parallel with the trend of the four ir- 

 regularly shaped plateaus upon which rise 

 the Tonga Islands. They are the summits 

 of a great ridge over 200 miles in length, 

 sloping very gradually to the westward and 

 being somewhat more steep to the eastward, 

 into deeper water, towards the smaller plat- 

 forms from which rise the volcanic peaks of 

 the group. The plateaus of Tonga- Tabu, 

 Namuka, Hapai, and Vavau, being sepa- 

 rated by deep valleys connecting the eastern 

 and western flanks of the ridge. These 

 four plateaus rise abruptly from the 100 

 fathom line. The extremity of the south- 

 ern one is occupied by Tonga- Tabu Island. 

 The land behind the cliffs of its southern 

 coast rises to a height of over 250 feet and 

 slopes northward very gradually to form the 

 low land which occupies the north coast of 

 the island, and is, except, at Mount Zion 

 and Cook Hill, not more than from 10 to 20 

 feet above the level of the sea. At Cook 

 Point (and along the southern coast) three 

 terraces are indicated. The northern coast 

 is deeply indented by shallow bays, full of 

 islands, reef flats, and reef patches, on 



