182 "ALBATROSS" TEOPICAL PACIFIC EXPEDITION. 



to half a mile in width, giving the western ridge the appearance of being 

 flat-topped (PI. Ill, fig. 1), while the eastern ridge is only here and there 

 flat-topped (PI. 114). As we steamed around the southern point, we could 

 look up into the divide of the central basin between the slopes of the par- 

 allel ranges, and look into the drainage basin which occupies the central 

 part of the island (PI. 212, fig. 4). 



It is quite probable that the central part of this basin was once occupied 

 by a lake, or a pool, or finally a morass, such as still exists immediately back 

 of the gap, opposite English Roads, where the river has cut a deep canon 

 into the western ridge, perhaps as far as the third terrace. We can readily 

 imagine erosion and denudation to have gone on at such a rate that the 

 ridge flanking the central part of the basin may have been cut down, at 

 some period during its elevation, so that the opening should lead from the 

 English Roads into this basin, and change it into a huge sound. Thus 

 might have been formed an interior lagoon of comparatively small size as 

 compared with the rest of the island, similar to that of Nomuka, having, 

 nothing to do with elevation or subsidence, and yet resembling in every 

 respect what is called a raised atoll, similar to some of those we have 

 described. 



While this was taking place, the range on the east side would j^robably 

 still be continuous, and its highest points rise to perhaps 400 or 500 feet, 

 while on the west the various gaps to be seen between the flat-topped 

 summits would have widened out into huge openings, and the western 

 slopes changed into a reef flat, varying in width from half a mile to one and 

 a half miles, the highest point of the western ridge rising perhaps to 200 or 

 250 feet on the western face. On the southern face a deep indentation, 

 which might or might not have been connected with the central basin, 

 Avould occupy the place now taken by the more gentle slopes of the two 

 ridges flanking the central basin on the southern side of the island. 



At the south point there are four very distinct terraces, and the fifth 

 and sixth, which rise to a height of 1036 feet, can be traced somewhat 

 indistinctly. Vertical cliffs extend north in continuation of the fourth 

 terrace, along the eastern face ; those rising from the shore are cut back 

 generally to the top of the third terrace. At the northern point the island 



