598 MR. J. J. LISTER ON THE GEOLOGY 



Kotu and Matnlvii, which, as seen from the sea, appeared to me to 

 be of the same nature as those above described in the Nomuka 

 group. The only confirmatory evidence that I can offer is a 

 remark on the island of " Kotoo " in the narrative of Capt. Cook's 

 Voyage to the jN^orthern Hemisphere (vol. i. p. 271), where it is 

 stated that this island '* terminates in reddish clayey cliffs." 



Leaving the Hapai Group, I will now attempt to describe the 

 island of Eua, lying to the south-east of Tongatabu, (For the map of 

 this island, see PI. XXIII.) Eua is somewhat oval in shape, but 

 pointed at the two ends ; the long axis is directed almost exactly 

 north and south. It is about 12| miles long, rather more than 4 

 miles broad, and attains a height of 1078 feet. The island is 

 formed of a basis of volcanic rock, in great part covered by lime- 

 stone. A ridge of high ground traverses the island from north to 

 south, attaining a height of over 1000 feet at two points, one near 

 the middle of the ridge, the other about four miles to the south. 

 Eetween these two points the general level of the ridge is from 800 

 to 1000 feet. The volcanic formation comes to the surface over a 

 great part of this high ground, and where it is bare of vegetation is 

 readily recognized by its bright red colour; but patches of limestone 

 occur in many places, sometimes in large projecting masses, like 

 that which forms the south summit, sometimes weathered down 

 into groups of isolated pinnacles standing on the volcanic basis. 



Xorthward the ridge descends gradually to an elevation of 

 about 500 feet and extends at this level, as a long flat-topped 

 plateau or terrace, to the north end of the island. This will be 

 referred to as terrace h. The volcanic basis appears in irregular 

 patches along the centre, but its eastern and western sides are 

 bordered by cliffs of limestone, some 200 feet in height, whose 

 base evidently marks an old shore-line at a previous stage of eleva- 

 tion of the island. 



The whole eastern side, presented to the trade wind, is very 

 abrupt, and rises in range above range of limestone-cliffs, the 

 steep slopes between them being covered with dense wind-swept 

 forest. The descent is interrupted along the greater part of this 

 aspect by a narrow terrace, from which on the one hand perpendicular 

 cliffs descend to the sea, and on the other a slope of debris leads to the 

 foot of the range of cliffs which limit the central ridge along its 

 whole length. This terrace is, however, absent opposite the middle 

 of the eastern aspect, and here a steep slope extends directly from 

 the foot of the higher range of cliffs to the sea. The volcanic 

 basis is exposed on this slope, and at the shore are projecting 

 dykes of intrusive rock. Farther to the south the terrace is again 

 interrupted by a break occupied by a small terrace at a lower 

 level. At this point also a dyke appears on the shore at the foot of 

 the cliffs. 



Along its western aspect the central rilge is well-defined at the 

 northern and southern ends, being bordered by limestone cliffs. 

 The middle part of this aspect is broken up by small valleys which 



