68 FOYE. 



The author studied the basaltic body (see Figure 32) and concluded 

 that it was a dike, but saw no direct evidence of out-welling flows. 

 The summit of the hill represents the outcrop of the dike. The 

 coarsely vesicular character of the mass would indicate that the 

 injected mass was here close to the surface. The dike is the more 

 remarkable for this very fact. It is 250 to 300 feet thick, strikes 

 about N. 70° E. and dips 55° S. E. It may be traced for 600 to 700 

 yards along the northwestern side of the island. Limestone was seen 

 on both hanging wall and foot wall. There was no evidence of con- 

 tact alteration of the limestone. The vesicles of the contact basalt 

 are large and very fresh-looking. If they had even been subjected 

 to water circulation below the sea-level, they would probably have 

 been filled with calcitic or chalcedonic amygdules, but they were 

 found to be entirely empty. The freshness of the rock as a whole 

 and the absence of amygdules point to the probability that the dike 

 was intruded later than the uplift of the island. 



The question arises whether the dike magma ever reached the sur- 

 face. The dike projects as a lone ridge, the highest point on the island, 

 and dips away inland, presenting a steep escarpment to the sea. The 

 face of the escarpment is the continuation of a very straight line of 

 limestone cliffs forming the northern side of the island. It is believed 

 that the surface outflows from the dike, if they ever existed, are 

 invisible because faulted beneath the sea. The down-faulted block 

 includes a small, northern sector of the original island, measuring 

 about one mile in length and a quarter of a mile in width. The 

 faulting postulated is suggested by: — 



(1). The regularity of the northern face of the island across both 

 limestone and volcanic rocks. 



(2). The existence of a parallel escarpment on the adjacent island 

 of Wangava. 



(3). Depths reaching as much as 150 fathoms at points close to 

 the shore. 



(4). The abrupt termination of the barrier reef on the east and the 

 west. 



(5). The improbability that the long scarp is a wa\e-cut cliff, 

 since it is situated on the leeward side of the island and since a distinct 

 wave-cut bench at the foot of the scarp is lacking. 



It appears, therefore, that after the uplift of the island, the (Hke was 

 intruded and then the island was diminished by down-faulting on the 

 north. 



The reef about Kambara is fringing for most of its length, but has 



