BY W. G. WOOLNOUGH. 447 



to the Medrausucu Range. This suggests that they occupy lines 

 of weakness (possibly faults) at right angles to the dominant 

 topographic line of weakness expressed by the said range. There 

 is strong evidence for considering both streams as antecedent to 

 the range, and for supposing that the Navua River was formerly 

 continuous with the Waidina. The breaking of connection took 

 place through a heavy fault along the line at present occupied 

 by part of the Wainikoroiluva, leaving a " horst" between that 

 stream and the Medrausucu Range. Most of the evidence for 

 these movements is topographic in character, but is none the less 

 extremely suggestive. The changes must have been very recent. 

 Granite areas are proved to exist as a basement under the 

 Korobasabasaga, and further south at the head waters of the 

 Waimanu. 



iv. — Wainivalaii Valley. 



I made a journey from Nabukaluka on the Waidina to 

 Narokorokoyawa, our headquarters, along the valley of the 

 Wainivalau. A prospector, Mr. Harding, traversed part of this 

 region, but I was informed that no white man has previously been 

 right across it. Owing to the dangerous nature of the numerous 

 river-crossings (fords they cannot be called) I was compelled to 

 pack up my field book and instruments, and allow a native to 

 carry them. My notes on this portion of the island were there- 

 fore written up from memory three days after traversing it. 



From the gorge to Nadakuni, the stream hugs the eastern base 

 of the Medrausucu Range; thence it turns eastwards and enters 

 the Waidina just below Nabukaluka. Its bed is not so wide as 

 that of the Waidina, but I believe its volume is nearly as great, 

 a fact already commented on in connection with its probable 

 piracy of the head waters of the Waieliu. It enters the main 

 stream with a very swift current, and at quite a noticeable grade; 

 and as is usual under such circumstances, the bed of the Waidina 

 for some -miles above and below the junction, is very much 

 choked with coarse alluvial deposits. About a mile above 

 Nabukaluka, convex curves of the two streams approach 

 within an eighth of a mile of one another. As the divide is of 

 34 



