i 5 4 A NATURALIST IN THE PACIFIC chap. 



the east with the Thambeyu or Mount Thurston Range by a 

 broken chain of mountains, of which Koro-mbasanga is the most 

 conspicuous. It is connected by an elevated col with Mount 

 Mbatini and the Mariko Range to the southward. The name of 

 Koro-tini has been applied to this range because it is familiar to 

 the natives. It signifies " ten towns," and was given to a once 

 populous district on the slopes of the lofty bluff overlooking on 

 the north the mouth of the Ndreke-ni-wai. I crossed the range in 

 four places, namely, between Waisali and Sealevu, between Mbale- 

 mbale and Vandrani, between Vatu-kawa and Vandrani, and 

 between Nukumbolo and Sueni. 



(i) Traverse of the Koro-tini Range from Waisali 

 TO Sealevu. — Starting from Waisali by the Narengali track, I 

 ascended the east slope of the Waisali Saddle, as described on 

 page 146, until an elevation of about 750 feet was reached, when 

 my way lay to the northward across the Koro-tini Range to 

 Sealevu. At 850 feet a singular altered tuff was displayed in 

 position in a stream-course. It shows calcite and pyrites, and is 

 interesting from the fact that although it is made up largely of 

 basic glass the tuff does not seem to have undergone the pala- 

 gonitic change. 



Afterwards, there was a fairly steep ascent to the summit of 

 the range, 2,400 feet above the sea, which has merely a ridge-like 

 crest. Between an elevation of 1,400 feet and the top there are 

 exposed at the surface compacted coarse and fine palagonite-tuffs 

 and agglomerate-tuffs formed of the same materials. They contain 

 often abundant organic remains, such as valves of " Cardium " and 

 " Pecten " shells, macroscopic tests of Foraminifera, and some 

 curious scale-like bodies, showing a concentric structure and about 

 an inch across, which look like fish-scales. It is probable that these 

 interesting rocks extend to a greater elevation than 2,400 feet, 

 which was merely the highest level reached in the traverse, but is 

 not the highest point of the range. 



These deposits are made up in mass of a more or less 

 palagonitised basic glass originally containing phenocrysts of 

 plagioclase and pyroxene. The palagonitic process is nearly 

 always far advanced ; but it is seen in all its stages, the least 

 altered materials fusing under the blow-pipe into a black glass. 

 The fragments are usually sub-angular in the case of the coarse 

 tuffs ; but small rounded pebbles up to half an inch in size and 

 fine water-worn gravel are not infrequent. The matrix is composed 

 of palagonitic debris, portions of crystals of plagioclase and 



