EOTA. 377 



after examining the charts of the Ladrones to find that Rota, as well as 

 Guam, consisted of elevated coralliferous limestone. The western extremity 

 of Rota is formed by a long rectangular peninsula ; its terraces are most 

 distinctly marlced and five periods of elevation are clearly to be distin- 

 guished (PL 199, fig. 2). The western peninsula is connected by a narrow 

 neck with the main island (PI. 233, fig. 5), a huge mass of coralliferous 

 limestone sloping equally in all directions, but most distinctly terraced 

 (PI. 199). In Sosanjaya Bay and off the northwestern shore of Rota the 

 island is flanked by a narrow reef fiat (PI. 233, fig. 5). The outliers and 

 horse-heads on the western shore (PL 233, fig. 5) indicate the amount of 

 erosion to which this island has been subjected. 



On Rota the terraces marking the successive elevations of the southern 

 Ladrones are admirablj^ preserved. At a distance of three miles off shore 

 five terraces conhl be distinguished. The summit of the island is ahiaost 

 level (Pis. 199, fig. 2; 233, fig. 5). Coming from the south we could see 

 no indication of any volcanic outbursts. The spit forming the southwestern 

 extremity of Rota, separating Sosanlagh and Sosanjaya Bays, also shows 

 remarkably well-defined terraces (PI. 199, figs. 1, 2). There are four of 

 these on the southernmost spit, and, when facing the main island, at least 

 seven terraces are plainly indicated. The face of the southern spit is riddled 

 with caves (PL 199, fig. 2). The lower terrace is deeply undercut, showing 

 traces of two stages of elevation, one not more than three or four feet, 

 identical in height vi^ith the low terrace described at Cabras Island. Look- 

 ing across the low land separating the southern promontory of Rota from 

 the main island, we could see numerous caverns in the vertical face of the 

 cliffs oi: the main mass of Rota. As we steamed north we observed that 

 the slope of tlie northwestern point, as well as the character of the vege- 

 tation, indicated a volcanic outburst at that extremity of the island (Pis. 199, 

 fig. 1 ; 233, fig. 5). 



It is probable that others of the southern islands of the Ladrones we did 

 not examine are, like Rota and Guam, elevated coralliferous masses forming 

 the summit of an extensive limestone plateau through which more recent 

 volcanic rocks liave burst at different points. After volcanic outbursts the 

 elevated coralliferous limestone beds have often been denuded and eroded 



