V 



12 FERGUSON. 



THE LIMESTONE ISLANDS. 



The three limestone islands lie to the westward of the rest of the 

 Batanes and topographically are in marlced contrast to them. 



The island, of Ibujos consists entirely of coral limestone rising in steep 

 cliffs to a height of- over 60 meters. These surromid the island, excej^t 

 on the eastern side where the land rises gently from the fringe of sand 

 dunes and small ponds aroimd the shore, in contrast to the 300-meter 

 agglomerate cliffs of the island of Sabtan less than 2 kilometers distant. 

 (See PI. IX.) The surface of Ibujos is gently rolling, but without any 

 streams or definite stream valleys. This condition is partly due to the 

 solubility of the rock which allows water to run off in underground 

 channels, but it is also in large part an effect of the recent date of the 

 uplift, which has not allowed sufficient time for the streams to form 

 valleys. The soil seems to be volcanic ash rather than limestone. 



DESQUET. 



Desquey, a little island to the west of Ibujos, is entirely cliff-bound 

 and inaccessible, but otherwise seems to be exactly like Ibujos. 



Isbayat, the largest island of tlie group is likewise entirely surrounded 

 by cliffs, the only landings being steps cut in the rock in one place, and 

 a series of ladders in the other. From the deck of the steamer the cliffs 

 seemed to be similar to the limestone cliff of Diojo Point on the north 

 of Batan Island, and I am told by joeople who have visited the island 

 that the land slopes downward from the top of the cliffs toward the 

 villages which are situated in small '"sinks." This fact inclines me to 

 believe that Isbayat is formed of limestone, rather than that it is of 

 volcanic origin. The island is said to be the most fertile of the group, 

 but has a reputation for unhealthf ulness, the* natives of the other islands 

 suffering from fever . whenever they go there. Between Isbayat and 

 Batan, and in a less degree throughout all the islands, there are extremely 

 powerful and complex tidal currents which render the passage between 

 the individuals of the group extremely dangerous, so that almost the only 

 communication with the outside world is when an occasional steamer 

 takes on a load of cattle from the Isbayat pastures. 



SUBMARINE CONFIGDRATION. 



The soimdings given on the chart are very few and these for the most 

 part (see map No. 3) do not reach to bottom, but record "no bottom" 

 at depths of from 35 to over 100 fathoms. However, meager as the 

 information is, it will be of interest to examine it in some detail. 



South of Botel Tobago there seems to be a bench of al^out 100 fathoms 



