22 FERGUSON. 



the boats across the reef at high tide^ often a dangerous proceeding. 

 However, tlie barrier reef reaches its greatest development on the eastern 

 shore of Ibujos ; there it has a width of nearly a kilometer, and is 

 unbroken by any inlets. On the west shore there is no coral and the 

 limestone clifls sink sharply into deep water. The same is true of the 

 cliff-bound island of Desquey. 



VTJLCANISM. 



Volcanic activity may be regarded as a physiographic accident, inter- 

 fering with, but independent of the normal cycle of uplift, erosion and 

 ultimate peneplanation. In the history of the Batanes, vulcanism has 

 played an important part. The islands themselves owe their origin to 

 volcanic outbursts of some kind and volcanic activity has been a factor 

 in all stages of their history. There seem to have been periods of lava 

 eruption during the time that explosive outbursts were building up the 

 agglomerate mass. This is shown by the andesite of Xatao Point, which 

 may be a flow. The lavas which have extended from the Batanes volca- 

 noes are all basic, consisting of andesites and basalts, and although no 

 general series can be made out, the more recent of them seem to be the 

 more basic. 



Volcanic activity during the period of pre-Miocene degradation, is 

 shown by the dikes which cut through the agglomerate, particularly near 

 Ajao Point in Sabtan. During the time of uplift, the locus of volcanic 

 action seems to have shifted to the east and north, building up the 

 Siayanes, Inem and Iraya. Activity gradually died out, first at the 

 north, and now the only volcano of a chain of three and possibly four 

 which retains its symmetrical form is Mount Iraya, with its double (or 

 triple) crater indicating long periods of quiescence between those of 

 activity. The present interval of quiescence has lasted so long that 

 the volcano has passed through the solfataric and hot-sf)ring stage, 

 the center of activity having shifted still farther to the southward, to the 

 Babuyanes Islands. The history of the Batanes Islands may be looked 

 upon as a constant struggle of the land for its existence, with vulcanism 

 and coral reef-building in opposition to marine, and to a less degree, 

 stream erosion, uplift and depression being the factors really controlling 

 the struggle. 



HUMAN RESPONSE TO PHYSIOGRAPHIC CONDITIONS. 



The natives of Batan and Sabtan were divided into three warring clans 

 whose boundaries depended upon topographic features before the coming 

 of the Spaniards and the abandonment of their savage life. In Sabtan, 

 where communication is easy on the east coast, the people were united 

 under one chief. Batan, on the other hand, having a natural barrier in 

 the range running west from Mabatuy point was divided into two clans. 

 The earlier village-forts were naturally built upon commanding eminences, 



