ERUPTION OF TAAL VOLCANO. 77 



years, according to the natives, and the former escape of gas was unknown 

 to them. Abella analyzed the water from San Eaymundo, the flow of 

 which he related to Taal Volcano, and found the following main mineral 

 constituents : 



Constituent. ^^^\^^^ 



Free carbonic acid 0.36 



Calcium bicarbonate 0.58 



Magnesium bicarbonate 0.13 



Sodium sulphate 0.11 



Sodium chloride 0.31 



Ferrous arsenate Trace. 



The temperature of the spring was 32°. The trace of arsenic com- 

 pounds is interesting because of their frequent association with mineral 

 veins. 



In speculating as to the probable origin of this carbon dioxide, an 

 observation made by Adams ^- while studying this region, claims atten- 

 tion. "In making an excursion south of Lemer}- along the beach to 

 Point Ligpo, a limestone was found included by basalt and evidently 

 metamorphosed by contact with the igneous rocks into a Yery dense 

 stone. A peculiarity of this limestone * * * ^^^^^ ^^^ presence of 

 small cavities, or druses, lined with clear quartz crj'stals." Point Ligpo 

 is only a few kilometers from Lemer}^ and it is not improbable that 

 similar basalt flows or intrusions underlie the adjacent valley where these 

 fissures formed. Local coral reefs may have been built during the 

 intermittent deposition of volcanic tuff and now be covered by later beds. 

 In any case inclusions of limestone, metamorphosed and subjected to 

 the action of mineral-bearing waters, would probably evolve carbon 

 dioxide and such action along the plane of recent Assuring woiild account 

 for the escape of carbon dioxide. 



CHANGES IX ELEVATION. 



The subsidence of the lower Pancipit Yalley (evidently the upper part 

 of the valley did not subside) has been mentioned. The extent of this 

 subsidence can not be given exactly but was probably not greater than 3 

 meters at any place. About 1 kilometer of macadamized road west of 

 LemeiT is now covered at high tide with perhaps 50 centimeters of water. 



It is estimated that this road was formerly from 1 to 2 meters above 

 high tide. There is an apparent subsidence of a few centimeters on the 

 west side of the fissure which opened in Talisay. 



The most striking subsidence noted was that of Volcano Island itself. 

 Here it was general around the whole perimeter, amounting to more than 

 3 meters in places. Longos Point was cut in two and the resulting 

 small island is separated by water a meter in depth from the main island. 



"This Journal, Sec. A (1910), 5, 100. 



