228 ^^6 Philippine Journal of Science isie 



of a former cone and concludes that the elevation of the tuff could 

 be explained more rationally as part of a raised fault block. 

 Mount Macolod on the southeastern shore of the lake, which had 

 also been considered as a part of the former volcano, Adams 

 found to be an eruptive mass unlike the fragmental tuff on the 

 other side of the crater and, therefore, not reasonably to be 

 accepted as part of the old cone. He accounts for the lake as the 

 result of peripheral faulting and subsidence around a volcanic 

 center which contained a number of vents, as evidenced by 

 historic eruptions in which activity manifested itself at several 

 points in the lake. 



The water in Taal Lake has a slightly brackish taste. The 

 following analysis, published by Cox,^ represents the composition 

 of a sample taken in 1905: 



Table I. — Analysis of water from Taal Lake. 



Parts per million. 



Silica (SiO,) 31.5 



Iron (Fe) and aluminium (Al) 4.2 



Calcium (Ca) 53.4 



Magnesium (Mg) 49.4 



Sodium (Na) 456.3 



Sulphuric ions (SOi) 191.3 



Chlorine (CI) 720.0 



Volcano Island and the shores of Taal Lake formerly sup- 

 ported a large population of fishing and agricultural people, but 

 since the eruption of Taal Volcano in 1911, when 1,335 people 

 were killed, permanent habitations are not permitted on the island 

 nor around parts of the lake perimeter. 



In connection with Taal Lake the crater lake within the vol- 

 cano should be mentioned. Prior to the eruption of 1911 the 

 crater of Taal Volcano contained several small lakes of hot 

 water, one of which was always boiling. After the eruption, 

 however, a single lake about 1 kilometer in diameter occupied 

 the crater. When the first descent into the crater was made 

 following the eruption, the surface of this lake stood 70 meters 

 below sea level," but subsequently it rose until at the present time 

 it is about at sea level. The water of this lake is hot (boiling at 

 places) and highly mineralized as is shown by the following 

 analysis by Cox.^^ 



• This Journal, Sec. A (1911), 6, 96. 

 "Ibid. (1911), 6, 78. 

 " Loc. cit. 



