468 ADAMS AND PRATT. 



confusion in regard to the "lava flows" of Mayon probably has resulted 

 from loose visage of the term. During this reconnaissance made around 

 the base of the volcano, special attention was given to the character of 

 the materials which descended during the eruption of 1897. No molten 

 lavas reached the sea or the base of the cone as sometimes has been 

 stated. It is probable that molten lavas issued only from near the 

 summit and seldom descended more than one-third of the slope before 

 cooling. The lower part of the lava flows mapped by Coronas consisted 

 of fragmental materials containing large angular masses of solidified 

 lava. It is reasonable to suppose that most of the ejectamenta fell 

 near the summit of the cone and that the lavas which were poured out 

 cooled on the unstable materials of the slopes of the volcano, and tmder 

 the influence of gravity the accumulations broke down and descended 

 in the form of rock streams or avalanches while they were still hot 

 and in part incandescent. The lines of the descent were in many 

 cases along the deeply eroded water courses. On Coronas's map, from 

 which ,text figure 3 is adapted, the paths of descent, called lava flows, 

 correspond in most cases with the drainage. 



Tiui Hot Springs. — The most noted hot springs of this region are 

 near Tiui; they have been described by Jagor, von Drasche, and Abella. 

 Abella considered them as subordinate volcanic emanations of Malinao. 



Hot water accompanied by sulphurous gas issues at a place termed Jigabo, in 

 the bed of a small stream, the Naga. This place has the nature of a fumorole. 

 The stones in the river bed have been largely decomposed by the chemical 

 action of the waters, and the ground and stones in places are coated with a 

 sulphurous efflorescence. This spot^ is but a short distance to the west of 

 Tiui. A small bath house has been constructed, and a pit walled up with 

 stones serves as a pool for bathing. The temperature of the bath is regulated 

 by conducting the desired amount of cool water from the stream into the ditch 

 which leads the hot water to the pool. Farther up the stream there is a place 

 where some gases emanate from the groimd and the water is somewhat mineral- 

 ized. Naglagbong, which lies down the stream, is the principal point at which the 

 hot waters of Tiui are found. There is a pool about 20 meters in diameter 

 filled nearly to the rim with water, which steams very slightly. Around it 

 there is a white, silicious deposit which shelves out over the water. The pool 

 is transparent, and in the depths the water has beautiful, blue colorings, and 

 fantastic, silicious deposits may be seen forming the sides of the basin and the 

 narrow, irregular opening in the bottom. There is white, silicious sinter near by, 

 covering a considerable area and grading ofif into bluish mud. Many minute 

 cracks and vents occur in the sinter, from which small quantities of sulphurous 

 gas, mixed with steam, arise. 



The water near by in the shallow pools is hot, and bubbles of gas break on 

 its surface at some places. The silicious sinter has been built up in a low, 

 irregular, convex area on which there is what is termed the white cone. This place 

 at one time must have contained a central opening in which the hot waters arose. 

 The silica deposited from the water gradually built a rim around the opening and 

 then sealed its mouth, leaving a small basin-like depression on the top. To the 

 northwest on the white cone, there is another large pool of hot water and beyond 



