XII, C, 4 Brown, Merrill and Yates: Volcano Island 183 
was violent owing to its movement and suffocating owing to its heat, its 
_ burden of mud, and a content. of sulphur dioxide, 
This blast broke the trees and ground the bark to shreds 
(Plate VII, figs. 1 and 2). Pratt says: 
The odor of sulphur dioxide was strong during the eruption and probably 
this gas or its oxidation product was effective in killing vegetation. 
The fall of ash was apparently not particularly heavy. Ac- 
cording to Pratt— 
The greatest fall of material within the devastated area was on the west 
slope of the volcano. The maximum thickness of 2 meters noted here 
occurred where the ash and small fragments had drifted into an old water 
course. However, the ridges adjacent were all but bare, and therefore an 
estimate of 20 to 30 centimeters for the average maximum depth of fall for 
this vicinity is probably reasonable. 
Concerning the temperature of the ejecta he writes: 
With the exception of the small number of incandescent stones, ejecta 
from this eruption were apparently not much hotter than boiling water. 
The mud appears to have been very injurious to vegetation 
as is shown by the following statement made by Cox:"* 
While a considerable amount of coarse material fell on the island, the 
mud that was carried to a distance was comparatively finely divided, and in 
this respect not greatly unlike road dust. The mud was cool wherever its 
fall was observed, and it descended in the manner of rain, without violence. 
Leaves retained only a thin coating on their upper surfaces, yet within 
a few hours. many of them had fallen. Ordinary road dust may fall on 
plants to any thickness without serious injury. 
Cox gives an analysis of ash collected on the island shortly 
after the eruption. According to this writer, nothing was found 
that should be injurious to plants. He believed, however, that 
this analysis did not give a correct idea of the composition of 
the ash at the time of its fall, and says that there were two pos- 
sible sources of injuries to plants, namely, sulphuric acid and 
large quantities of salts of iron, which are often popularly called 
sulphur. These salts give free acid by hydrolysis when in 
solution. Worcester lays great stress on injuries done by acid. 
Subsequent examination of the island showed that the vegeta- 
tion was very largely destroyed. In the extreme northern part 
the destruction was less complete than elsewhere. Plate VIII, 
fig. 1, shows the site of the former village of Pirapiraso just after 
the eruption. The town is obliterated, while the aérial parts of 
the vegetation appear to be dead. The ground on the steeper 
* Cox, Alvin J., The composition of the fine ejecta and a few other in- 
organic factors of Taal Volcano, Philip. Journ. Sci. A 6 (1911) 93-97. 
