208 Philippine Journal of Science 1917 
mineral content was derived would certainly not be favorable for 
plant growth. 
In order to determine something of the chemical character of 
the soil at the present time, we collected samples from the sur- 
face soil to a depth of 10 centimeters at the crater rim, in the 
grass area at the north end of the island, and in a tree-covered 
area on the northern slope of Mount Pirapiraso. A partial 
analysis of these soils was made for us by Mr. A. S. Argiielles, 
of the Bureau of Science. The results are given in Table II. 
None of the soils contained appreciable amounts of chlorine. 
Those from the crater rim and the grass ar 6 a showed very ex- 
cessive quantities of soluble sulphates. The humus and nitrogen 
content of the soil at the crater rim is extremely low; that of 
the grass area is much too low for a good soil ; while even that 
of the tree-covered area is considerably lower than the average 
for Philippine soils. 
The above-mentioned soil samples from the grass and the tree- 
covered areas contained plant roots. In the same grass area an- 
other sample of soil was taken under the roots at a depth of from 
7 to 25 centimeters. The humus and nitrogen content was con- 
siderably lower than that for the surface layers, while the soluble 
sulphate content was very much lower. Another sample, taken 
on the upper slopes of the crater at a depth of from 5 to 25 centi- 
meters, showed about the same percentage of humus as the sur- 
face sample, while the nitrogen content was even less. 
Determinations of soil acidity (Table II) were made on sam- 
ples of soil from the crater slopes and from the grass-covered 
area at the northern end of the island. In each case the acidity 
is very high, while that of the soil on the slopes of the crater 
is so extreme (0.155 per cent) that we would expect it to be 
very harmful to the vast majority of plants. 
The chemical analysis just discussed certainly indicates that 
the soil of most of Volcano Island would form a very poor sub- 
stratum for the growth of plants. 
There is considerable evidence to show that water-soluble 
materials have been taken from the soil of Volcano Island at 
a fairly rapid rate. The land near the northwestern part of 
Bombon Lake near Ambulong is composed of nearly horizontal 
beds of water-laid volcanic tuff through which there is a great 
seepage of water. An analysis of a sample of water taken from 
a large spring in the volcanic tuff at Ambulong (Table III) 
” Pratt, W. E., Philippine lakes, Philip. Journ. Sci. All (1916) 223-237, 
pi. I. 
