66 Account of the Floating Island 
at the depth of about four feet under water. 
A quantity of air or gaseous matter is distri- 
buted through the whole substance of the 
island; but not pretending to determine the 
particular species, I contented myself with 
ascertaining it to be inflammable. The thick- 
ness of earth, as before observed, is about six’ 
feet, under which is water of a depth corres-, 
ponding to the height that the island has risen; 
in some places three, in others six feet, and 
more when the water is high: at the bottom: 
of this subterranean water is found a very fine. 
soft, whitish substance; the resemblance of 
which to peat ashes, almost persuaded me that, 
vegetable matter may, under peculiar circum, 
stances, be converted toa similar state, with= 
out a perceptible combustion. At the depth, 
of eighteen feet, the clay becomes very, inti 
and not easily penetrated. 
After an absence of eight years, it press 
about the 20th of July 1808, and increased: 
for a few days till it might be about eighty, 
yards in length, it then remained with little 
alteration for some weeks ; although the depth 
-of the lake varied during the time, its height 
above water continued much the same, (viz. 
about a foot;) it then lowered gradually 
for some time, till the beginning of October, 
when a flood covered it, and it was seen no 
more till the year 1813, when it rose about 
