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and periodically subject to droughts, rains, heavy floods, inun- 
dations, and denudations. Some of the lagoons become dry, 
and the thick mud at the bottom, when in a moist state, 
incloses alligators and other amphibious reptiles during the 
dry season. They remain entombed like eels, in a somewhat 
dormant state, and come to life again in the rainy season if the 
dry lagoons be not in the interim, too thickly covered by 
gravel. In the upper regions during the rainy seasons land- 
slips occur daily, and large masses of forests and trees of 
colossal dimensions are brought down, and the banks of the 
rivers and the lower plains become frequently strewed over 
with the debris. Some of the large marshes and lagoons are 
often changed in a day into plains of gravel, and the sandy 
plains are converted into lagoons teeming with life. The delta 
of the Am azon exposed to these periodical floods comprises 
an area equal to one-half of England. 
I remember a great flood and an avalanche which occurred on 
February 19th, 1845, on the eastern flank of the central Andes. 
Immense masses of ice and boulders gave way on the upper 
part of the Paramo de Ruiz, in latitude 5° north, and came 
down the ravines in awful torrents of muddy water, with ice, 
large granitic and porphyritic boulders, broken fern-trees, &c., 
laying waste many square leagues of the hot plains below. 
The destruction of human beings, animals and property was 
immense. Two or three rivers in the plains were choked, and 
their channels changed; and over many square miles of the 
fertile plains were deposited several feet of sand and gravel, 
inclosing trunks of trees belonging to the upper cold regions 
mixed with those flourishing in the hot countries below. The 
tobacco, sugar and guinea-grass plantations were completely 
destroyed, and upwards of 1,000 natives perished by this 
glacial deluge, or avalanche, in less than twelve hours. The 
quantity of sand and gravel deposited on that day was esti- 
mated at upwards of 250 millions of tons. The ice and 
boulders brought down from the snowy region to the hot 
plains below killed a very large quantity of fish and reptiles. 
The beds of sand and gravel may be still seen occupying a 
very large area, and in places clothed with rank vegetation, 
but the catastrophe is almost forgotten amongst the inhabit- 
ants. Were an ardent young student of geology, trained in 
the recently-accepted geological theory, to visit this district 
now, and examine the formation, he might possibly conclude 
that it belonged to the glacial period, and was of very remote 
antiquity. I could mention various and extensive changes 
which have taken place in the interior and along the coast of 
South America since the Spanish conquest, but I need not 
