6 
CHANGES OF LEVEL. 
soil between Valencia and G-uigue, the little hills rising 
abruptly in the plain east of the Cafio de Cambury, some ot 
which (el Islote and la Isla de la ISTcgra or Caratapona) 
have even preserved the name of islands, sufficiently prove 
that the waters have retired considerably since the time of 
Oviedo. "With respect to the change in the general form 
of the lake, it appears to me improbable that in the seven- 
teenth century its breadth was nearly the half of its lengthy 
The situation of the granite mountains of Mariara and of 
Gruigue, the slope of the ground which rises more rapidly 
towards the north and south than towards the east and 
west, are alike repugnant to this supposition. 
In treating the long- discussed question of the diminution 
of the waters, I conceive we must distinguish between the 
different periods at which the sinking of their level has 
taken place. Wherever we examine the valleys of rivers, or 
the basins of lakes, we see the ancient shore at great dis- 
tances. No doubt seems now to be entertained, that our 
rivers and lakes have undergone immense diminutions ; but 
many geological facts remind us also, that these great 
changes in the distribution of the waters have preceded all 
historical times; and that for many thousand years most 
lakes have attained a permanent equilibrium between the 
produce of the water flowing in, and that of evaporation and 
filtration. Whenever we find this equilibrium broken, it 
will be well rather to examine whether the rupture be 
not owing to causes merely local, and of very recent date, 
than to admit an uninterrupted diminution of the water. 
This reasoning is conformable to the more circumspect 
method of modern science. At a time when the physical 
history of the world, traced by the genius of some eloquent 
writers, borrowed all its charms from the fictions of imagi- 
nation, the phenomenon of which we are treating would 
have been adduced as a new proof of the contrast these 
writers sought to establish between the two continents. 
To demonstrate that America rose later than Asia and 
Europe from the bosom of the waters, the lake of Tacarigua 
would have been described as one of those interior basins 
which have not yet become dry by the effects of slow and 
gradual evaporation. I have no doubt that, in very remote 
times, the whole valley, from the foot of the mountains of 
