DONE

la laguna de Valencia"* (* "Enormous body of the lake of Valencia."), fourteen leagues in length and six in breadth.
He affirms that at a small distance from the shore the lead finds no bottom; and that large floating islands cover the
surface of the waters, which are constantly agitated by the winds. No importance can be attached to estimates
which, without being founded on any measurement, are expressed in leagues (leguas) reckoned in the colonies at three
thousand, five thousand, and six thousand six hundred and fifty varas.* (* Seamen being the first, and for a long time
the only, persons who introduced into the Spanish colonies any precise ideas on the astronomical position and distances
of places,the legua nautica of 6650 varas, or of 2854 toises (20 in a degree),was originally used in Mexico and
throughout South America; but this legua nautica has been gradually reduced to one-half or one-third, on account of
the slowness of travelling across steep mountains, or dry and burning plains. The common people measure only time
directly; and then, by arbitrary hypotheses, infer from the time the space of ground travelled over. In the course of
my geographical researches, I have had frequent opportunities of examining the real value of these leagues, by
comparing the itinerary distances between points lying under the same meridian with the difference of latitudes.)
Oviedo, who must so often have passed over the valleys of Aragua, asserts that the town of Nueva Valencia del Rey
was built in 1555, at the distance of half a league from the lake; and that the proportion between the length of the
lake and its breadth, is as seven to three. At present,the town of Valencia is separated from the lake by level ground
of more than two thousand seven hundred toises (which Oviedo would no doubt have estimated as a space of a league
and a half); and the length of the basin of the lake is to its breadth as 10 to 2.3, or as 7 to 1.6. The appearance of the
soil between Valencia and Guigue, the little hills rising abruptly in the plain east of the Cano de Cambury,some of
which (el Islote and la Isla de la Negra 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 seventeenth century its breadth was nearly the half of its length. The
situation of the granite mountains of Mariara and of Guigue, 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 distances. 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 imagination, 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 Cocuyza to those of Torito and Nirgua, and from La Sierra de Mariara to
the chain of Guigue, of Guacimo, and La Palma, was filled with water. Everywhere the form of the promontories,
and their steep declivities, seem to indicate the shore of an alpine lake, similar to those of Styria and Tyrol. The same
little helicites, the same valvatae, which now live in the lake of Valencia, are found in layers of three or four feet thick
as far inland as Turmero and La Concesion near La Victoria. These facts undoubtedly prove a retreat of the waters;
but nothing indicates that this retreat has continued from a very remote period to our days. The valleys of Aragua
are among the portions of Venezuela most anciently peopled; and yet there is no mention in Oviedo, or any other old
chronicler, of a sensible diminution of the lake. Must we suppose,that this phenomenon escaped their observation, at a
time when the Indians far exceeded the white population, and when the banks of the lake were less inhabited? Within
half a century, and particularly within these thirty years, the natural desiccation of this great basin has excited
general attention. We find vast tracts of land which were formerly inundated, now dry, and already cultivated
with plantains,sugar-canes, or cotton. Wherever a hut is erected on the bank of the lake, we see the shore recedingfrom year to year. We discover islands, which, in consequence of the retreat of the waters, are just beginning to be
joined to the continent, as for instance the rocky island of Culebra, in the direction of Guigue; other islands already
form promontories, as the Morro, between Guigue and Nueva Valencia,and La Cabrera, south-east of Mariara; others
again are now rising in the islands themselves like scattered hills. Among these last, so easily recognised at a distance,
some are only a quarter of a mile,others a league from the present shore. I may cite as the most remarkable three
granite islands, thirty or forty toises high, on the road from the Hacienda de Cura to Aguas Calientes; and at the
western extremity of the lake, the Serrito de Don Pedro, Islote, and Caratapona. On visiting two islands entirely
surrounded by water, we found in the midst of brushwood, on small flats (four, six, and even eight toises height above
the surface of the lake,) fine sand mixed with helicites, anciently deposited by the waters. (Isla de Cura and Cabo
Blanco. The promontory of Cabrera has been connected with the shore ever since the year 1750 or 1760 by a little
valley, which bears the name of Portachuelo.) In each of these islands may be perceived the most certain traces of the
gradual sinking of the waters. But still farther (and this accident is regarded by the inhabitants as a marvellous
phenomenon) in 1796 three new islands appeared to the east of the island Caiguira, in the same direction as the
islands Burro,Otama, and Zorro. These new islands, called by the people Los nuevos Penones, or Los Aparecidos,* (* Los
Nuevos Penones, the New Rocks. Los Aparecidos, the Unexpectedly-appeared.) form a kind of banks with surfaces quite
flat. They rose, in 1800, more than a foot above the mean level of the water.It has already been observed that the
lake of Valencia, like the lakes of the valley of Mexico, forms the centre of a little system of rivers, none of which have
any communication with the ocean. These rivers, most of which deserve only the name of torrents, or brooks,*are twelve
or fourteen in number. (* The following are their names: Rios de Aragua, Turmero, Maracay, Tapatapa, Agnes
Calientes, Mariara,Cura, Guacara, Guataparo, Valencia, Cano Grande de Cambury, etc.) The inhabitants, little
acquainted with the effects of evaporation, have long imagined that the lake has a subterranean outlet, by which a
quantity of water runs out equal to that which flows in by the rivers.Some suppose that this outlet communicates
with grottos, supposed to be at great depth; others believe that the water flows through an oblique channel into the
basin of the ocean. These bold hypotheses on the communication between two neighbouring basins have presented
themselves in every zone to the imagination of the ignorant, as well as to that of the learned; for the latter, without
confessing it,sometimes repeat popular opinions in scientific language. We hear of subterranean gulfs and outlets in the
New World, as on the shores of the Caspian sea, though the lake of Tacarigua is two hundred and twenty-two toises
higher, and the Caspian sea fifty-four toises lower,than the sea; and though it is well known, that fluids find the same
level, when they communicate by a lateral channel.

The changes which the destruction of forests, the clearing of plains,and the cultivation of indigo, have produced
within half a century in the quantity of water flowing in on the one hand, and on the other the evaporation of the soil,
and the dryness of the atmosphere, present causes sufficiently powerful to explain the progressive diminution of the
lake of Valencia. I cannot concur in the opinion of M. Depons*(who visited these countries since I was there) "that to
set the mind at rest, and for the honour of science," a subterranean issue must be admitted. (* In his Voyage a la Terre
Ferme M. Depons says, "The small extent of the surface of the lake renders impossible the supposition that evaporation
alone, however considerable within the tropics, could remove as much water as the rivers furnish." In the sequel, the
author himself seems to abandon what he terms "this occult case, the hypothesis of an aperture.") By felling the trees
which cover the tops and the sides of mountains, men in every climate prepare at once two calamities for future
generations; want of fuel and scarcity of water.Trees, by the nature of their perspiration, and the radiation from their
leaves in a sky without clouds, surround themselves with an atmosphere constantly cold and misty. They affect the
copiousness of springs, not, as was long believed, by a peculiar attraction for the vapours diffused through the air, but
because, by sheltering the soil from the direct action of the sun, they diminish the evaporation of water produced by
rain. When forests are destroyed, as they are everywhere in America by the European planters, with imprudent
precipitancy, the springs are entirely dried up, or become less abundant. The beds of the rivers, remaining dry during a
part of the year, are converted into torrents whenever great rains fall on the heights. As the sward and moss
disappear with the brushwood from the sides of the mountains, the waters falling in rain are no longer impeded in
their course; and instead of slowly augmenting the level of the rivers by progressive filtrations, they furrow, during
heavy showers, the sides of the hills, bearing down the loosened soil, and forming sudden and destructive inundations.
Hence it results, that the clearing of forests, the want of permanent springs, and the existence of torrents, are threephenomena closely connected together. Countries situated in opposite hemispheres, as, for example, Lombardy bordered
by the Alps, and Lower Peru inclosed between the Pacific and the Cordillera of the Andes, afford striking proofs of
the justness of this assertion. Till the middle of the last century, the mountains round the valleys of Aragua were
covered with forests. Great trees of the families of mimosa, ceiba, and the fig-tree, shaded and spread coolness along
the banks of the lake. The plain, then thinly inhabited, was filled with brushwood, interspersed with trunks of scattered
trees and parasite plants, enveloped with a thick sward, less capable of emitting radiant caloric than the soil that is
cultivated and consequently not sheltered from the rays of the sun. With the destruction of the trees, and the increase
of the cultivation of sugar, indigo, and cotton, the springs, and all the natural supplies of the lake of Valencia, have
diminished from year to year. It is difficult to form a just idea of the enormous quantity of evaporation which takes
place under the torrid zone, in a valley surrounded with steep declivities, where a regular breeze and descending
currents of air are felt towards evening, and the bottom of which is flat, and looks as if levelled by the waters. It
has been remarked, that the heat which prevails throughout the year at Cura, Guacara, Nueva Valencia, and on the
borders of the lake, is the same as that felt at midsummer in Naples and Sicily. The mean annual temperature of the
valleys of Aragua is nearly 25.5 degrees; my hygrometrical observations of the month of February, taking the mean
of day and night, gave 71.4 degrees of the hair hygrometer. As the words great drought and great humidity have no
determinate signification, and air that would be called very dry in the lower regions of the tropics would be regarded
as humid in Europe, we can judge of these relations between climates only by comparing spots situated in the same
zone. Now at Cumana, where it sometimes does not rain during a whole year, and where I had the means of
collecting a great number of hygrometric observations made at different hours of the day and night, the mean
humidity of the air is 86 degrees; corresponding to the mean temperature of 27.7 degrees. Taking into account the
influence of the rainy months, that is to say,estimating the difference observed in other parts of South America
between the mean humidity of the dry months and that of the whole year; an annual mean humidity is obtained, for
the valleys of Aragua,at farthest of 74 degrees, the temperature being 25.5 degrees. In this air, so hot, and at the
same time so little humid, the quantity of water evaporated is enormous. The theory of Dalton estimates, under the
conditions just stated, for the thickness of the sheet of water evaporated in an hour's time, 0.36 mill., or 3.8 lines in
twenty-four hours. Assuming for the temperate zone, for instance at Paris, the mean temperature to be 10.6 degrees,
and the mean humidity 82 degrees,we find, according to the same formulae, 0.10 mill., an hour, and 1 line for
twenty-four hours. If we prefer substituting for the uncertainty of these theoretical deductions the direct results of
observation, we may recollect that in Paris, and at Montmorency, the mean annual evaporation was found by
Sedileau and Cotte, to be from 32 in. 1 line to 38 in. 4 lines. Two able engineers in the south of France, Messrs.
Clausade and Pin, found, that in subtracting the effects of filtrations, the waters of the canal of Languedoc, and the
basin of Saint Ferreol lose every year from 0.758 met. to 0.812 met.,or from 336 to 360 lines. M. de Prony found
nearly similar results in the Pontine marshes. The whole of these experiments, made in the latitudes of 41 and 49
degrees, and at 10.5 and 16 degrees of mean temperature, indicate a mean evaporation of one line, or one and three-
tenths a day. In the torrid zone, in the West India Islands for instance, the effect of evaporation is three times as
much, according to Le Gaux, and double according to Cassan. At Cumana, in a place where the atmosphere is far
more loaded with humidity than in the valley of Aragua, I have often seen evaporate during twelve hours, in the
sun, 8.8 mill., in the shade 3.4 mill.; and I believe, that the annual produce of evaporation in the rivers near
Cumana is not less than one hundred and thirty inches. Experiments of this kind are extremely delicate, but what I
have stated will suffice to demonstrate how great must be the quantity of vapour that rises from the lake of
Valencia, and from the surrounding country, the waters of which flow into the lake. I shall have occasion elsewhere
to resume this subject;for, in a work which displays the great laws of nature in different zones, we must endeavour to
solve the problem of the mean tension of the vapours contained in the atmosphere in different latitudes, and at
different heights above the surface of the ocean.A great number of local circumstances cause the produce of
evaporation to vary; it changes in proportion as more or less shade covers the basin of the waters, with their state of
motion or repose, with their depth, and the nature and colour of their bottom; but in general evaporation depends only
on three circumstances, the temperature, the tension of the vapours contained in the atmosphere, and the resistance
which the air, more or less dense, more or less agitated, opposes to the diffusion of vapour. The quantity of water that
evaporates in a given spot, everything else being equal, is proportionate to the difference between the quantity of
vapour which the ambient air can contain when saturated, and the quantity which it actually contains.Hence itfollows that the evaporation is not so great in the torrid zone as might be expected from the enormous augmentation
of temperature; because, in those ardent climates, the air is habitually very humid.

Since the increase of agricultural industry in the valleys of Aragua,the little rivers which run into the lake of
Valencia can no longer be regarded as positive supplies during the six months succeeding December. They remain dried
up in the lower part of their course,because the planters of indigo, coffee, and sugar-canes, have made frequent
drainings (azequias), in order to water the ground by trenches. We may observe also, that a pretty considerable river,
the Rio Pao, which rises at the entrance of the Llanos, at the foot of the range of hills called La Galera, heretofore
mingled its waters with those of the lake, by uniting with the Cano de Cambury, on the road from the town of Nueva
Valencia to Guigue. The course of this river was from south to north. At the end of the seventeenth century, the
proprietor of a neighbouring plantation dug at the back of the hill a new bed for the Rio Pao. He turned the river; and,
after having employed part of the water for the irrigation of his fields, he caused the rest to flow at a venture
southward, following the declivity of the Llanos. In this new southern direction the Rio Pao, mingled with three other
rivers, the Tinaco, the Guanarito, and the Chilua, falls into the Portuguesa, which is a branch of the Apure. It is a
remarkable phenomenon, that by a particular position of the ground,and the lowering of the ridge of division to south-
west, the Rio Pao separates itself from the little system of interior rivers to which it originally belonged, and for a
century past has communicated, through the channel of the Apure and the Orinoco, with the ocean. What has been
here effected on a small scale by the hand of man, nature often performs, either by progressively elevating the level of
the soil, or by those falls of the ground occasioned by violent earthquakes. It is probable, that in the lapse of ages,
several rivers of Soudan, and of New Holland, which are now lost in the sands, or in inland basins,will open for
themselves a course to the shores of the ocean. We cannot at least doubt, that in both continents there are systems of
interior rivers, which may be considered as not entirely developed;and which communicate with each other, either in
the time of great risings, or by permanent bifurcations.The Rio Pao has scooped itself out a bed so deep and broad,
that in the season of rains, when the Cano Grande de Cambury inundates all the land to the north-west of Guigue,
the waters of this Cano, and those of the lake of Valencia, flow back into the Rio Pao itself; so that this river, instead
of adding water to the lake, tends rather to carry it away. We see something similar in North America, where
geographers have represented on their maps an imaginary chain of mountains,between the great lakes of Canada and
the country of the Miamis. At the time of floods, the waters flowing into the lakes communicate with those which run
into the Mississippi; and it is practicable to proceed by boats from the sources of the river St. Mary to the Wabash, as
well as from the Chicago to the Illinois. These analogous facts appear to me well worthy of the attention of
hydrographers.The land that surrounds the lake of Valencia being entirely flat and even, a diminution of a few inches
in the level of the water exposes to view a vast extent of ground covered with fertile mud and organic remains.* (* This
I observed daily in the Lake of Mexico.) In proportion as the lake retires, cultivation advances towards the new shore.
These natural desiccations, so important to agriculture, have been considerable during the last ten years, in which
America has suffered from great droughts. Instead of marking the sinuosities of the present banks of the lake, I have
advised the rich landholders in these countries to fix columns of granite in the basin itself, in order to observe from
year to year the mean height of the waters. The Marquis del Toro has undertaken to put this design into execution,
employing the fine granite of the Sierra de Mariara, and establishing limnometers, on a bottom of gneiss rock, so
common in the lake of Valencia.It is impossible to anticipate the limits, more or less narrow, to which this basin of
water will one day be confined, when an equilibrium between the streams flowing in and the produce of evaporation
and filtration, shall be completely established. The idea very generally spread, that the lake will soon entirely
disappear,seems to me chimerical. If in consequence of great earthquakes, or other causes equally mysterious, ten
very humid years should succeed to long droughts; if the mountains should again become clothed with forests, and
great trees overshadow the shore and the plains of Aragua, we should more probably see the volume of the waters
augment,and menace that beautiful cultivation which now trenches on the basin of the lake.While some of the
cultivators of the valleys of Aragua fear the total disappearance of the lake, and others its return to the banks it has
deserted, we hear the question gravely discussed at Caracas, whether it would not be advisable, in order to give
greater extent to agriculture, to conduct the waters of the lake into the Llanos, by digging a canal towards the Rio
Pao. The possibility* of this enterprise cannot be denied, particularly by having recourse to tunnels, or subterranean
canals. (The dividing ridge, namely, that which divides the waters between the valleys of Aragua and the Llanos,lowers so much towards the west of Guigue, as we have already observed, that there are ravines which conduct the
waters of the Cano de Cambury, the Rio Valencia, and the Guataparo, in the time of floods, to the Rio Pao; but it
would be easier to open a navigable canal from the lake of Valencia to the Orinoco, by the Pao, the Portuguesa, and
the Apure, than to dig a draining canal level with the bottom of the lake. This bottom, according to the sounding, and
my barometric measurements, is 40 toises less than 222, or 182 above the surface of the ocean. On the road from
Guigue to the Llanos, by the table-land of La Villa de Cura, I found, to the south of the dividing ridge, and on its
southern declivity, no point of level corresponding to the 182 toises, except near San Juan. The absolute height of this
village is 194 toises. But, I repeat that, farther towards the west,in the country between the Cano de Cambury and
the sources of the Rio Pao, which I was not able to visit, the point of level of the bottom of the lake is much further
north.) The progressive retreat of the waters has given birth to the beautiful and luxuriant plains of Maracay, Cura,
Mocundo, Guigue, and Santa Cruz del Escoval, planted with tobacco, sugar-canes, coffee, indigo, and cacao; but
how can it be doubted for a moment that the lake alone spreads fertility over this country? If deprived of the
enormous mass of vapour which the surface of the waters sends forth daily into the atmosphere, the valleys of
Aragua would become as dry and barren as the surrounding mountains.

The mean depth of the lake is from twelve to fifteen fathoms; the deepest parts are not, as is generally
admitted, eighty, but thirty-five or forty deep. Such is the result of soundings made with the greatest care by Don
Antonio Manzano. When we reflect on the vast depths of all the lakes of Switzerland, which, notwithstanding their
position in high valleys, almost reach the level of the Mediterranean,it appears surprising that greater cavities are not
found at the bottom of the lake of Valencia, which is also an Alpine lake. The deepest places are between the rocky
island of Burro and the point of Cana Fistula, and opposite the high mountains of Mariara. But in general the
southern part of the lake is deeper than the northern: nor must we forget that, if all the shores be now low, the
southern part of the basin is the nearest to a chain of mountains with abrupt declivities; and we know that even the
sea is generally deepest where the coast is elevated, rocky, or perpendicular.The temperature of the lake at the surface
during my abode in the valleys of Aragua, in the month of February, was constantly from 23 to 23.7 degrees,
consequently a little below the mean temperature of the air. This may be from the effect of evaporation, which carries
off caloric from the air and the water; or because a great mass of water does not follow with an equal rapidity the
changes in the temperature of the atmosphere, and the lake receives streams which rise from several cold springs in the
neighbouring mountains. I have to regret that, notwithstanding its small depth, I could not determine the
temperature of the water at thirty or forty fathoms. I was not provided with the thermometrical sounding
apparatus which I had used in the Alpine lakes of Salzburg, and in the Caribbean Sea. The experiments of Saussure
prove that, on both sides of the Alps, the lakes which are from one hundred and ninety to two hundred and seventy-
four toises of absolute elevation* (* This is the difference between the absolute elevations of the lakes of Geneva and
Thun.) have, in the middle of winter, at nine hundred, at six hundred, and sometimes even at one hundred and fifty
feet of depth, a uniform temperature from 4.3 to 6 degrees: but these experiments have not yet been repeated in lakes
situated under the torrid zone. The strata of cold water in Switzerland are of an enormous thickness. They have been
found so near the surface in the lakes of Geneva and Bienne, that the decrement of heat in the water was one
centesimal degree for ten or fifteen feet; that is to say, eight times more rapid than in the ocean, and forty-eight times
more rapid than in the atmosphere. In the temperate zone, where the heat of the atmosphere sinks to the freezing
point, and far lower, the bottom of a lake, even were it not surrounded by glaciers and mountains covered with
eternal snow, must contain particles of water which, having during winter acquired at the surface the maximum of
their density, between 3.4 and 4.4 degrees,have consequently fallen to the greatest depth. Other particles, the
temperature of which is +0.5 degrees, far from placing themselves below the stratum at 4 degrees, can only find
their hydrostatic equilibrium above that stratum. They will descend lower only when their temperature is augmented
3 or 4 degrees by the contact of strata less cold. If water in cooling continued to condense uniformly to the freezing
point, there would be found, in very deep lakes and basins having no communication with each other (whatever the
latitude of the place), a stratum of water, the temperature of which would be nearly equal to the maximum of
refrigeration above the freezing point, which the lower regions of the ambient atmosphere annually attain. Hence it is
probable, that, in the plains of the torrid zone, or in the valleys but little elevated, the mean heat of which is from
25.5 to 27 degrees, the temperature of the bottom of the lakes can never be below 21 or 22 degrees. If in the same