Physico-Geographical Features—Deficiency of Information—Barometer—Colonel Williamson—Lieutenants Gibbon, Herndon and Maury—SeÑor Moro—Popagayos—Influence of the Andes—Climate—Rainy Season—Colonel Hughes —Statistics—Population—Indians—Vegetation—Building Materials—Woods—Geology.

The present chapter includes certain physico-geographical features subsidiary to the duties of the engineer and explorer. The object of this paper excludes all matter, not possessing practical value for this purpose, and admits of little more than mere mention.

The previous chapters indicate a deficiency in information in regard to the following routes:

The elevation of the passes upon these routes should be definitely fixed. The instrument which must determine the question of practicability is the Wye spirit-level. If the capacity of the harbors are insufficient for the largest class of ships, or can not be made available at a reasonable cost, further examination is unnecessary.

BAROMETER.

Notwithstanding the improved formulÆ, and more careful method of observation recommended by Lieut.-Col. Williamson, Corps Engineers, the barometer is subject to peculiar and anomalous variations, along the slopes of the Cordillera of the Isthmus and the Andes. Lieuts. Gibbon and Herndon refer to this phenomenon. Lieut. Maury attributed the effect to the damming or piling up of the trade-winds against the mountains. A recent traveler in the valley of the Amazon, I. Orton, observed the same phenomenon, but objects to Maury’s theory.

Sr. Moro makes the following observations: “If, under these circumstances (prevalent winds), barometrical observations are made simultaneously on both sides of the Sierra, on the side of the Gulf, they will exhibit a lower elevation than the true one, the error being greater as that station may happen to be lower down or more towards the north; but if time should admit of waiting until the weather be equally fine on both sides (which seldom happens), then the difference between the levels of the barometrical columns is insensible.”

Ventosa is peculiarly windy, and Nicaragua is subject to the Popagayos, a species of monsoon, upon the Pacific coast. But the more placid climate of the Atrato is similarly affected. “It is known as an established fact,” remarks Capt. Kennish, “that the clouds seldom pass over the Cordillera toward the Pacific, but are attracted by the mountains, and disgorge themselves on the Atlantic side; hence the reason of the perpetual rain, thunder, and lightning in the Atrato Valley, while on the Pacific coast there is scarcely any rain for eight months of the year.”

This unequal meteorological condition affects the barometer, and General Michler observed unaccountable discrepancies in the readings of two barometers when he reached the Hingador. With this exception, the results of this officer’s observation were as close an approximation to the truth as can be expected in a reconnaissance, but it is impossible to say what given observation may be affected by some unknown cause.

A comparison of hypsometric determinations with the same altitudes, ascertained by the spirit-level, will furnish some important elements for eliminating errors. But this operation doubles the labor of the surveyor, and time and cost of his explorations.

The errors of the barometer have led to singular inferences, and the errors of observers to many more. Humboldt, La Condamine, Boussingault, give a decreasing pressure along the Andes; and Orton, taking this statement for granted, asks, “Are the Andes sinking?” The evidence of geological and historical periods is, that the Andes and sea coast are rising. The exceptions to this rule are local, and perhaps only in appearance.

These objections to the use of this instrument only apply to situations where the spirit-level can not be used. To determine heights inaccessible to any other instrument, or for simultaneous observation of the meteorological condition of an extensive area of country, the portability of the barometer render it invaluable.

The height of the barometric column, on the Pacific slope of the Andes, according to Orton, is 29.930. He gives two values for the Atlantic side, 29.997 and 29.932. Michler gives the Atlantic coast of the Atrato 29.874.

CLIMATE.

A well-defined rainy season prevails for the most part throughout the Isthmus, and permits the selection of suitable weather for the operations of the engineer. Rain varies with proximity to the mountains, etc., but the interval from December to May may be regarded as the dry season. The seasons are sometimes reversed, as in Costa Rica. There the dry season prevails upon the Pacific coast from November to April, but on the Atlantic the contrary prevails. Fall of rain in Honduras from May to October is 90.89 inches.

The tierras templadas, or elevated table-lands, are universally healthy, and the climate in those regions possesses a charm which belongs exclusively to the tropics. The unhealthy influences of the marshes and sea-coast is much exaggerated, and may be said to cease during the winter or dry season.

Col. Hughes, who visited the most insalubrious part of the Isthmus, remarks that travelers, “who live like civilized beings,” have little to fear from the climate. The writer spent six months, chiefly near the sea-coast of Columbia, during part of the time compelled to sleep among the swamps of the delta of the Magdelina, and although exposed to the sun during the day, and sleeping in the open air at night, not one case of febrile sickness occurred in the party of which he was a member, nor were more than two cases of fever observed among the natives during the period of residence.

The temperature varies with the elevation above the sea. Thermometric records are of small value without the monthly and daily means of localities.

The following table may give some general notion of their range:

Fahrenheit.

	TEHUANTEPEC.	HONDURAS.	BELIZE.	COSTA RICA.	NICARAGUA.	ATRATO.
May	90°	71°	71°	57°	71°	Average
June	88°					during
April	83°	to	to	to	to	February
May	88°	89°	84°	85°	90°	75.2
December and January	74°

In Guatemala average maximum 88.7°. Minimum 38.9°.

Statistics, governmental and social, of Central America, are very uncertain. The revolutionary condition of a society, in which it is the interest of the chiefs to impose unjust burdens on the people, and of the people to deceive; where, before an enumeration can fairly begin, the government which authorized it may be deposed, and another substituted in its place; the poverty, anarchy, and social demoralization which result, are circumstances very unfavorable to a correct determination of the resources of the country, or the number of its population.

The following figures may not be free from this uncertainty, but give the best approximation that could be obtained:

Population of the States of Central America.

	SQUARE MILES.	POPULATION.
Tehuantepec	...	61,000
Costa Rica	23,000	150,000
Nicaragua	48,000	290,000
San Salvador	9,600	294,000
Guatemala	43,380	907,500
Honduras	42,000	350,000
Panama, including Darien	...	168,000
		2,220,500

This population is of a mixed character, composed of Europeans, Mestizoes, Indians, Negroes, and Zambos; the European element being largely in the minority.

INDIANS.

Explorers in every part of the Isthmus, with the exception of Darien, give favorable accounts of the temper of the natives. Trautwine, who crossed the divide at several points in the province of ChÓcÓ, regarded a bundle of cigars as the best passport. General Michler depended on the natives for provisions during a part of his survey, and was never disappointed.

But the Darien and San Blas Indians have been permitted to threaten and murder with impunity. They have been further emboldened by the timid behavior, and exasperated by the conduct of expeditionists. Had the hostile demonstration of the savages against Codazzi and Gisborne, and the massacre of four of Capt. Prevost’s men, been promptly punished, subsequent exploring parties might now pass through the country unmolested.

Strain, who thoroughly distrusted them, acknowledges that in one case his suspicions were unjust. After dismissing his guides, he remarks that he “was afterward convinced that the Caledonia Indians, and their Sucubti friends, intended to lead them by the most direct route to the Savana, and that they were prevented doing so by the Indians of the Chuquanaque, or the Chuqunos, whom they met on the seventh day’s march, and whom from the first excited suspicion.” It would appear that this unfortunate expedition would have been better served by a little more confidence in these “formidable Indians,” as Gisborne calls them, and a little acquaintance with their language, than by the fortitude it afterward exhibited in encountering the trials which befell it.

When misfortune appeals so strongly to sympathy, as it does in this case, criticism becomes an ungracious task. Throughout this paper we have omitted much in observing the rule, laid down for ourselves, to indicate what should be done, rather than notice what should not have been done. We therefore quote with pleasure the following graphic account of the difficulty of cutting a way through the tropical undergrowth, which we find in Mr. Gisborne’s narrative:

Cutting the way, “we were wading along the river margin, or facing clusters of prickly stems sometimes backing this mass of vegetation. Every step had its difficulty, and every difficulty was attended with additional bodily suffering; but our hearts nearly failed when an interminable mangrove wood extended as far as the eye can reach.

“The twisted and interlaced roots, some eight feet high, grew out of a bed of slimy mud, left by the tidal waters, making progress a succession of gymnastic feats, in which the gift of balancing had no small share. Hand and foot were equally occupied, and every muscle was called into play; nearly an hour’s perseverance had only advanced us a few hundred yards.”

Another description of the same character will exhibit some of the difficulties: “Occasionally a swamp, growing an impenetrable mass of vegetation, delayed our progress and expended our energies in fruitless hacking. The only way to get through many of these cienegas was to fall on one’s back into the middle of the matted vegetation, and then compress a place the length of one’s self, which those behind trod down. After persevering in this manner for several hundred yards, an inlet would be reached with a soft, muddy bottom, and waist deep from the flood. On the other bank, the same mode of progress had to be adopted, until prickly palms, and still more prickly creepers, made a variety in the difficulty and suffering.”

Strain met with similar obstruction. “Hitherto, Strain had led the party, every day cutting a path with his cutlass. This was most laborious, and Mr. Truxton insisted on going ahead in his place. The undergrowth was exceedingly dense, and composed, for the most part, of ‘pinello,’ or little pine, a plant resembling that which produces the pineapple, but with longer leaves, serrated with long spines, which produce most painful wounds, especially as the last few days’ march had stripped the trousers from many of the party.”

The best way to clear these obstructions has been found to employ natives, with machetes. This method, invariably adopted in Central America, has been recommended by Admiral Davis, who also advises the explorer to carry with him a good supply of canned and concentrated provisions.

BUILDING MATERIAL.

Suitable stone is found without difficulty. Hydraulic cement will probably have to be imported, although hydraulic limestone is said to have been found in the States of Vera Cruz and Oazaca.

The explorer will find difficulty in discovering building sand. The sea beaches may afford suitable sand for hydraulic work. Bricks can be manufactured, without difficulty, at many points.

WOOD AND TIMBER.

The following, from the account of Lloyd and Sidell, gives the local names and character of the most useful species:

Mr. Loyd gives a list of ninety-five varieties of woods, of which list the above are the most valuable.

GEOLOGY.

A mere enumeration of the geological specimens, which is all that present knowledge upon this subject will permit, is not thought desirable in this paper. Speculations and theories, if not premature, would be out of place.

The physical geography of Central America is the proper subject for a treatise. We have already seen how the table-lands of Guatemala, from four to five thousand feet above the level of the sea, sink to an insignificant height at Panama and Nicaragua. “There is no spot on the globe,” says Humboldt, “so full of volcanoes as this part of America, between 11° and 13° of latitude.”

Two or three volcanoes, Fuego and Agua, in the State of Guatemala, are 14,000 and 12,000 feet high. Some of the volcanoes of Nicaragua reach a height of 7,000 feet. A common and remarkable characteristic of all of them is, that they rise in a conical form from the plain.

Gold and silver produce of Central America.

	GOLD.	SILVER.	BOTH METALS.
1804 to 1848	$8,800,000	$4,400,000	$13,200,000
1848 to 1868	5,000,000	3,000,000	8,000,000
Total	$13,800,000	$7,400,000	$21,200,000

The mines of the Provinces of Panama and the Veraguas are not worked so extensively as they deserve to be. A small quantity of gold is annually produced in the Republics of Nicaragua, Honduras, Costa Rica, and San Salvador. The Costa Rican mint, in 1852, coined between fifty and one hundred thousand dollars annually. The actual gold product is estimated at ten times this amount. The most important mines in new Granada (Colombia) are found in the State of Antioquia. In 1868, the yield was $1,500,000 gold; $193,000 silver. The detritus of all the rivers of this State is auriferous. An English company works the Marmato gold mine and the Santa Anna silver mine, near Honda, on the Magdelina River. They have provided twelve stamping mills, representing one hundred and ten heads, which crush from ten to nineteen thousand tons per year, yielding, on an average, eleven pennyweights eleven grains of gold per ton.

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