out its great extent, and on entering it from the sea, no shoals are to be met with; everywhere a good anchorage is to be found. The bottom is of compact sand, and a great proportion of it is mixed with clay.

The depth is almost regularly graduated. It presents at from 350 to 8,000 feet distance from the shore a progressive running from 17 to 53 feet, and averaging for the first thousand feet two feet increase per hundred feet, and about six inches per hundred feet for the following thousand feet.

The greatest difference that has been observed in the level of the water was six and a half feet.

Besides the variable winds, which are rather light, and the land and sea breezes of the morning and evening, two prevalent winds, the north-northeast and south-southwest winds reign during a great portion of the year on the southern coast of the Isthmus. The first of these two atmospheric currents is not felt at sixty miles east of La Ventosa, beyond the Barra de Tonala, nor at sixty-two miles west, beyond the mountain of Chahuhé, which bounds on the west the lagoon of Tengulunda.

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The north-northeast wind usually begins to blow about the fifteenth of October, and ceases in the forepart of April. In the month of November it blows without interruption, and at that time it reaches its maximum. Towards the middle of December it ceases during intervals of from ten to twelve days, and then begins anew to blow one or two weeks. These alternations or interruptions and renewals are reproduced at short and unequal periods. But the length of the period of discontinuance goes on gradually increasing until the wind only blows one day, and finally ceases completely.

In winter and in summer, during the prevalence of the southerly and northerly winds, the current of the sea is from east to west; its greatest velocity is about one mile and a half per hour. This

continual movement in the waters of the Pacific is only discernible at a distance of about 6,000 feet from the shores of La Ventosa.

The bay of La Ventosa is much safer than the harbor of Vera Cruz. Violent tempests frequently render the latter inaccessible during several days, and even when the north wind blows, the communication between the town and the vessels in the harbor is interrupted.

An extract from a letter of Captain Mott, of the steamer "Gold Hunter," which anchored at Ventosa, states as follows. This is dated April 11th, 1851.

"I am much pleased with this port, Ventosa. The holding-ground is excellent, and the depth of six and seven fathoms almost all over the bay very convenient. During the four days we have been here, we have had two fresh southerly winds, and two strong northers. The former did not agitate the sea much, and the latter, though blowing very strong, has not straightened out the chains. We are still riding by the 'bight,' which is buried in the clay bottom."

Referring again to Commander Temple's report, he says: "From all the foregoing considerations, I am of opinion that La Ventosa is not only the best, but the point for a harbor on the Pacific coast of the Isthmus. It is a far safer and better port than either Valparaiso in Chili, or Monterey in California, ports in constant use the year throughout. I speak from personal observation, as well as from an examination of the several charts, and their similarity of outline has suggested the comparison; for, although the indentation of the coast is possibly a little deeper at each of these places than at La Ventosa, yet they are both open to the northward, and as the general 'trend' of the coast is nearly north and south, the prevailing gales blow directly along the shore and into these harbors, creating a heavy swell, and often forcing vessels to 'slip and go to sea' for safety; whereas

at La Ventosa the 'trend' of the coast is east and west, so that the northers' blow directly off shore, and create no swell whatever. The danger being from the sudden strain brought upon a cable by the surging of a vessel in a sea-way, and not from the steady strain caused by the wind, it follows that northers may be disregarded in an estimate of the safety of this anchorage, as was satisfactorily shown in the case of the Gold Hunter. But northers, although frequent during the winter, and seldom occurring at other seasons, are the only gales that blow in this region. The southerly winds, characteristic of the summer and autumn, are nothing more than thunder squalls of short duration, and incapable of raising a sea. Even the fresh and steady sea breezes that prevailed during the latter portion of our stay at La Ventosa, were unaccompanied by any increase of swell.

"The chart of La Ventosa shows a moderate and almost uniform grade of bottom, beginning with three fathoms at about 100 yards from the beach, and deepening to seven and eight fathoms at a distance of 1,000 yards."

There are few localities where maritime works are not more or less desirable for the protection of vessels against the sea, and at La Ventosa a breakwater forming an inner basin will be desirable ultimately, but the harbor admits at present of daily use without any artificial works, which are only called for in view of extended freighting operations.

VI.

GEOLOGY AND MINERALOGY.

THE geological structure of the Isthmus is less clearly marked than that of the adjoining more ele

vated district of Mexico. Much of the gentle slope of the northern plains is covered over with clay, sand and gravel, and so densely wooded, that no appearance of the rock formation is discernible. The same may be said of the plains on the southern shore. On the middle more elevated regions the conformation is more evident.

The tertiary clays, gravels, and beds of detritus which cover up so much of the Isthmus along the line of survey, extend on the north side almost to the summit-level, and the base of the hills which lie east and west of it. These deposits being found pretty uniformly spread, even to the depth of thirty feet in some places, as at a point north of the summit-level, and between it and the river Almaloya, are evidences of the slow and tranquil elevation of this portion of the Isthmus above the sea, and of its comparatively quiescent condition since a very distant epoch.

Granite and granitiform rocks do not occupy much extent of surface upon the Isthmus, but appears in the higher elevation of the mountain ranges, and in the debris brought down by the rivers.

The prevailing formations is the metamorphic in the various forms attendant upon a granitic nucleus. Slates, primitive limestone and sandstones appear in great variety, and the building stone usually found in this formation are abundant in the hills.

Iron is found in abundance in many points of the Isthmus, and that of Tarifa especially appears to be of excellent quality. The veins of iron ore in the immediate vicinity of San Juan Guichicovi are the richest and most extensive known to exist on the Isthmus. Tin is also found in extremely rich deposits some distance beyond in the Cerro de los Mijes. As regards the precious metals, which made the department of Oajaca once so famous, there is a tradition still prevalent from the time of the conquest that the mountains of Mijes and the upper Uspanapan contain very rich gold and silver mines.

The existence of gold in great quantities in this neighborhood is too well attested, both by tradition and history, to admit of any doubt. The question of its profitable working, however, is a matter yet to be determined.

The following extract shows how over abundant and easily obtained it was at one period upon the Isthmus.

Bernal Diaz, in recording the account of the expeditions of Gonzalo de Umbria and the gold which he brought, says: "Neither did Diego de Ordas, who had been sent to the river Coatzacoalcos, return with empty hands."

Again, in reference to the march of Sandoval : "Twenty of the caziques and principal personages soon made their appearance, bringing with them a present of gold dust in ten tubes, besides various pretty ornaments."

At another place, in the same connection: "We arrived in the province, and began diligently to explore the mines, accompanied by a great number of Indians, who washed the gold dust for us in a kind of trough from the sand of three different rivers. In this way we obtained four tubes full of gold dust, each about the thickness of the middle finger. Sandoval was highly delighted when we brought him these, and concluded that the country must contain rich gold mines,"

"The expedition of Alvarado to Tehuantepec, in 1522, seems to have been attended with far greater success. Bernal Diaz, speaking of this expedition, says: "Among the more powerful tribes who submitted on this occasion, was that of the Tecuantepec (Tzapotecs), whose ambassaders brought with them a present in gold, stating, at the same time, that they were at war with their neighbors, the Tutepecs, who had commenced hostilities with them because they had submitted to the Spanish crown. This tribe in