The position of the fort constructed there has been fixed by repeated observations in latitude 37° 21´ 43"; longitude, west of Buenos Ayres, 39´ 4"; variation 15° east. It stands upon a small eminence, one of a lower group of hills which skirts the more elevated range beyond, and from which it is divided by the bed of a streamlet, which, after passing the works, about a quarter of a league to the eastward, and being joined by another from the westward, forms the river Tandil, which runs north till lost in the marshes in that direction already spoken of. It is screened to the west and north-west by a range of hills rising 300 or 400 feet above it, the summits of which are strewed with large masses of quartzose rock, having a very remarkable appearance when seen from a distance. The highest part of the range of the Tandil, about two leagues to the south-east of the fort, was ascertained to be about 1000 feet above the level of a small stream which runs along its base. It is visible from a distance of forty miles. The height of this part of the range gradually falls off till lost in a wide plain or vale, about twelve miles eastward of the fortification.
The climate in winter was found to be very cold; the prevailing winds from the south and south-west.[44] In the month of April the thermometer was twice 1½° below freezing-point; but variations of 20° and even 30° in the course of the day were of common occurrence. In that month (April) the highest of the thermometer was 68°, the lowest 28½°; in May the highest was 61°, the lowest 31°; in June the highest was 72°, the lowest 39°; in July the highest was 79°, the lowest 41°. In the summer the heat was almost insufferable, particularly in the low lands; but in the spring and autumn, which are the best seasons, the weather was found temperate and very agreeable.
Whilst the fort was building on the Tandil, communications were opened with the Indians residing near the Ventana, proposing to them to join in active operations against the Ranqueles tribes—the Spaniards thinking, as on other occasions, to invoke the tribes in war with each other, and to profit by the weakening of both parties; but the Indians were this time upon their guard. They saw clearly enough that the march of such an army into their territory could have only one object,—the forcible occupation of their lands,—and they took their measures accordingly with their usual astuteness and cunning. Assenting, apparently, to the general propositions made to them, they invited the Buenos Ayrean general to repair with his principal officers to the neighbourhood of the Ventana, there to enter into the definitive treaties. They probably hoped by some ruse to get the governor himself into their hands, and were greatly disappointed at his only sending his second in command, General Rondeau, to treat with them. Rondeau marched into their territory with a force of 1000 men, passing to the west of the Tinta mountains, and, after going some distance, was met by the principal Caciques, with a large assemblage of their fighting men; and here commenced a negociation, in which the Buenos Ayrean general was fairly outwitted. The Indians, affecting distrust, proposed that some officers of consequence should be sent to them as hostages during the conferences, offering, on their part, to place some of their principal Caciques in the power of the general. Rondeau fell into the snare, and took his measures so badly, that, before the exchange was made, his officers were suddenly made prisoners, and carried off at a gallop, enveloped by a cloud of Indians, who were soon out of sight. His cavalry was in no condition to follow the savages into the pampas, and he returned to the Tandil with the conviction that the Puelches tribes, as well as the Ranqueles, were combined in one and the same determination to have no more friendly intercourse with the Christians.
After this affair nothing further was attempted, except to send out a party to explore the continuation of the range of the Tandil to the coast, of which the following was the result.
It has been already said that the range of the Tandil gradually declines to the eastward till broken by a wide vale, which commences about twelve miles from the new fortification; the vale in question extends for a distance of forty-two miles:—many streams run through it, some few of which, inclining towards the coast, fall into the sea, though the greater part of them are lost in swamps in the low lands which intervene. It is the greatest break in the chain, and, from its rich pastures, a favourite resort of the Indians. They call it the Vuulcan, which signifies, in their language, an opening; and thence the sierra, which bounds it to the eastward, also takes its name. In many maps it is written Volcan, which has led to the erroneous idea of there being a volcano in those parts.
From the Vuulcan the range runs in a continuous line for thirty-six miles towards the sea, presenting, for the most part, towards the north the appearance of a steep dyke or wall. On the summits are extensive ranges of table-land, well watered, and with good pasturage, to which the Indians, who are well acquainted with the craggy ravines which alone lead to them, are in the habit of driving their horses and cattle, knowing that the nature of the ground requires but little care to prevent their straying. At a short distance from the coast the hills break off in stony ridges, running down to the sea, and forming the headland of Cape Corrientes, in latitude 38° 6´, and further south a line of rocky cliffs, which bounds the shore as far as Cape Andres.
Upon the borders of a lake a short distance from Cape Corrientes were discovered the remains of the settlement formed by the Jesuits in the year 1747,—a site chosen with all their characteristic sagacity, well suited for an agricultural establishment, of easy access to the sea, and with great capability of being rendered defensible. It is a striking proof of the indomitable nature of the pampas tribes that all the efforts of the missionary fathers to reduce them to habits of order and industry only ended in disappointment, and, after years of fruitless endeavours, to their being obliged to fly from an establishment where their lives were no longer safe. The Indians of the pampas, like the Arabs of the desert, inseparable from their horses, and wild as the animals they ride, were not, like the more docile people of Paraguay, to be subjected to the strict rules and discipline which it was the object of the fathers to introduce amongst them. The vestiges of their buildings, and the fruit-trees planted by them, are the only evidences remaining of their pious but unavailing labours.
Although this spot was in many respects a very inviting one for an agricultural settlement, it wanted the principal requisite of some tolerable roadstead or harbour to facilitate any direct communication from Buenos Ayres by sea with the new line of frontier, an object of great importance if possible to secure. The coast was vainly explored in search of one from Cape Corrientes some way to the south, and to the north as far as the great lake called the Mar-chiquita, which empties itself into the sea by a narrow channel, capable, perhaps, of being deepened by artificial means, so as to form a harbour for small vessels; but even this seemed extremely doubtful, and depending on a further examination and survey, which the officers were not at the time prepared to undertake.
Under these circumstances, it was thought advisable to postpone the construction of any further works till a more accurate survey of the coast should be made. This was subsequently commenced, and carried as far as Bahia Blanca, which was reported to be the only situation from the Salado on all the line of coast intervening which combined a tolerable harbour for shipping with the capability of being made a good defensible position. Although this was far beyond the line of frontier at first contemplated, which only reached to the range of the Vuulcan and Tandil, other considerations eventually determined the government of Buenos Ayres to extend their boundary to that point. Not only did it appear that Bahia Blanca was the only place capable of being made a harbour on the coast, but the want of some such harbour to the south became more than ever apparent when the war broke out with Brazil, and the River Plate was placed under blockade by the emperor's fleet; and, although that war at first necessarily diverted the attention of the government of Buenos Ayres from the completion of their original plan, it forced upon them a more enlarged view of their position, and led to the final adoption of an infinitely better boundary-line than that which was first thought of merely as a check upon the Indians.
The line in question, which was finally adopted in 1828, and which forms the present nominal frontier of the province of Buenos Ayres towards the pampas, will be found upon the map drawn about north-north-east, from the fort built on the river Naposta, which falls into Bahia Blanca, to the Laguna Blanca, another point occupied as a military position, at the western extremity of the range of the Tapalquen; thence it runs north by the fort of Cruz de Guerra to Melinqué, the north-west point of the province. It will be obvious, on reference to the map, that, whilst this line embraced within it an infinitely greater extent of country than that at first projected, it was in reality, being straight, a shorter one, and required less defences than the ranges of the Tandil and Vuulcan, supposing all the passes to be fortified.