We had yet ten days to wait before we embarked. During this interval, we employed ourselves in preparing the plants we had collected in the beautiful valleys of Galicia, which no naturalist had yet visited: we examined the fuci and the mollusca which the north-west winds had cast with great profusion at the foot of the steep rock, on which the lighthouse of the Tower of Hercules is built. This edifice, called also the Iron Tower, was repaired in 1788. It is ninety-two feet high, its walls are four feet and a half thick, and its construction clearly proves that it was built by the Romans. An inscription discovered near its foundation, a copy of which M. Laborde obligingly gave me, informs us, that this pharos was constructed by Caius Sevius Lupus, architect of the city of Aqua Flavia (Chaves), and that it was dedicated to Mars. Why is the Iron Tower called in the country by the name of Hercules? Was it built by the Romans on the ruins of a Greek or Phoenician edifice? Strabo, indeed, affirms that Galicia, the country of the Callaeci, had been peopled by Greek colonies. According to an extract from the geography of Spain, by Asclepiades the Myrlaean, an ancient tradition stated that the companions of Hercules had settled in these countries.
The ports of Ferrol and Corunna both communicate with one bay, so that a vessel driven by bad weather towards the coast may anchor in either, according to the wind. This advantage is invaluable where the sea is almost always tempestuous, as between capes Ortegal and Finisterre, which are the promontories Trileucum and Artabrum of ancient geography. A narrow passage, flanked by perpendicular rocks of granite, leads to the extensive basin of Ferrol. No port in Europe has so extraordinary an anchorage, from its very inland position. The narrow and tortuous passage by which vessels enter this port, has been opened, either by the irruption of the waves, or by the reiterated shocks of very violent earthquakes. In the New World, on the coasts of New Andalusia, the Laguna del Obispo (Bishop's lake) is formed exactly like the port of Ferrol. The most curious geological phenomena are often repeated at immense distances on the surface of continents; and naturalists who have examined different parts of the globe, are struck with the extreme resemblance observed in the rents on coasts, in the sinuosities of the valleys, in the aspect of the mountains, and in their distribution by groups. The accidental concurrence of the same causes must have everywhere produced the same effects; and amidst the variety of nature, an analogy of structure and form is observed in the arrangement of inanimate matter, as well as in the internal organization of plants and of animals.
Crossing from Corunna to Ferrol, over a shallow, near the White Signal, in the bay, which according to D'Anville is the Portus Magnus of the ancients, we made several experiments by means of a valved thermometrical sounding lead, on the temperature of the ocean, and on the decrement of caloric in the successive strata of water. The thermometer on the bank, and near the surface, was from 12.5 to 13.3 degrees centigrades, while in deep water it constantly marked 15 or 15.3 degrees, the air being at 12.8 degrees. The celebrated Franklin and Mr. Jonathan Williams* (* Author of a work entitled "Thermometrical Navigation," published at Philadelphia.) were the first to invite the attention of naturalists to the phenomena of the temperature of the Atlantic over shoals, and in that zone of tepid and flowing waters which runs from the gulf of Mexico to the banks of Newfoundland and the northern coasts of Europe. The observation, that the proximity of a sand-bank is indicated by a rapid descent of the temperature of the sea at its surface, is not only interesting to the naturalist, but may become also very important for the safety of navigators. The use of the thermometer ought certainly not to lead us to neglect the use of the lead; but experiments sufficiently prove, that variations of temperature, sensible to the most imperfect instruments, indicate danger long before the vessel reaches the shoals. In such cases, the frigidity of the water may induce the pilot to heave the lead in places where he thought himself in the most perfect safety. The waters which cover the shoals owe in a great measure the diminution of their temperature to their mixture with the lower strata of water, which rise towards the surface on the edge of the banks.
The moment of leaving Europe for the first time is attended with a solemn feeling. We in vain summon to our minds the frequency of the communication between the two worlds; we in vain reflect on the great facility with which, from the improved state of navigation, we traverse the Atlantic, which compared to the Pacific is but a larger arm of the sea; the sentiment we feel when we first undertake so distant a voyage is not the less accompanied by a deep emotion, unlike any other impression we have hitherto felt. Separated from the objects of our dearest affections, entering in some sort on a new state of existence, we are forced to fall back on our own thoughts, and we feel within ourselves a dreariness we have never known before. Among the letters which, at the time of our embarking, I wrote to friends in France and Germany, one had a considerable influence on the direction of our travels, and on our succeeding operations. When I left Paris with the intention of visiting the coast of Africa, the expedition for discoveries in the Pacific seemed to be adjourned for several years. I had agreed with captain Baudin, that if, contrary to his expectation, his voyage took place at an earlier period, and intelligence of it should reach me in time, I would endeavour to return from Algiers to a port in France or Spain, to join the expedition. I renewed this promise on leaving Europe, and wrote to M. Baudin, that if the government persisted in sending him by Cape Horn, I would endeavour to meet him either at Monte Video, Chile, or Lima, or wherever he should touch in the Spanish colonies. In consequence of this engagement, I changed the plan of my journey, on reading in the American papers, in 1801, that the French expedition had sailed from Havre, to circumnavigate the globe from east to west. I hired a small vessel from Batabano, in the island of Cuba, to Portobello, and thence crossed the isthmus to the coast of the Pacific; this mistake of a journalist led M. Bonpland and myself to travel eight hundred leagues through a country we had no intention to visit. It was only at Quito, that a letter from M. Delambre, perpetual secretary of the first class of the Institute, informed us, that captain Baudin went by the Cape of Good Hope, without touching on the eastern or western coasts of America.
We spent two days at Corunna, after our instruments were embarked. A thick fog, which covered the horizon, at length indicated the change of weather we so anxiously desired. On the 4th of June, in the evening, the wind turned to north-east, a point which, on the coast of Galicia, is considered very constant during the summer. The Pizarro prepared to sail on the 5th, though we had intelligence that only a few hours previously an English squadron had been seen from the watch-tower of Sisarga, appearing to stand towards the mouth of the Tagus. Those who saw our ship weigh anchor asserted that we should be captured in three days, and that, forced to follow the fate of the vessel, we should be carried to Lisbon. This prognostic gave us the more uneasiness, as we had known some Mexicans at Madrid, who, in order to return to Vera Cruz, had embarked three times at Cadiz, and having been each time taken at the entrance of the port, were at length obliged to return to Spain through Portugal.
The Pizarro set sail at two in the afternoon. As the long and narrow passage by which a ship sails from the port of Corunna opens towards the north, and the wind was contrary, we made eight short tacks, three of which were useless. A fresh tack was made, but very slowly, and we were for some moments in danger at the foot of fort St. Amarro, the current having driven us very near the rock, on which the sea breaks with considerable violence. We remained with our eyes fixed on the castle of St. Antonio, where the unfortunate Malaspina was then a captive in a state prison. On the point of leaving Europe to visit the countries which this illustrious traveller had visited with so much advantage, I could have wished to have fixed my thoughts on some object less affecting.
At half-past six we passed the Tower of Hercules, which is the lighthouse of Corunna, as already mentioned, and where, from a very remote time, a coal-fire has been kept up for the direction of vessels. The light of this fire is in no way proportionate to the noble construction of so vast an edifice, being so feeble that ships cannot perceive it till they are in danger of striking on the shore. Towards the close of day the wind increased and the sea ran high. We directed our course to north-west, in order to avoid the English frigates, which we supposed were cruising off these coasts. About nine we spied the light of a fishing-hut at Sisarga, which was the last object we beheld in the west of Europe.
On the 7th we were in the latitude of Cape Finisterre. The group of granitic rocks, which forms part of this promontory, like that of Torianes and Monte de Corcubion, bears the name of the Sierra de Torinona. Cape Finisterre is lower than the neighbouring lands, but the Torinona is visible at seventeen leagues' distance, which proves that the elevation of its highest summit is not less than 300 toises (582 metres). Spanish navigators affirm that on these coasts the magnetic variation differs extremely from that observed at sea. M. Bory, it is true, in the voyage of the sloop Amaranth, found in 1751, that the variation of the needle determined at the Cape was four degrees less than could have been conjectured from the observations made at the same period along the coasts. In the same manner as the granite of Galicia contains tin disseminated in its mass, that of Cape Finisterre probably contains micaceous iron. In the mountains of the Upper Palatinate there are granitic rocks in which crystals of micaceous iron take the place of common mica.
On the 8th, at sunset, we descried from the mast-head an English convoy sailing along the coast, and steering towards south-east. In order to avoid it we altered our course during the night. From this moment no light was permitted in the great cabin, to prevent our being seen at a distance. This precaution, which was at the time prescribed in the regulations of the packet-ships of the Spanish navy, was extremely irksome to us during the voyages we made in the course of the five following years. We were constantly obliged to make use of dark-lanterns to examine the temperature of the water, or to read the divisions on the limb of the astronomical instruments. In the torrid zone, where twilight lasts but a few minutes, our operations ceased almost at six in the evening. This state of things was so much the more vexatious to me as from the nature of my constitution I never was subject to sea-sickness, and feel an extreme ardour for study during the whole time I am at sea.
On the 9th of June, in latitude 39 degrees 50 minutes, and longitude 16 degrees 10 minutes west of the meridian of the observatory of Paris, we began to feel the effects of the great current which from the Azores flows towards the straits of Gibraltar and the Canary Islands. This current is commonly attributed to that tendency towards the east, which the straits of Gibraltar give to the waters of the Atlantic Ocean. M. de Fleurieu observes that the Mediterranean, losing by evaporation more water than the rivers can supply, causes a movement in the neighbouring ocean, and that the influence of the straits is felt at the distance of six hundred leagues. Without derogating from the respect I entertain for the opinion of that celebrated navigator, I may be permitted to consider this important object in a far more general point of view.