For some years, I have spent several days of the summer on the privileged island of Tenerife, in the Orotava valley, for which the eminent naturalist Alexander von Humboldt felt a special attraction when he paid a visit to the island in June 1799, during one of his scientific expeditions.  After an ascent up the Teide, Humboldt recorded his observations, which contain more references to the plant species than to geological and volcanic studies. Nevertheless, his notes on the calculations of the Teide’s height, carried out by the French navigators Borda and Varela are of particular interest.  Humboldt’s studies on Tenerife are described in his work “Viaje a las islas Canarias”, published in 1816, of which we will examine part of his account.

This modest contribution aims to link the height of this towering volcano (at 3,718 metres, it is Spain’s highest summit) with navigation to the Canary Islands from earliest times, when the Teide’s peak often helped to orientate mariners.

Any visitor to Tenerife will see how the trade winds bring clouds that often shroud the view of the Tiede’s from the island itself. The clouds form what is locally known as a “sea of clouds”. Above this layer of cloud, the air clears, on occasions allowing the summit to be sighted from great distances above the cloud cover. This phenomenon, observed by many of the mariners in those waters, provided a point of reference to guide them on their ocean voyages. However, the precise position of a ship could not be pinpointed until the invention of reflecting instruments and the determination of the exact height of the Teide, a calculation that was carried out by Borda’s scientific expedition.

Navigating in the Canary Islands in antiquity.

As many accounts confirm, the Canary Islands, and more specifically Tenerife, were already known back in antiquity, although mythological accounts are sometimes mistaken for real history.

The renowned historian Professor Gómez-Tabanera wrote, “Without pronouncing for the moment on this early Phoenician arrival to the New World, we can nevertheless agree that the Phoenicians sailed the Atlantic coasts beyond the Strait of Gibraltar, making landfall at the Canary Islands”. Of the many other existing records of mariners of antiquity plying the waters around the Canary Islands, possibly Pliny provides the most extensive information in his “Naturalis Hiatoriae”.

Eustaquio Villalba, in his recently published book “El Teide una mirada histórica”, holds that “the first humans to reach the Canary Islands were mariners from the Mediterranean and from the Straight of Gibraltar (Tartessians, Phonecians, Phoceons, Cubeos, Etruscans, etc.). He points to two discoveries: Phoenician pottery on unearthed on the island of Graciosa, dating from 1100 B.C. and various types of seeds found in the Don Gaspar cave on Tenerife dating from 8th century B.C., a period coinciding with Phoenician expansion. Villalba’s superb work is complemented by a brief and documented survey by Agustín Isidro de Lis and Fancisco La-Roche Brier on the history of calculating the height of the Teide, to which we will refer shortly.

 The list of Greek and Latin scholars who speak of the “Macaron Nesoi”, the “Fortunate Insulae”, the “islas Purpurarias”, the “Islas de los Bienaventurados” and a long list of other names by which the Canary Islands were known is long. Some surviving accounts, halfway between reality and myth, complicate matters, though they deserve to be real, if only for their descriptive beauty. We seek to recall what is closer to reality, without forgetting legends like St Brendan’s Isle, the Garden of the Hesperides and Atlantis.

In the late middle ages, some European navigators embarked once again to challenge the “Mar Tenebroso” on Atlantic voyages. The first expeditions sailed from the so-named Italian maritime republics, particularly Genova, though Majorcans also participated on these expeditions, and were later followed by seafarers from Huelva, Venice, Normandy, and so forth. Then, from the 15th century onward, with the discovery of America, these maritime voyages became more frequent.

Among the names associated with the first known expeditions were the Vivaldi brothers Ugolino and Vadino, who in 1291 set sail to “ire in Levante ad partes Indiarum”. Demetrio Ramos writes that Majorcan pilots joined this expedition aboard the galleys Alegranza and San Antonio, which sailed down the African coast and probably made landfall at the Canary Islands, although it is plausible that some continued on to Niger. Ugolino Vivaldi’ son, Leone, searched for his father in various places in Africa without luck.

Other mariners such as the Genovese Anoniotto Usodimare, who reached the islands of Cape Verde, might have sailed through the Canary archipelago, although no record corroborates this. On the other hand, around 1312, Lancerotto Malocello or Mailosel, also from Genoa, landed at Lanzarote, where he remained some 20 years and gave his name to the island. This name features in the famous Catalan atlas compiled by the Majorcan Jew Abraham Cresques in 1375 and in earlier portolanos.

In 1341, a new expedition sailed from Portugal, this time financed by Florentines, carrying seafarers from Florence, Genoa, Spaniards from Castile and other regions … This expedition, according to Demetrio Castro, was not recorded until 1827, the year Nicolaso de Recco’s manuscript was published. Regarding the Teide, the manuscript, also published by Eustaquio Villalba, reads, “There also exists an island on which they did not wish to land because a certain marvel would occur on it. They say that it has a mountain that, according to their calculations, is thirty miles high or more, which can be seen from very far and on whose summit a certain whiteness can be made out… They sailed around the island and observed the same from all sides, thus fearing they were in the presence of an incantation, they had not the valour to land”.

The information pertaining to an expedition in 1393 is unclear. Father Mariana wrote thus of the voyage: “the most noteworthy endeavour of this year (1393) was the voyage to the Canaries”.

 Demetrio Castro argues that there is no accurate record of further voyages to the Canary Islands at the end of the fourteenth century other than the one of 1393, and adds that only Ortiz de Zúñiga in his “Seville Annals”, referring to 1399, indicates that “it was common practice in those times to sail from Seville and from the ports of Andalusia to the Fortunate Islands”, which bears out Father Mariana’s account.
Guillermo Céspedes del Castillo indicates that the Andalusian expeditions to those islands commenced in 1393 and did not cease in the ensuing years.

 The next voyage led by the Normans Gadifier de la Salle and Jean de Bethencourt, vassals of the King Enrique III of Castile, made landfall at the archipelago in the early fifteenth century and remained on the islands nearly thirty years without fulfilling their mission. It was the Catholic Kings who conquered the islands, which they regarded as vital to pursue their Atlantic policy.

Few records exist from the fifteenth century relating to the Teide, although Villalba cites one, the “Chronicle of the discovery and conquest of Guinea”, by Gomes Eanes de Zurara (1448), whose text reads; “The seventh (island)  which is Tenerife or the Inferno, because it has on its summit a crater that discharges smoke. The height of the Teide and its terrifying eruptions are frequently reported in the chronicles of mariners from those centuries.

In about 1455, the Venetian explorer Alvise di Cada Mosto, under the mandate of Don Enrique the Navigator, charted the West African coasts and is credited as having discovered the Cape Verde archipelago. It is evident that during this voyage Cada Mosto sighted the Canaries and refers to them thus in his account: “Tenerife is one of the tallest islands in the world, since on a clear day it can be made out from a great distance; and trustworthy mariners report having seen it, in their opinion from a distance of sixty or seventy Spanish miles, since in the centre of the island stands an extremely tall, diamond-shaped peak that burns continuously”. Subsequently Cada Mosto wrote that the distance from the foot to the summit spanned fifteen Portuguese leagues, the equivalent of sixty Italian miles. Let us attempt to find the equivalence of these data to modern-day measurements.

Cartography and the Canary Islands

The Canary Islands were known from antiquity, yet did those early mariners know its geographical position? In his research on Pliny’s accounts, P.T. Kayser concludes that the archipelago’s position had been surveyed with relative accuracy. This is also borne out in P. Meirat’s research on the voyage of the Carthaginian explorer Hanno, as the scholar Marcos Martínez points out in his research on this and other classical studies.
The portolanos from the late middle ages already feature the archipelago or at least a part of it, such as that drawn by the Majorcan Angelino Dulcert in 1339, which shows only Lanzarote and Fuerteventura, geologically the oldest of the Canary Islands. The celebrated Catalan Atlas by the Majorcan Abraham Cresques from 1375 shows the entire Canary archipelago. Both documents are held in the Paris National Library and constitute two key pieces of Majorcan medieval cartography, which in reality are the first portolanos of the Majorcan school, whose cartographic work extended into the mid sixteenth century (1569),  when, as Julio Rey Pastor corroborates, “the Mercator map projection resolved the problem of charting exact routes between any two points”. Noteworthy from among the copious cartography of the Canary Islands is the map by Leonardo Torriani from 1592, partially reproduced by Juan Tous Meliá in 1996.

  

Astronomy and the calculation of longitude. The choice of the first meridian.

In 1666, at the request of Colbert, minister of French King Louis XIV, the Academy of Sciences of Paris and its observatory was set up. In 1675, King Charles II of England began building work on the Greenwich Observatory on Greenwich Hill, which today stands next to the naval museum and the hospital of the same name. The observatory was run by John Flamsteed, who was succeeded by Halley, Bradley and the eminent Maskelyne, who held the post for forty-four years, between 1764 and 1818.  These scientific institutions, devoted to the study of celestial bodies, contributed to determining longitude at sea. In Spain, after the scientific expedition to the viceroyalty of Peru at the request of Jorge Juan, the Royal Observatory of Cadis was set up in 1753.  At the same time, numerous expeditions were mounted around the globe by men such as Boungaville, Capitan Cook, and other explorers, who made a significant contribution to the knowledge of new lands. With the discovery of longitude, a host of cartographic projects were carried out. An obligatory reference in the new surveys was to pinpoint the place chosen as the first meridian. Salvador García Franco claims that Ptolemy had established the one that runs through the island of El Hierro.  The Dutch placed the first meridian in the Canary Islands, crossing the summit of the Teide. A meeting convened by Cardinal Richelieu agreed to adopt as the first meridian the line that crosses the westernmost part of El Hierro. In order to locate the exact geographical position of the El Hierro, a French expedition was despatched in 1724, commanded by Louis Feullé. It also calculated the height of the Teide at 4,313 metres, which, as de Lisa and La Roche Brier corroborated, has a margin of error of only 16%.

Some years later, in 1771, aboard the “La Flore”, Verdún de Crenne, P. Pingré and Jean Charles Borda sailed to the Canaries. According to previously cited authors, their mission was to “test the models of marine chronometers to achieve the greatest precision in extreme seafaring conditions, whose inventors were contesting in France priceless rewards”.
The mission ended in failure, owing to serious errors in the calculations made.

As a result, in 1776 “La Bussole” and “L’ Espiégle, the first under the command of Borda, also known as Caballero Borda, were sent to Tenerife.

According to García Franco, “chevalier Borda joined the French navy at the age of thirty without having attended the Academy, and this eminent scientist, who served his country with honour…” Finally, in 1738, the English  chose the Greenwich meridian as the source of the longitudes.

García Franco claims that Borda had devised a repeating circle entirely exempt of the defects of Mayer’s circle. García Franco later adds that Borda surpassed by far Mayer’s invention. He made the telescope shorter, so the lens did not reach the centre of the circle, and separated the horizontal mirror from the periphery, achieving a notable improvement so that the telescope was able to receive the reflected image either from the right or from the left.

Martínez Hidalgo writes that Jean Charles Borda joined the navy from the army, and describes him as an extremely erudite man who carried out his duties with great diligence. He adds that Borda devised the repeating circle that bears his name, originally invented by Tobias Mayer, a series of trigonometric tables that were later published by Delambre, and carried out many experiments to establish the laws of fluid resistance, to which he adds that Borda was a member of the Academy of Sciences of Paris.

Caballero Borda met the renowned Capitan Cook in Tenerife, ( between 1 and 4 August) who before sailing from Plymouth on 8 July 1776 had received among other instructions from the British Admiralty to make a port of call at the Canary Islands, before setting out on his third voyage of exploration. The two navigators exchanged some information, after which Borda began preparations for his mission to establish the exact position of Santa Cruz and calculate the exact position and height of the Teide.

The latest advances in chronometry allowed sailors to gauge with greater precision the longitude of the Teide and, furthermore, obtain its position by calculating its height with a sextant. The preparations and the execution of these calculations are described in detail by Isidro Agustín de Lis and Francisco de la Roche Brier in their excellent work “ La medición histórica del “Teide”, annex to the documented study by Estaquio Villalba  titled “ El Teide una mirada histórica”.  

 The result of Borda’s calculations showed a height of 3,712 metres, with a minimum error, since the Teide’s precise height, subsequently measured with more sophisticated instruments, is 3,718 metres.

Ever since I first saw the mountain, I have never failed to feel a fascination for its imposing height. Each morning, when I am in the Orotava valley, I  take in its majestic shape before the trade winds shroud it in a “sea of clouds”. Little wonder that the Teide instilled such fear in the earliest navigators as they watched its Teide’s violent volcanic eruptions.

Ricardo Arroyo Ruiz Zorrilla

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