1752 Ulloa and Juan Map of the Andes in Ecuador

This is a rare, 1752 map of Ecuador's La Sierra region, from Carchi Province in the north to Cañar Province in the south. It encompasses one full degree of arc along the Quito meridian, and represents the first scientific survey of this high Andes valley. It appeared in the 1752 French and German editions of Antonio de Ulloa and Jorge Juan's Relacion Historica del Viaje a la America Meridional, a landmark work of South American geography, culture, history and science produced to report the two scientist's labors for the French Geodesic Mission, which were carried out in what is modern Ecuador over ten years. Specifically, the map shows the triangulations performed by Juan (his work indicated by solid lines) and Ulloa (dotted lines) during the expedition. It mapped Ecuador's Central Valley with unparalleled precision, marking rivers, towns and major peaks from El Angel, to Quito, to El Tambo. Towns of various sizes are differentiated with a key; relief is shown in hachure. Forests and plains are shown pictorially. Roads are marked with a dotted line, and bridges over rivers are indicated as well.

Goals of the The French Geodesic Mission: Earth! Just How Round Is It, Anyway?

Led by Charles Marie de La Condamine, the Geodesic Mission was intended to determine whether Newton's theory on the oblate nature of the globe - that it was not truly spherical, but slightly flattened at the poles (narrower from pole to pole than across the equator). Scientists disagreed: Cassini, for example, theorized that the distance was greater at the poles. To resolve the issue, it would be necessary to measure a degree of arc near the Equator, measure a degree of arc nearer the North Pole, and compare the two. Condamine's part of the project was to survey a measurable length of a meridian along the equator. This required that Condamine and his colleagues precisely survey a length of the high valleys of the Andes - literally the only place in the world where such a survey was practicable in the 1730s. Ultimately, the project determined that the Earth is indeed not perfectly spherical but is oblate, i.e. flattened at the poles - as per Newton

Publication History and Census

This map appeared in Voyage historique de l'Amérique méridionale fait par ordre du roi d'Espagne, published in Amsterdam and Leipzig in 1752 in what appears to have been a single edition. (The map in the 1748 Spanish edition was a different engraving altogether.) The volume is catalogued in only four institutional collections according to OCLC, and the separate map is held only by the Sachische Landesbibliothek and the ETH-Bibliothek in Zurich. The map is scarce on the market, having been catalogued only four times since 1987.