Looking for a Point of Observation in the South of the World: Global Astronomical Networks in the Nineteenth Century

One of the main problems of astronomy in the mid-nineteenth century was to calculate the stellar distances and build a system of measurements that would allow to know the positions of the stars, distances, orbits, etc. This scientific task required the search of a point of observation in the south of the world that would allow comparing data between both hemispheres of the earth. In 1847 Christian Ludwig Gerling of the University of Marburg in Germany, suggested that the solar parallax could be calculated by measuring the position of Venus near its lower conjunction from observatories in distant latitudes, but close in a same meridian. James M. Gillis, an astronomer at the United States Naval Observatory, proposed to Gerling an expedition to Chile in order to do observations that would be compared with those made in the United States. This talk aims to analyze the uncertainties and difficulties to build global networks of astronomical knowledge. This will be done by studying the unpublished correspondence between Gillis and Gerling. This correspondence allows us to understand the discussions between both scientists about the planning and preparation of this southern expedition, the choice of the observation point, the methodological scope of the fieldwork and the possible use of the equipment in a different hemisphere.