We propose to apply the methodological perspective of "l'histoire croisée" to the study of the work carried out by Spanish antifascist scientists who had to go into exile after the defeat of the Republican forces in the Spanish war (1936-1939). Two case studies will be chosen for this purpose; the launching in Mexico of the journal "Ciencia" in 1940 and the work of the Spanish-Mexican medical historian Germán Somolinos, who was the promoter of the edition of the complete works of the 16th century physician Francisco Hernandez by the Universidad Nacional Autónoma de Mexico in 1959.
Throughout more than three decades, until 1975, the journal Ciencia became the main voice for Spanish Republican scientists dispersed in their diaspora throughout the Americas and Europe. But also a platform for collaboration of these scientists with colleagues from other countries, mainly from Mexico, intertwinning scientific interests and collaborative research programs.
In the case of Germán Somolinos, who was one of the contributors to the journal "Ciencia", the unfolding of his work as a historian of medicine was produced by a double interaction. Through his obsession with reconstructing the life and work of the humanist physician Francisco Hernández, the first European scientist to carry out a systematic survey of Mexican medicinal plants in the 1570s, with the help of Amerindian specialists, and through his interactions with his Mexican colleagues in the Academia Nacional de Medicina in his systematic studies on the history of Mexican medicine from Pre-Columbian times to the contemporary era.

In the initial decades of the 20th century, radiology underwent a relatively rapid period of development. It advanced in Germany, France, South America, and other regions. The advent of this paradigm constitutes the central theme of my presentation. I will commence with an overview of the origins of radiology in France and the contributions of Marie Curie during the First World War (1914-1918). I will then examine the connections between this French radiology and the subsequent development of the field in Colombia during the 1920s and 1930s. This provides an illustrative example of the circulation of knowledge, linked to the arrival of Europeans in Bogotá and the subsequent departure of Colombians to Europe. In the second phase of the study, the conditions for the success of the new paradigm will be examined. Following the recognition of X-rays' properties, which commenced following their purely scientific discovery, these were applied to the examination of the human body and to therapy. These applications took on an unsuspected scope almost immediately after the war. Consequently, they are examined from the perspective of wartime and peacetime. Finally, a few lines of research on the subject are presented.

Pedro Peralta y Barnuevo (1663–1743) was a major figure in the development of modern science in Latin America, particularly in the realms of astronomy and mathematics. Serving as the fifth Cosmographer Major and professor of mathematics at the Real Universidad de San Marcos in Lima, Peralta's work exemplifies the rich scientific practice in Latin America and its exchanges with European contexts during the early 18th century.

This presentation examines Peralta's pivotal contributions to astronomy, emphasizing his detailed observations of lunar and solar eclipses, comets, and the precise determination of Lima's geographical coordinates. Employing instruments such as quadrants and telescopes, Peralta's work proved instrumental for navigation, cartography, and the broader understanding of celestial phenomena. His efforts in calculating the latitude and longitude of Lima were not only foundational for local geography but also integrated into global astronomical charts, reflecting a bidirectional flow of knowledge between the New World and Europe.

Peralta's interactions with European scholars, such as his correspondence and data exchange with members of the French Academy of Sciences, highlight the international collaborative efforts of the time. Despite technological and logistical challenges, his work was recognized and utilized by European astronomers, demonstrating the role Latin American scholars played in the global scientific community.

The presentation also delves into the intellectual networks and institutions in colonial Peru that facilitated scientific inquiry and education. His contributions underscore the local adaptation of European scientific methods and the creation of unique knowledge in response to the specific geographical and cultural context of Latin America.