Cosmography was an elusive science for its practitioners, and to some extent it still is for historians. Starting from Jacopo Angeli's translation of the title of Ptolemy's Geography as ‘cosmographia’, its Renaissance incarnation is intertwined both with long-standing academic disciplines such as geometry and astronomy and with an assortment of scientific practices whose variations often depended upon political, social and institutional conditions. Thus cosmography's disciplinary identity, in the Renaissance and later, appears to vary considerably not only diachronically, but also synchronically in different intellectual contexts and scientific systems. María Portuondo's book investigates the inflection given to the discipline by Spanish cosmographers at the height of the Siglo de oro.

The book's title refers to the policy of secrecy adopted by the Spanish monarchy with regard to scientific data concerning the New World. Restrictions on the circulation of documents containing information of strategic, defensive and monetary value were imposed to preserve the Spanish strategic advantage in its colonial expansion. Geographical maps and nautical charts are obvious examples of items that needed to be safeguarded, as their content, if revealed to foreign agents, could damage the state or endanger its growing economy. In a fast-expanding empire with a relatively limited amount of manpower and little control over overseas frontiers and communication channels, the Spanish monarchy quickly realized that control of sensible information would become a crucial defence against possible challenges to its hegemony in the New World. Hence, starting from the early sixteenth century, the two main institutions overseeing commerce and navigation (the Casa de la Contratación) and the executive and judicial powers in the colonies (the Council of Indies) acted in conjunction with the crown to restrict access to key data such as historical, geographical, ethnographical and natural-historical accounts. Portuondo's reconstruction traces the institutional history of how the secrecy policy was conceived, formalized and institutionalized in the period between 1510 and 1571, when the Ordenanza del Consejo de Indias were approved, and how it was subsequently abandoned during the reign of Philip III (1598–1621) ‘under new rules of noble patronage that now rewarded public production’ (p. 259, original emphasis) – and of course the fact that ‘toward the end of the sixteenth century, keeping geographical information secret was becoming an increasingly futile exercise’ (p. 264). While Portuondo acknowledges from the start that political and institutional history must play a primary role in the characterization of Spanish cosmography, the role of individual cosmographers, their intellectual biographies, their careers and practices are by no means overlooked, but are often at the centre of the narrative. Figures such as Juan de Ovando at the Council of Indies; Rodrigo Zamorano, employed by the Casa de la Contratación between the 1580s and his death in 1620; Juan López de Velasco, the first cosmographer–chronicler major appointed by the Council of Indies in 1571; and Andrés García de Céspedes, cosmographer major of the Casa at the turn of the century, played leading roles in shaping the outlook of cosmography as a discipline in Spain. In this perspective, which looks at the relations both between individuals and between individuals and institutions, Portuondo's narrative traces a pattern of change starting with a historical-geographical approach, as epitomized by Velasco's Geografía y descripción universal de Indias, which brings together ethnographical, climatological and hydrographical descriptions, and Céspedes's more distinctive cartographical interests that resulted in the reform of the official map of the empire (1598) and the Regimento de navegación y hydrografía (1606), a publication that marked the definitive easing of the secrecy policy and became the new standard in Spanish navigational manual. By the early 1600s the mathematical aspects of cosmography, namely those producing hydrographic and geodetic data and other forms of graphic representation of the Spanish-ruled territories, were separated from text-based descriptions, such as chronicles and earlier forms of cosmography. This divorce was reflected in the establishment of two different positions: the cosmographer and the chronicler (Chapter 7). Finally, Portuondo's book not only provides historians with a wealth of information on the too-often neglected (at least by the English-speaking academic world) subject of the history of science in Spain, but also helps to formulate alternative hypotheses on processes of change in science. In Spain, she argues, it was the ‘utilitarian mandate’ imposed on cosmography by the state's interests that led to the demise of the ‘humanistic heritage in favour of quantifiable and discrete modes of collecting, compiling and presenting the New World’ (p. 300).

In sum, this is a well-documented and well-written book that will appeal to both specialists and the more general public as it provides access to a not-easily accessible but significant portion of the history of early modern cosmography and lays the foundation for further historical and theoretical enquiries into the discipline.