The reasons why the University of Chicago Press published the English translation of Dohrn-van Rossum's study on time and time reckoning in the Middle Ages originally written in German, are obvious. The author displays an enormous knowledge about the history of clocks and about the impact of the measuring of time in the Middle Ages. His monograph proves to be well organized and clearly written, and invites the reader to a thorough examination of medieval mentality with respect to time.
The book is divided in ten chapters that are arranged chronologically. After an introductory chapter on the consequences of the introduction of the mechanical clock on medieval mentality, Dohrn-van Rossum first studies the methods of time-keeping in antiquity, then turns to medieval hours, daily routines in monastic life, and the computus. The fourth chapter covers the largest ground in the entire book as here the author deals with medieval horologia and the development of the wheeled clock. He examines water clocks in Christian Europe and in the Islamic world, discusses the astrolabe, the "mercury clock," astronomy as a framework for time-measuring, the emergence of clock bells in cities, hour- striking clocks, hourglasses and the first pocket clock.
In the fifth chapter we learn about the tremendous increase in the dissemination of clocks in public and in churches during the fourteenth and fifteenth centuries. Subsequently, Dohrn- van Rossum pays attention to late-medieval clockmakers, to communal bells, municipal signal systems (seventh chapter), and to the introduction of modern hour-reckoning (eighth chapter). The introduction of "early-modern" time measuring devices also deeply influenced the organization of labor in the cities beginning in the fifteenth century (ninth chapter). Here the author considers the introduction of "work bells" which were used to structure the work time in the medieval industry, but he also stresses that the "hourly wage" was mostly an invention of the eighteenth century.
In the tenth chapter Dohrn-van Rossum turns to the international mail delivery organization (von Taxis) in the Hapsburgian empire established in the early sixteenth century, and concludes with some remarks on the development of the modern postal system in the nineteenth century.
The great strength of this study rests in the careful treatment of the technical-historical inventions as they were dealt with in the chronicles, and in the author's untiring efforts to consider the social-political implications of the new time- measuring mechanisms that were to transform medieval society at large. Dohrn-van Rossum works both as a technical historian, fully capable of explaining mechanical details of new time measuring devices, and as a historian of science when he examines astronomy and instruments such as the astrolabe. Most important, though, prove to be his investigations of mental history by focusing on attitudes towards time, time measuring, and economy. Over and over the author turns to medieval chroniclers and reflects upon their observations regarding clocks and the measuring of time. Fortunately, he has not limited his investigation to German sources, but has taken all of medieval Europe into account.
Another indisputable strength of this study seems to be the author's meticulous interpretation of a wide range of medieval accounts referring to clocks and their installations in monasteries, churches, towers, and at market places. Finally, the wealth of illustrations make this book a very pleasant scholarly contribution. The subject index included at the end demonstrates the astonishing range of topics covered in this book. Dohrn-van Rossum has written not only a standard-setting history of the hour, but also a history of time consciousness in the Middle Ages and of the early modern age.