The first part of this volume centres on Daniel Bernoulli's two prize-winning essays sent to the Paris "Academie des Sciences" in the 1740s. The first of these papers deals with the improvement of inclination compasses, giving a detailed analysis of the reasons for the great deviations observed in conventional instruments and suggesting alternative constructions; the second, written in collaboration with Daniel's brother Johann II Bernoulli, expounds a theory of magnetism based on Cartesian vortices of subtle matter. The second part is dedicated to Bernoulli's work on the technology of time measuring, especially in connection to the determination of longtitude at sea. This section also contains two prize essays submitted to the Paris academy.