This volume concludes the second series of Leonhard Euler's Opera Omnia. It contains Euler's contributions to cosmic physics. Most substantial is the Essay on the Tide, which shared the prize awarded by the Paris Academy of Science in 1740. Other topics are the constitution of the atmosphere, ocean currents and winds, comets, the resistance of the aether, the lunar atmosphere, and the shape of the earth. The papers collected in this volume span a period from 1727 to 1775. They show Euler's lasting interest in questions of cosmic physics.