On the basis of N.E. Zhukovsky's ideas, it is shown that stress tensor and speeds of deformation tensor only approximately describe a force's condition in a liquid. This book presents the new vector form of the Newton's law for a viscous liquid and considers the method of calculation of a flow of bodies by a viscous liquid on the basis of "a hypothesis of replacement". This book can be useful to scientists and engineers working in areas connected with hydrodynamics.