Abstract
Part I.
1) New terms are introduced in the equation of motion of a viscous fluid in order to generalize Fujiwhara-Sakakibara's transverse resistance.
2) The microscopic mechanism in the fluid, on account of which the existence of the new terms are admitted of, are explained briefly.
Part II.
1) It is demonstrated by making use of the new equation that: “If an incompressible viscous fluid is moving irrotationally under the influence of conservative forces, there will never arise a vortex spontaneously. But if there once occursa vortex for some extraneous reason, it can either grow or die out by itself.”
2) We know by our daily experience that if we remove the plug of a washbasin, a rotational motion of water is very liable to occur. This phenomenon is accounted for dynamically by means of the new equation of motion.
3) The difference that lies between the rôle of the ordinary viscosity and that of the new term is discussed. The former acts on the vortex so as to diffuse its vorticity, while the latter tends to concentrate or accumulate the vorticity.
