Additional comments

Abstract

My initial comments applied to Dr. Hsieh's original paper. His reply contains an additional assumption not made previously; namely, that the vortex always consists of the same fluid particles. Also, he now considers a fixed region in the vicinity of the center, rather than following a "fictitious point at the surface moving so as to remain directly under the center of the upper vortex." In view of these changes, it appears desirable to add a few remarks.