1. See my previous paper in the Philosophical Magazine November 1872 “On a Method of detecting the Phases of Vibration in the Air surrounding a Sounding Body, and thereby measuring directly in the vibrating air the length of its Waves and exploring the form of its Wave-surface.”
2. In this paper I give the credit of the suggestion on which I founded my micrometer to M. Radan, but I find that it is due to Zoch Pogg. Ann. cxxviii