Note on a Formula in Solid Geometry

In the issue of the Journal for February last, Mr. Gulasekharam gave under this title a neat solution of the problem of calculating the angles between the lines in which a cone is cut by a plane through its vertex. The following method of dealing with the same problem is neither original nor new; I myself had it from Dr. Bromwich several years ago, and there is an echo of it in § 7°34 of my Multilinear Functions of Direction.