In examining a specimen of the rhyolitic lava-flow of the Rocehe Rosse, Lipari, in the collection of the Royal College of Science, London, I was struck by tile fact that the areas of pure black glass visible upon the fractured surface were each bordered by a band of spherulitic matter, the convex surfaces of the spherulites being directed inwards towards tile glassy area. The specimen, collected by Prof. J. W. Judd, F.R.S., evidently comes from a portion of the flow which has become breceiated during movement of the viscid mass; intermingling of glassy and hemicrystalline matter has occurred, and an approach to the structure of the well-known "Piperno" of Naples has resulted. But the irregular little lumps of obsidian have not received their spherulitic crust from any chilling effect that they may have had upon the surrounding groundmass; the spherulites belong to the glass-fragments themselves, and are not deposited upon their surfaces.