The author explained that he was glad to be able to bring before the Society some apparatus illustrative of Dr Crookes's splendid researches on what he calls radiant matter. This he was able to do by the skill of Mr Gimingham, who had prepared some splendid vacuum tubes for him lately. He valued those researches very highly, because they brought most conclusive evidence to bear upon the truth of the kinetic theory of gases; because they gave us a clear insight into the action of the electric current and discharge; because they promise to help us in forming a notion of what electricity really is; and because we may also hope from these researches to get some knowledge of the nature of molecules.