Whilst the greatest effort has been made to ensure the quality of this text, due to the historical nature of this content, in some rare cases there may be minor issues with legibility. MY friend Mr. J. Arthur Hill, having been more or less concerned in various remarkable experiences, thinks it desirable to publish them, and at the same time to discuss briefly the general subject from a reasonable point of view and in the light of a considerable knowledge of what has been done by others. He has asked me to introduce his little book to the Public; and accordingly I have pleasure in testifying to the careful and responsible truthfulness which characterises his presentation, and to the unemotional habit of mind with which he regards these phenomena.