NEARLY everyone who has become at all acquainted with popular German scientific works will have at some time fallen in with this well-known book by Dr. Muller. It first appeared in the year 1856, and received particular favour, in that in the first place it was really popularly written, and secondly, that it was useful as a book of reference for many questions which dealt with every-day phenomena. The book reached its fourth edition in 1875, and since then none other has appeared, except the one that we now have under consideration. Nineteen years have thus flown by since Dr. Muller undertook the last revision, and in this period one is not at all surprised to find that accepted views on many points have undergone great changes, and in some cases entire revolutions. Joh. Muller's Lehrbuch der Kosmischeti Physik. Funfte umgearbeitete und vermehrte Auflage, von Dr. C. F. W. Peters. (Braunschweig: Friedrich Vieweg und Sohn, 1894.)