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Rh. Men unfamiliar with the symptoms of an approaching breakdown of their mental powers, frequently work on blindly until comes the fall from which no power can lift them. Sleeplessness is one of the most significant warnings, and should never pass unheeded. In this connection, the author's remarks on the use of chloral hydrate, as an agent for promoting sleep, serve as a timely warning against that deadly remedy. Its action on the nerve-centres is destructive, and it produces a permanent condition of brain-bloodlessness fatal to mental vigor. Hygiene is the subject of an able discussion. The book will, unquestionably, prove of great value to those who read it carefully. It is not, however, intended as a family prescription-book, but as a safeguard against disease. In every case of actual sickness, it advises that the family physician be sent for.

prefatorial remarks of the author announce that this book is a faint outline of a new and vast field of research, intended to give prominence to the more important points, rather than a finished and detailed history of cave-exploration.

Caves have in all ages, and in all countries, been regarded with feelings of superstitious veneration; here, as the dwelling-places of the sibyls and nymphs, there, as the shrines of Pan, Bacchus, Pluto, the seat of the oracles of Delphi and Mount Cythæron, and in the far East they were connected with the mysterious worship of Mithras. These feelings long secured them from intrusion and exploration. At length, in the sixteenth and seventeenth centuries, they were thrown open for examination by the desire which then arose in Germany to possess the "ebur fossile" or "unicorn's horn," a supposed infallible specific for the cure of many diseases. The "unicorn's horn" was to be found in the caves, and the search for it revealed the remains of lions, hyenas, elephants, and many other tropical or strange animals. At first these remains were supposed to have been washed thither from the tropics by the Deluge. Then the truth began to dawn that the animals lived in the surrounding country, and that the bones of such as were not cave-haunting were dragged into the caves by such as were. This truth was first enunciated by Rosenmüller in 1804. Between 1825 and 1841, an Englishman, the Rev. J. McEnery, discovered in Kent's Hole, near Torquay, the first "flint implements" ever observed, in a cave along with the bones of extinct animals, and he suggested that they proved the existence of man at the same time with those animals. But he died in 1841, leaving his suggestion scornfully repudiated by the scientific world; although, in 1840, Mr. Godwin Austin, by independent researches, verified its truth. It was not until after 1859 that the significance of this discovery came to be generally perceived and admitted. It, of course, immediately revolutionized the prevailing notions of the antiquity of man, while the previously-accepted theory of Rosenmüller unmistakably indicated the occurrence of remarkable geographical and climatal changes over the continent of Europe. The work before us traces the rise and progress of cave-exploration; considers the physical history of caves, that is, their formation, whether by sea or volcanic action; enumerates the most remarkable caves, with the objects they have yielded; treats of the character of the early inhabitants of Europe, and of the fauna of the same period, as indicated by the remains discovered; and, finally, of the climatal and geographical changes that have occurred since those deposits were made. The style is clear and vigorous, and the text is interspersed with numerous illustrations. The work will commend itself to all who have a desire to know something of what humanity was in that hazy period which stretches backward of the earliest records.

little book is designed for the use of the chemical student. Explanatory of its object, the author says, in his preface, that, during lectures, the student being