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Rh rather to confirm their illustrious discoveries."

Of his travels, explorations, sufferings, and adventures, during the last nine years, not much is yet known, but it is hoped that records will be found giving additional information concerning the geography of interior Africa.

The readers of the will be pained to learn of the recent and sudden death of this brilliant young writer, with several of whose masterly papers they have become acquainted in the pages of this periodical. He died January 2d, at the age of twenty-six, of an attack of acute peritonitis, the result of a cold contracted by attending the funeral of a friend. The son of a distinguished physician, he was born at Belfort, in 1847. He studied at the Colmar Lycee, and there acquired a taste for chemistry. He attended the chemical lectures of Würtz at the College de France; and, at the age of sixteen, he made full abstracts of the course, which were so well done, that Würtz sent the copy to the printer with scarcely any alteration. He was recommended by Prof. Würtz to the editor of the Moniteur Scientifique, and had been employed upon that journal since 1864. He pursued original wort in chemical physiology, and discovered the possibility of substituting, in the bones of animals, phosphate of magnesia and of strontia for phosphate of lime. He has published several important papers besides those that have been reproduced in the, the most interesting of which will continue to appear in our pages. He was of very amiable disposition, strongly attached to his friends and teachers, and much beloved by all who knew him. His short career was in a remarkable degree successful, as he had attained a reputation and influence in France which is usually reached only by men in the riper years of life. His papers are being prepared for the press in Paris, and will be also separately republished in this country.



speak, in another place, of the importance of the great principle of the conservation of energy as a fundamental truth of modern science. The literature of this subject has hitherto been copious, but, as it has been mainly the product of minds engaged with the original research, it has often been so technical and complicated as to be difficult to popular apprehension. The writers have generally been too busy with the investigation to give the needed attention to the art of familiar statement. No subject was in greater need of thorough simplification and careful elementary treatment. Dr. Balfour Stewart, the distinguished physicist of Kew Observatory, and Professor of Owens College, was solicited to undertake this task for the "International Scientific Series." this he consented to do, and, although master of the philosophy, and entitled to a place among its original investigators, he has shown that he can enter into the spirit and do the indispensable work of the pure teacher. His book has been written in the simplest language, with abundant and familiar illustrations, so that the ordinary reader, by its perusal, can get a complete understanding of the elements of the subject. His volume is quite remarkable for its clearness and the success with which it explains many of the hitherto difficult parts of the subject.

Dr. Stewart, as we have said, is a physicist, and he has wisely limited himself to the operations of the law, as disclosed in physical phenomena. But, to give completeness to the volume, an appendix has been added incorporating two able essays, by distinguished men who have studied the question in its vital and mental relations. Prof. Le