The comprehensive work on Human Physiology, by Dr. Flint, approaches its completion; 2,000 pages of it are done, and another volume of perhaps 500 more will finish the treatise. This is the most considerable effort yet made by an American in physiology, and the work, by its extent and thoroughness, will prove an honor to American science. Although covering extensive ground, and dealing with a wide range of topics, Dr. Flint's work is by no means a mere compilation. Its author is a working physiologist; a careful and industrious experimenter, he has done much, both in the way of original investigation, and in testing and verifying the investigations of others. The first volume of the series treats of Blood, Circulation, and Respiration; the second of Alimentation, Digestion, and Absorption; the third of Secretion, Excretion, Nutrition, Animal Heat, Movements, Voice, and Speech; and the fourth of the interesting and complicated subject of Nervous Structure and Nerve-actions. This is the most obscure and difficult of all the branches of physiology, and it is consequently that division of the science in which clear and definite knowledge being most wanting, its place is supplied by speculation and hypothesis. Dr. Flint has been very careful to guard against the danger that here arises, and to limit his exposition to those facts and conclusions which may be regarded as fairly and decisively settled. In his preface, he says: "The present volume treats of the physiological anatomy and the functions of the nervous system, as they appear to a practical physiologist, accustomed to accept nothing that is not capable of positive demonstration or well-sustained inference. Adhering conscientiously to the positive method of study, the author has endeavored to present an account of the nervous system which, though it will undoubtedly be extended by future investigations, is made up mainly of statements of facts that will probably not undergo serious modification as we advance in our knowledge of the subject. He has considered the properties and functions of the cerebro-spinal and sympathetic nervous systems mainly from this point of view; and has touched but slightly upon psychology, which has long been considered a science by itself. The special senses have been deferred, to be taken up in the fifth and last volume of the series." Dr. Flint's work is written in a remarkably clear and agreeable style; and, although he would probably not himself claim that it is a popular treatise, as it must needs deal with many things that are unfamiliar to the common mind, and clothed in scientific language, yet his pages are nevertheless in a high degree attractive to all intelligent persons who are interested in the higher problems and processes of life. His work will be as valuable for reading and reference in the libraries of laymen as in those of the professional student, and for this purpose we know of no work upon physiological science that equals the present. It is just the treatise for reference in school libraries. Our popular physiological text-books are necessarily very meagre and often unsatisfactory, and it is therefore desirable that some larger work should be at hand for consultation. Flint's "Physiology of Man" will be well suited for this purpose, not only from its fulness and authenticity, but also from the convenience of its form, which is in several handy volumes, instead of an unwieldy single volume.
An instructive description of Niagara and its surroundings, not a mere traveller's guide to its sights and curiosities, but an account of it as a great natural phenomenon, was much needed, and the want has been well supplied by the neat little handbook just issued by Sheldon. The author observes in his preface that, of all places so extensively known, Niagara Falls is probably the least known; the mass of people being quite satisfied with it as a grand spectacular sensation. To the geologists, however, it has ever been an interesting study, while the number of those who share their interest, who care to understand it as well as to see it, to know something of its past and future as well as of its present, must