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places the population is maintained or increased by immigration, or by the children of recent immigrants. The fidelity of these to the duties of marriage is largely due not to the reason but to useful superstition. Intellectual inquiry invites infidelity. Skepticism has no soul, nor has it breeding power. Man must have a belief to be in earnest. The skeptics disappear, the superstitious survive, but progress can not live without intellectual activity. This is incompatible with the infallibility demanded for the integrity of superstition. So long as there is progress there must be intellectual independence. Here, then, is the dilemma—skepticism and sterility, or superstition and stagnation; progress to extermination, or perpetuation of life without improvement. This problem, and others kindred to it, are those for which I have sought a solution." Finally, the main motive of the work is declared to be the necessity of reproduction in man to enter any demonstrable future. The subjects of Sex, Marriage, Husband Choice, Wife Choice, The Child, Hints to the Husband, A Word to the Wife, and Religion, are discussed.

The Theory of Heat. By Thomas Preston. New York: Macmillan & Co. Pp. 719.

The author's object in preparing this volume has been to treat the science of heat in a comprehensive manner, so as to produce a tolerably complete account of the whole subject in its experimental as well as in its theoretical aspect. He has consequently enjoyed a freedom in his choice of subject-matter and mode of exposition which would not have been possible in a work designed to meet the requirements of some particular class of persons preparing for examinations or engaged in practical pursuits. The nobler aspect of science as an instrument of education and culture is kept in mind throughout, and the principle is enforced that an acquaintance with a number of facts does not constitute a scientific education, and there is no royal road to learning other than that by which it is pursued for its own sake. The most fruitful method of exposition, it is observed, is not necessarily that by which a given number of facts may be recorded in the shortest space, but rather that by which they may be most easily assimilated by the mind and most comprehensively grasped in their general bearings and mutual relations; and this is the method which is most calculated to advance knowledge and raise the intellectual character of the individual. The historical method of treatment is preferred, as admitting the most constant comparison of theory with the results of experiment and the closest scrutiny at every step of the development. With this is combined a due amount of detail in description and explanation to secure instruction and such suggestion and criticism as may excite intellectual life and independent thought on the part of the student. The classical experiments are given in detail, and in addition such other investigations are noticed as will give the student a general idea of the work that has been done in each department up to the present time. In the introductory chapter, or "preliminary sketch," some remarks are given on the general effects of heat and on the meaning of the terms used in the subject, the theories of heat are reviewed, and the subjects of matter and energy and the theories concerning them are discussed. In the subsequent chapters, thermometry, dilatation, calorimetry, change of state, radiation and absorption, conduction, and thermodynamics are considered. Such subjects as the steam engine and the theory of solutions are omitted, as having obtained separate treatment in special works. The kinetic theory of gases has been entered into so far as to meet the immediate requirements of the subject in hand; and the suggestion is made that it, with some other subjects usually dealt with in treatises on heat, are deserving of treatment in a separate volume.

Science and Christian Tradition. By Thomas H. Huxley. Collected Essays, Vol. V. New York: D. Appleton & Co. Pp. 419. Price, $1.25.

This volume contains ten of Prof. Huxley's vigorous magazine articles, first published in the years 1887 to 1891, to which is prefixed the Prologue to his volume entitled Controverted Questions. Among these essays are his series of three on agnosticism, and his two on the Gadarene swine miracle in controversy with Mr. Gladstone, while the others deal mainly with other miracles of the New Testament. In the essay on The Value of Witness to the Miraculous, Prof. Huxley scrutinizes certain mediæval miracles