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ber of specimens of plants and animals, selected by Mr. Calkins to represent the more interesting groups of organic forms, are printed in colors upon cards for convenience of handling in the class-room. It needs not to be said that these illustrations are beautifully executed, and cannot fail to prove in a high degree attractive to children. That they have been executed with care and correctness, under the vigilant direction of Mr. Calkins, there can be no doubt. As to their utility in education, that will depend entirely upon the teacher and the policy of the school. If employed as guides to the study of real objects, they cannot fail to be helpful; but, if subordinated to the usual system of study, and accepted in place of the things they represent, they will have simply the value of excellent pictures, and will add to the already immense mass of hindrances and stumbling-blocks which the schools interpose between the minds of children and the objects of Nature.

The Stone Age, Past and Present, by E. B. Tylor; and Theory of Nervous Ether, by Dr. Richardson, F. R. S. Boston: Estes & Lauriat. Price, 25 cents.

This is No. 9 of "Half-Hour Recreations in Popular Science." The first paper is a popular account of the stone age, or, as the author puts it, "of that period in the history of mankind during which stone was habitually used as a material for weapons and tools." This period he divides into two parts, the first of which he calls the Unground Stone Age, when the implements employed were merely chipped out, and used in a comparatively rough and imperfect shape. Such implements are found in greatest abundance in the Drift or Quaternary Deposits, and in the early bone-caves, and consist largely of chipped flints, apparently designed for spear-heads, arrow-heads, scrapers, knives, etc. The second or later division of the period above referred to—the Ground Stone Age—is characterized by the employment of ground and often polished instruments of stone, much more perfect than the chipped forms, and therefore denoting a higher stage of human progress. Stone implements are found in nearly every part of the world, and, whatever their source, show a remarkable uniformity of pattern. This latter feature the author accounts for partly on the principle that man does the same thing under the same circumstances, and partly on the belief that the art was derived by one race from another. The evidences of the stone age, brought to light in the countries hitherto explored, take up the remainder of the paper. Any one wishing a general idea of what is at present known on this interesting subject, will be well repaid by a perusal of this essay.

The theory of a nervous ether we will give in the author's own words: "The idea attempted to be conveyed by the theory is, that between the molecules of the matter, solid or fluid, of which the nervous organism, and indeed of which all the organic parts of the body are composed, there exists a refined, subtile medium, vaporous or gaseous, which holds the molecules in a condition for motion upon each other, and for arrangement and rearrangement of form; a medium by and through which all motion is conveyed; by and through which the one organ or part of the body is held in communion with the other parts, and by and through which the outer living world communicates with the living man—a medium which, being present, enables the phenomena of life to be demonstrated, and which, being universally absent, leaves the body actually dead; in such condition, i. e., that it cannot, by any phenomenon of motion, prove itself to be alive." The paper is devoted to an elucidation of this theory.

Insects of the Garden: Their Habits, etc. By A. S. Packard, Jr. Boston: Estes & Lauriat. Price, 25 cents.

This is the first part of a volume from the pen of Prof. Packard, entitled "Half-Hours with Insects," to be issued in twelve parts, of about 36 pages each, by the above house. Beginning with some general considerations on the relations of living objects to one another, the author passes thence to the subject of agriculture, and the manner in which its interests are affected by the incursions of insects. Numerous instances are given of their terrible destructiveness to crops, which, though apparently insignificant when estimated, say, for