Page:Popular Science Monthly Volume 19.djvu/562

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munity. As we pass upward in the scale, the differentiation increases, and there is a consequent division of labor, some of the cells being devoted to one kind of work, while others engage in a special labor for the community. Instead of the sum of the vital forces possessed by an individual being confined to a single cell, they are scattered through a large amount of growing tissue.

The seat of vitality is protoplasm, and wherever there is enough of this vitalized substance to grow and reproduce its kind, there we have an individual—a unit of life. It may be concentrated in a single cell, or distributed through many cells, the number and distribution being determined by the amount of dependence of the growing cells upon each other. The greater the division of labor, the higher the form of life, and the more difficult to recognize the individual; but, whenever it is found, it consists of a mass of protoplasm, usually contained in one or more cells, capable of growth under proper conditions, and ultimately reproducing its kind.


SOME few weeks ago a letter appeared in the "Times," signed "F.R.S.," describing a "box of lightning" which the writer had brought over from Paris for the purpose of submitting it to Sir William Thomson. Since then a long discussion has taken place on the subject of the invention and its usefulness. To begin with, we fully share the regret of Professor Tyndall, who has written a letter on the matter, that so much loose nomenclature has been introduced into the subject. The term "electric storage of energy" appears to us to be singularly unhappy. What is known as a condenser, or a Leyden-jar, is truly an instrument for the electric storage of energy, because, when charged, its parts are in a condition of molecular strain, which is recognized as an electrical phenomenon; and the release of this state of strain invariably produces at first some of the phenomena of electricity in motion. But in the case of M. Faure's secondary battery, which is the invention under discussion, although it is charged by a current of electricity and gives out a current of electricity, the form of the store of energy which it contains is not that of electrical stress or strain, but that of chemical separation—a form of potential energy which can be caused, under certain circumstances, to become kinetic energy in the form of heat. However, the term has now become established, and, being convenient, will probably survive. But it is to be hoped that the real state of things will be thoroughly and publicly explained by our leaders of science, so that the use of this form of words may not cause a confusion in scientific ideas.