546 THE POPULAR SCIENCE MONTHLY. 



munity. As we pass upward in the scale, the differentiation increases, 

 and there is a consequent division of labor, some of the cells being de- 

 voted 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. 







"THE ELECTEIC STORAGE OF ENEEGY." 



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 Wil- 

 liam 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, 

 w^hen 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 bat- 

 tery, 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 be- 

 come 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. 



