Another foundation stone of science is the law of the conservation of matter. J. J. Thompson, from experimental work, explains certain observations by the existence of substances called electrons, a thousand times smaller than hydrogen, which we have regarded the lightest chemical element. The electrons appear to carry an electric charge. One farther step is then taken by the Cambridge professor, who says these corpuscles are electricity. They are attenuated matter. Electricity is a form of energy. We need no law for the conservation of the matter. Ostwald has taught that when one struck his shin on a chair in the dark, it was not the solid wood, but the force involved which produced the sensation. One would not have been conscious of the existence of the obstacle, but for the energy. Matter is energy. Here one is on the boundary lines of experimental science and dealing with a metaphysical problem. It must not be forgotten, however, that two hundred years ago any suggestion of the Röntgen rays could well have been placed in a similar category. Whether the explanations be accepted or not, it may be noted that Lodge has already illustrated, by beautiful lecture experiments, the possibility of a practical utilization of the facts of some of the observations. Fog is easily dissipated through the agency of electricity. The application of the principle on a gigantic scale, to a city like London, may yet be realized. There are in the world, as is well known, numerous organisms belonging to the vegetable kingdom that do not resemble at all any of those things we are accustomed to look upon as plants. These bacteria are extremely small. They are from .00002 to .00004 inch in diameter. They are studied, not by ordinary vision, but by means of microscopes and by microscopes of only the very best kinds. They are, also, studied by their effects. They propagate very rapidly. Starting with one organism they may grow, within twenty-four hours, to 281,470,000,000 individuals. This rapidity of growth does not actually take place in nature; it is checked through natural conditions, or through excretions of the organism inhibiting such propagation. We hear a great deal as to the production of virulent diseases through the agency of bacteria; but, while there are evil bacteria, there are, also, bacteria that are good. In short, we may understand, that all good bacteria are not dead bacteria. These bacteria exist in very large numbers in the soil. The upper portion of rich garden soil may contain, on an average, from one to five millions per cubic centimetre. This number may be very much greater, depending upon the amount of decomposed matter that is present and the favorable conditions for their propagation.