Faraday's distinguished successor, Professor Tyndall, in his admirable and generous tribute to his famous predecessor, says: "As far as electricity has been applied _for medical purposes_, it is almost exclusively Faraday's." How much of addition to human comfort that one sentence includes, who can estimate? And who can calculate the money-value to commerce in the production of instruments used in the application of electricity to medicine? Professor Tyndall continues: "You have noticed those lines of wire which cross the streets of London. It is Faraday's currents that speed from place to place through these wires. Approaching the point of Dungeness, the mariner sees an unusually brilliant light, and from the noble Pharos of La Hève the same light flashes across the sea. These are Faraday's sparks, exalted by suitable machinery to sunlight splendor. At the present moment (1868), the Board of Trade and the Brethren of the Trinity House, as well as the Commissioners of Northern Lights, are contemplating the introduction of the magneto-electric light at numerous points upon our coast; and future generations will be able to point to those guiding stars in answer to the question, what has been the practical use of the labors of Faraday?" SIEMENS One of the most useful of modern men was Sir William Siemens, who was born in 1823 and died in 1883. The year before his death he was president of the British Association, and was introduced by his predecessor, Sir J. Lubbock, with the statement that "the leading idea of Dr. Siemens's life had been to economize and utilize the force of Nature for the benefit of man." It is not our purpose to give a sketch of his life, or a catalogue of his many inventions, all of which were useful. It was his comprehensive and accurate study of the universe which led him to discover, as he thought, that it is a vast regenerative gas furnace. The theory has been that the sun is cooling down; but Dr. Siemens saw that the water, vapor, and carbon compounds of the interstellar spaces are returned to the sun, and that the action of the sun on these literally converted the universe into a regenerative furnace. On a small scale, in a way adapted to ordinary human uses, and by ingenious contrivances, he produced a regenerative gas furnace which so utilized what had hitherto been wasted that, in the last lecture delivered by Michael Faraday (1862) before the Royal Society, he praised the qualities of the furnace for its economy and ease of management; and it soon came into general use. It is probably impossible to calculate the amount of saving to the world due to his practical application of the theory of the conservation of force to the pursuits of industry. It has changed the processes for the production of steel so as to make it much cheaper, and so revolutionized ship-building. The carrying power of steel ships is so much greater than that of iron ships that the former earn twenty-five per centum more than the latter.