of individual facts and observations, colligated by minor laws and analogies, but unilluminated as yet by the broad light of any great and all-embracing general principles. Since Dalton's atomic theory, indeed, no philosophic generalization of the very first magnitude has been introduced into chemistry. But generalizations of the second order—vastly interesting to chemists, and to chemists alone—have been made in such numbers as to defy enumeration; wider conceptions have in many ways sprung up; the science has assumed a new form; and some of the results of spectrum analysis and of the new chemistry lead to the hope that this science too is on the eve of arriving at that stage of far-reaching fundamental truths, which it is the special function of our generation to bring about.
Mathematics has also undergone a new development, scarcely capable of being rendered comprehensible to the lay intelligence.
The applications of physical, electrical, and chemical science in the great mechanical and industrial inventions of our iron age, belong elsewhere, and are already familiar in many respects to all of us. Railways slightly antedate the epoch; the telegraph is just coeval with it. The first submarine cable was in 1851, the first transatlantic in 1866. Electro-plating, the steam-hammer, the Armstrong gun, the Bessemer process, must not be forgotten. Other triumphs of applied science fall more fitly under another heading.
Among the concrete sciences, astronomy has made vast advances during the past half-century. Lord Rosse's great telescope was set up at Parsonstown in 1844. Two years later, Leverrier and Adams made their curious simultaneous discovery of the planet Neptune. But it is not so much in new lists of suns or satellites—though the name of these alone has, indeed, been legion—as in the fresh light cast upon the nature and constitution of older ones, that our age has been most singularly successful. The invention of the spectroscope, and the rapid development of spectrum analysis, have placed in the hands of astronomers a method and an instrument inferior in value only to the telescope itself. It is not so long since Comte dogmatically declared we could never know anything of the chemical composition of the fixed stars. Scarcely were the words well out of his mouth when the invention of the spectroscope and its application to the spectra of incandescent bodies brought the investigation of the elements in the sun and stars well within the reach of human possibility. The successive researches of Wheatstone, Foucault, Secchi, Bunsen, Kirchhoff, and Norman Lockyer, exactly covering our fifty years, have at last enabled us to prove almost with certainty the presence in the solar envelopes of several metals already known in the earth's crust, such as potassium, sodium, calcium, iron, nickel, and chromium. So delicate is the spectroscopic test, that it renders possible the detection of so small a fraction as 1200,000,000 part of a grain of sodium. And by revealing bright lines in the spectrum not
