decrement of magnetic force from the poles to the equator as the most important result of my American voyage." The subject arrested the attention of the British Association, which made special arrangements for its careful study. While living at Quito, Humboldt gave what he deemed first-hand study to the nature and cause of earthquakes and arrived at conclusions which were strengthened, as he believed, by similar studies in the same region by Bousingault, twenty-three years later. Bousingault's treatise on earthquakes, Humboldt accepted as the best and most authoritative ever written. Its theories will hardly be regarded as final by scientists of our time. Eocks, Humboldt declares, without any qualification are in the process of formation and disintegration. He divides them into eruptive, sedimentary, metamorphic and conglomerate rocks. The importance of the subject of paleontology is recognized in "Cosmos," but is treated almost as if it were a new science. Agassiz's work on "Fossil Fishes," in which more than 1,700 species were described, is given the honor it deserves. But open minded as Humboldt was to every suggestion of scientific men and ready to accept any well-authenticated statement, he was very cautious about departures from old and prevailing theories. Since his time, meteorology, as he predicted it would, has become a science of much practical value. Geology, mineralogy and paleontology have made giant strides. Chemistry has almost entirely changed its character, even its terminology has become new. The advance in physics almost defies description. Since Humboldt died Lord Kelvin, Clerk Maxwell of Edinburgh and Herz of Germany have done their epoch-making work on light. Lines of magnetic force and the character of the magnetic field are better understood than when Faraday gave his attention to them and through his discoveries received the warmest praise from Humboldt. Electricity as a science and in its practical applications has developed one might say almost entirely since 1859. Of radium and radio-activity, whose secrets Monsieur and Madame Curie and Rutherford have done so much to make known, Humboldt knew nothing. Nor had he any conception of the character and extent of the revelations from the heavenly bodies which studies in astro-physics have brought. But of science as it was in his day, and for some years after his death, he was a master and as competent as he himself believed and as others admit him to have been to make such general statements concerning its triumphs and promise as to show the careful reader of "Cosmos" even now the foundations upon which the scientific progress of the last half century has rested.
