tions of Lyell and Dana, but nearer doubtless to the latter than to the former. Ramsay's paper "On the Glacial Origin of Certain Lakes" was published in 1862; and the past quarter-century has witnessed the rise, culmination, and decline of a glacial period in the explanation of the origin of lakes. Some writers have carried the theory to so extreme a length as to make the great lakes of our Canadian frontier exclusively or chiefly the results of glacial erosion. But the climate has ameliorated, and the theory of glacial erosion has melted into more moderate proportions. Twenty-five years ago the Darwin-Dana theory of the origin of barrier reefs and atolls by subsidence, stood, as it had stood for a score of years before, almost unquestioned; but, within the past two decades, we have seen the rise, and, I think I may say, the decline, of a formidable rival. Murray's theory of the formation of atolls, by the more rapid growth of the corals at the periphery of the shoal upon which they are growing, the gradual extension of the reef upon a foundation formed by a talus of blocks of coral. rock, and the widening and deepening of the lagoon by solution, seemed to many so complete and satisfactory an explanation of facts as to render unnecessary the hypothesis. of a vast subsidence of the oceanic bottom. The Duke of Argyll, who, as King James said of Lord Bacon, "writes of learning like a Lord Chancellor," made the assumption that the subsidence theory had been certainly disproved the basis of a wholesale charge of dishonesty against scientific men, alleging that there had been a conspiracy to suppress the new views, because scientific men were unwilling to admit the fallibility of their idol, Darwin. But, in fact, the simple reason why there has been no general celebration of the funeral of the Darwin-Dana theory is, that it is not dead. The renewed study of the subject has indeed somewhat modified, but has not disproved, the doctrines taught by those two great masters. It is, indeed, true, that an atoll may be formed without subsidence. It is none the less immensely probable that the great number of atolls in the Indian and Pacific Oceans do owe their origin to a vast subsidence of the ocean bottom. It is a very significant fact that, whereas Archibald Geikie, in the first edition of his "Class-Book of Geology," published in 1886, gave only the Murray theory for the explanation of atolls, completely ignoring the Darwin-Dana theory, he states both theories in his second edition, published four years later, expressing no preference between them. The year 1867 is important in the history of American Geology, as being the date of the beginning of geological exploration under the auspices of the National Government. Previously to that time, geological work had been carried on only incidentally, in connection with expeditions undertaken for some other object, as in the case of the Pacific Railroad Explorations and the Mexican Boundary Survey. In these and other expeditions undertaken by the government previously to 1867, the place of geology was, as Clarence King has well expressed it, only that of a camp-follower. Since 1867, we have had the energetic explorations and the elaborate reports of the Survey of the Territories, the Survey of the Fortieth Parallel, the Survey West of the One Hundredth Meridian, and the Survey of the Rocky Mountain Region; and now, on still larger scale, and with still richer results, the United States Geological Survey. Among the contributions which these Surveys have given to geological science, may be mentioned the recognition and discussion of laccolites, a new type of igneous eruptions, the revelation of the history of Lakes Bonneville and Lahontan, the study of the wondrous canyon system of the Colorado and its tributaries, and the investigation of the complicated orogenic movements of the Rocky Mountains. It was not in vain that the group of brilliant geologists whose names are associated with the history of these Sur veys studied a region in which the topographical features are developed with a largeness of scale and a simplicity of structure unparalleled elsewhere in the world. The share which different nations have taken in the development of geological science, is dependent not alone upon the genius of individual workers, but in large measure upon the peculiar geological conditions of the various countries in which they have worked. It was in the presence of the varied mineral wealth of the Harz Mountains that Werner laid the foundations of Mineralogy and Lithology. The magnificent display alike of igneous and of aqueous agencies in the Highlands of Scotland helped to guide Hutton to those theoretical views which were the beginning of modern Dynamical Geology. The remarkable completeness with which, in so small an area, the English series of formations is developed, enabled William Smith to lay the foundations of Stratigraphical Geology more satisfactorily than would probably have been practicable in any other country in the world. The wealth of vertebrate fossils in the Paris Basin gave opportunity for Cuvier to create the science of Paleontology. The distinctive contribution of the United States to geological science seems to be the theory of topographic evolution, including the distinction of antecedent, consequent, and superimposed drainage, and the doctrine of base-levels. It is true that a beginning had been made in this line of work long before. As carly as 1847 Ramsay had perceived that the summits of a number of the Welsh mountains lie in an inclined plane extending from Snowdon down to the sea, and had formulated the conception of plains of marine denudation. Jukes, and still more distinctly Archibald Geikie, had recognized that, in the so-called plains of marine denudation, the greater part of the work of erosion is really effected by subaerial agencies. But it required the study of our western plateaus to develop the doctrine of base-levels into the form which it has taken in the writings of Powell and Gilbert. To the last quarter-century belongs the development of modern Lithology, or Petrography. It was in 1862 that Sorby called the attention of Zirkel to some microscopic slides which he had prepared, and thenceforward Zirkel devoted his life to the systematic development of the new mode of investigation. The year 1867 was the date of the first general work in which the subject of Lithology was treated from the new standpoint-the "Philosophie der Geologie" of the lamented Vogelsang. While the modern Lithology is characterized especially by the application of the polarizing microscope to the examination of thin sections, microscopic work has been supplemented by new methods of analysis, such as the use of solutions of high specific gravity for the separation of the various ingredients of rocks, and the application of powerful electro-magnets for the isolation of ironbearing minerals. Too much time for your patience, though too little for the adequate treatment of the subject, has been given to the history of the two sciences especially cultivated by our Association, Biology and Geology. Only a passing glance can be given to the progress of other sciences. In 1867, there was no refracting telescope in any astronomical observatory with an object-glass of more than eighteen inches diameter. That size has been doubled in the objective of the telescope of the Lick Observatory. In 1867, Spectroscopic Astronomy was yet in its infancy. revelations of the physical constitution of the heavenly bodies, and their motions relative to the earth, its discovery of double stars too remote for any telescope to resolve, were yet in the future. The investigations of Newton and Schiaparelli on the relation of comets and meteors were published about the beginning of the period which we have under review. Twenty-five years ago the doctrine of the Conservation of Energy was still a new idea struggling for acceptance, although Joule's determination of the mechanical equivalent of heat had been made as early as 1850. Carpenter had already announced the correlation of physical and vital forces; but that phase of the general doctrine was still counted heterodox. Ferrel had given the key to the true theory of the winds as early as 1856; but twenty-five years ago his work was generally ignored. His views have in fact found their way into the text-books on Meteorology and Physical Geography only within the last few years. During the last quarter-century there has been an immense expansion of the quantitative, in distinction from the merely qualitative, study of electrical phenomena, and a vast development of the practical applications of electricity. The earliest successful trans-oceanic telegraph cable was laid in 1866-only one year before the date at which our survey of scientific progress begins. Essentially, therefore, to this quarter-century belongs the development of submarine telegraphy, as well as the invention of the telephone, and the practical development of electric lights and electric motors. Twenty-five years ago we were accustomed to speak of certain substances as "permanent gases," in distinction from carbon dioxide and certain other substances, gaseous under ordinary conditions, but capable of liquefaction under the action of cold and pressure. The phrase and the idea have been abolished by the brilliant experiments of Pictet and Cailletet. Twenty-five years ago Avogadro's generalizations in regard to the molecular constitution of gases were just in process of resurrection, and the new chemical formulas were gradually displacing the old ones. At that time Organic Chemistry still wore an aspect of something like magic or supernaturalism, and had not yet become simply the chem |