W. A. Rogers, its builder, with which a millionth of an inch can be easily measured, and with careful adjustment even one twenty-millionth of an inch. In principle the apparatus is an application of Prof. A. A. Michelson's interferential refractometer, the interference of light-waves from mirrors attached to a standard and to a compared metallic bar enabling the observer to determine minute movements with a precision hitherto impossible.
An inquiry into the properties of paraldehyde and metaldehyde by Profs. W. R. Orndorff and John White illustrated the inferences whereby the chemist is able to body forth the respective positions in a molecule of the atoms which compose it. In the Anthropological Section the songs of sequence of the Navajoes were rendered by a phonograph, an instrument which promises to be as indispensable as the camera to the serious traveler. A discussion of the most animated kind took place in this section between Rev. G. F. Wright and Mr. W J McGee on certain evidences adduced by the former of preglacial man, Mr. McGee maintaining that the evidence was merely probable and not conclusive.
Half a century ago science was an affair of a few individuals, and a laboratory of any kind was to most people only a curiosity. The man who devoted himself to the study of Nature was looked upon as a visionary having neither place nor function among the contributors to human welfare; scientific methods in the arts were rarely heard of; natural knowledge had no part or place in education; and, besides an occasional learned treatise, two or three technical periodicals met all the needs of scientific publication.
But all this has now been changed. The last half of the nineteenth century will long be memorable as the period during which science achieved a prominent if not a leading place in nearly every department of human activity. The wonderful advance of discovery, closely followed as it has been by numerous practical applications, has wrought a revolution in many fields, until in the arts, in commerce, in education, and even in the professions, science may justly claim to exercise a controlling influence.
With all this there has come an enormous increase in the volume of scientific literature. Scores of scientific periodicals are engaged in the work of disseminating the results of investigation and books by the hundred are published every year in which the methods and conclusions of science are given more permanent record. The accumulation of material from this ceaseless and ever-increasing activity is already so great that ready means of access to it becomes an urgent need of the hour.
But it is only with a subdivision of this great body of knowledge that we are here specially concerned. In the early days of the scientific awakening just alluded to, it was only natural that the results obtained by workers in science should for the most part remain the possession of the student and investigator. That science, however, had a message for the people was not long in being perceived. Side by side with its many important industrial applications there had grown up a vast body of scientific knowledge only needing suitable interpretation to make it available for the masses. Under the stimulus supplied by a few enthusiastic public teachers there gradually arose a demand for this new kind of knowledge that would brook no refusal. In obedience to this desire of the public we have seen issuing from the press during the last twenty-five or thirty years a steadily growing stream of popular scientific literature embodying the ablest thought of the time, and much of it the direct product of our most distinguished scientific men.