Page:Popular Science Monthly Volume 26.djvu/148

This page has been proofread, but needs to be validated.


British Association Addresses.—Professor Roscoe's address before the Chemical Section was on "The Progress of Chemistry since 1848." The author made the year 1848 a dividing line between the epoch of Berzelius, which closed then, and that of Dumas and Wurz, which closed in 1884. The differences between the two epochs are shown in the distinct views which were entertained as to the nature of a chemical compound. According to the older notions, the properties of compounds were determined largely by the qualitative nature of their constituent atoms, and these were arranged so as to form a binary system. According to the newer view, it is mainly the number and arrangement of the atoms in a molecule that regulate the characteristics of a compound, which is to be regarded, not as built up of two constituent groups of atoms, but as forming a single group. The theory of substitutions, the relation of atomic weights and volume-combination, the prominent part assigned to organic radicals, the doctrine of valency or atomicity, and Mendelejeff and Lothar Meyer's periodic law, under which we may predict the nature and place of as yet undiscovered elements, and the study of isomeric phenomena, are also distinctive marks of the later chemistry. The artificial synthesis of a few coloring-matters and of kairine, a febrifuge as powerful as quinine, are among its most noteworthy achievements. Of the work that has been done in the determination of chemical constants, the labors of Mallet on aluminum, of J. P. Cooke on antimony, and of Thorpe on titanium, are especially mentioned. The speaker gave accounts of the progress that has been made in spectrum analysis, and the close distinctions of the molecular properties and constitution of bodies which it has made possible. Other indications of progress are given in Sir William Thomson's speculations on the probable size of the atoms; Helmholtz's discussion of the relation of electricity and chemical energy; and the theory of the vortex-ring constitution of matter, as suggested by Sir William Thomson and worked out by Mr. J. J. Thomson. Much experimental attention is now given to thermo-chemistry. The discovery of the liquefaction of the gases by Pictet and Cailletet, including Andrews's discovery of the critical point, indicates a connection, long unseen, between the liquid and the gaseous states. Deville's investigations of the laws of dissociation have opened out entirely fresh fields for research, and given new, important, and interesting views concerning the stability of chemical compounds. Professor Roscoe considered the best method of educating chemists to consist in giving them as sound and extensive a foundation in the theory and practice of the science as their abilities will allow, rather than in forcing them prematurely into original preparations and investigations.

Mr. W. T. Blanford, President of the Geological Section, presented some remarks upon contradictions which had been observed in certain districts, in the determination of the age of geological formations as indicated by their fossils. The most of them occur where a land or fresh-water fauna or flora assigned to a particular formation rests upon a marine bed of apparently later origin: as in Greece, where the supposed Miocene fauna of the Pikermi beds overlie strata with Pliocene mollusca; and in certain described places in India, Australia, and South Africa. Only one case of contradiction between two marine formations is known, and that is in dispute. In making choice between the two witnesses, geologists take the marine formations; for marine faunas and floras are more widely diffused than those of the land, and more nearly uniform throughout the world. Thus, of fishes, eighty families are typically marine, and twenty-nine are confined to fresh water; of the first, fifty are universally or almost universally distributed; while of the second, only one is found in five of Wallace's regions, and not one is met with in all the six regions. Among plants, so uniform is the marine vegetation of the world, that no separate regions can be established in the ocean, while Drude makes fourteen on the land. It appears to the author that at the present day the difference between the land faunas of different parts of the world is so vastly greater than that between the marine faunas that, if both were found fossilized, while there would be but little difficulty in