scientific truths should be popularly put forward in simple, untechnical language, and made accessible to all." Later, in his chairman's address before the Chemical Subsection of the American Association, in 1878, he had this subject in mind, and mentioned it as part of the work of the section "to attract public attention to the subjects that interest us, and to do what we can to secure for chemistry a wider appreciation and greater means for development.... If the general public," he said later in his address, "is not interested in chemistry, it is because we as chemists have neglected a part of our duty. We have but to speak, in order to command the public ear." Another side of scientific advancement to which Professor Clarke's working life has proved him much attached is presented in this address at the American Association meeting of 1878, and more minutely as to the particular point we have in mind in an article on Laboratory Endowment, in the tenth volume of the Popular Science Monthly. In the association address he insisted strongly upon the physical side of chemical research, stated briefly as the study of the phenomena which occur during the reactions in chemical experiments, or of the transformations of energy, and upon the importance of the co-ordination of studies separately pursued to the systematic and permanent advancement of the science; for which purpose he considered endowed laboratories for research extremely desirable. In such laboratories adequate corps of thorough specialists should co-operate in those investigations which individuals could not undertake; every worker should be assigned to definite, positive duties, the accurate and careful performance of which would eventually be sure to advance exact knowledge. The work would be hard routine, and the real value of the institution would be independent of everything sensational, and would rest upon considerations of the most severely practical kind. As an example of such work he mentioned the study of the connection between the composition of a substance and its physical properties. Supposing this taken up systematically by a well-organized body of investigators, the first step would be to determine, carefully and with the utmost rigor, the physical properties of the elements. Each one of these substances would have to be isolated in quantity and in a chemically pure condition, such as has never been attained as to some--a labor which would of itself involve a great amount of research. Then would come the measurement of physical relations, thermal, electrical, optical, magnetic, mechanical, and so on; and the determination of all their "constants" under widely varied conditions, notably of pressure and temperature; labors which would in many cases involve the comparative testing of various methods of research, and often the invention of new experimental processes. The number of elements and of their compounds which should be taken up in