April 14, 1922] 



SCIENCE 



405 



Richards) are related in a linear way to many 

 of the properties of the elements and their 

 salts. 



From the average of the most logical values 

 of the effective radii of atoms and ions of the 

 alkali metals and the halogens it is found that 

 the space functions of the third powers of the 

 radii are as follows: for halogen ions, cs„ (ratio 

 of cube of radii X 6.063 X lO--' to gram-ionic 

 volume) — .44; for halogen atoms, 9„ = .25 

 (agreeing with van der Waal's postulate); for 

 alkali ions, cp„ -— .25; and for alkali atoms, 

 qjj, — .52. In othei' words the volume of the 

 halogen ion is roughly 44-25 that of the atom, 

 and the alkali ion 25-52 of the corresponding 

 atom. Upon this simple basis the molecular 

 volumes of the alkali halides are found to be 

 dependent as 3.35 X 10-^(r^i,ai-ioa + 



l-76r\,K.ion)- 



Finally there are many linear relationships to 

 be found among the other elements: e. g., the 

 molecular volumes of the cuprous, silver and 

 thallous halides and the stability of the triam- 

 mines of these halides, to the atomic volumes 

 or ionic sizes of cuprous copper, silver and 

 thallium; the atomic volumes of calcium, stron- 

 tium and barium (in some cases also lead), to 

 the molecular volumes of practically any alka- 

 line earth salt, or the stability of the hexam- 

 mines of the metals (e. g., Ca. 6 NH,) to the 

 ionic sizes of the alkaline earths; the molecular 

 volumes of various sulfides, selenides and tel- 

 lui'ides to the size of sulfide, selenide and tel- 

 luride ions; the molecular volumes of the 

 oxides to the atomic volumes of titanium, zir- 

 conium and cerium; and numerous linear rela- 

 tionships between the molecular volumes, sta- 

 bility, percentage contraction and heats of 

 dissociation of complex compounds and the 

 molecular, atomic and ionic dimensions of the 

 constituents of the whole complex molecule. 

 These will be considered in a separate paper. 



The general method of representing the 

 properties of salts as functions of the dimen- 

 sions of their constituent ions (or of the atomic 

 volumes of the constituent elements) is of 

 such fundamental importance that an extensive 

 study of the characteristics of these surfaces 

 is now being made in collaboration with Pro- 

 fessor A. C. Lunn and Professor W. D. Har- 



kins of this university. As has been stated 

 some of these surfaces are planes, while most 

 of the others are doubly ruled. 



George L. Clark 

 University of Chicago, 

 Februasy 3 



THE AMERICAN ASSOCIATION FOR 



THE ADVANCEMENT OF SCIENCE 



SECTION L (1) HISTORY OF SCIENCE 



The History of Science section was organ- 

 ized on a temporary basis at the Chicago 

 meeting of the American Association for the 

 Advancement of Science, December, 1920. At 

 the Toronto meeting, December, 1921, it was 

 formally organized, and recognized by the 

 Council of the American Association for the 

 Advancement of Science as a sub-section in 

 Section L (Historical and Philological) 



This step now assures the future of the His- 

 tory of Science movement in the United States. 

 The movement has been growing steadily, not 

 alone in active interest and research Ijy various 

 scholars, but by the fact that our colleges, uni- 

 versities and technical schools are taking cog- 

 nizance of its place in the curriculum of science 

 and technology. 



If we are, at all, to enter a new epoch of 

 science teaching, and give more emphasis to 

 the humanistic element in our sciences, it is 

 evidently time now to consider the matter. 

 Science, that which we love to call pure science, 

 has been too long dominated by the ulterior 

 motive of materialism. 



The fact that the American Association for 

 the Advancement of Science has recog- 

 nized the value and purpose of History of 

 Science, and accorded it a place in its compre- 

 hensive activities, indicates a step forward, 

 not alone in the "Association" progress, but in 

 science, and in educational methods as well. 



A movement that can be fostered by two 

 large and widely different organizations, such 

 as the American Historical Association and the 

 American Association for the Advancement of 

 Science, is doubly assured of success and 

 future stability, in relation to other intellectual 

 movements. 



The Toronto meeting was in charge of a local 



