ARTICLE PDF RIGHTS AND PERMISSIONS Reprints and permissions ABOUT THIS ARTICLE CITE THIS ARTICLE Books Received. _Nature_ 106, 651 (1921). https://doi.org/10.1038/106651b0 Download citation

* Published: 01 January 1921 * Issue Date: 13 January 1921 * DOI: https://doi.org/10.1038/106651b0 SHARE THIS ARTICLE Anyone you share the following link with will be able to read this

content: Get shareable link Sorry, a shareable link is not currently available for this article. Copy to clipboard Provided by the Springer Nature SharedIt content-sharing initiative