Research index·Journal articleNotesNature·20 Dec 1917DOI10.1038/100309a0Journal articleNotesNature · 1917 · SubscriptionDOI10.1038/100309a0ReadRead at the publisherSaveCiteAdd to literature reviewPaywalledThe full text is at the publisherOpen it at the publisher to read it.Read at the publisherDiscussionAdd to the discussionTopicsPhilosophyRelated papersMoreDetailsPublished, publisher, issueSuggest a correction or report
