Foster, Sir Michael Man, unscientiﬁc man. . . is often content with ‘the nearly’ and ‘the almost.’ Nature never is. It is not her way to call the same things which differ, though the difference may be measured by less than the thousandth of a milligramme or of a millimetre, or by any other like standard of minutemess. And the man who, carrying the ways of the world into the domain of science, thinks that he may treat Nature’s differences in any other way than she treats them herself, will ﬁnd that she resents his conduct; if he in carelessness or in disdain overlooks the minute difference which she holds out to him as a signal to guide him in his search, the projecting tip, as it were, of some buried treasure, he is bound to go astray, and, the more strenuously he struggles on, the farther will he ﬁnd himself from his true goal.