strict demonstration as also the refutation of a proposed explanation becomes correspondingly difficult. IV I turn to another point, in some respects the most important of all; I refer to the readiness with which we interpret as the remarkable frequency of coincidences what is due to a strong interest in a given direction. Inasmuch as we observe what interests us, a recently acquired interest will lead to new observations--that is, new to us, however familiar they may be to others. Take up the study of almost any topic that appeals to human curiosity, and it takes no prophet to predict that within a short time some portion of your reading or your conversation, or some accidental information, will unexpectedly reveal a bearing on the precise subject of your study, often supplying a gap which it would have been most difficult otherwise to fill; but surely this does not mean that all the world has become telepathically aware of your needs and proceeded to attend to them. Some years ago I became interested in cases of extreme longevity, particularly of centenarianism, and for some months every conversation seemed to lead to this topic, and every magazine and newspaper offered some new item about old people. Nowadays my interest is transferred to other themes; but the paragrapher continues quite creditably to meet my present wants, and the centenarians have vanished. When I am writing about coincidences, I become keen to observe them; such for example as this: I was reading for the second time an article on "Mental Telegraphy" (by Mark Twain in "Harper's Monthly Magazine," December, 1891); I was occupied with what is there described as a most wonderful coincidence, the nearly simultaneous origination by the author and by Mr. William H. Wright of a similar literary venture,--when I happened to take my eyes from the page and saw on my desk a visiting-card bearing the name, "W. H. Wright." It was not the same W. H. Wright, but a gentleman whom I had met for the first time a few hours before, and have not seen since. Had I not been especially interested in this article and its subject, the identity of the names would certainly have escaped my attention, and there would have been no coincidence to record. Quite apropos both of coincidences and of their dependence upon personal interest, I find recorded in a current magazine the experience of one who became enthusiastically interested in thoroughbred cats: "Strangely enough--for it is a thing which is recurrently strange--I, who had rarely seen any printed matter relating to cats, now found the word in every newspaper. Adopting a new interest is like starting a snowball; as long as it moves, it gathers other particles to itself."