If we consider the logical ease with which the successful solution of one portion of a problem suggests the next step; how imperceptibly and yet effectively sentiments and points of view and the spirit of the time are disseminated; how many persons there are in this busily reflective era occupied with similar thoughts and schemes, and how readily they may come into communication; how many are anxiously studying the popular taste and demand to determine what literary venture or mechanical invention is likely to be timely and successful; how the possession of a common inheritance, patriotic interests, education, literature, political arena, social usages, newspaper intelligence, household conveniences, and the endless everyday factors of our complex, richly detailed existence all contribute to our common life,--shall we wonder that some two or half a dozen intellects should give expression to similar thoughts at nearly the same time? Would it not be infinitely more wonderful if such coincidences did not constantly occur? In the more original contributions to literature, science, and inventions, such thought-correspondences should be rarer; and certainly this is true. Contrast the number of striking similarities in the higher walks of literature and science with those that occur in small inventions. Hardly a day passes without the coincidence of two persons thinking of devices for accomplishing the same purposes, so essentially similar that patents could not be given to both. It is certainly not difficult to understand why several different patterns of typewriting machines should be invented nearly simultaneously, and it would not be altogether mysterious if, at the first, two inventors had independently reached the idea of a writing-machine at nearly the same time. The experience of offering an article to an editor and receiving a reply to the effect that another article dealing with a similar topic in a similar way was already awaiting the compositor is not unusual. It is true that these coincidences are of a minor order, but it seems desirable to emphasize the frequency of these minor forms in order to suggest the law-abiding character of the rarer or the more striking forms; for this is just what the normal distribution of such phenomena would lead us to expect.