I conclude this chapter with a passage from the life of Columbus by Washington Irving which affords a fitting parallel from history in the higher development and union of two formerly hostile Kingdoms, and the moral of it is clear and simple. But as a forensic junior I beg to enter a _caveat_ to the effect that though the name of Columbus occurs no suggestion is made of the discovery of a New World. “It has been well observed of Ferdinand and Isabella that they lived together not like man and wife whose estates are in common, under the orders of the husband, but like two monarchs strictly allied. They had separate claims to sovereignty in virtue of their separate Kingdoms, and held separate councils. Yet they were so happily united by common views, common interests, and a great deference for each other, that this double administration never prevented a unity of purpose and action. All acts of sovereignty were executed in both their names; all public writings subscribed with both their signatures; their likenesses were stamped together on the public coin, and the royal seal displayed the united arms of Castile and Aragon.” CHAPTER V. METHOD OF PROOF. In a matter of scientific inquiry one cannot go far wrong if one follows the advice of Henri Poincaré, who lays down certain principles of method; four of these are the following:-- (1) The most interesting facts are those which can be used several times, those which have a chance of recurring. (2) The facts which have a chance of recurring are simple facts. (3) Method is the selection of facts, and accordingly our first care must be to devise a method. (4) We should look for the cases in which the rule established stands the best chance of being found fault with. The groups of facts described in the succeeding chapters are in agreement with these principles in the main, and are perhaps like a dust heap for their intrinsic value. But one knows that before now among a good deal of _débris_ a rusty key has been found which has opened a cabinet containing certain treasures, and in the hands of someone else than the finder has produced useful results.