with the discoveries of natural science—botany, for instance. In one way we take a historical series of events and work out the known items of the series, and range the persons and places of our action, until we know where to look for the missing links, and go to look for them and find them. Such a success, and every student of original sources working with zeal and modesty may hope for such, is in a small way like that of the astronomer who, when from calculating the perturbations and so on of the heavenly bodies he has inferred the existence of a hitherto unknown planet, some bright evening and with a new improved glass discovers the real planet of which he has been thinking, and sees in it, not only a great new fact of science, but a proof of the correctness of his computations, a substantial reward for his efforts. And the other is that in every such search, be it successful or not, the inquirer, who is wide awake, is sure to come upon material that is even more valuable than what he looks for; makes discoveries that are not less delightful because they are accidental.
Of course it may be said that a great deal of useless knowledge is accumulated in this way; what good can be done, it may be said, by analysing Matthew Paris, and determining how much of his narrative is drawn from ancient charters, or foreign letters, lives of saints, or such stribiligines: it is his historic power and authority that gives them value, not they that give authority to him. Not quite so, I think, and even if it were so, there might be a lesson in the mere proof of the fact; the analysis is necessary for the due estimate of his value as a historian; the writer who can pass such an ordeal where it is possible to apply it, may be trusted where it is not possible to apply it. But I take the higher ground and say, how far can any knowledge be said to be useless? there may be much useless learning, I allow; accumulations of other men's thoughts, and crude heaps of second-hand memories that are alike useless to their owner and to the world. But not real knowledge, not a substantiated fact, however remote it may seem from the interests and uses of the day, or the object of the day. It may serve to complete a chain of demonstration, the necessity of which is not as yet apparent; it may furnish,
