Abundant illustrations might be collected in evidence of the well-known truth that the burden of knowledge may diminish the energy of action; but this is rather outside of what we are considering, which is the influence of knowledge upon the intellectual and not the active life. I regret very much not to be able to suggest anything like a safe rule for the selection of our knowledge. The most rational one which has been hit upon as yet appears to be a simple confidence in the feeling that we inwardly want to know. If I feel the inward want for a certain kind of knowledge, it may perhaps be presumed that it would be good for me; but even this feeling is not perfectly reliable, since people are often curious about things that do not closely concern them, whilst they neglect what it is most important for them to ascertain. All that I venture to insist upon is, that we cannot learn any new thing without changing our whole intellectual composition as a chemical compound is changed by another ingredient; that the mere addition of knowledge may be good for us or bad for us; and that whether it will be good or bad is usually a more obscure problem than the enthusiasm of educators will allow. That depends entirely on the work we have to do. Men are qualified for their work by knowledge, but they are also negatively qualified for it by their ignorance. Nature herself appears to take care that the workman shall not know too much--she keeps him steadily to his task; fixes him in one place mentally if not corporeally, and conquers his restlessness by fatigue. As we are bound to a little planet, and hindered by impassable gulfs of space from wandering in stars where we have no business, so we are kept by the force of circumstances to the limited studies that belong to us. If we have any kind of efficiency, very much of it is owing to our narrowness, which is favorable to a powerful individuality. Sometimes, it is true, we meet with instances of men remarkable for the extent of their studies. Franz Woepke, who died in 1864, was an extraordinary example of this kind. In the course of a short life he became, although unknown, a prodigy of various learning. His friend M. Taine says that he was erudite in many eruditions. His favorite pursuit was the history of mathematics, but as auxiliaries he had learned Arabic, and Persian, and Sanskrit. He was classically educated, he wrote and spoke the principal modern languages easily and correctly;[1] his printed works are in three languages. He had lived in several nations, and known their leading men of science. And yet this astonishing list of acquirements may be reduced to the exercise of two decided and natural tastes. Franz Woepke had the gift of the linguist and an interest in mathematics, the first serving as auxiliary to the second.