Physical science did not occupy all his leisure. He wrote much. At different periods of his imprisonment, which cannot be precisely fixed, he composed a variety of treatises. He discussed many questions of politics, theoretical and practical. In his _Prerogative of Parliaments_ he undertook to prove by an elaborate survey of past relations between the Crown and the Legislature, that the royal power gains and does not lose through regular and amicable relations with the House of Commons. The _Savoy Marriage_ is a demonstrative argument against the proposed double family alliance between Savoy and the House of Stuart. Of that, and of his _Discourse of the Invention of Ships_, his _Observations concerning the Royal Navy and Sea Service_, and the _Letter to Prince Henry on the Model of a Ship_, I have already spoken. He composed _A Discourse on War in General_, which is very sententious. From his notebooks he collected, in his _Arts of the Empire_ and _The Prince_, better known as _Maxims of State_, a series of wise, almost excessively wise, thoughts which had occurred to him in the course of his eager reading. An essay on the _Seat of Government_, and _Observations concerning the Causes of the Magnificency and Opulency of Cities_, show equal exuberance of learning, chiefly classical, though they cannot be said to be very conclusive. The former reads as if it had been meant for an introduction to a contemplated ampler view of polity. He must have studied not merely general, but economic politics, if the _Observations touching Trade and Commerce with the Hollander_ _and other Nations_ be by him. That remains a matter of doubt. Both Oldys and a recent German writer ascribe the work, published under five varying titles, to John Keymer, the Cambridge vintner, who is said to have composed, about 1601, _Observations upon the Dutch Fishery_. Ralegh more commonly has the credit of it. The dissertation, first printed inaccurately, and under a different heading, in 1650, shows minute statistical information, though it propounds, as might be expected, not a few economic fallacies. Its aim is the not very generous one of abstracting the carrying trade from Holland. The author engages, if he should be empowered to inquire officially, to enrich the King's coffers with a couple of millions in two or three years. [Sidenote: _Moral and Metaphysical Essays._]