To turn from warfare to more peaceful matters--for the full story of Danubian warfare would make a volume by itself larger than this--it is interesting to find that John Kepler, one of the founders of modern astronomy, lived here for some years, and here married in 1613, a portionless orphan named Susanna Reutlinger. In a letter to a friend, Kepler reviewed the various qualifications of no fewer than eleven “candidates for his hand,” and explained the reasons that decided him in his choice. It seems so curiously unromantic a beginning, that it is pleasant to learn from the astronomer’s biographers that the marriage turned out well. We get a glimpse of the scientist at home in a letter which Sir Henry Wotton wrote to Francis Bacon in 1620:-- “For a beginning let me tell your Lordship a pretty thing which I saw coming down the Danuby, though more remarkable for the application than for the theory. I lay a night at Lintz, the metropolis of the higher Austria, but then in very low estate, having been newly taken by the Duke of Bavaria, who, _blandiente fortuna_, has gone on to the late effects. There I found Kepler, a man famous in the sciences, as your Lordship knows, to whom I purpose to convey from hence [Vienna] one of your books, that he may see that we have some of our own that can honour our king, as well as he hath done with his _Harmonica_. In this man’s study I was much taken with the draft of a landscape on a piece of paper, methought masterly done: whereof inquiring the author, he bewrayed with a smile it was himself; adding, he had done it, _non tanquam pictor, sed tanquam mathematicus_. This set me on fire. At last he told me how. He hath a little black tent (of what stuff is not much importing) which he can suddenly set up where he will in a field, and it is convertible (like a windmill) to all quarters at pleasure, capable of not much more than one man, as I conceive, and perhaps at no great ease; exactly close and dark, save at one hole, about an inch and a half in diameter, to which he applies a long perspective trunk, with a convex glass fitted to the said hole, and the concave taken out at the other end, which extendeth to about the middle of this erected tent, through which the visible radiations of all the objects without are intromitted, falling upon a paper which is accommodated to receive them: and so he traceth them with his pen in their natural appearance, turning his little tent round by degrees, till he hath designed the whole aspect of the field. This I have described to your Lordship, because I think there might be good use made of it for chorography: for otherwise to make landscapes of it were illiberal, though surely no painter can do them precisely.” The thing upon which Wotton dilated was the camera obscura of which he had evidently not heard before, though it had been described sixty years earlier by Baptista Porta, to whom the invention is sometimes attributed.