HERWART VON HOHENBURG was a highly stimulating correspondent. His scientific curiosity was insatiable ; his official duties as Bavarian Chancellor precluded personal research ; and he accordingly deputed to the busy brain of Kepler the working out of problems which engaged his scanty leisure, while baffling his powers. The pressure of his demands was, indeed, so severe that Kepler at times bewailed himself in confidential quarters over the grinding labours they imposed upon him: but he could ill afford to quarrel with a patron who was as generous as he was inquisitive ; and he thus continued to evolve for his benefit the stores of curious learning and adventurous theory of which some considerable specimens have lately been unearthed, and are now presented to the public. Ungedruckte wissenschaftliche Correspondenz zwischen Johann Kepler und Herwart von Hohenburg, 1599. Erganzung zu: Kepleri Opera Omnia, ed. Chr. Frisch. Nach den MSS. zu Munchen und Pulkowa edirt von C. Anschutz. (Prag: Victor Dietz, 1886.)