of the BIS on account of several original scientific articles in the Journal of the British Interplanetary Society . In 1959 his book Grondbeginselen van de Ruimtevaart appeared, followed in 1960 by an English translation: Principles of Astronautics and in 1965 in a much enlarged second edition. At the date of the first edition, this book was the first to treat the whole field of astronautics in a succinct though scientific manner. A Russian(!) edition was also issued. In 1961 he was invited to attend the First International Symposium on Analytical Astrodynamics, which was held at the University of California. After the symposium he held a lecture on Interplanetary Orbits for personnel of Douglas Aircraft. In 1964, after 12 years as director of the institute, he retired permanently. In 1970 he was elected an Honorary Member of the Dutch Astronautical Society and in the same year an Honorary Member of the Bond voor Materialenkennis. He published many articles in the Journal of the B.I.S. and in the British periodical Spaceflight, as well as in Astronautica Acta and several Dutch periodicals. Furthermore he read papers for several international Astronautical Congresses. Through his education and career, Vertregt gained an incentive to take an interest in many sciences and arts. During his study at the Technical School at Dordrecht, where he learned mathematics, chemistry, physics and mechanical and chemical engineering, he studied Greek and Latin for himself in order to get a better understanding of the special features of these civilisations. From early youth he had learned English, French and German, and later in life he added Italian and Spanish. Moreover, from youth he had an absorbing interest in history and read widely in it and the history of art. In this manner he got a broad viewpoint on a vast terrain of human endeavour. Wanting to make this accumulated knowledge useful, he described the history of the civilisation of the countries of the Mediterranean and Western Europe in his book The Threefold Way. He also designed a Martian Calendar. Marinus Vertregt died in 1973 at Sliedrecht, Netherlands. In 1979 a lunar crater was named after him on request of the Dutch Astronautical Society. Sources Gartmann, H. (1956), "Vlucht in de ruimte", translated from German by E. Franquinet, Amsterdam/Brussel, Elsevier. Article from Spaceflight about the Vertregt Martian calendar 1897 births 1973 deaths 20th-century Dutch astronomers Scientists from Dordrecht