The ultimate in sailing is a rig without a hull. Under this title the Scientific American published in March 1975 a reworked version of a paper written by J. G. Hagedoorn. Not knowing Mendel Hagedoorn, one would be inclined to ignore it as an absurd and impractical invention. But reading the article, one soon discovers that the author has a thorough understanding of the performance of a conventional sailing boat and that the proposed "ultimate sailing" is the result of a careful step by step investigation, the theory being continuously tested by experiments. Inspired by the Polynesian proa, Mendel removed the keel from the hull and placed it at the end of an outrigger to windward. At a later stage he eliminated the outrigger and connected the keel directly with a flexible leash to the sail. The keel was thus attached to a paravane, and experiments showed that this assembly could be towed by the sail, with the hull following passively. The inevitable next step was to let the sail also lift the hull out of the water. The ultimate sailing system is a combination of two "kites," one in the air and one in the water, with the sailor in between.
     This whole project reflects the typical traits of Hagedoorn's character: imagination, nonconformism and perseverance. Also, the manuscript is typically Hagedoorn. Again the clear definition of the problem, reducing it to simple proportions to make the essentials stand out, the use of accurate pictures meticulously drawn in proper perspective, the theory properly verified by experiments, the result at least a better insight and often a useful product.
     Born in Verrières-le-Buisson near Paris on August 8, 1912, Mendel Hagedoorn entered the Physical Institute of the University of Utrecht as a student in 1930. In 1948 he joined Shell and worked in their Exploration and Production Laboratory as a research geophysicist until 1968, when he became a full-time professor at the University of Leiden. He retired in 1977 and moved to the Canary Island of Palma, where he and his family still live. Mendel Hagedoorn has written numerous papers, many of them internal research reports for Shell. One paper, done in 1960, describes his experiments with a vertical spread.
     Six papers have been published in geophysical journals. I understand that the publication which he personally treasures most is the one on the Plus-Minus method, published in 1959. This paper offers a very practical tool for interpreting seismic refraction data, and apart from being an homage to Thornburgh, it is a highly instructive tutorial. This educational aspect is also characteristic for his well known paper A process of seismic reflection interpretation, which earned him the Conrad Schlumberger Award in 1976. At that time migration was a very topical issue and people remembered that no one had ever presented a better tutorial on the migration process than Mendel Hagedoorn.
     The other day, a Nobel prize winning economist who had written a new booklet was interviewed on the Dutch radio. The reporter asked, "How is it possible that such a learned man like you can write such a simple and lucid story?" The answer to that silly but understandable question was: "If you really have something to say then it is not difficult to communicate with people of good common sense." Judging his work by this yardstick we are all pleased that the SEG bestows Honorary Membership on Mendel Hagedoorn.

     Willem Goudswaard