before that time he had in 1564 obtained a cross-staff divided by transversals.[1] He says himself that Bartholomæus Scultetus had got the idea of this method of subdivision from his teacher Homilius, and now taught it to him; but in a letter to the Landgrave (of 1587) Tycho states that he was seventeen years of age when he at Leipzig learned the use of transversals for subdividing a straight line from Homilius.[2] The latter died, however, in July 1562, when Tycho was only 1512 years old, and had only been a few months at Leipzig, and it is therefore more probable that Scultetus really was the means of imparting the idea to Tycho. At all events, Tycho did not attempt to claim the invention for himself, though it was afterwards often attributed to him. But whether Homilius really was the first inventor is more than doubtful, and Scultetus himself has even stated that the method was already known to Purbach and Regiomontanus.[3] We can, however, scarcely believe this to have been the case, as it would be difficult to explain why the method had never come to light, even though Walther notoriously guarded the belongings of Regiomontanus with a curious fear of their being known; and in the Scripta of Regiomontanus there is no trace of his having used so excellent a method. Curiously enough, there are two other names mentioned in connection with this invention. In his book Alæ seu scalæ mathematicæ[4] Digges states that transversals were first applied to the divisions on the cross-staff by the English instrument-maker Richard Chanzler, and Reymers Bär mentions that the
- ↑ Mechanica, fol. G., 2nd page; Progymn., p. 671.
- ↑ Epist., p. 62.
- ↑ "Von allerlei Solarien, das ist, himmlischen Circeln und Uhren . . . durch Bart. Scultetum, Görlitz, 1572," quoted by R. Wolf, Astr. Mittheilungen, xxxiii. p. 90.
- ↑ London, 1573, fol. I. 3, where there is a drawing of a rectilinear scale with transversals.
