HELMHOLTZ, in his "Handbuch der physiologischen Optik" (1867), stated that the demonstration of the blind spot of the eye, the discovery of which was communicated by the Abbé Edme Mariotte to the Royal Academy of Sciences in France in the winter of 1667–68, was given before the King of England in 1668. Dr. J. Bröns, of Copenhagen, in a monograph on "The Blind Spot of Mariotte" (London: H. K. Lewis and Co., Ltd., 1939. 12s. net), proves that this statement is erroneous, and brings forward strong evidence of the manner in which it arose. In 1776, Georg Simon Klügel, professor of mathematics in the University of Helmstädt, published a translation of Joseph Priestley's "The History and present state of Discoveries relating to Vision, Light and Colours" (London, 1772). On p. 144 of the translation there is a footnote as follows: "(a) Smith's Opticks, Remarks, p. 6 (d. d. Ausg. S. 367). Oeuvres de Mariotte, p. 496. (Der Versuch ist 1668 vor dem Konige von England gemacht. Birch, T. 2, p. 281. Haller's Phys., T. 5, p. 470, K.) "The reference to Birch shows that the communication to the Royal Society was made by Oldenburg, and not by Mariotte, and there is good evidence that the king was not present at that, or indeed any other, meeting. The reference to Albrecht von Haller, also a footnote, is in his "Elementa physiolgise corporis humani" (Lausanæ, 1763), also contained in his "Anfangsgründe der Physiologie", S, p. 470, Berlin-Leipzig, 1772. This reads as follows: "Factum ann. 1668 coram S. Reg. Maj. T. Birch, T.II, p. 281. Exstat oper. Mariot, p. 496, Ed. Holl.". Dr. Bröns thinks that Klügel expanded the footnote to "Factum anno 1668 coram Sua Regia Majestate", adding his translation "Der Versuch ist 1668 vor dem Künige von England gemacht", whereas it should read "Factum anno 1668 coram Societate Regise Majestatis"—"the experiment was shown before the Royal Society".