=A.D. 1661.=--Somerset (Edward), second Marquis of Worcester, an English inventor, announces, in his “Century of Inventions” that he has discovered “a method by which at a window as far as the eye can discover black from white, a man may hold discourse with his correspondent, without noise made or notice taken; being, according to occasion given, or means afforded, _ex re nata_, and no need of provision beforehand: though much better if foreseen, and course taken by mutual consent of parties.” This method, he asserts, he can put into practice “by night as well as by day, though as dark as pitch is black.” REFERENCES.--Dircks’ “Life of Worcester,” p. 357; “Dictionary of National Biography,” Vol. LIII. pp. 232–237. =A.D. 1662.=--Rupert (Prince Robert), of Bavaria, son of Frederick V, elector palatine, and one of the founders of the Royal Society of London, is credited with the discovery of the curious glass bubbles called “Rupert’s drops.” These are merely drops of glass thrown, when melted, into water, and thus becoming suddenly consolidated into a shape somewhat resembling the form of a tear. The globular end may be subjected to quite a smart stroke without breaking, but if a particle of the tail is nipped off, the whole flies into fine powder with almost explosive violence. “Mr. Peter did show us the experiment (which I had heard talked of) of the chymicall glasses, which break all to dust by breaking off a little small end; which is a great mystery to me” (Samuel Pepys, “Diary,” January 13, 1662). Sir David Brewster discovered that the fracture of these unannealed drops was accompanied by the evolution of electrical light, which appears even when they are broken under water. Mr. Bennet observed that when one of the drops was placed upon a book, the latter was electrified negatively. REFERENCES.--The articles on “Annealing,” “Optics,” and “Electricity” in the “Encyclopædia Britannica”; also the biography in “Penny Cycl.,” Vol. XX. pp. 226–227; Le Cat, “Memoir,” London, 1749–1750, or _Philos. Trans._, XLVI. p. 175. =A.D. 1665.=--Grimaldi (Francesco Maria), Italian philosopher (1618–1663), member of the Order of Jesuits and an associate of the astronomer Giovanni Battista Riccioli (at A.D. 1270) is the author of the important work “Physico mathesis de Lumine ...” which cites the discovery of magnetism produced by the perpendicular holding of an iron bar. REFERENCES.--_Phil. Trans._ for 1665; “Engl. Cycl.,” article “Biography,” Vol. CXI. p. 207; Larousse, “Dict.,” Vol. VIII, p. 1531. And, for Riccioli’s works, see Houzeau et Lancaster, “Bibliog. Gén.,” Vol. III. p. 238; “Journ. des Sçavans” pour 1665 et 1666, pp. 642–647.