If much be confusion which concerns Thomas Vaughan, all is chaos in respect of Eirenæus Philalethes. He would appear to have emigrated to America at a comparatively early period. The Amsterdam original edition of his _Experimenta de Præparatione Mercurii Sophici_, which was issued by Daniel Elzevir in 1668, describes that work as _ex manuscripto philosophi Americani, alias Æyrenæi Philalethes, natu Angli, habitatione Cosmopolitæ_. In this way, those who have refrained from identifying him with Thomas Vaughan, carefully confuse him with George Starkey, also an Anglo-American, who claimed a familiar acquaintance with Philalethes, and who, owing his initiation to him, may be considered his philosophical son, but not his _alter ego_. Starkey returned to London, and wrote several chemical books, some of which detail the transmutations performed by Philalethes in the apothecary’s trans-atlantic laboratory. He died of the plague in London in 1665, while Eirenæus continued publishing for many years after that date, and lived for some time on intimate terms with the illustrious Robert Boyle, who, however, has given us no biographical particulars concerning him. Not the least curious fact in the history of this mysterious adept is the apparently complete disappearance of numbers of his printed works, which an authentic list extends to some forty volumes, some of which seem perfectly unknown and unheard of by bibliographers and collectors alike. Langlet du Fresnoy enumerates several manuscript treatises, but gives no clue to their whereabouts. It is from the books of Philalethes himself that we must be contented to glean the scanty facts of his life. The thirteenth chapter of the _Introitus Apertus ad Occlusum Regis Palatium_ contains the following remarkable account of its author:--