In all that relates to the famous cave known through the middle ages as the "Purgatory of Saint Patrick", as well as the Story of Luis Enius -- the Owain Miles of Ancient English poetry -- Calderon was entirely indebted to the little volume published at Madrid, in 1627, by Juan Perez de Montalvan, entitled "Vida y Purgatorio de San Patricio". This singular work met with immense success. It went through innumerable editions, and continues to be reprinted in Spain as a chap-book, down to the present day. I have the fifth impression "improved and enlarged by the author himself," Madrid, 1628, the year after its first appearance: also a later edition, Madrid, 1664. As early as 1637 a French translation appeared at Brussels by "F. A. S. Chartreux, a Bruxelles." In 1642 a second French translation was published at Troyes, by "R. P. Francois Bouillon, de l'Ordre de S. Francois, et Bachelier de Theologie." Mr. Thomas Wright in his "Essay on St. Patrick's Purgatory," London, 1844, makes the singular mistake of supposing that Bouillon's "Histoire de la Vie et Purgatoire de S. Patrice" was founded on the drama of Calderon, it being simply a translation of Montalvan's "Vida y Purgatorio," from which, like itself, Calderon's play was derived. Among other translations of Montalvan's work may be mentioned one in Dutch (Brussels, 1668) and one in Portuguese (Lisbon, 1738). It was also translated into German and Italian, but I find no mention of an English version. For this reason I have thought that a few extracts might be interesting, as showing how closely Calderon adhered even to the language of his predecessor. In all that relates to the Purgatory, Montalvan's work is itself chiefly compiled from the "Florilegium Insulae Sanctorum, seu vitae et Actae sanctorum Hiberniae," Paris, 1624, fol. This work, which has now become scarce, was written by Thomas Messingham an Irish priest, the Superior of the Irish Seminary in Paris. No complete English version appears to have been made of it, but a small tract in English containing everything in the original work that referred to St. Patrick's Purgatory was published at Paris in 1718. As this tract is perhaps more scarce than even the Florilegium itself, the account of the Purgatory as given by Messingham from the MS. of Henry of Saltrey is reprinted in the notes to this drama in the quaint language of the anonymous translator. Of this tract, "printed at Paris in 1718" without the name of author, publisher or printer, I have not been able to trace another copy. In other points of interest connected with Calderon's drama, particularly to the clearing up of the difficulty hitherto felt as to the confused list of authorities at the end, the reader is also referred to the notes.