ONE by one, at long intervals, there come to light new letters of Mozart and the originals of those letters which are to be found in a shortened and frequently garbled form in Nissen's and Jahn's biographies and in the collections of Ludwig Nohl and Gustav Nottebohm. The present letter to his father,(l) now in the possession of Frau Maria Floersheim-Koch, who has generously allowed me to publish it, is of great interest, not only on account of the period to which it belongs, but also because it helps to solve a problem which so far has baffled all students of Mozart's operas. The letter is written on the first two sides of a folded sheet and