This letter, which has been printed in almost every book on the violin, would take up rather more space than can be afforded in this sketch. It is admirably clear and is divided into three parts, the first giving advice on bowing, "pressing the bow lightly but steadily, upon the strings in such a manner as that it shall seem to _breathe_ the first tone it gives, which must proceed from the friction of the string, and not from percussion, as by a blow given with a hammer upon it,--if the tone is _begun_ with delicacy, there is little danger of rendering it afterwards either coarse or harsh." The second section of the letter is devoted to the finger-board, or the "carriage of the left hand," and the last part to the "shake." Maddalena Sirmen received her instruction first at the conservatory of Mendicanti at Venice, after which she took lessons from Tartini. She also composed a considerable quantity of violin music, much of which was published at Amsterdam. About 1782 she, emulating the example of Madame Mara, appeared as a singer at Dresden, but with comparatively small success. Regina Sacchi, who married a noted German violoncellist named Schlick, was celebrated for her performances on the violin. She was born at Mantua in 1764, and educated at the Conservatorio della Pieta at Venice. This lady was highly esteemed by Mozart, who said of her, "No human being can play with more feeling." When Mozart was in Vienna, about 1786, Madame Schlick was also there, and solicited him to write something for the piano and violin, which they should play together at a concert. Mozart willingly promised to do so, and accordingly composed and arranged, _in his mind_, his beautiful sonata in B-flat minor, for piano and violin. The time for the concert drew near, but not a note was put upon paper, and Madame Schlick's anxiety became painful. Eventually, after much entreaty, she received the manuscript of the violin part the evening before the concert, and set herself to work to study it, taking scarcely any rest that night. The sonata was played before an audience consisting of the rank and fashion of Vienna. The execution of the two artists was perfect and the applause was enthusiastic. It happened, however, that the Emperor Joseph II., who was seated in a box just above the performers, in using his opera-glass to look at Mozart, noticed that there was nothing on his desk but a sheet of blank paper, and, afterward calling the composer to him, said: "So, Mozart, you have once again trusted to chance," to which Mozart, of course, graciously acquiesced, though the emperor did not state whether he considered Mozart's knowledge of his new composition, or Madame Schlick's ability to play with him unrehearsed, constituted the "chance."