Your article on the "Patrons of Astronomy," in the Mirror, No. 328, brought to my recollection the following anecdote, for the truth of which I can answer, having received it from Mr. Watson, well known as the most celebrated private optical instrument maker in Europe, and at the time living on intimate terms with the late Mr. Arnold, the most eminent watchmaker of the day. When the late Sir William Herschel's great telescope was first exhibited at Slough, among other scientific men who went to see it was Mr. Arnold, who took Mr. W. with him. Neither of them thought much of it, though it was praised by the multitude; as it was, with its constructor, patronized by the late king and his consort, for Herschel was a German, as you well know. A few astronomical amateurs, who thought as Mr. Arnold did, proposed to Mr. Adams, of Fleet-street, then astronomical instrument maker to the king, (by whom Mr. Watson was employed,) to get Watson to make an instrument in opposition to Herschel's. The order being given by Adams, Watson set about the work, and had made some progress in the construction of the instrument, when the circumstance found its way to the ears of royalty. Orders were immediately sent to Mr. Adams to put a stop to the work, or he should no longer be optician to the king. Watson did not proceed, but could never learn the cause of the counter-order, till after a lapse of several years, when a stranger called on him, in Valentine-place, Blackfriars-road, and after putting several questions to him about his instruments, related to him the cause of the counter-order; upon which Mr. Watson showed him the progress he had made, and which I have also seen. This story I heard related by Mr. Watson at a dinner party at Mr. Arnold's, at Well Hall, near Eltham, where were also Mr. Dollonds, and Mr. J. R. Arnold, the son. A Constant Reader. August, 24, 1828. Our Correspondent will perceive that we have qualified some phrases of his letter, but that all the facts appear.