Letter, from Thomas Maclear to Sir John Herschel, dated at Royal Observatory, Cape of Good Hope Autograph letter signed by sender. The zenith sector was brought by the Wellesley and is now at the Observatory. Outlines some observations he hopes to make with it. Is about to write to R. Thom[p]son. Has some important matters to discuss with John Frederick William Herschel when he calls. 12 December 1837