Correspondence on new inventions and techniques, as well as trials of existing equipment, including the Greenwich spectroscope (with plans, drawings and suggestions), the transit circle, the altazimuth, the double edge micrometer and others. The correspondents include J.A. Broun, W. Huggins, W.H.M. Christie and W. De La Rue. There are also scales for old micrometers, a water pressure card, sketches for eyepieces and two photographs of a German heliometer.