Read of JH's intention to prepare general catalogue of nebulae. Encloses list of unpublished nebulae found at Harvard over past 15 years. Finds similarity in form but difference in theory between JH's equations for curve of object glasses ['On Aberrations of Compound Lenses and Object Glasses' (1821)] and those of K. A. Steinheil and C. F. Gauss. Asks about Josef Fraunhofer's theory.