A New General Catalogue of Nebulae and Clusters of Stars, Being the Catalogue of the Late Sir John F. W. Herschel. E-book. Formato PDF John Frederick William Herschel   -  Forgotten Books, 2017  - 

In the case of form, the scale was supposed arranged in the order: round, very little extended, elliptic or oval, considerably extended, pretty much extended, much extended, very much extended, extremely extended.