Extra-galactic nebulae, by Edwin Hubble 68428 [Author: Edwin Hubble] [Link: https://www.gutenberg.org/6/8/4/2/68428] [Files: 68428-0.txt; 68428-h.htm] Thanks to an anonymous Project Gutenberg volunteer (This book was produced from images made available by the HathiTrust Digital Library.) Regards, Al