This is a collection of 30 volumes of 'The Penny Cyclopaedia of the Society for the Diffusion of Useful Knowledge', according to one source there was a 31st book, but unfortunately no copy of it could be found to include here. Besides these books the 'Society' also published a weekly magazine 'The Penny Magazine of the Society for the Diffusion of Useful Knowledge' that lasted 14 years, each year of the magazine was also bound into a single volume. These can be found at http://archive.org/details/ThePennyMagazineOfTheSocietyForTheDiffusionOfUsefulKnowledge
The magazines were edited and published in London by Charles Knight & Company, in New York by William Jackson, and in Boston by Joseph H. Francis., in Philadelphia by Orin Rogers, and in Baltimore by W. N. Harrison.
Each volume of the encyclopedia takes a look at various subjects, some of the articles have an accompanying illustration.
They were digitized by Google are where available from the site http://books.google.com/ (as of July 22, 2012) the books are in the "Public Domain in the United States", and Google allows these files to be freely available for non-commercial use, and that they 'Maintain attribution' as to that they scanned them and where the files came from.
Volume 01: A - Andes
Volume 02: Andocides - Athanagilde
Volume 03: Athanaric - Bassano
Volume 04: Bassantin - Bloemaart
Volume 05: Blois - Buffalo
Volume 06: Buffon - Charles's Wain
Volume 07: Charleston - Copyhold
Volume 08: Copyright - Dionysius
Volume 09: Dionysius - Erne
Volume 10: Ernesti - Frustum
Volume 11: Fuego, Tierra Del - Haddingtonshire
Volume 12: Hadley, John - Intestina
Volume 13: Intestines - Limoges
Volume 14: Limonia - Massachusetts
Volume 15: Massagetae - Muridae
Volume 16: Murillo - Organ
Volume 17: Organ - Pertinax
Volume 18: Peru - Primates
Volume 19: Primaticcio - Richardson
Volume 20: Richardson - Scander-Beg
Volume 21: Scanderoon - Signet
Volume 22: Sigonio - Steam-Vessel
Volume 23: Stearic Acid - Tagus
Volume 24: Tai-Wan - Titlarks
Volume 25: Titles of Honour - Ungula
Volume 26: Ungulata - Wales
Volume 27: Wales - Zygophyllaceae
Supplement to, Volume 1, Abati - Gyrosteus
Supplement to, Volume 2, Habenaria - Zingiber
The Second Supplement to Penny Cyclopaedia of the Society for the Diffusion of Useful Knowledge
*According to 'The Book Seller, page 575. Booksellers Association of Great Britain and Ireland, Publishers' Association - June 2, 1877' there is also a book called "The Third Supplement to Penny Cyclopaedia" but I haven't found any library that carries it, and it might possibly not exist.