 Many illustrious contributors were recruited to this edition, including Sir David Brewster, Thomas de Quincey, Antonio Panizzi and Robert Stephenson.James Wilson did all of Zoology, Dr. Hampden did all of Greek philosophy, and William Hosking contributed the excellent article Architecture.Thomas Thomson, who wrote Chemistry for the 3rd edition supplement 40 years earlier, was recruited to write that article again for the 7th edition.