 Rather than revising the main text of the encyclopedia with each edition, Constable chose to add all updates to the supplement.It's probable that the 6th edition only exists because of the need to remove the long s, which had gone out of style, from the font, which required the whole encyclopedia to be re-typeset.The Supplement to the 5th edition was finished in 1824, and was sold with those sets, as well as with sets of the 6th edition, to be delivered at its completion.