editor, and it was he who enlisted the assistance, as contributors, of the most eminent men of science then living in Scotland. Professors Robison, Thomas Thomson and Playfair were the most notable of these specialist contributors, and a Supplement in two volumes was issued in 1801 to allow them to extend their work to those earlier letters of the alphabet which had already been issued by MacFarquhar. It was their labours which first gave the Encyclopædia Britannica its pre-eminent standing among works of reference, and prepared the way for it to become, as a later editor claimed, not merely a register but an instrument of research, since thereafter the leading specialist in all departments were invited to contribute their unpublished results to its pages.
In the Fourth Edition, published by Andrew Bell in twenty volumes from 1801 to 1810, the principle of specialist contributions was considerably extended, but it was only brought to such degree of perfection as was possible at the time by Archibald Constable, "the great Napoleon of the realms of print," who purchased the copyright of the Encyclopædia Britannica soon after Bell's death in 1809. Constable lavished his energy and his money on the famous "Supplement to the Fourth, Fifth and Sixth Editions," which in 1813 he commissioned Macvey Napier to edit. It was with the appearance of this Supplement that the Encyclopædia Britannica ceased to be a purely Scottish undertaking, and blossomed out into that great cosmopolitan or international enterprise which it has since become. The most eminent writers, scholars and men of science in England and on the continent of Europe, as well as in Scotland itself, were enlisted in the work: Sir Walter Scott, Jeffrey, Leslie, Playfair and Sir Humphry Davy, Dugald Stewart—who received the then unprecedented sum of £1000 for a single contribution—Ricardo, Malthus and Thomas Young, with foreign men of science like Arago and Biot. From this time onward, indeed, a list of the contributors to successive editions of the Encyclopædia Britannica would be a list of the most eminent British and American writers and thinkers of each generation; the work had become the product of the organized co-operation of acknowledged leaders of the world's thought in every department of human knowledge. For this advance the credit is mainly due to Constable.
The Fifth and Sixth Editions, each in twenty volumes, issued by Constable between 1815 and 1824, were practically reprints of the Fourth, the Supplement—issued in six volumes from 1816 to 1824—being considered adequate to supply their deficiencies. The Seventh Edition, edited by Macvey Napier on the same lines as the Supplement, of which it incorporated a great part, was brought out by a new publisher, Adam Black, who had bought the copyright on Constable's failure. This edition was issued from 1830 to 1842, and was comprised in twenty-one volumes, which included a general index to the whole work. The Eighth Edition, under the editorship of T. Stewart Traill, was issued by the firm of A. & C. Black, from 1853 to 1860, in twenty-one volumes, with a separate index volume.
The Ninth Edition was then undertaken by the same firm on a scale which Adam Black considered so hazardous that his refused to have any part in the undertaking, and he accordingly advertised his retirement from the firm. This Edition began to appear in 1875, under the editorship of Thomas Spencer Baynes, and was completed in 1889 by William Robertson Smith. It consisted of twenty-four volumes, containing 21,572 pages and 302 plates, with a separate index volume. Adam Black's prognostications of failure were signally falsified by the success of the work, of which nearly half a million sets—including American pirated and mutilated editions—were ultimately sold. The great possibilities of popularity for the Encyclopædia Britannica in Great