Lexicon Technicum: or, An Universal English Dictionary of Arts and Sciences: Explaining not only the Terms of Art, but the Arts Themselves was in many respects the first alphabetical encyclopedia written in English. Although the emphasis of the Lexicon Technicum was on mathematical subjects, its contents go beyond what would be called science or technology today, in conformity with the broad eighteenth-century understanding of the terms "arts" and "science," and it includes entries on the humanities and fine arts, notably on law, commerce, music, and heraldry. However, the Lexicon Technicum neglects theology, antiquity, biography, and poetry.
The Lexicon Technicum was the work of a London clergyman, John Harris (1666-1719). Its professed advantage over French dictionaries of the arts and sciences was that it contained explanation not only of the terms used in the arts and sciences, but also of the arts and sciences themselves. Harris issued a three-page proposal for this work in 1702, and the first edition of the first volume was published in London in 1704. The first volume contains 1220 pages, 4 plates, and many additional diagrams and figures within the text. Like many early English encyclopedias, the pages are not numbered; numbering may have been thought unnecessary as readers could search by its alphabetical arrangement.
Volume 2, which was also alphabetized from A through Z, was first published in 1710. The second volume contains 1419 pages and 4 plates, with a list of about 1300 subscribers. A previously unpublished treatise on acids by Sir Isaac Newton was included in its original Latin along with Harris's English translation, perhaps without the latter's permission or encouragement. A large part of the volume consists of mathematical and astronomical tables, since Harris intended his work to serve as a small mathematical library. He provided tables of logarithms, sines, tangents, and secants, a two-page list of books, and an index of the articles in both volumes under 26 heads, filling 50 pages. The longest lists are for law (1700 articles), surgery, anatomy, geometry, fortification, botany, and music.