Manuscript copies, in a single hand, of various published texts treating the art of surveying. The volume is inscribed (on the recto of the first leaf) "H: Overton 1757", apparently in the same hand as the rest of the work. The copyist may be Henry Overton, a contemporary London publisher of maps and engraved views. It does not appear Overton ever published the collection. The first section, 37 p., offers an introduction to trigonometry and its application to the art of surveying. This text consists of verbatim excerpts from The young trigonometer's compleat guide, by Benjamin Martin (first published at London, 1736). From part 2 of Martin's work, the manuscript copies chapter 7, Plain trigonometry applied to surveying, or measuring of land; and also of other plain superficies, and chapter 8, Plain trigonometry, applied to altimetry, and longimetry; or the measuring of heights, depths, and distances, both accessible and inaccessible. Also copied exactly, in pen and black ink with occasional wash, are all the diagrams illustrating Martin's text. The next section, 12 p., consists of short treatments of four topics: the graphometer, height, the "meridian line", and surveying a harbour. All four of these texts are copied (with varying completeness) from the matching terms found in A new and complete dictionary of arts and sciences (first published at London, 1753-4). Each of the four topics is illustrated with a full-page diagram, the first two of which are copied from the published text. The final section, written in a diluted black ink, is a copy of a paper by William Molyneaux, titled "A demonstration of an error committed by common surveyors in comparing of surveys taken at long intervals of time arising from the variation of the magnetic needle, by Wm. Molyneaux, Esqr. F.R.S.," published in the Philosophical Transactions of the Royal Society in 1697. The paper articulates a particular concern for avoiding disputes which could arise between neighbors over land boundaries if magnetic variations were not taken into consideration. In addition to the tipped-in full-page illustrations or plates, there are numerous diagrams within the text.
