Also in ink on verso, a crossed-out text of which 500 words are extant; incipit "plane of which the representation is to be drawn, and the place of the Eyes. [Paragraph] The General principle [on which--crossed out] of Perspective [is the--crossed out] supposes pencils of rays...." Ancillary geometric drawings in ink and pencil on recto and verso. In pencil on recto: "No 32". Military topographic map. Covers the towns of Cortlandt, Ossining, Mt. Pleasant, Yorktown and Newcastle in Westchester County, New York. Shows roads running through Peekskill, Croton, Ossining, Scarboro, Millwood, Tompkins Corners, Pleasantville, Chappaqua, Pinge Bridge, Yorktown Heights and Yorktown. Also shows buildings and owners’ names, landforms and streams. Pen-and-ink, pencil on laid paper. Shows relief by hachures. Soiled, stained, foxed, creased, frayed, and abraded. Razor cuts and pinpricks for copying. Mounted on cloth, bound and cropped, disbound and silked by subsequent owners. Cleaned after removal of backings 1999; some fill remains. Sheathed in mylar. Title proper from recto is the work of a later editor--Simeon DeWitt or his assign--subsequent to 1820. Title from verso is in Erskine’s hand and may be cited as such. Index title, statement of responsibility, date, series title and series numbering also by Erskine, but on separate index sheet filed at head of series. Watermarks: lily, monogram.