4to. (6) ff., 60 pp., including several historiated and putti woodcut initials, and 8 full-page and 9 half- and three-quarter page engraved plates. Bound in brown morocco, raised bands on gilt spine, signed F. Bedford. Book labels of Charles Fairfax Murray, Philip and Frances Hofer, and Harvard College Library (de-accessioned). Dusty title and scattered leaves with some toning, spotting or soiling; a few leaves cropped. Generally good. The elegant engravings (with the full-page illustrations set in landscape settings) are free adaptations of the woodcuts that appeared in the French-language edition (Paris, 1555).
Rare first edition of the earliest description in Italian of the surveying instrument termed by Kiely "the most popular triangulation instrument on the Continent" (Surveying Instruments, p. 226).
The basic design takes its departure from Münster’s "trigonus" described in the Rudimenta Mathematica (1551), but substitutes a solid board or table for the stationary ruler and an alidade for the two revolving rulers, thus allowing direct drawing in the field. The addition of the table is Foulon's most important contribution according to Kiely, growing out "of the desire to avoid mathematical calculations as far as possible by the employment of graphical methods" (p. 228). The instrument proved quite popular and was much imitated: the second instrument described by Philip Danfrie in his Declaration de l'Usage du graphometre (1597) is virtually identical to Foulon's holometre (see illustrations in Boffito, plates 51 & 52).
* Adams F-802; Mortimer 197 (this copy; de-accessioned); Boffito, Gli Istrumenti, p. 81, no. 30, plates 51-2; Kiely, Surveying Instruments, 229-31 and bibliography 186.
The elegant engravings (with the full-page illustrations set in landscape settings) are free adaptations of the woodcuts that appeared in the French-language edition (Paris, 1555).