The need to make topographical measurements, i.e. to "measure the Earth", dates back to ancient times. Until the XVIth century, however, such surveying was done by simply measuring lengths with balls and string. In the 1500s, with the growth in trade resulting from the new geographical explorations, the surveyor’s profession became more important and new techniques and instruments were developed. A decisive moment came in the next century with the launching of massive land survey campaigns by the rulers of all countries and the new possessions.
It is not surprising, therefore, that the main instrument of land-surveying - the theodolite - developed in that period. Before then, land-surveying instruments, able only to measure horizontal angles, went under the names of planisphere or Holland circle; in Italy they were called circolo o squadro azimutale o teodolite semplice and in France cercle d’arpentage.
It was the Englishman Leonard Digges who in the XVIth century suggested mounting on the azimuth plate a vertical semicircle and an alidade sighting device (replaced in the next century by a small telescope), thus creating an altazimuth instrument that he called theodolite; contemporaneously, the German Martin Waldseemüller had also proposed the same type of modification to the circumferentor. In this way, instruments that could measure only horizontal angles were called simple or azimuth theodolites.
This circumferentor has half-degree divisions and two fixed pinnules around its edge. On an alidade are two movable pinnules together with one unthreaded and two threaded holes, most probably used for the mounting of some kind of accessory which suggests it was also employed as an altazimuth instrument.
It carries the words Haye á Paris, a craftsman about whom nothing is known. The Académie des Sciences possesses - according to Daumas (op. cit.) - a compass and a quadrant with the same signature, while at the National Maritime Museum at Greenwich there is a proportional divider and a sundial.
M. Daumas (1953), p. 97.
L. Digges (1571).
An Inventory of the Navigation and Astronomy collections in the National Maritime Museum Greenwich (1970-73).
M. Holbrook (1992), pp. 35 and 74.
G. L’E. Turner (1991), p. 198.