Antonio Cagnoli (Zante 1743-1816), diplomat of the Venetian Republic, had founded a private observatory in Verona, fitting it out with various top quality instruments. During the cannonade that Verona was subjected to in 1796 by the French army, this observatory was seriously damaged and Napoleon had the surviving instruments bought and divided among the Observatory of Bologna, the Brera Observatory and the Scuola del Genio. Thus, in 1801, by order of the Directory of the Cisalpine Republic, Brera was assigned a parallactic telescope by Mégnié and Bologna a movable quadrant measuring 3 Parisian feet, equal to 2.54 Bolognese feet (c. 97 cm) by the same craftsman. The assignation was recorded in the Strumenti provvisti dalla Repubblica Cisalpina (Reg. Spec. Ist. Naz. Scienze, vol XII, on 27 February 1801, Arch. Dip. Astron. Bologna).
Two Mégnié were working in Paris at the end of the XVIIIth century. Pierre was probably the name of the craftsman who made this quadrant, for which in 1779 he received half of a 2400 lire prize put, up by the Paris Académie des Sciences five years earlier (Daumas op. cit.). Though Mégnié did not succeed in winning the title "Ingenieur en instruments de mathematiques de l’Académie" that was on offer with it, the instrument did nonetheless earn so much praise that it went on to won the 2600 lira Monthyon prize.
The quadrant and accessories are described in the 1843 inventory drawn up by Ceschi:
"Quadrant by Cagnoli with 2 and ½-foot radius, supported by a very strong ingot iron stand. The whole quadrant is made of metal. The telescope, fitted with lens and eyepiece, is pivoted at the centre of the quadrant which is of metal, and passes near the graduated centre together with a vernier accurate to one half arcminute. A small clamp which is attached to the limb of the quadrant by a screw and to the telescope by another screw allows small movements to be made. By the effect of four screws at the base of the instrument and with the help of a perpendiculum, the plane of the quadrant, which can be rotated even in small movements on a vertical axis protruding from a graduated Azimuth circle, can be made vertical."The accessories, unfortunately later lost, consisted of:
"A reflector attached to the telescope from the lens; a lamp for illuminating the reflector; a handle to adjust the screws in the base; four small iron plates placed under the aforementioned screws; an iron handle for the other screws; a tin vessel which receives the ball of the perpendicular."The stand with azimuth movements and the graduated circle still existed in 1935, as can be seen in a photograph taken to illustrate the first model of the multi-mirror telescope built by Guido Horn-d’Arturo (Pubblicazioni Oss. Astron. Bologna, III, p.23, 1935). This photo also helped in the reconstruction of the stand, carried out by G. Morigi in 1988.
E. Baiada, A. Braccesi (1983), p. 125
M. Daumas (1953), p. 361.
E. Miotto, G. Tagliaferri, P. Tucci (1990) pp. 47, 112.