An extremely fine and rare 18th-Century lacquered-brass Chevalier no. 1 theodolite, signed Charles Chevalier Ingénieur Opticien Palais-Royal 163 Paris N o 1. , in the original walnut carrying case -- 30.5cm. (12in.) wide See Colour Illustration and Detail The 26.6cm. (10½in.) long telescope has rack and pinion focusing to the eyepiece lens and is held in two round brass mounts with retaining screws with knurled edges. These are mounted on a brass bar with a screw clamp and micrometer fine adjustment to the edge of the vertical circle. A cross bar serves as the alidade with the signature at one end and a silvered vernier scale -21°-0-21° at either end. The verniers are arranged to read off the vertical circle's silvered degree scale, divided in four quadrants, labelled every 10° and with 1/3° subdivisions. The vertical circle is connected to a horizontal cylindrical brass bar, at the other end of which is a large counter-weight. A large bubble level is mounted above, and the bar is raised on a slightly tapering brass column over the horizontal circle. This is graduated around the circumference with two degree scales, of amplitude and azimuth, labelled every 10° with ½° subdivisions. The whole circle can be rotated to read off a fixed brass vernier graduated for -30°-0-30°. The mounting also incorporates a screw clamp, micrometer fine adjustment and three adjustable screw feet. The instrument fits into a walnut base plate with recesses for the objective and eyepiece lens dust-covers and three different sized turning handles with knurled edges. On this base plate, the instrument is held in the box by means of a shaped piece of walnut with felt padding that acts as a lock when braced beneath two pieces of walnut attached to the inside of the door and the back of the case. The case has two iron handles, two iron hooks and eyes and a brass plaque on the top engraved for Dolfus Aussel .
An extremely fine and rare 18th-Century lacquered-brass Chevalier no. 1 theodolite, signed Charles Chevalier Ingénieur Opticien Palais-Royal 163 Paris N o 1. , in the original walnut carrying case -- 30.5cm. (12in.) wide See Colour Illustration and Detail The 26.6cm. (10½in.) long telescope has rack and pinion focusing to the eyepiece lens and is held in two round brass mounts with retaining screws with knurled edges. These are mounted on a brass bar with a screw clamp and micrometer fine adjustment to the edge of the vertical circle. A cross bar serves as the alidade with the signature at one end and a silvered vernier scale -21°-0-21° at either end. The verniers are arranged to read off the vertical circle's silvered degree scale, divided in four quadrants, labelled every 10° and with 1/3° subdivisions. The vertical circle is connected to a horizontal cylindrical brass bar, at the other end of which is a large counter-weight. A large bubble level is mounted above, and the bar is raised on a slightly tapering brass column over the horizontal circle. This is graduated around the circumference with two degree scales, of amplitude and azimuth, labelled every 10° with ½° subdivisions. The whole circle can be rotated to read off a fixed brass vernier graduated for -30°-0-30°. The mounting also incorporates a screw clamp, micrometer fine adjustment and three adjustable screw feet. The instrument fits into a walnut base plate with recesses for the objective and eyepiece lens dust-covers and three different sized turning handles with knurled edges. On this base plate, the instrument is held in the box by means of a shaped piece of walnut with felt padding that acts as a lock when braced beneath two pieces of walnut attached to the inside of the door and the back of the case. The case has two iron handles, two iron hooks and eyes and a brass plaque on the top engraved for Dolfus Aussel .
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.jpg "Source: Christie's")
.jpg "Source: Christie's")
