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<p>[QUOTE=&quot;springfld.arsenal, post: 309657, member: 54&quot;]Text accompanying picture I linked above</p><p><br /></p><p>THE HYDROGRAPHIC CIRCLE OF ROLLET DE L&#039;ISLE, French, late 19th century, finely signed &quot;Lorieux, A. Hurlimann, Succ&#039;r a Paris.&quot; The 10-1/2&quot; (27 cm) diameter brass circle is fitted with four mirrors, two of them mounted on the rotating index arm and set back-to-back at a fixed angle, a large-light-gathering-power telescope, and a hinged turned wood handle. An inset circular scale is divided every 0.5 from -10 to +200 half-degrees. The index arm has clamp, fine motion tangent screw, vernier to one-fiftieth of a degree, and magnifier. The instrument is equipped with its full complement of accessories, all original: two solar filters, two right angle sights, seven interchangeable filters, two adjusting tools, three spare mirrors, fitted mahogany case 13&quot; (33 cm) square, and key. Only the screwdriver and loupe are lacking. Condition is absolutely superb throughout. The circle functions basically as a sextant, except there are two &quot;horizon&quot; mirrors, and two &quot;index&quot; mirrors, disposed so that one pair is useful at smaller angles, the other pair at larger ones. Readings are possible from 0 degrees straight ahead all the way to 180 degrees directly behind the observer -- as one mirror view becomes foreshortened, the other takes over automatically.</p><p><br /></p><p>This is the remarkable invention of M. Rollet de l&#039;Isle, French hydrographic engineer to the Marine (and world-famous proponent of the Esperanto language). It was still advertised in 1911 (by Ponthus &amp; Therrode, successors to Hurlimann, who in turn was successor to the well-known firm of Lorieux established in 1845), as the model adopted by the French hydrographic marine services. A very rare example of this innovative design, in splendid condition. (8194) $7200.[/QUOTE]</p><p><br /></p>

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