French rule for the construction, engraving and readout of military charts, c. 1800.
Stock Number: 9221
IMPORTANT HIGH-PRECISION CHART RULE, French, c. 1800, signed "Ferat a Paris; Depot G'al. de la Guerre 81."
8-3/4 x 2-3/4 inches (22 x 7 cm)
Country of manufacture
IMPORTANT HIGH-PRECISION CHART RULE, French, c. 1800, signed “Ferat a Paris; Depot G’al. de la Guerre 81.” This heavy gilt brass rule, 8-3/4″ x 2-3/4″ (22 x 7 cm), is exquisitely engraved on both sides with reduction scales of equal parts, the scales numbered 4, 5, 6, and 7. Each scale is linearly divided, with transversal scale at the end subdividing the main divisions down to 1/100 or 1/50 part. Designed for the metric system, they are labeled with the scale reductions and usages, e.g., “Echelle de 2 Millimetres pour 100 Metres (Pour les dites Cartes reduites et a graver).” Besides scales for the engraving of charts, there are ones for use on maps of the “Reconnaissances Militaires,” and for the “Canevas de la Topographie” (the baseline grid topographic maps). Divided with high precision, one still sees many of the layout marks, and engraving guidelines. Condition is fine noting some scratches and minor discolorations. It is complete with its original protective card case. This is the first “official” French rule we have had designed for the construction, engraving and readout of military charts. It was part of the War Department’s “Depot General” which was charged with furnishing the necessary charts and plans to the armies, as well as training Geographical Engineers. It is further significant in being signed by the maker. Ferat is recorded from 1799 to 1806, relocating frequently, through four different Paris addresses over seven years (see Marcelin). The young Gambey worked for him. The fineness of Ferat’s engraving is truly exceptional.
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David and Yola Coffeen both have enjoyed academic careers, as planetary astronomer and as linguist/educator. But since 1982 (yes, 1982!) they have been full-time dealers in early scientific and medical instruments, under the name Tesseract. Selling primarily by catalogue (over 100 issued so far) they also have a web presence at www.etesseract.com, and can be contacted at [email protected]