A very rare universal brass altitude portable sundial called “Régulateur Universel”, circa 1830.
The instrument entirely made in lackered brass is signed on the round base “Dericquehem, rue du Colombier-Jacob, No. 18, à Paris.” and again on the long limb “Dericquehem, rue du Colombier-Jacob, No. 18, à Paris.”
On the limb, the engraving is particulary elegant.
The instrument measures 33,5 cm height and th round base 10,5 cm diameter.
The long squarre column is engraved by 0 to 25 cm each divided in 10 millimeter, so it is engraved in 250 millimeter when the little additionnel block is added on the bottom of the limb.
A squarre plum bob can be hanging from the folding arm at the top of the graduated rod.
The use of this very unusual, but quite elegant, sundial is given by Dericquehem in a book published in 1824 (then in 1828 and posthumous in 1856) entitled, “Régulateur universel, instrument portatif et de nouvelle invention pour connaître l’heure vraie au soleil à tous les instants du jour et sur tous les points du globe.”
The condition is very good.
“In it he instructs the user to level the instrument, allowing the plumb line to just graze the column edge, to extend the gnomon (checking if necessary that it is truly perpendicular to the column with an iron set square!), to swivel the column until the gnomon points toward the sun (i.e., toward the sun’s azimuth), and to read (in centimeters, millimeters, and tenths) the length of the gnomon’s vertical shadow falling on the column. The apparent (i.e., “true”) solar time is then found by consulting the extensive tables in Direcquehem’s book, where shadow length on the instrument is tabulated versus latitude (from 35° – 52°) and date throughout the year. Further tables give series numbers, corresponding to latitudes, for numerous towns in France and cities worldwide. The “regulator” was marketed as a device for accurately setting and correcting clocks and watches, and for determining terrestrial latitudes and longitudes.” (David Coffeen in Tesseract catalogue 104, number 4)
The sundial come with its original box. Excellent condition despite some part with old dust.
For another example, see Tesseract catalogue 104, item 4.
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Established by Alexandre Piffault in 2014 and based in Paris at 5 rue de Condé, 75006, very close to Odéon, Le Zograscope specializes in antique and rare books in Science, Medicine and Technology, and rare antique instruments in the same fields. We have especially a strong interest in early and continental microscopy, early and special mathematical/drawing instruments, medical and surgical instrument, and rare technology.