A very rare simple measuring instrument with the rare French signature Jacques Langlois which is early 18th century. Jacques Langlois was apprentice of Butterfield.
The vertical brass bar carries a scale divided into inches and lines ; the horizontal brass bar is equipped with a fine sliding friction-tight along the bar.
The arms of the horizontal were placed on the edges of an opening. The sliding bar would be lowered inside the cavity until it touched bottom.
The depth would then be measured with precision.
The present depth or maybe marking gauge is divided in 54 lines, so 4 1/2 French inches, measuring 122mm.
Despite some usual mark of uses, fine and genuine condition.
We can not the superb and large signature of the rare Jacques Langlois.
A rare, early and simple measuring instrument for physics, chemistry or tooling.
For a close example but late and with the addition of a precision vernier, see the “Duc de Chaulnes” depth gauge in the Galileo Museum :
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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.