Peter M. Hopp C.Eng. M.B.C.S.
My original article, The Boucher Calculator in the Inaugural
Issue of the Gazette in Autumn 2000 described a variety of these devices from a
number of makers. I have since found
another fascinating example, probably the seminal device.
The Oxford Museum of the History of Science
Browsing through the
illustrations of slide rules in their collection on the web (www.mhs.ox.ac.uk)
I found an early Boucher made in France. This is extremely similar to the
illustration of the Pocket-watch device, including signature, shown in UK
Patent 4310/1876, Figure 1 in my article.
Two of the three pictures are shown below, the third shows the
calculator in its box. The high quality
device, illustrated below with its accompanying notes, is somewhat different to
all the other Boucher devices from the other manufacturers. Incidentally, the Le Havre address is the
same as that quoted in the early Calculigraphe instruction book, showing a very
close relationship between Boucher and the Calculigraphe. There are no indications on this device as to
manufacturer or date it was made.
Figure 1: early French Boucher calculator
Inventory no. 54348 -
Old Label Text
BOUCHER'S CIRCULAR LOGARITHMIC CALCULATOR post 1876.
Inscribed "Cercle à Calcul / Bté S.G.D.G." and "A. BOUCHER. 5,
rue du Canal. HÂVRE." on one side, and with the script initials "A.
B." on the other. The instrument has two faces, one for numbers, the other
(spiral) for sines and tangents. The main key turns the logarithmic scale and
the smaller key large pointers on each face. Using the two pointers (one fixed)
on the face shown, any interval on the scales (the outer being uniform, the
inner logarithmic) may be recorded, and by the subsequent movement of the
scales added to any other part of the scales.
The accuracy achieved is somewhat less than one would demand of a short (5
inch) slide rule. The trigonometrical scales are fixed, and their only advantage
over tables is that they permit easy interpolation.
See Breveté, no. 114,520, 13th September 1876. Boucher's patent specification
(no. 4310) was taken out in 1876.