ies of this single-digit adder were built,
though many multiple-order key-driven
machines were in the U.S. by the end of
the 19th century.
Early “process computer.” For the
construction of his splendid Strasbourg
astronomical clock, Schwilgué devel-
oped several complicated machines, in-
cluding a very precise milling machine
for producing complex gears (circa
1827) and a large, specialized calculat-
ing machine (circa 1830); for dating and
technical details, see Bruderer and Mei-
lensteine. 6 This device, which is driven
by a crank and a weight, helped Schwil-
gué compute the values needed for the
settings of his milling machine. He
manually transferred the calculations to
a paper tape he would then place in a box
beside the milling machine. These num-
bers controlled the machine. It might
thus be considered a simple “process
computer” (or precursor). As far as is
known, Schwilgué constructed only one
such highly specialized machine.
Several books and papers were published by Schwilgué’s collaborators and
successors (foremost Alfred Ungerer of
France) with a short description and
picture of the milling machine. The
machine is also mentioned in a biography of Schwilgué’s son, Charles.
To my surprise I came across Schwilgué’s adding machine (see Figure 5) in
December 2014 in Strasbourg. Both devices are today in the Musée historique
Other historic calculating devices
include the common slide adders (see
Figure 6). These inexpensive, mass-
produced instruments were manu-
calculation machine (1834) developed
by Luigi Torchi of Italy, but little is
known about it today.
In general, authors writing about the
history of computing regard the device
(1850) of Du Bois D. Parmelee of the U.S.
as the “first” key-driven adder, 33 sometimes citing the Schilt machine (1850)
by Victor Schilt, a Swiss watchmaker
from Solothurn who had worked with
Schwilgué. This calculation aid, now in
the collection of National Museum of
American History in Washington, D.C.,
was shown in 1851 at the Great Exhibition in London. However, the leading
publications on computer history do
not mention Schwilgué’s key-driven
adder. It is not known how many cop-
Figure 7. Polar planimeter invented by
Jakob Amsler in 1854 was used to calculate
surfaces by applying differential and integral
calculus. Only one manufacturer remains
active today, Gebrüder Haff GmbH, Pfronten,
Germany. Courtesy of Amt für Vermessung,
Figure 5. Schwilgué’s large adding machine that probably facilitated the calculations needed
to produce the complex gears of the astronomical clock of Strasbourg Cathedral; the original
weight drive is lost. Courtesy of Mathieu Bertola, Musée historique, Strasbourg, France.
Figure 6. Slide adder devised by the French manufacturer Louis Troncet in 1889; the tens
carry is semiautomatic, needing a mechanism that looks like a cane. Such an instrument is
also able to perform subtractions and is sometimes combined with multiplication tables.
Courtesy of Herbert Spühler, Stallikon, Switzerland.
Figure 8. Music boxes are still produced by
the Swiss firm Reuge and often presented
as gifts; the melodies were originally stored
on (exchangeable) pegged brass cylinders,
though the cylinders were later replaced
by (cheaper) perforated disks. Courtesy of
Reuge SA, Sainte-Croix, Switzerland.