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Title: Chronological (machine)
Original Title: Chronologique (machine.)
Volume and Page: Vol. 3 (1753), pp. 400–401
Author: Denis Diderot
Translator: Stephen Boyd Davis [Middlesex University,]
Subject terms:
Original Version (ARTFL): Link

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Citation (MLA): Diderot, Denis. "Chronological (machine)." The Encyclopedia of Diderot & d'Alembert Collaborative Translation Project. Translated by Stephen Boyd Davis. Ann Arbor: Michigan Publishing, University of Michigan Library, 2009. Web. [fill in today's date in the form 18 Apr. 2009 and remove square brackets]. <>. Trans. of "Chronologique (machine.)," Encyclopédie ou Dictionnaire raisonné des sciences, des arts et des métiers, vol. 3. Paris, 1753.
Citation (Chicago): Diderot, Denis. "Chronological (machine)." The Encyclopedia of Diderot & d'Alembert Collaborative Translation Project. Translated by Stephen Boyd Davis. Ann Arbor: Michigan Publishing, University of Michigan Library, 2009. (accessed [fill in today's date in the form April 18, 2009 and remove square brackets]). Originally published as "Chronologique (machine.)," Encyclopédie ou Dictionnaire raisonné des sciences, des arts et des métiers, 3:400–401 (Paris, 1753).

Chronological (machine). Imagine a combination of several component charts brought together to form a single large one. The height of this larger chart is hardly a foot; its length is necessarily very considerable. However long, it is divided [along the top edge] into small equal parts, alternately black and white, like those marking out degrees on the great circle around a globe. There are as many of these sections as the years which have elapsed from the creation of the world to our own time. Each of these sections marks one year of the world’s existence. This chronological scale is formed by conjoining three great epochs; the first stretches from the creation of the world to the foundation of Rome; the second, from the foundation of Rome to the birth of Jesus Christ; the third, from the birth of Jesus Christ to our own time.

This chronological line or scale is divided at intervals of ten years by perpendiculars crossing the chart from top to bottom. Starting from each division of the scale, there lie, in between each pair of such lines, other perpendiculars which are dotted. From the position of each of these lines perpendicular to the chronological scale, dotted or otherwise, arise other lines, dotted or solid, parallel to each other and to the chronological scale, which extend the whole length of the chart and divide its entire height. The lines perpendicular to the chronological scale are the lines of contemporaneity ; those parallel to the chronological scale are the lines of duration .

All the events located on any one of the perpendiculars of the scale began at the same moment in the time-span; all the events located on another perpendicular to the scale which is closer to our own time have continued or ended together. The lines parallel to the scale, contained between two such perpendiculars, indicate the duration of these events; and, since the ends of the two perpendiculars touch two points on the scale at the top, we can see where in the time-span of the world contemporary events have begun and ended. And with the help of other perpendicular and parallel lines, we learn how much before and after one another non-contemporary events have begun and ended; and according to the place that these parallels occupy on the perpendiculars, we ascertain the places in the world where the events have occurred.

As for the quantity and variety of facts, it is immense; it includes all those of any importance mentioned in history, from the foundation of an empire to the invention of a machine; from the birth of a potentate to that of a skilled workman. Symbolic markings, clear and quite few in number, indicate clearly the standing of the person, and sometimes a moral quality, good or bad.

It seemed to us that this chart could save a great deal of time for the knowledgeable, and labour for the learner. From it has been created a highly serviceable machine, as we shall explain, by fixing it to two parallel cylinders, the chart rolling off the top of one cylinder onto the top of the other, and in so doing exposing quite a large interval of time, and in succession the whole train of time and events, whether descending from the creation of the world to ourselves, or ascending from our own time as far back as the creation.

Description of the chronological machine. Essential elements. The chronological machine is made in two identical halves, and each of these halves is made up of two panels A ( see the Chronology plate in the Plates of Science and Arts [1] ) one and a half lignes [1 ligne = 1/12 of an inch] or two lignes thick: two parts of each of these two panels require our attention; one forms a circle four inches in diameter; the other emerges from this circle at a tangent, six inches long and an inch high, in which have been made, at four lignes from the upper edge, two mortices each of an inch and a half, to receive the tenons of the panel B described next.

A plate B , sixteen inches long, not including the two tenons at each end, and five and a half inches wide, and of the same thickness as panels A .

Two little rollers or cylindrical rods, four lignes in diameter and sixteen inches long.

One of which, C, is terminated by two spikes of solid metal wire which serve as its axle.

The other, D, has a similar point at one end acting as an axle, and at the other end the crank described next.

A crank composed of three parts. A handle E of turned wood, two inches long and of suitable thickness. A solid metal wire F, one and a half lignes thick, of which one end forms an axle for the handle, which it passes all the way through; the other is inserted into one of the ends of the roller D , to complete its axle; and the connecting part is curved into a semi-circle to assist the operation of the crank. And a little button G , serving to keep the handle in place on its axle, on which it moves freely.

Two small metal hooks H , of which one is located on the circular part of the panels A , serve to hold the machine closed; the other, located at the end of the extension of the same panel A , serves to fix the machine open.

Two little loops I , made of solid wire, located in the corresponding place on the other panel A , serve to receive the hooks H .

Finally four small plates made of thin brass L , about two lignes thick and seven or eight long, serve to hinge the two halves of the machine.

Construction of the machine. The mortices of the two panels A , which are positioned edge-on, receive the tenons of the panel B , which is laid horizontally and fixed with strong glue.

Holes made in the panels A , at the top of the circular part, on a level with the mortices, receive the points of the axle of the roller C , which is as a result positioned alongside panel B , two lignes away from it, and higher than it by one ligne .

Another hole, made in the middle of the circular part of one of the panels A , receives the point of the axle of the roller D ; and a similar hole, likewise made in the centre of the other panel A , is pierced by the end of the solid metal wire F , which forms the axle of the crank and also terminates the axle of the same roller D , and in this way one half of the machine is formed: the other is constructed in a similar way, and both are connected together by means of the plates L , fixed in pairs, one inside and one outside the upper edge of the extensions of the panels A , using two small pins which pass through the panels and are flattened at both ends, in such a way however that these little plates can turn on the pins, which serve as axles. The upper corner of the panels A has been rounded so that the two halves may be folded one on the other when it is desired to close the machine.

The two ends of the chronographic chart are glued to the rollers D , around which they are coiled, so that in turning one of the cranks, we can very easily cause the entire chart to move to and fro from one roller to the other. The rollers C , turning on their own axes, lessen any rubbing of the chart, and allow it to move easily. The panels B serve as a table on which to unroll before our eyes a section of the chart encompassing not less than a hundred and forty years. A sheet of card of suitable size, fixed all around the perimeter of the circular part of the panels A , forms for each of the rollers D a cylindrical container which serves to protect the chart; and this card, folded back on itself at its upper edge, one inch from the edge of the rollers C , encloses a little iron rod, fastened by its two ends to the edge of the panels A, and gives it sturdiness.

When the machine is folded upon itself and closed up, the chart is found to be protected at every point, and so kept very secure.

The author of this machine is M. Barbeu du Bourg, doctor of Medicine, and professor of Pharmacy at the University of Paris. It is easy to see from the price which he has put on his invention that service to the public has been his principal motive. The chart consists of thirty-five engraved sheets. In order to encourage men of letters to help his chart reach the degree of perfection which he intends it to achieve, he is offering to give a free copy to all persons of rank in the republic of letters, such as authors, academicians, doctors, journalists, teachers, librarians, college principals, prefects, etc who are kind enough to return to him their original copy complete with the remarks, opinions, corrections, observations, and other crossings-out which they have added to it.


1. [According to Richard Schwab, this plate was never in fact produced. Schwab, Richard N. 1984. Inventory of Diderot’s Encyclopédie. Vol. VII. Inventory of the Plates. The Voltaire Foundation, University of Oxford. 264.]