Author(s) Caus, Salomon de
Title Les raisons des forces mouvantes...
Imprint Frankfurt, J. Norton, 1615
Localisation Heidelberg, Ruprecht Karls Universitäts Bibliothek, L 1639-1 Folio Res I-3
Subject Gardens, Hydraulic engineering, Machines
Transcribed version of the text


     Strangely, the title does not correspond to the contents of the work which includes a Livre troisiesme traitant de la fabrique des orgues.  In order to understand the reasons for this omission, we must refer to the accompanying privilege.  On October 17, 1614, Salomon de Caus obtained from Louis XIII a privilege to publish four books: Raisons des forces mouvantes avec plusieurs machines tant utiles que plaisantes; De la Theorie & Pratique de Musique; Constructions de quelques machines hidrauliques; Desseings de grotes Artificielles et Fontaines.  The first and the last of these books are the only ones indicated in the frontispiece of the present publication.  The second resulted in the Institution Harmonique, also available in 1615 in Frankfurt, at Jan Norton's shop.  The Livre troisiesme traitant de la fabrique des orgues of the present publication could correspond to a part of the book indicated in the privilege, Constructions de quelques machines hidrauliques.  In fact, in the dedication to Princess Elizabeth in the Institution Harmonique (September 15, 1614), Salomon de Caus refers to an unfinished treatise, "De la fabrique des machines hidrauliques, commencé soubs mon bon maistre d’heureuse memoire le Serenissime Prince de Galles, ou par lesdites Machines, il se pourra représenter avec le cours de l’eau une parfaite harmonie".  This hypothesis is partially corroborated by the closing declaration: "je mettray fin pour le present a ce troisiesme livre esperant avec le temps d’en faire encore un ou seront montrees quelques machines fort rares & que je tiens fort secrettes…" and also by the fact that this third book, unlike the first two, does not include frontispiece, dedication or copperplate engravings.  All this leads one to believe that the work was published in 1615 with corrections, and was probably put together hastily from previous works, perhaps in order to present all of the areas of competence that Salomon de Caus had already put into practice during his career that was still to be fruitful. There was nevertheless a wish to keep the privilege for a later publication.
The first book of Raisons des forces mouvantes is in many ways outstanding.  It differs from contemporary theaters of machines by presenting definitions, theorems and problems, affirming a theoretical intent.  The definitions establish the general framework of the Aristotelian physics of four elements.  The eighteen theorems provide the data for mechanical theory applied to hydraulics.
The second remarkable feature is that Salomon de Caus approaches each theorem from the point of view of the ratios, that is, the proportions of driving forces (and not of equilibrium).  This approach allowed him to put forward the composition of the forces pushing against each other, which was later acclaimed as one of the first expressions of the idea of composed force or momentum.  Lastly, the thirty-five problems are applications of the properties of driving forces in thirty-five machines as useful as they were agreeable.
Another remarkable feature is the care taken to give the reader elements of information which, in other theaters of machines were left to builders to appreciate: "plans orthographiques", sometimes in scale, precise dimensions, or the nature of materials (the composition of certain mortars).  These last remarks refer also to books 2 and 3.
The whole work places Salomon de Caus in an uncommon position in relation to contemporary mechanical engineers, through this combination of theory and practice and of physics and mechanical engineering in the very body of the work where recourse to the theoretical is both demanded and always limited to the useful and the essential.  In this respect one cannot fail to notice his very special interest in possible applications of the Spiritali of Hero of Alexandria, at that time recently republished in Italian, applications of the use of "artificial fire" to produce steam power, but also, "natural fire", the sun, to start certain fountains flowing. If in the nineteenth century he was rashly praised as the inventor of the steam engine, those in our century, steeped in "solar power", might perceive a precursor in him.

Hélène Vérin (Centre national de la recherche scientifique, Paris) – 2009


Critical bibliography

C. Maks, Salomon de Caus 1576-1626, Paris, Jouve & Cie, 1935.

L. Morgan, Nature as Model. Salomon de Caus and Early Seventeeth-century Landscape Design, Philadelphia, Pennsylvania, University of Pennsylvania Press, 2007.

L. Châtelet-Lange, "Salomon de Caus, contestation d’un mythe", Bulletin de la Société de l’Histoire de l’Art français, 1988 (1989), pp. 25-32.