He wrote a number of books and pamphlets: a book on stoves,[2] on making sundials,[3] on using a "sector" or "proportional instrument" (a simple calculator),[4] and on using "Napier's bones"[5] (another calculator) – among other works.
In the 1620s and 1630s, he was a portrait painter in Cologne, Germany.[6]
He wrote a book called Unterschiedliche bisshero mehrern Theils Secreta oder verborgene, geheime Kunste (Various until now mostly Secreta or hidden, secret arts), which was published in Oppenheim in 1616. The first five chapters of this book deal with communicating via a crude Aldis lamp.
Franz Kessler, Holzsparkunst [The Art of Saving Wood] (Frankfurt am Main, (Germany): Anthoni Hummen, 1618).
Reprinted in French as: François Keslar, Épargne bois, c'est à dire, nouvelle et par ci-devant non commune, ni mise en lumiere, invention de certains et divers fourneaux artificiels, etc. … [Wood Saver, that is, the new and hitherto neither commonplace nor well-known invention of some and various fireplaces, etc. …] (Oppenheim, Germany: Jean-Théodore de Bry, 1619).
Franz Kessler, Das erste Fundament von Sonnenuhren [The basics of sundials]. (Frankfurt, (Germany): 1605);
Franz Kessler, Das andere Fundament allerley Sonnenuhren zu reissen [Other basics [required] to design all sorts of sundials] (Frankfurt, (Germany): 1611);
Franz Kessler, Bericht von allerley Linien, rechten Sonnenuhren [Report on all the lines [that are required to design] proper sundials]. (Nürnberg, (Germany): 1611).
Franz Kessler, Kurtzer einfältiger und doch aussführlicher verstandlicher Bericht: Wie ein jeglicher der mathematischen Kunst Liebhaber, gantz ringfertig, das uberauss compendios - scioterische gnomische oder geometrische und ringköstige Proportional Instrument, auss seinem unumstösslichen wahren Grund, selber lernen machen und ins Werck richten soll. Allen Sonnuhristen, Geometris, Bawmeistern, wie auch allen Mahlern, Bildhawern, Steinmetzen und Schreinern zu sonderem gefallen an jetzo zum ersten-mal an Tag geben. [Short, simple and yet detailed, comprehensible report: How any lover of the mathematical art, quite readily, shall teach himself – from its indisputable, true basis – and put to work the extremely comprehensive, gnomonic [i.e., used as a sundial ("gnomon" or "Skiotheron" (shadow seizer))] or geometric and inexpensive proportional instrument. Brought forth now for the first time to please particularly all sundial makers, geometers, architects, as well as all painters, sculptors, masons and joiners.] (Oppenheim, (Germany): Johan Theodor de Bry, 1612). Available on-line from the library of the University of Kiel.
Franz Kessler, Eygendtlicher Bericht von Nutzen und Gebrauch dess Proportional-Instruments Francisci Kesslers von Wetzlar. Durch welche man erstlich in unglaublicher Geschwindigkeit und schneller Eyll, nach allem Astronomischen Scioterischen oder Sonnuhrischen auch Geometrischen erfordern, alle grosse oder kleine ungetheilte Quadrantriss in ihre begerte Grad und Minuten … [True report on the advantage and use of the proportional instrument of Franz Kessler from Wetzlar. By which one [can divide] firstly with unbelievable speed and quick dispatch – as all gnomon or sundial makers also geometers require – all large or small undivided quadrants into their desired degrees and minutes.] (Oppenheim, (Germany): Johan Theodore de Bry, 1612).
Franz Kessler, Künstliche Rechenstäblein zu vortheilhafftiger und leichter manifaltigung, Theilung wie nicht weniger Außziehung der gevierdten und Cubischen Wurtzeln; allen Rechenmeistern, Ingenieuren, Bawmeistern, und Landmessern, uber die Maß dienlich. [Ingenious calculating sticks for profitable and easy multiplication, division as no less for the extraction of square and cubic roots; handy beyond measure to all calculators, engineers, architects, and surveyors.] (Frankfurt, (Germany): Jacob von der Heyden, 1618). Available on-line from the library of the University of Göttingen.
Unterschiedliche bishero mehrentheils Secreta oder verborgene geheime Künste. Deren die erste, genannt Ortforschung, dadurch einer dem andern die freye Luft hindurch über Wasser und von sichtbaren zu sichtlichen Orten, alle Heimlichkeiten offenbaren und in kurzer Zeit zu erkennen geben mag. Die andere Wasserharnisch, dadurch jemand etliche Stunden ohne Schaden Leibes und Lebens unter Wasser seyn kann, nach Belieben seyn Vorhaben zu verrichten. Die dritte Lufthosen, mit welchen man wunderlich über See und Wasser nach Wohlgefallen ganz künstlich gehen kann. Sammt beygefügten wohlerdachten Schwimmgürtel, welchen jedermann so wohl bey jetzt benennten Wasserkünsten, als sonst andern Wasserreisen nur Noth zu gebrauchen hätte. Alles ohne Zauberey und Schwarzkunst, den recht göttlich - natürliche Geheimnissen - Liebhabern zu gefallen beschreiben; mit Figuren geziert und erstlich an den Tag gegeben, durch Franz Keßler Conterf. von Wetzlar 1617. [Various hitherto mostly Secreta or hidden secret arts. (1) The first of which, called "reconnaissance", whereby one may communicate openly and quickly all secrets to another person through the open air, over water and between places visible to each other. (2) The other, a water harness [i.e., a diving bell that the diver bears on his shoulders via a harness], whereby anyone can be under water for several hours without harm to life and limb, to execute one's plans at will. (3) The third, waders with air-filled floats, with which one can go wondrously across sea and water at one's pleasure quite ingeniously. Together with an attached, well-conceived swimming belt, which anyone would have to use during the above-mentioned water arts as well as during other water-travel (in distress only). All without sorcery and black magic, written to please the truly godly lovers of natural secrets; adorned with illustrations and first brought forth by Franz Keßler, portraitist from Wetzlar in 1617.] (Oppenheim, (Germany): Hans Dietrich von Bry, 1617). A 1722 edition of this book is available on-line from the state library of Sachsen-Anhalt. Illustrations of Kessler's (1) signaling apparatus, (2) diving bell, and (3) inflatable waders.
