Book review Published in June 2014 Issue of ANTIQUARIAN HOROLOGY (Ticehurst, UK) Reposted here by the Author with the permission of AHS A Significant Addition to the Literature on Jost Bürgi, the Most Important Clock Maker of the World in the late 16[SUP]th[/SUP] Century. Jost Bürgi, Kepler and the Emperor – Clockmaker, Instrument Maker, Astronomer and Mathematician, 1552-1632. [Jost Bürgi, Kepler und der Kaiser – Uhrmacher, Instrumentenbauer, Astronom, Mathematiker – 1552-1632] By Fritz Staudacher (with a Preface by Jürgen Hamel). Published in German, 2013 by Verlag Neue Zürcher Zeitung, (Zürich, Switzerland.) ISBN 978-3-03823-898-0. 293 pages; 27x20 cm, hardcover. 244 illustrations (many historic images, photographs of instruments, facsimiles of documents, mostly in color). 543 footnotes referring to an comprehensive 10 page bibliography; Appendix: Biographic Timeline (5 p.), Name index. Available for Swiss Francs 58 (ca, US$ 70, plus postage) from the publisher at http://www.nzz-libro.ch/buecher/geschichte/jost-burgi-kepler-und-der-kaiser.html. Reviewing the history of horology is becomes evident that the progress from the simplest and crudest devices to the higher sophistication and greater accuracy was not a smooth and continuous development but a process that sometimes seemed stalled, but at times moved forward in leaps and bounds. And - like most of mankind’s achievements - it was usually specific individuals that were responsible for the big leaps: In the late 16[SUP]th[/SUP] century it was a Swiss born clockmaker named Jost Bürgi (sometimes spelled Buergi in English) active at the court of Wilhelm IV, Count of Hessen, in Kassel (Germany) who invented the cross-beat escapement, and built both the first clocks and the astronomical observation instruments that were orders of magnitude above the state of the art that revolutionized astronomy, and ultimately ushered in modern times by destroying mankind’s geo-centric view of the universe. But surprisingly there is no monograph (and very few articles in periodicals) in English that describe the life oeuvre and achievements of this polymath who built the first clocks that were able to measure time to within a second. And in French the situation is similar: One chapter in the 1946 book by Defossez on 17[SUP]th[/SUP] century horology. Even the German language bibliography makes for a short list (and most are long out of print): 1. John Leopolds 1986 ‘Astronomen, Sterne, Geräte’ is a most thorough description of the instruments at the court in Kassel (including Bürgi made items), and provides the best overview of the instruments during his Kassel years; 2. Mackensen’s 1989 history of the historic Kassel Observatory also frequently refers to Bürgi and his instruments; 3. Leopolds and Pechsteins monograph on Bürgis small celestial globe (a private publication of only a few hundred copies, for the then owner of the piece, Joseph Fremersdorf) and is extremely scarce; 4. the very good, but small book by Ludwig Oechslin on the same item published 2000 (and the only one still in print) by the Swiss National Museum in Zürich (which now owns the piece); 5. the hereto only Bürgi biography (2000) by Oechslin was supposed to be part two the National Museum book, but only got published privately, and is hard to find; 6. finally in 2007 the Museum in Kassel published Karsten Gaulke's: ‘Der Ptolemäus von Kassel : ‘Landgraf Wilhelm IV. von Hessen-Kassel und die Astronomie’, the first scholarly description of the major Bürgi pieces currently preserved in Kassel. But until the book under review by Fritz Staudacher was published in late 2013 there never was major book on Jost Bürgi overall oeuvre, and on his pivotal, but vital role in shaping the modern world. For any horologist interested in the earliest phases of precision timekeeping and astronomical complications on clocks that scarcity of other sources alone should trigger a ‘must buy this’ decision for the new book. In this case the excuse ‘But I cannot read German’ is invalid, because this reviewer feels that the 244 illustrations alone are worth the price of this reasonably priced publication. While not all chapters of the book will be equally interesting to the reader with a horological background several are worth studying in detail: Chapter 3 (25 pages) specifically deals with – and shows images of - the surviving timekeepers built by Bürgi: The seconds beating, Prague made [now Dresden] observatory clock of 1625 [a’ twin’ of the now lost 1585 clock for Kassel]; The 1583, three month running, calendar clock with a daily rewound weight remontoire in Kassel [possibly the oldest surviving remontoire clock]; The ‘Wunderuhr’ of Kassel, ca. 1595, the oldest known clock with a cross-beat escapement The ‘Equation Clock’ of 1591, a small table clock, often referred to as the ‘Solar and Lunar Anomalies Clock’, showing the highly accurate relative position of the sun, the moon (including eclipses) and the fixed stars (astrolabium dial) through the use of epicyclical and differential-epicyclical gearing. The ‘Viennese Planetarium clock’ made 1604 in Prague, the first timepiece known to show five planets circling the sun. This is the only one of the five planetarium clocks that -according to the surviving contemporary documentary evidence – Bürgi designed and built that survives to the present. And last but not least Burgos crowning mechanical achievement the ‘Rock Crystal Clock’ with a transparent mechanized celestial globe, made 1622 to 1627 (built for the imperial Kunstkammer and still kept at the successor to that institution the Kunsthistorisches Museum in Vienna). Staudacher does not classify the mechanized celestial globes as’ timekeepers’, and deals with them separately in Chapter 6 (16 pages). Bürgi did not invent mechanized celestial globes, Christian Heiden in Nürnberg, and Eberhald Baldewein in Kassel preceded him, but already Bürgis first attempt around 1581exceeded the work of his predecessors both regarding precision and additional functions, such as for instance a minute hand. Five of these marvels of technology made by Bürgi (or six if you include the ‘Rock Crystal Clock’ which incorporates a miniature mechanized celestial globe of 56mm diameter) survive to the present, and this reviewer has had the privilege of seeing all six artefacts. Bürgis notes indicate that he made eight such machines in his lifetime, five of them have survived: The globe now at the Swiss National Museum in Zürich, made 1594, is the last and smallest (diameter 14.2 cm), the most complex example, as well as the one (thanks to Ludwig Oechslin) best documented in a publication. It features unevenly spaced gear teeth to account for the elliptical eccentricity of the earth’s path around the sun, and compensates for the effect of the incline of the earth’s rotational axis on the equation of time with epicyclical gearing. It also is the only Bürgi artefact currently in the makers country of origin. The museum in Kassel is privileged to have held on to two examples made by Bürgi while employed at the court there, one dating from ca. 1581, the other one somewhat later, possibly as late as 1592. The one now in Weimar (formerly exhibited in Dresden) is possibly the oldest surviving example. The Bürgi celestial globe exhibited in the Conservatoire des Arts et Métiers in Paris is mechanically similar to the second Kassel example and once had a ‘day of the week indicator sitting on top. It got to France (from Heidelberg) as war spoils in the late 1600s. A sixth related machine, partially made by Bürgi, though strictly speaking not a celestial globe, but an astrolabe clock with mechanized armillary sphere rotating once a day, the latter part probably made by Bürgi. It was made in Prague, and has been royal Swedish property since the last year of the 30 year war in 1648. Another part of the book (Chapter 4, 15 pages) deals with the non-horological scientific instruments built by Bürgi including his astronomical observation sextants and quadrants (predating the use of optics in astronomical observations)which were considered in their days the most accurate and easiest to use instruments available anywhere. But Bürgi also invented the proportional compass with movable pivot, a key instrument for astronomers working with celestial globes, and he made surveying triangulation instruments. The author also deals in detail with Bürgis achievements as an observing astronomer (Chapters 5 and 9) both during his tenure in Kassel (1579-1603), and as the imperial clockmaker to the court of Emperor Rudolf II at the Haradschin castle in Prague (1603-1631), where he also became the key astronomical observer for Kepler (who was a more theoretical astronomer), and where Bürgi was the third highest paid employee of the court, and the workshop provided to him by the Emperor was within a stone’s throw of the imperial palace. Chapter 7 (22 pages) deals with Bürgis achievements as a mathematician. Most historians of math today credit Bürgi –independently of Napier- as the co-inventor of logarithms, whose ability to substitute additions for multiplications, and subtractions for divisions, was essential to the spherical geometry an everyday tool for astronomer when recording the position and paths of heavenly bodies (stars and planets). Bürgis contribution to mathematics also include the most accurate table of sine values available at the time, and the invention of the decimal fraction. As should be clear by now, this book -even if it is the detailed biography of the most talented clockmaker of his era globally- is much more than a “horological book”; and therein also lie its shortcomings. The Swiss author is a recently retired, former corporate communications executive of technology company who has become infatuated with Bürgis role in the transition from the medieval age to the modern era. But he is neither an academic, nor a historian, nor a horologist. Therefore – for this reviewers taste – this biography (while thoroughly exploring the societal impact of Bürgis work and achievements) falls short of my expectations when it comes to dealing with or providing technical, horological and history of science details of the physical artifacts that Bürgi has left us. For that perspective the interested reader must still fall back to the on the modest, 100 page, sparsely illustrated, paperback biography: “Jost Bürgi – by Ludwig Oechslin” (published in 2000, in German, Verlag Ineichen); and the only place I know that sells that book is the gift shop at the horological museum in La Chaux-de-Fonds. I am nevertheless grateful to Fritz Staudacher for having created his Bürgi book; there is so much otherwise hard to access information there. Any attention this enigmatic, underaknowleged horological genius clockmaker of the 16[SUP]th[/SUP] century from Lichtensteig in the Toggenburg valley of, Switzerland can get is well deserved. [P.S. As you must have figured out by now, this reviewer is a somewhat biased, committed fan of Jost Bürgi.] Fortunat F. Mueller-Maerki, Sussex NJ, USA March 2013  The primary reasonably accessible, somewhat detailed, English language description of Bürgi instruments is within: Maurice & Myer: The Clockwork Universe [Catalogue of the 1980 Exhibit in Washington DC], The Smithsonian Institution, ISBN 0-88202-188-5, particularly the essay by Maurice (p.87-102), and the catalog entries for the three Bürgi pieces exhibit: Catalog No. 52, 116 and 119.