In the _Bulletin_ series, the first of which was issued in 1875, appear longer, separate publications consisting of monographs (occasionally in several parts) and volumes in which are collected works on related subjects. _Bulletins_ are either octavo or quarto in size, depending on the needs of the presentation. Since 1902 papers relating to the botanical collections of the Museum of Natural History have been published in the _Bulletin_ series under the heading _Contributions from the United States National Herbarium_, and since 1959, in _Bulletins_ titled "Contributions from the Museum of History and Technology," have been gathered shorter papers relating to the collections and research of that Museum. The present collection of Contributions, Papers 34-44, comprises Bulletin 240. Each of these papers has been previously published in separate form. The year of publication is shown on the last page of each paper. FRANK A. TAYLOR _Director, United States National Museum_ * * * * * Contributions from the Museum of History and Technology: Paper 35 THE BORGHESI ASTRONOMICAL CLOCK IN THE MUSEUM OF HISTORY AND TECHNOLOGY by SILVIO A. BEDINI DEVELOPMENT OF ASTRONOMICAL CLOCKS 32 DESIGNER BORGHESI 33 CLOCKMAKER BERTOLLA 34 FIRST BORGHESI CLOCK 38 SECOND BORGHESI CLOCK 41 BORGHESIAN THEORY OF THE UNIVERSE 54 LAST YEARS 57 THE CLOCKS OF BARTOLOMEO ANTONIO BERTOLLA 59 APPENDIX 71 BIBLIOGRAPHY 76 [Illustration: Figure 1.--THE DIAL PLATE of the Borghesi clock, showing the horary and astronomical indications which are automatically presented.] _Silvio A. Bedini_ _The Borghesi Astronomical Clock_ _In the Museum of History and Technology_ _The history of the 18th-century Borghesi astronomical clock is described here from contemporary source material. The evolution of its design by Father Francesco Borghesi and the building of the complex mechanism devised by the clockmaker, Bartolomeo Antonio Bertolla, is a story of the vision of one man turned into reality by another. The result of their collaboration is the unique, astronomical timepiece now in the Museum of History and Technology._ THE AUTHOR: _Silvio A. Bedini is curator of mechanical and civil engineering in the Smithsonian Institution's Museum of History and Technology._ "... All this work I had performed eagerly, so that, while in my room, I might contemplate leisurely, both during the day and in the night, the true face of the heavens and of the seas unobscured by clouds, even though I had no astronomical equipment."[1]