Meton, an astronomer of Athens, discovered in 432 

 B.C. that after a period of 19 years the new and the 

 full moons returned on the same days of the month 

 as they had before, and this is called the cycle of the 

 moon. The Greeks were so impressed with this 

 calculation that they had it inscribed in letters of 

 gold upon stone, hence the golden number. The 

 First Council of Xicaea in A.D. 325 determined that 

 Meton's cycle was to be used to regulate the movable 

 feasts of the Church. 



Immediately above the chapter rings is an opening 

 through which the orb of the sun is visible. 



THE CHAPTER-RING ASSEMBLY 



In a separate chapter in his second volume, entitled 

 "Descriptio Authomatis Summa totius Operis 

 Mechanici" (Description of the Automaton — Sum- 

 mary of the Complete Mechanism), Father Borghesi 

 provided a description of the functions of the various 

 indicators, prefixing it with the short poem shown in 

 figure 18. He then continues: 



In the middle of the frontispiece, as at the center of 

 the universe, the terraqueous globe of the week revolves, 

 with a daily motion turning from right to left, bringing 

 with it from the round window the coming day and at 

 die circumference the circle of hours common to the sun, 

 to the moon, to the fixed stars, to the head and tail of the 

 dragon, and to the raging sea. 



The second circle revolves the synodic-periodic measure 

 of the raging sea, the days of the median lunar-synodic 

 age, the signs and individual degrees of the signs of the 

 distance of the moon from the middle of the sun within 

 die time of 29 terrestrial revolutions, hours 12. 44. 3. 13. 

 This circle revolves likewise from right to left around the 

 center of the earth. In this second circle, another little 

 orb revolves, bringing with it the epicycle of the moon, 

 in which the little circle of the moon (whose illuminated 

 middle always faces towards the sun), running from left 

 10 right through the signs of the anomaly; within 13 

 revolutions of the earth, hours 18.39.16. It descends 

 from apogee to perigee and in just as many others it 

 returns from perigee to apogee, to be carried down thus 

 to true, back and front from the longitude and distance 

 from the sun and from the middle of the earth. 



The third circle (on which I have tried to indicate 

 astronomically-geometrically in their places, the degrees 

 of lunar latitude both in the south and in the north, and 

 some fixed stars, those, namely, which can be separated 

 by us from the moon which goes between) from left to 

 right turns around the center of the earth, stretching 

 out the head and tail of the dragon, on the inside above 

 the second circle for noting and measuring the sun (but 



I should rather say the earth), and the eclipses of the 

 moon, within 346 revolutions of the earth, hours 14.52.23. 



The fourth circle, in which the heaven of the fixed 

 stars, reduced to the correct ascent of our times, the signs 

 of the zodiac and the individual degrees of the signs, the 

 months of the year and the single days of the month can 

 be seen, likewise makes its journey around the earth 

 from left to right in 365 terrestrial revolutions, hours 

 5.48.56.; that is, within a median astronomical year. 

 Above this annual orb, the sun, in its small epicycle, 

 gliding through the 12 signs of the anamoly, within the 

 space of 182 terrestrial revolutions, hours 15.6.58., from 

 left to right, falls from apogee to perigee; and. within 

 the same time, rises from perigee to apogee, and brings 

 with it. the index, namely its central radius, inhering 

 to the axis of the equatorial orb and cutting the four 

 greatest circles from the center. 



When the sun has been moved around, Iris shows from 

 six windows the era, that is, the current year. Two 

 winged youths take their place next to Iris, carrying the 

 Julian period: namely, the Roman indiction, the cycle 

 of the sun and the golden number, on a leaf of paper held 

 between them. The imperial eagle stands out on top 

 (as if added to the frontispiece) carrying on its breast the 

 dominating planet and in its talons the ecclesiastical 

 calends (that is. the dominical letter and the epact). 



ATTACHMENTS FOR ADJUSTMENT 



Two attachments, in the form of small superimposed 

 dials are situated at the base of the dial plate, at either 

 side and immediately below the fourth chapter ring. 

 In his second volume, Father Borghesi stated that 

 they "are not moved from inside the clock, but the 

 one at the right [inscribed concitat and retardat] serves 

 for loosening [accelerating;] and tightening [retarding] 

 time; that is, the reins of the perpendicular." 



In other words, the purpose of this attachment is for 

 adjusting the pendulum to make the clock operate fast 

 or slow. The second attachment, which appears at 

 the left, and which is inscribed "Claudit" (close) 

 and "Aperit" (open) serves the purpose of ". . . 

 preparing the mechanism in a moment, as swiftly as 

 you wish, for sustaining the astronomical experiments 

 of which you will hear later; when these things have 

 been done, it restores the mechanism to its natural 

 motion at the same speed." 



This adjustment relates to the final section of Father 

 Borghesi's second book, entitled "Chronologo-Astro- 

 nomicus Usus Authomatis" (Chronological-Astro- 

 nomical Use of the Automaton), which is translated 

 from the Latin in its entirety: 



48 



Bl Ml UN 240: CONTRIBUTIONS FROM THE MUSEUM OF HISTORY AND TECHNOLOGY 



