luminous bodies are eclipticall) in opposition al night. 

 Since lunar eclipses appear to .ill people as being of 



the same magnitude and duration, and begin and 

 dissipate at the same absolute moment ol tunc, I 

 decided to reveal another I. net of this spectacle on 

 the right side of the center ol the clock (see chaptei 1 1 1 

 above). I heir, al the time of the true ecliptic full 

 .is the pointer of the third little index shows, 

 you can ascertain the hour-, etc., of duration, and 

 the inches of greatest obscuration. The little moon 



attached to the index is ,i model of I lipsed 



moon. 



IX 



Thus, with the aid of this machine, solar and lunar 

 eclipses of the past can lie recalled and future ones 

 can he foreseen. Indeed, if the index of prime min- 

 utes is speeded up by hand, whose wheel imparts 

 i to the other indices and shields, then. 

 the dials and openings will foretell the year, month, 

 day, hour, etc., of any future eclipse. I foresaw that 

 the times would thus he evolved too slowly, and that 

 the clock wheels would he considerably worn by 

 repeated experiments (if, for instance, by tin' rotation 

 of the index of prime minutes, to whose period only 

 a single hour corresponds, the future new and full 

 moon ecliptics were being investigated). Therefore, 

 I took care that the wheel which immediately com- 

 municate'; motion to the index of the synodic moon 

 should he so litted internally to the mechanism that 

 l.\ the reversal of an) external index, the wheel would 

 be removed from its proper position; whenever 

 desired, it could be quickly and most accurately 

 restored to its proper place. 



In this way, since the close meshing of the wheels is 

 released, you can extend the experiment for many 

 years, even lor man) centuries. You have only to 

 guide with your hand the index of the synodic moon 

 on the circles, always intenllv observing whether, in 

 the passage which this index in.ikes over the little 

 index, both pointers of the little index are hidden by 



the segments of the circle. Having observed this, 



look at the index moved by hand, for if tin- has 

 carried the solar disk halfway between the two larger 

 segments of the circle to the region of the hidden little 

 index, then you will know that eclipse will be a solar 

 eclipse. < )n the other hand, you will know that it will 

 be a lunar eclipse, if the index (moved by hand) has 



carried the moon, situated between the two smaller 

 segments ol the i irele, to the sami , the 



hidden pari ol the circle). I he solar disk and the 



lim.i: disk alternately will reveal to Volt the (: 



-tames of both eclipses. The current year vvill be 

 given by the Julian period, reducible to an) • 

 epoch, 'd in the solar cycle, the golden 



number and the Rom. in ivile. The month of the 



nd also the day of the month will be indicated 



by the pointer ol the little index, hist on the right 



side of the clock. And what I have said ol future 



eclipse- should be e<|iiallv understood ol i 



I .is the index, wlni h can In- moved either w.iv 



at will, is moved in rev erse. 



I in, illy, though 55 wheels were employed to 



u\ dials, ill are driven by one source ol power 

 aot exceeding the third part of a Germanic hun 

 weight which, suspended at the geometric height of 

 live feet 'about the ordinary stature of a man), keeps 

 the whole machine in operation for a hundred dav- 

 and more. 



Although the machine repeats hours and quarter 



hours at will and. COnsequendy, the number ol wheels 



and the rest of the apparatus necessary for these 

 functions is thereby increased, it has not grown to an 

 unwieldy size, however much one might erroneously 

 imagine it to be. It does not exceed the bulk of 

 ordinary clocks hanging from a wall; indeed, it 

 scai cely equals these. 



The entire machine, ready for operation, doe t 



weigh more than 156 ounces, although it i- m 



steel or brass throughout and further weighted with 



two bells and a lather large bra-s dial-plate. 



i i| course, there are main more things to 1" 

 especially about the mechanical structure ol the 

 wheels, but fearing to tire my kind reader unduly I >> 

 exceeding the bounds ol .1 summary, I am forced to 

 put an end, though unwillingly, to this sulhciently 

 shortened explanation ol the work. I have hope of 

 giving satisfaction to many more when I shall have 

 Communicated 10 the learned world another and 

 completely new automatic work, grander than this 

 1 one. It is already theoretically completed in 

 all its calculations, but still to be worked out mechani- 

 cally from the very beginning, if but God, thrice Best 

 and Greatest, bless the undertaking and mercifully 

 grant life and health — to whom be in, and from, and 

 through all things, all honor and glory in eternity and 

 beyond. 



I'AI'IR 35: till BORGHKSI ASTRONOMICAL CLOCK 



O 



