tion for each distance of the sun from its apogee or 

 perigee in degrees, and in sufficiently small parts of 

 degrees, with the title added above in their proper 

 places, whether an addition is to be made to the mean 

 location of the sun or a subtraction from the same, 

 so that the true longitude of the sun may be calculated. 

 Three circles are assigned to the lowest index, of which 

 30 degrees of distance of the moon from its nodes 

 comprise the larger. The middle circle is based on 

 the hypothesis of the mean invariable diameters (that 

 is, of the sun, the moon, and the terrestrial shadow), 

 and is divided into hours and quarters of duration. 

 The last circle is divided by the trigonometric laws 

 into the inches of magnitude of lunar eclipses. 

 Lying between these circles, there is another eccentric 

 circle (black with a spot) exhibiting the shadow 

 of the earth, in which the little moon sinks itself, 

 carried by the lowest index. In any ecliptic full moons, 

 the patent number of inches of immersion somehow 

 affects the minds of the cultured, but also the scheme 

 of maximum obscuration affects the eyes of the 

 illiterate themselves. 



IV 



( )f the three indices which revolve from the left, the 

 uppermost completes its cycle within 12 hours, just as 

 the hour index. The middle one with two pointers 

 on diametrically opposite sides, carries the marks of 

 conjunction and opposition of the luminous bodies, 

 with a movement equal to the course of the sun from 

 lunar apogee or perigee. The lowest index, fitted 

 with a single pointer, indicates the motion of the moon 

 from its apogee or perigee. Under these three indices, 

 there is situated a common circle, divided into 12 

 parts, each of which are further divided into 30 parts 

 through its outer circumference. I have said a com- 

 mon circle, for, with respect to the first index, the 

 division represents 12 hours, and the double subdivi- 

 sion representing the double set of minutes of the hours 

 serves for an excitator for anytime at all, at will. For 

 as often as the little index reaches the twelfth hour, 

 first being moved by hand wherever you prefer, a 

 little hammer strikes the little bell many times. But 

 if you observe the second or the third index, the first 

 division provides the signs, and the subdivision of the 

 signs gives the individual degrees of the distance of 

 the sun from the lunar apogee, or of the moon from 

 its apogee, respectively. To this is added two other 



interior circles from the same center: to the larger is 

 inserted the equation of the center of the moon in its 

 conjunctions and oppositions; and on the smaller the 

 equation of the same moon in its quarters, astronom- 

 ically-geometrically proportioned to the distance of 

 the moon from its apogee or perigee. In the first 

 case, the equation is to be subtracted from the mean 

 longitude of the moon, descending from apogee to 

 perigee; in the second case, to be added to the mean 

 longitude of the moon ascending from perigee to 

 apogee; and, in the third semicircle of the index, as 

 the rubric directs, common to both equations, added 

 around the center. 



V 



Perpendicularly under the center of the machine, 

 two other indices are carried about one and the same 

 center. The one nearer to the observer — bearing in 

 one of two points diametrically opposite the small 

 disk of the sun, in the other the disk of the moon — 

 runs a course equal to the motion of the sun from the 

 head or the tail of the dragon (Draco). The other, of 

 simple construction, marked with a small moon, 

 signifies in like manner the motion of the moon from 

 the head or the tail of the dragon. 



Immediately below, there is a larger circle, common 

 [referring] to both these indices, which is divided into 

 12 parts. Each of these parts in turn, in the outer 

 periphery, is subdivided further into 30 parts, which 

 are the 12 signs of the zodiac and the individual 

 degrees of the signs of distance of the sun and the 

 moon from the head of the dragon. 



In the second circle is read the latitude of the moon, 

 measured by degrees, etc., on a trigonometric scale, 

 by signs and degrees of distance of the moon from its 

 nodes, that is, from the head or tail of the dragon. 

 When the second index is descending from the head 

 of the dragon to the tail, the latitude will be to the 

 north of the solar path; that is, the ecliptic. On the 

 other hand, it will be south of the ecliptic when the 

 same index is returning upward from the tail to the 

 head of the dragon as advised by the title inscribed 

 on the third circle. 



Finally, on the fourth and last circle are seen more 

 prime minutes of the circle for reducing the orbit 

 of the moon to the ecliptic. That the true longitude 

 of the moon may be obtained more accurately, these 

 must be subtracted from the longitude of the moon 



72 



11 I I KILN 240: CONTRIBUTIONS FROM THE MUSEUM OF HISTORY AND TECHNOLOGY 



