434 SEC. 11. ASTRONOMY. 



the day and night. These are paired with eight characters of the denary 

 cycle and four of the famous eight diagrams of the Book of Changes. The 

 inside of the ring bears the names of the 12 states into which China was in 

 ancient time divided. An equatorial circle is fixed inside the frame, within 

 which a sphere turns on two pivots at the poles of the azimuth. This is 

 made up of an equatorial circle and double ring ecliptic, an equinoctial circle, 

 and double ring solstitial colure. The equator is divided into 28 unequal 

 portions marked by the names of a like number of constellations of unknown 

 antiquity. The ecliptic is divided into 24 equal parts. All these circles are 

 divided 'into 365 degrees, corresponding to the days of the year, and each 

 degree is divided into 100 parts, as the centesimal division prevailed for 

 everything less than degrees, till the arrival of Father Verbiest in the 17th 

 century. 



No. 2. Armillary sphere on the terrace of the observatory at Pekin, made 

 under the direction of Father Verbiest ; see Thomson's " Illustrations of China 

 " and its People." 



No. 3. Celestial globe on the terrace of the observatory at Pekin ; see 

 Thomson's " Illustrations of China and its People." 



1914b. Model of Hipparchus 5 Astrolabe, showing how 

 that astronomer observed longitudes, and was enabled to determine 

 the precesssion of the equinoxes. J. Norman Lockyer, F.R.S. 



1914f. Photograph of the 9-62 inch Equatorial of the 



U.S. Naval Observatory, Washington, U.S.A. 



Rear- Admiral C. H. Davis, U.S.N. 



This instrument was made by Merz & Mahler and has been in use since 

 1845 in the observations of planets, comets, double stars, etc. The objective 

 has been polished and refigured by Alvan Clark & Sous. The instrument 

 differs in no important particular from those of the same makers at Berlin, 

 Dorpat, etc. Its focal length is 14 feet 4'5 inches, it aperture is 9*62 English 

 inches (9 French inches). 



Photograph of the 26-inch Equatorial of the U.S. Naval 

 Observatory, Washington, U.S.A. 



Rear-Admiral C. H. Davis, U.S.N. 



This instrument was constructed by Alvan. Clark & Sous of Cambridge, 

 U.S., and has a focal length of about 390 inches and an aperture of 26 inches, 

 and is thus the largest refractor in the world. A full description of it may 

 be found in the Washington Astronomical Observations for 1874, Appendix I. 

 Its work has been, since 1873, the observation of the faint satellites of the 

 outer planets, difficult doub'e stars, and of nebulae. 



Photograph of the Transit Circle of the U.S. Naval Obser- 

 vatory, Washington, U.S.A. 



Rear-Admiral C. If. Davis, U.S.N. 



This instrument was mounted in 1866, and was made by Pistor & Mar- 

 tins of Berlin. Its focal length is 12 feet 0-1 inch and its aperture is 8.52 

 inches. A full description of it may be found in Washington Astronomical 

 Observations for 1865, and also in the same publication for 1874, Appendix I. 



Photograph of the Transit Instrument and Mural Circle 



of the U.S. Naval Observatory, Washington, U.S.A. 



Rear-Admiral C. H. Davis, U.S.N. 



