358 



SEC. 11. ASTRONOMY. 



1836a. Small Hand Speculum Polishing Machine, 



constructed and used by Sir William Herschel to polish specula of 

 7 feet focus (6 in. aperture). Smaller machines for smaller specula 

 were made of this construction, and are in part preserved. The 

 polishing machines used to figure and polish large specula (18 in. 

 and 49 in. diameter) for the 20 foot and 40 foot telescopes used at 

 Slough and at the Cape of Good Hope were of the same con- 

 struction as this instrument and of proportionally larger size. 



Prof. A. S. Herschel. 



1836b. Brass foot used in place of the lead block to carry 

 the furrowed pitch rubber or polisher revolving with the bed plate 

 of the machine, to whose centre it is fastened down by screws. 

 For the largest sized mirrors these brass plates were used as well 

 as for smaller sizes to replace the lead foundation or bearer of the 

 pitch. Prof. A. S. Herschel. 



EYE-PIECES AND OBJECTIVES. 



1837. Objectives and Eye-pieces of the 17th and 18th 

 centuries, the greater part of which were ground and polished by 

 Christian and Constantine Huygens. 



Professor Dr. P. L. Rijke, Ley den. 



No. 1. Objective of 120 ft 



No. 2. 

 No. 3. 

 No. 4. 



No. 5. 

 Nos. 6 8* 7, 

 No. 8. 

 No. 9. 

 No. 10. 



84 

 85 

 43 

 43 

 34 

 34 

 34 



J. Bearing the signature of Const. Huygens. 



eachj 



Bearing the name of Chr. Huygens. 

 Bearing the signature of Chr. Huygens. 

 10 ft. 8 in. Bearing the name of Chr. Huygens. 

 No. 11. Bearing the name of Hartsoeker. 



No. 12. Objective of 32 ft. Bearing the signature of Marcell. 

 Nos. la and b. Eye-pieces of 7^ and 8 inch, to use with objective No. 

 No. 2a. 6 



No. 5a. 



No. 7a. 



No. 8a. 3 



No. lOa. 



1. 

 2. 

 5. 



7. 



8. 



10. 



1838. Photograph of the Lens by which Huygens dis- 

 covered Saturn's King. Professoi- Buys-Ballot, Utrecht. 



- This lens is stated to be the same by which Christian Huygens made 

 out Saturn to be surrounded by a ring. It bears the inscription " X. 3 FEBR. 

 (Febr. 1655), Admovere oculis distantia sidera nostris." 



1840. Metal for a Newtonian Reflector, with several 

 wooden eye-pieces, but without tube or mounting, by Hadley. 



Royal Society. 



