932 APPENDIX. 



wheel has its right position to the writing on the perforated paper, the letter 

 desired will appear printed on the paper. (2 photographs, 7 drawings, and 

 a more detailed description follow.) 



17O9c. Contact Breaker, with two discs, which can be 

 displaced, and sliding springs on glass inlets. 



Prof. Dr. Dove, Berlin. 



(See Transactions of the Royal Academy of Sciences at Berlin, 1841, 

 p. 296.) 



1722a. Davis' Quadrant or Back Staff. The first marine 

 instrument for taking altitudes of the sun with reference to the 

 visible horizon. This instrument was the prelude to Hadley's 

 quadrant and the reflecting sextants and circles of the present day. 

 The property of the Royal Astronomical Society, presented 'by 

 R. J. Lecky. Robert J. Lecky, F.R.A.S. 



1722b. Double Reflecting Circle, by Capt, Owen, R.E. 

 The property of the Royal Astronomical Society. 



Robert J. Lecky, F.R.A.S. 



This invention of the late Capt. Owen, R.E., is peculiarly valuable for the 

 readiness with which two observations or " sights " can be taken with it, 

 without removing the instrument from the eye, e.g., in a lunar observation 

 at sea the altitude of the star and the lunar distance may be taken with great 

 rapidity, as well as in other observations. 



The two circles each six inches diameter are divided on silver and read by 

 three verniers on each to 20 seconds of arc, and the glasses being placed 

 between the circles are well defended from accident at sea. It has other 

 adaptations of much ingenuity. 



1754a. Ancient Astrolabe, supposed to have belonged to 

 the Spanish Armada. Robert J. Lecky, F.R.A.S. 



This instrument was found under a rock in the island of Valencia, Ireland, 

 1845, within view of the place where three vessels of the Spanish armada 

 were wrecked, and from the style of its finish and workmanship is supposed 

 to have belonged to one of them. 



1757a. Large Bronze Astrolabe, which belonged to King 

 Philip II., of Spain. Archceological Museum, Madrid. 



Near the handle are the following inscriptions, giving the date and name 

 of the maker : 



Philippe Rege. Gtialterus Arsenius Frisi Nepos Lonanii fecit an 1555. 

 The diameter of this instrument, is 0'59 m . 



1757b. Bronze Astrolabe, made in the 16th century. 

 Diameter, * 32 m . Archceological Museum, Madrid. 



1757c. Arabian Astrolabe. Made at Toledo, A.D. 1067. 

 Diameter, 0'24 m . Archceological Museum, Madrid. 



Astrolabe made at Toledo as stated in the Arabic inscription engraved at 

 the back : " In the month of Shawan. One of the works superintended by 

 " Ibrahin Ibu Said, the Muazini, Assohli, at Toledo. In the 459th year of 

 " theHegira." 



