346 SEC. 11. ASTBONOMY. 



2. The time in the prime vertical. 



3. When it is turned through 90, the polar altitude, according to the 



method of Bessel. 



4. The polar altitude, according to Falcot's method, where the difference 



between the north and south zenith distance is measured by the 

 micrometer screw. 



1771. Portable Catoptric Transit Instrument, with a 

 telescope horizontally resting in collars, and revolving only on its 

 own optic axis. Invented and constructed by C. A. Steinheil, 

 sen p . 



Conservatorium of the Math, and Phys. Collections of 

 Bavaria (Prof. Dr. Seidel). 



The construction of this instrument is described by its inventor in Schu- 

 machers Jahrbuch fur 1844 (Stuttgart and Tubingen, published by Cotta), 

 p. 3, et seg. 



177 la. Reflecting Transit Instrument. 



W. Watson and Son, London. 



In this the image of the star is received on a mirror, and then viewed by 

 looking down through a small telescope placed in such a position as to be most 

 convenient for observation ; the telescope is stationary, but the mirror moves 

 in the plane of the meridian, so can be directed to any point in it, and obser- 

 vations t taken without those inconvenient positions of the observer, so often 

 necessary with transits of ordinary construction. 



1772. Azimuth Quadrant, constructed by Uletz in 1700. 

 H. G. Van de Sande Bakhuysen, Director of the Observa- 

 tory, Ley den. 



1773. Astronomical Quadrant, said to have been the 

 property of Napier of Merchiston, the inventor of logarithms. 



University of Edinburgh. 



The telescopes attached are evidently of much more recent and clumsy 

 workmanship than the instrument itself. They are reported to have been 

 added by a " college baillie " (in the days when the university was under the 

 government of the town council), who fancied that he was thereby enhancing 

 the value of his gift to the university. 



1774. Quadrant, by Butterfield, of Paris. 



Kew Committee of the Royal Society, Kew Observatory. 



A brass quadrant, on a wrought-iron pedestal, carrying a telescope, with 

 object glass \ in. in diameter, and 2 ft. 3 ins. focal length. The quadrant is 

 divided with a diagonal scale, and is provided with a case for hanging a plumb- 

 line. 



1775. Quadrant, formerly belonging to Tycho Brahe. 



Royal Museum in Cassel (Director Doctor Pinder). 



This instrument is the astronomical quadrant of Tycho Brahe. The 

 altitude quadrant, as well as the azimuth dividing circle, are made of brass ; 



