352 



CATALOG UK. — PIIACTICAL ASTBON'OMY. 



Ilerschel's lamp micrometer. Ph. tr. 1782. 

 163. 



For ascertaining an^lar situations, by comparison with 

 ,two lamps viewed by the other eye, one of them moveable 

 everyway. Makes Lyra subtend .35 J3". 



■Herschers dark and lucid disc aud peri|)hery 

 micrometers. Ph. tr. 1783. 4. 



A light circle being compared with a darlc one on aliglit 

 ground, the light one appears the larger. 



Ussher on telescopes for viewing stars in the 

 day. Ir. tr. 1788. 37. 



The highest magnifiers the best. 



Englefield on Bradley's rhomboid microme- 

 ter. 4. Bath. 



Pigott on the comparative magnitudes of 

 the stars. Ph. tr. 1785. 135. 



Suggests, that they may be measured by ascertaining how 

 much light, thrown into the telescope, will efface them. 



Wollaston on a system of wires. Ph. tr. 

 1785. 346. 



A rhombus instead of a rhomboid, for ascertaining right 

 ascensions and declinations. 



Am. tr. II. 181. Nich. 8. 1.319. 



Rittenhouse uses spiders' webs instead of wires, for mi- 

 crometers. 



.Cavallo on a micrometer. See Optical In- 

 struments. 



E. -Walker on Bradley's mode of observing 

 transits. Nich. 8. H. 22. 



Astronomical micrometers and photometers. 

 Zach. Eph. III. 318. 



Burckhardt on a quadrangular system of 

 wires. Zach. Mon. corr. I, 120. 



Burckhardt on micrometers. M. Inst. To be 

 printed in the S. £. 



Theodolites. 



Theodolites with verniers. Leup. Th. Ar. t, 



37 . . 42. 

 Circles. E. M. Pi. V. Marine. IV. 

 *iloy's account of the great theodolite, with 



its microscopes and microiueters. Ph. tr. 



1790. 135. 



Ramsden's improved theodolite. Ph.tr. 1795, 



457. 

 A small theodolite of Ramsden. Pli.tr. 1797. 



507. 

 Theodolites. Enc. Br. Art. Geometry. 

 Ofvcrbom's theodolite. Zach. Mon. corr. 



IV. 334. Fig. 

 Bohnenbergeron acircle of Baumaun. Zach. 



Mon. coiT. VI. 465. 



Fixed InstrumtiUs. 

 ' Transit Instruments, 



Derham's transit instrument. Ph. tr. 1704. 



XXIV. 1578. 

 Roemer's simple transit instrument. M." Ber-!. 



1727. 111.276. 

 Gensanne's transit instrument A. P. 1736. 



II. 120. Mach. A. VII. 55. 

 Ussher on illuminating the wires of a transit 



instrument. Ir. tr. 1788. II. 13. 

 Wollaston on atransitcircle.Ph.tr. 1793. 133. 

 A transit instrument by Ramsden. Ph. tr. 



1795.419. 

 Cjmierer and Pasquich on the errois of a 



transit instrument. Zach. Mon. corr. VI. 



34, 176,481. 

 A transit instrament. Cavallo. N. Ph. IV. 



PI. 29. f. 0. 



Mural Quadrants. 

 See Quadrants. 



Zenith Sectors. 



*A zenith sector by Ramsden and Berge. 

 Mudge. Ph. tr. 1803. 383. 



Account of a Zenith Sector, described by Major Mmdgz. 

 From the Jowrnah of ike Royal Inslitulion. II. 



The external frame of the instrument is of mahogany, 

 constituting a truncated pyramid, on a base of six feet 

 square, tapering to a vertex of three. The internal frame, 

 which immediately supports the sector, revolves on a ver- 

 tical axis, terminating below in a cone, which rests in x 



