288 



CATALOGUE. — OPTICAL INSTRUMENTS. 



Ilanisden on the eyeglasses of telescopes 

 applied to mathematical instruments. Ph. 

 tr. 1783. 94. 



Corrects the chromatic abeiration nearly in the manner 

 of Ealer and Boscovich, and proposes to remedy the cur- 

 vature of the first image, by placing a planoconvex lens a 

 little beyond it, with the flat side towards it. By complet- 

 ing the investigation; it will be found, that in order to pro- 

 duce the greatest effect, the distance of the first image from 

 the lens should be between a half and the whole of its ra- 

 dius ; and in this case the centre of curvature of the mean 

 image formed by the lens will be about the length of the 

 ladius beyond Che lens, supposing it to have been at first a 

 plane. Thus, for an object glass of 2 feet focal lengch, the 

 radius of curvature of the mean image being about 9 inches, 

 if the image be about 2 inches distant from a planoconvex 

 lens of 4 inches radius, the effect of the curvature of a 

 circle of <S inches will be produced, which will make the 

 mean image a little concave towards the eyeglass, as it 

 ought to be. The radial focus is little affected by this 

 arrangement. Y. 



Adams's auzometer. Roz. XXII. 65. Fig. 



For measuring the magnitude of the pencil of rays. 



Oriani on the improvement of telescopes. 



Soc. Ital. III. 664. 

 Cassini on the interposition of a resinous 



jubstance between the lenses of an object 



glass, by Rochon and Grateloup, 1785. 



A. P. 1787. 30. 



In order to lessen the partial reflection. 



An eyeglass with a prism for observations 

 near the zenith. Ph. tr. 1790. 155. 



Schrbter on a telescope of Schrader. Com- 

 mentat. Gott. 1791- XI. M. 32. 



Kliigel's new double object glass. Commen- 

 tat. Gott. 1795. XIII. M.28. 



Free from all aberration. Taking the mean refractive 

 powers 1.53175 and 1.58121, and the dispersive powers 

 .00580 and .00937, after Beguelin, the focal distance from 

 the posterior surface being loooo, the focal length of the 

 convex lens is 3123, of the concave 4397, the radius of 

 the anterior surface of the first is 2168, of the posterior 

 7092, its thickness 79 : that of the anterior of the second 



4600, of the posterior 5740, the thickness 31 ; the distance 

 of the lenses 31, their aperture 937. 



Kiligel Hind. Arch. II. 191. 



Kliigel here gives, for the same refractive powers, in 

 looooths of the focal length of the convex lens, the first 

 radius 6943, the second 22712, the thickness 250, the 

 distance of the lenses 100, the focal length of the second 

 14074, the first radius 14840, the second I8211, the thick- 

 ness 100, the joint focus 32058, the aperture 321 6; and 

 this he says is correct at a considerable distance from the 

 axis, 



Burja. A. Berl. 1797. ii. 8. 



Thinks that where much light and a small field is wanted, 

 object glasses not spherical may be employed with advan- 

 tage. 



Burja on achromatic glasses. A. Berl. 



1798. 3. 

 Blair on achromatic telescopes. Ed. tr. III. 



3. Nich. II. l.Gilb. VI. 129. 

 Blair's patent refracting telescopes. Repert 



VII. 15. 

 *Robison, Enc. Br. Art. Telescopes. 



Says, that Blair's object glass with fluids performs admi- 

 rably. 



Nicholson's iris. Nich. I. 180. 



Nicholson's remarks on Grateloup's object 

 glasses. Nich. Gilb. VI. 151. 



Account of Schrader's 26 feet reflecting tele- 

 scope. Ph. M. I. 113. 



Varley on the magnifying powers of tele- 

 scopes. Ph. M. IV. 87. 



Browne's telescope with a perforated plane 

 mirror. Repert. XI. 21. 



After Martin. 



Adams's patent portable telescope tubes. 



Repert. XV. 156. 

 Cavallo. Nat. Ph. 



Dimensions of two object glasses of Dollond. Two 

 double convex lenses, with a double concave interposed, 

 radii 28, 40, 20.9, 28, 28.4, 28.4 inches, beginning from 

 the object; focal length 40 ; and 28, 35.5, 21.1, 25.75, 

 26,28; focal length 40.3. 



