410 SEC. 11. ASTRONOMY. 



1819. Day Telescope of Ippolito Mariani, a Florentine, 

 surnamed il Tordo ; first practical optician ; taught by Galileo. 

 Object-glass, 103 mm. in diameter. The eye-glass is composed of 

 two lenses, plano-convex, of mm. 48 in diameter. The second and 

 third lenses are similar to the eye-glass. 



The Royal Institute of " Studii Supcriori" Florence. 



1820. Day Telescope of Campani, romano, object-glass 

 47 mm. in diameter eye-glass, double convex, 27 mm. in diameter ; 

 second and third lenses the same. 



The Royal Institute of " Studii Superiorly Florence. 



Campani's well known telescopes are to be found in many observatories ; 

 some of them are 70, 100, 150, and even 210 palmi Komani in length. 



1821. Telescope by Amici. 



The Royal Institute of" Studii Superior i" Florence. 



1830. Volume, Experiments in Natural Science Accademia 

 del Cimento. 



The Royal Institute of <c Studii Stiperiori," Florence. 



1831. Telescope, by Chr. Huygens. The objective ground 

 and polished by him, and bearing his signature. 



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



Its focal distance is 3-906 m., and aperture 0-0616 m. The eyepiece is 

 composed of three convex lenses. The lens a, the nearest to the objective, 

 and the lens b, following it, have a focal distance of 0' 105 m., and an aper- 

 ture of 0'04 ; the lens c has a focal distance of 0*079 and an aperture of 

 0'038 m. The distance between a and b is 0*212 m. ; that between b and c 

 0*182 m. The eye should be placed at a distance of 0*058 from the lens c. 

 The lenses b and c serve only to rectify the images. 



1831b. Telescope by Campani. 



Royal Museum, Cassel (Director, Dr. Pinder). 

 The tube is wood ; it measures, when drawn out, 16 feet. This was bought 

 in Rome by Landgrave Charles. 



1831g. Two Telescopes (Achromatic), made by Dollond, 

 about 1765, for the Russian expeditions for the observation of the 

 transit of Venus in 1769. 



The Imperial Academy of Sciences, St. Petersburg. 



Object-glasses of 3*6" and 2-8" aperture, focal length 11*2' and 8-5'. There 

 are several of each size in possession of the Academy. As they are not 

 designated by numbers or other distinct marks, it cannot exactly be made out 

 which of them has been used by the different observers. 



1832. Terrestrial Refractor, made by Van Deyl, at Am- 

 sterdam, in the year 1781. Teyler Foundation, Haarlem. 



183 la. Huygens' Aerial Telescope. Royal Society. 



1831b. Object-Glass by Huygens, 170 feet focal length. 



Royal Society. 



1831c. Object-Glass by Huygens. Royal Society. 



