176 SKC. 7. LIGHT. 



eyes ; the relief in objects made with vertical wires then disappears. If the 

 diaphragm which bears the two tubes is kept fixed, and the instrument turned 

 slowly round the left tube, very curious apparent motions occur in the objects 

 under observation. 



For the mathematical theory of this apparatus, see the " Nuovo Cimento," 

 2 d ser. t. xiv. 



813. Jewel Lens (Ruby) of -$ inch focus. Made by Mr. 

 Andrew Pritchard, at the suggestion of Sir David Brewster. 



(See Brewster's " Optics," 1831, p. 337.) John Spiller, F.C.S. 



81 3a. Vertical Apparatus for Projections. 



M. J. Duboscq, Paris. 



813b. Projecting Apparatus, for all phenomena of double 

 refraction and polarization. M. J. Duboscq, Paris. 



813c. Support, with Reflector, by Fresnel. 



M. J. Duboscq, Paris. 



\b. LANTERNS, CAMERAS, &c. 



814. Oxy-hydrogen Lantern, of new form, suitable for 

 lecturers. C. J. Woodward. 



The lantern is mounted on' a " Willis's stool," so that supports of various 

 kinds may readily be attached. The body of the lantern is swung between 

 two uprights, and can be clamped so as to send a beam of light at any angle j 

 this, combined with a rotatory motion in a horizontal plane, enables the 

 lecturer to direct a beam in any required direction. A rod carries lenses and 

 a mirror when it is required to throw the light vertically upwards on an object, 

 as, e.g., for cohesion figures. 



816. Camera Obscura. An early example, said to have 

 belonged to Sir Joshua Reynolds. South Kensington Museum. 



This camera when closed has the form of a large folio leather-bound book. 

 It is recorded to have been given by Sir Joshua Reynolds to Lady Yates, by 

 whose great grand-daughter, Mrs. J. R. Harrison, it was, in May 1875, 

 presented to the Museum. 



81 6a. Camera, by Colonel Laussedat. M. Lutz, Paris. 



816d. Camera Xiucida, invented and used by Dr. Wollaston. 



G. H. Wollaston, Clifton. 

 816g. Camera Lucida, with slight magnifying power. 



A. Nachety Paris. 



31 6h. Camera for Landscapes, by M. Gori. 



A. Nachet, Paris. 



816i. Camera Lucida, invented and used by Dr. W. H. 

 Wollaston. G. H. Wollaston. 



817. Improved Electric Lamp and Lantern for Lecturer's 

 use. John Browning. 



