Megadiascope. 



1225 



I 



Fig. 39. Xo. 9598. 1:6. 



. 

 eS 



g 



* 9587. Press, for bending glass, Fig. 37. with 2 glass strips, for demonstrating that glass B- <* 



becomes double refracting by bending 1. 2. o 



* 9588. Fresnel's Press, for showing that glass becomes double refracting when pressure is 



applied to it (M. P. II, 1, Fig. 734) 2. 15. 



* 9589. 8 rapidly-annealed glass sheets of different shapes (F i g. 38) 3. 0. 



* 9590. Crossed Glass shape (annealed), composed of two single pieces of glass mounted in cork 0. 10. 

 *9591. Rock Crystal 0. 6. 



* 9.392. Aragonite 0. 8. 



* 9593. Calcapar 0. 6. 



* 9594. Gypsum with movable hyperbolae 0. T. 



* '.'595. 2 gypsum plates for complementary colours, mounted in cork .Price each 3s. 6 d. 0. 7.0 



* 9596. - - d o., 1 ll wave-length Price each 4s. d. 0. 8.0 



* 9597. Gypsum figures (star. 10s., butterfly, 17s.) 1. 7.0 



For polarisation-projection by Paalzow's method 6 sliders with stands. No. 9523, 

 or 5 sliders, No. 9523 and 1 slider No. 9524 are necessary. 



Interference and Diffraction. 



9598. Complete Outfit for Interference and Diffraction Experiments, F i g. 39 16.10.0 



The outfit consists of the following: 1 cylindrical lens, 1 interference prism, 1 Fresnel ocular 

 micrometer. F i g. 22. .p. 1214. for measuring the wave-length, with red illuminating glass; 1 doubly 

 adjustable, rotary micrometer slit, 1 rotary slit with screw adjustment. 1 rotary double grating on gl. 

 3 screens for taking 12 diaphragms of various form of aperture and gratings and slits of different width. 

 All auxiliary apparatus are placed in a handsome case (Fig. 39). The set of diaphragms which we supply 

 with this outfit comprise: 1 diaphragm with sharp edge, 1 diaphragm with needle, 1 diaphragm with 

 hair, 1 diaphragm with a thick opaque thread, 1 diaphragm with a small round aperture, 1 diaphragm 

 with a large round aperture, 1 diaphragm with aperture half covered with mica, 1 diaphragm with rhombic 

 aperture, 1 diaphragm with triangle of holes, 1 diaphragm with two holes, 1 diaphragm with mesh of 

 holes, and 1 ditto with a row of holes. 



9599. Interference Mirror (Fresnel's), F i g. 20, p. 1214, with parallel micrometer motion, 

 micrometer screw with drum and graduations, on stand, of first-rate construction . 7. 0. 



9600. do., without parallel micrometer motion 4. 15. o 



9601. Fresnel Interference Mirror, with two black polished mirrors, reciprocally adjustable 



by means of micrometer screw, size 40x50 mm 2. 5. 



The items with an asterisk are absolutely necessary for carrying out the experiments. 





