280 



NEGRETTI AND ZAMBEA, HOLBORN VIADUCT, E.G., 



1061 



1062 



1063 

 1064 

 1065 

 1066 

 1067 



Brass Frame, for showing the transient polarising Each. 



structure communicated by Pressure to a piece of s> 



annealed glass 



Apparatus, for showing the same effect by the unequal 



application of Heat , 



Polarising Eye-piece of thin glass, in brass mounb 



Nicol's Single Image Calc-Spar Prism . . 12s., 15s, 1 10 



Nicol's Double Image Prism of Calc-Spar . 



Tourmalines of various sizes and colours . . 10s. 12 6 



Thin Selenite Plates of equal and unequal thickness, 



developing uniform or various colours 



Each. 

 a. d. 



10 



8 

 5 

 2 2 



18 



1 10 



030 040 



123 

 FIG. 1068. 



1068 Selenite Designs are formed of pieces of Selenite different in thickness 



arranged in a variety of forms, such as cubes or stars, for showing the 

 beautiful colours produced by the varying thickness of the film of Selenite. 



each 10s. 6d. 1 10 



1069 Design in Selenite, with motto on ribbon, "Forget-me- 



not _i (fig. 1068) 018 



1070 Thistle, in Selenite, with motto on coloured ribbon, 



" Dinna Forget "3 18 



1071 Tulip in Selenite 2 . 18 



1072 Selenite Design of a Gothic Church Window . 44 



1073 Circular Plate of Selenite, ground Concave, to develop 



the colours in rings ....... 16 



1074 Rhombs of Iceland or Double Refracting Spar, to show 



the multiplication of images afforded by peculiar 



structure of the crystal . . 5s. 6d., 7s. 6d. 10 6 1 10 



1075 Plates of Quartz, Arragonite, Amethyst, Topaz, Calc-Spar, Borax, Nitre, 



Beryl, Bochelle Salts, Sugar, Bi-chromate of Potass, Sulphate of Iron, 

 cut at right angles to their axes, for exhibiting coloured rings, compound 

 figures, bars and cross-bars, screws, and crosses, &c. 10s. 6d. 110 200 



1076 Sliders, with fish fins and scales, laminae of human cuticle, sections of teeth, 



bones, hoofs, horns, and tendon, various chemical salts and vegetable 

 productions, &c., preserved in Canada Balsam, to exhibit their polarising 

 structure ; adapted for the Table Polariscope . .016 026 

 1076* Microscopic Quartz Lenses, 2 10s. to 6 10s., according to Diameter. 



GLASS, QUARTZ, AND OTHER PRISMS, AND EVERY DESCRIPTION OF APPARATUS 

 OR OBJECTS PREPARED FOR EXPERIMENT WITH POLARISED LIGHT. 







Polarising Apparatus fitted to Table or Lime Light Microscopes. 



Polarisation of Light. By ~W. Spottiswoode, L.L.D., late President of the 

 .Royal Society, &c. New Edition with numerous Illustrations. Crown 8vo. 3s. 6d. 



