Prize Medal, 1851. Two Prize Medals, 1862, 



FOR MANY IMPORTANT 



INVENTIONS, ACCURACY, 



AMD EXCELLENCE. 



FIG. 810.- 

 NEGRETTI AND ZAMBRA'S ALUMINIUM BINOCULARS. 



807 The only novelties in Opera and Field Glasses exhibited at the International 

 Exhibition of 1862 were two by Messrs. Negretti and Zambra ; viz., the use of 

 Rock Crystal for lenses, and Aluminium for the mountings ; the extreme hardness 

 and brilliancy of the one, and the wonderful lightness of the other, render them 

 eminently useful in the construction of Field Glasses, &c. 



The principal use of Rock Crystal is for instruments required for service in 

 Tropical climates, where the great heat, combined with moisture, cause the ordinary 

 glass lenses to become dull and stained. The Rock Crystal retains its polish, gives 

 a very brilliant image, and is not so liable to become scratched as Glass. 



808 Rock Crystal 12-lens Combination Binocular Field Glasses, with 



Solid Leather Sling Cases and strap .... 10 10 



The difference of weight between Aluminium and the usual metal mountings 

 of Field Glasses, &c., is so great as always to excite astonishment, certainly one- 

 third less ; so that a very large instrument can be used with the greatest ease and 

 comfort. This extraordinary lightness is very valuable in hot climates, where the 

 slightest exertion becomes distressing, and a useful instrument is often thrown 

 aside on account of its weight. Negretti and Zambra are now manufacturing 

 Aluminium Opera and Field Glasses in a variety of sizes and forms, fitted with the 

 very finest lenses, weighing about one-third less than the ordinary instruments. 



809 Aluminium Opera Glasses. See Series YIII. and IX. 



810 Ditto Field Glass, as fig. 810 .. . . 10 10 12 12 



