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



Each. Each. 



681 Spectacle Cases, Leather, various forms and mountings 



6d. 1 050 



682 Oval and Bound Reading Glasses, in Horn cases 



(fig. 682) 2s. 6d. 5 076 



683 Ditto ditto t Tortoise -shell case (fig. 683) . . 1 10 220 



684 Ditto ditto in Pearl, with Silver mountings 



(fig. 682) 110 220 



685 Cylindrical Lenses, in oblong Horn, Yulcanite, or Metal 



Frames (fig. 685) .... 15s. 6d. ; 17s. 6d. 1 1 150 



686 Print Lenses, of various sizes, in turned Wood Frames, 



for viewing large Maps, Engravings, Photographs, &c. 



(fig. 686) ....... 21s. 1 11 220 



687 Magnifying Lenses, mounted in German Silver, with 



Wood Handles, suited for examining Photographs, 

 Engravings, &c. (fig. 687) 2s. 6d., 3s., 3s. 6d., 4s. 6d., 



5s. 6d., 7s. 6d., 8s. 6d., 10s. 6d., 12s. 6d. 15 150 



688 Ditto ditto with Ivory Handles and Gilt 



mountings 6s. 6d., 8s. 6d., 10s. 6d., 12s. 6d., 15s. 6d. 1 1 150 



689 Ditto ditto mounted in buffalo Horn or Ebonite 



(fig. 689) 3s. 6d., 4s. 6d., 5s. 6d., 6s. 6d., 7s. 6d. 10 6 12 6 



NEGRETTI & ZAMBRA'S THERMOSCOPIC SPECTACLES, 



FOR THE RELIEF OF WEAK, DIM, AND IMPERFECT VISION. 

 Enabling the wearer to read or work with comfort by Gas or Candle-light. 



690 These Spectacles are the result of a series of experiments, undertaken with the 

 view to the manufacture of a glass that should possess the power of arresting the 

 heat that proceeds from gas-light and other sources of artificial illumination. 



This desirable end having been attained by Messrs. NEGEETTI AND ZAMBEA, 

 they are enabled to supply Spectacles, the glasses of which possess this peculiarity; 

 that is to say, that the great heating power of gas and other artificial light is 

 rendered imperfectly inert as far as regards vision, and the amount of light that 

 enters the eye nearly equal to that which would do so through ordinary glasses ; 

 by this means the unsightly dark glasses are superseded, and greater comfort is 

 secured while reading or working by gas-light; at the same time the sight is 

 preserved from the pernicious effects of the heat, and the eyes are kept as cool as 

 when reading by ordinary daylight. The Thermoscopic Spectacles will be found, 

 therefore, to recommend themselves to those whose avocations require great 

 application to the desk, more especially during 'the winter months, in the banks 

 and public offices generally, where of necessity a vast amount of writing and 

 accountants' work has to be done by gas-light. 

 Price, in Best Steel Frames, with either Convex or Concave Lenses 



15 to 1 1 



