OPTICAL INSTRUMENTS. 373 



in one, and produce the effect of solidity. Tlie diagrams 

 are usually on cardboard, and about three inches wide, by 

 six or seven inches long ; twelve to twenty -five accom- 

 pany each instrument. The best effect is produced by 

 viewing- daguerreotypes; these are either on metal or 

 glass. For using those on glass, the bottom of the box is 

 cut out and sometimes supplied with a ground glass, the 

 pictures being viewed by the light through the glass with 

 the door shut. 



Price, according to quality, $3.50, $5.00, $6.00, and 

 $7.00. 



A plain article in tin frame, with 12 diagrams, $2.00, 

 $2.50, and $3.00. 



Daguerreotype views on metal, each $2.00. 

 glass, each $2.00. 



Claude Lorraine Mirror. " I don't know whether it 

 was the invention of the famous Italian artist, who was in 

 landscape paintings what Landseer is in the representa- 

 tion of animals ; or whether the mirror was so called be- 

 cause, like Claude Lorraine, it is said to improve upon 

 nature ; but, at all events, it is a great curiosity. Its con- 

 struction is the same with the ordinary looking-glass, 

 except that jet is used in place of quicksilver, and it is 

 intended to reflect only the inanimate world. The 

 Claude Lorraine mirror derives its value from the princi- 

 ple that all objects are more beautiful in miniature, which 

 renders their defects less apparent ; for the unsightly 

 strikes the eye with immediate pain, while that which is 

 perfect grows upon us more gradually. With this mirror, 

 you frame for yourself, as it were, little landscapes at 

 every turn, in which the sky is softer, the grass richer, 

 and the foliage more graceful, than anything you can see 

 without it." 



These mirrors are mounted in neat embossed morocco 

 cases. 4 by 5| inches, price $2.50. 



5 by 6 inches, price $4.50. 



6 by 7 inches, price $6.00. 



The Dioptric Lantern. (Fig. 794.) The Improved 

 Prismatic Dioptric Dissolving Apparatus, invented by 

 the Rev.St. Vincent Beechey, possesses, within less com- 

 pass than a single lantern of the ordinary description, all 



32 



