132 L. CASELLA'S CATALOGUE 



1578. Optical Model of Pyramid, proving that the intensity of light must be 



inversely as the square of the distance . . . 120 



1579. OPTICAL MODEL, showing long-sighted, short-sighted, and perfect vision. Nine 



rays of light, from an object entering a 3^-inch. glass eye are refracted by its 

 lens, showing the object inverted on the retina . . 400 



1580. Optometer (SMEE'S), for assisting to ascertain the power of glasses required to 



remedy defective vision, with instructions for use . . 2 10 



1582. GLASS PEISMS, plain, 2s. to . . . . 050 



1583. GLASS PEISMS, of superior flint glass, for illustrating the decomposition of light, 



on stand with ball and socket-joint, 15s. to . . . 110 



PHOTOGRAPHY. 



In the following list of photographic lenses and apparatus, including only the latest 

 improvements, for beginners, a few complete and economic sets are arranged as under, 

 to show the cost at which any one may practically enter upon the subject, completing 

 their work without any extra cost; the perfection, however, to which the photo- 

 graphic art has attained, requiring that each article should be separately enumerated, 

 the list of cameras and chemicals include only the latest improved, and such as are 

 perfect for their purpose in every way. The stands and other appliances are of the 

 same character. 



The following lenses by the most eminent English and foreign makers are perfectly 

 adapted to the various cameras enumerated, and are supplied at the same price as 

 charged by the makers. The lower priced lenses, though not so extensively known, are 

 however selected with the utmost care, and are found to give every satisfaction. 

 A specimen portrait of these last-named lenses may be had with the lens, when 

 required, without any extra charge. 



Sets of Photographic Apparatus, with chemicals, etc., etc., complete. 



1584. No. 1. For portraits on glass with double achromatic lens, in brass mounting 



with rack and pinion, expanding camera with stand, ground glass focussing 

 screen, and dark slide for three sizes of plates, gutta-percha bath and dipper, 

 plate box and glass plates; 6 oz. nitrate of silver solution, 2 oz. sensitive 

 collodion, 1 pint each developing and fixing solution, 2 oz. each black and 

 white varnish, in stoppered bottles, the whole packed in box complete 2 10 



1585. No. 2. LAEGEE SET OF APPAEATUS, as above, for plates 4 by 3f , and under, with 



lenses, camera, stand, etc., larger in proportion, and increased quantity of 

 chemicals . . ' . . . . . 550 



1586. No. 3. SUPEEIOE SET or APPAEATUS for portraits and views up to 4 by 3i, 



either on paper or glass, consisting of best double achromatic lens in brass 

 mounting, with rackwork and waterhouse diaphragms complete, superior 

 double-bodied camera in polished mahogany with tripod stand, ground glass 

 focussing screen, dark slide and plate holders for three sizes of plates, porcelain 

 bath and dipper, 3 doz. glass plates and 3 plate boxes, funnel, pressure frame, 



