Aplanatic Object-glasses. 257 



have well succeeded in the construction of the microscope of 

 Sig. Amici. But all these arrangements much augment the 

 price, and an observer ever so little practised will always find 

 the object easily enough by means of his hands. 



** The prices of our achromatic microscopes are as follows: — - 



'• Achromatic microscope, like Mr. Lister's — 300 francs. 



"The same, with the latest improvements, three eye-pieces, 

 and camera lucida for drawing the magnified objects — 400 

 francs. 



" Amician Microscope, one horizontal achromatic, the stage 

 giving all the motions to the object, with a micrometer screw, 

 five eye-pieces, two camera lucidas, hand magnifier, frog 

 trough, accessary apparatus, &c. One catadioptric microscope^ 

 mounted on the same stand, and adapting itself to the same 

 apparatus ; the two instruments inclosed in a mahogany case — 

 1000 francs. 



** We trust that the very moderate prices of these instruments, 

 together with the care which we bestow on their construction, 

 will procure us orders for them. Their superiority has been 

 duly recognized by the jury of the Exhibition of the Products 

 of Industry, which has been pleased to decree to us a silver 

 medal. 



** The Amician achromatic microscope is composed of a tube 

 seven inches long, at the extremity of which is placed a prism, 

 which reflects at a right angle the rays which come from the 

 object-glass, composed {as in our microscopes executed since 

 ]824) of four double object-glasses, which may be used sepa- 

 rately, or two, three, or four at a time. The stand is a square 

 bar, which has a rackwork, carrying a moveable stage, 

 which, by means of adjusting screws ingeniously disposed, 

 permits an object to traverse the field of view in every direction. 

 This disposition gives the power of determining the real dimen- 

 sions of objects submitted to observation by means of the 

 micrometer screw, which is placed at the side, while the camera 

 lucida affords the means of drawing their outline, and conse- 

 quently of measuring the magnifying power. 



The rays proceeding from the object which have passed the 

 object-glass, and have been rendered horizontal by the prism, are 

 received, by different eye-pieces disposed after the manner of 



