THE MICROSCOPE. 



may be mentioned Messrs. Goring, Lister, Coddington, Q,uecket, 

 Mandl, Dujardiu, Le Baillif, Seguier, De la Rue, and numerous 

 others. 



The eminent makers of the British and Continental capitals are 

 well known. Good instruments of the low-priced sort are made 

 by nearly all the opticians ; but those who have more especially 

 devoted their labours to the microscope, are Messrs. Ross, Smith 

 and Beck, Powell and Lealand, Pritehard, Varley, and Pillisdier, 

 in London; Messrs. Nachet, Charles Chevalier and George 

 Oberhauser, of Paris ; MM. Ploessel and Schieck, of Vienna ; and 

 M. Pistor, of Berlin. 



Without the intention of assigning any relative precedence to 

 these artists, we shall now present a brief description of some of 

 the instruments, according as they are severally mounted by 

 them. 



CHEVALIER'S UNIVERSAL MICROSCOPE. 



77. The mounting of this instrument has always appeared to 

 me to offer as many conveniences and advantages to the observer 

 as can be combined in such an apparatus. 



A mahogany case A, fig. 37, p. 1, containing a drawer B, in which 

 the instrument and its appendages are packed when out of use, 

 serves as its support. A strong brass pillar, c c, is firmly screwed 

 into the top of the case, and upon this pillar the entire instrument 

 is supported. 



The pillar c c sometimes is made in two lengths, which are 

 screwed one upon the other, by which means the height of the 

 instrument may be varied at pleasure, either one or both lengths 

 being used. 



An arm E c is attached by a joint at E to the summit of the 

 pillar c c, so that it can be moved on the joint E with a hinge 

 motion, and may thus be placed at any angle with the pillar c c. 

 In the figure it is represented at right angles with c c. 



To the middle B of the arm E c, a square brass bar D F G is 

 attached at right angles to E c, so that when E c is at right angles 

 to c c, the bar D F G is parallel to c c. In the face of the bar 

 D F G, which is presented to c c, a rack is cut. 



Two square pieces r and M are fitted to the bar D F G, and are 

 moved at pleasure upwards and downwards upon it by means of 

 pinions, having milled heads o and N. 



To the square piece r is attached the stage z, upon which the 

 object is placed, and maintained in its position by two springs, 

 one of which is shown in the figure. This stage is provided with 

 several adjustments, which have been already explained (31 

 et seq.}. It will be sufficient for the present to observe that it 

 is capable of being moved upwards and downwards with the 

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