80 HOW TO SEE WITH THE MICKOSCOPE. 



fitted with the society screw, whereby an objective 

 may be used with it. The rack-and-piuion adjustment 

 work so smoothly that a one-fourth inch objective may 

 be focussed with exactness. The mirror beneath the 

 stage is so adjusted upon a swinging arm that it may 

 be turned up over the stage for the illumination of an 

 opaque object. A revolving diaphragm, with various 

 sized openings, is attached to the under side of the 

 stage. The outfit consists of a single lens of one-inch 

 focus for dissecting and botanical work, and an achro- 

 matic objective of one-fourth inch focus, the same as 

 furnished with the economic microscopes, and one eye- 

 piece, giving a range of powers, with the draw tube, 

 of between 200 and 300 diameters, a pair of brass pliers, 

 two dissecting needles in ebony handles and a glass 

 plate with ledge. The whole packed in a neat mahog- 

 any case with lock. Several accessories are applicable 

 to this instrument. 



THE NEW NATIONAL MICROSCOPE. 



The stand which is fifteen inches in height, is con- 

 structed entirely of brass, of the highest finish and best 

 workmanship, having a broad, heavy tripod base. From 

 the centre of this base rises a stout column, to the top 

 of which is attached, by a firm joint, the Jackson model 

 arm, carrying the compound body, by which the inclin- 

 ation can be varied to any degree, from vertical to hori- 

 zontal, the whole instrument being perfectly steady and 

 free from tremor in any position. The very highest 

 powers may be used with it, as the body, being sup- 



