DESCRIPTION OF THE ACHROMATIC MICROSCOPE. 127 



most serviceable for this occupation, as the adjustment is 

 very readily made with them. The microscope, suitably 

 equipped, may be used for examining flowers without 

 either its stand and apparatus, or the clamp : the body, 

 with the arm above mentioned, being merely held 

 in the hand. A variation in the magnifying power is 

 obtained by sliding the body in and out, and thus avoids 

 the necessity of changing the object-glasses, which, 

 out of doors, would be attended with some risk of loosing 

 them. 



Sect. 9. Steadying Rods. — When we have recourse to 

 very high powers for making microscopic observations, 

 it is of consequence that the microscope be kept as 

 steady as possible, all motion, or tremor, being magnified 

 to the same extent as the object itself. Under such cir- 

 cumstances, it is often expedient to have one or two 

 sliding rods, whose upper extremities may be attached to 

 the eye- end of the body, and their lower to the feet or 

 pillar of the stand. When these rods are employed, all 

 their tightening screws must remain loose until the 

 instrument is set in the proper position — the moveable 

 stage, with its fine adjustment, put on, and the object- 

 glass, selected and adjusted to distinct vision by means 

 of the rack and pinion, in the usual way. When this ia 

 effected, the steadying rods may be clamped tight with 

 the pinching screws, and all subsequent adjustment to 

 distinct vision made by the fine adjustment, the rack and 

 pinion being now T considered immoveable. 



