MICROSCOPIC I:\STRIMK.\TS. 359 



is of brass, with a glass bottom, and used for containing 

 any liquid to be examined. Several test-objects, P, and 

 glass sliders are sent with the microscope. This instru- 

 ment in the vertical position is from fourteen to fifteen 

 inches high ; but the parts are made to separate in an 

 easy manner by screws, and every part neatly and 

 securely packed in a mahogany box with lock and key, 

 the blocks supporting the parts being lined Avith velvet, 

 and the box, inside and outside, well polished ; size of 

 box, ten inches long by eight wide, and three and a half 

 deep. Price $40.00. 



Ross Compound Achromatic Microscope, No. 3. This 

 is the same instrument as the preceding one, but having 

 several additions, as follows : One extra set of three 

 achromatic object-glasses of higher power; one extra 

 eye-piece of high power; and a stage with additional 

 plate, having a slow motion for extreme fine adjustment. 

 iFor the usual purposes of a compound achromatic micro- 

 scope, the magnifying power of the instrument (fig. 789) 

 is sufficient, and, unless the operator is skilled in the 

 operation of the instrument, the power is about as high as 

 can be used to advantage ; but there are those that prefer, 

 and others that require, a set of object-glasses of higher 

 power, in addition to the set usually supplied ; and to 

 give efficiency to the increased power a finer adjustment 

 than the rack and pinion motion is required ; and for this 

 purpose the stage is formed of two plates/ the upper one 

 being moveable by a fine screw arrangement, which is 

 attached to the under side of the lower plate ; by turning 

 a milled-head the two plates are separated, the upper one 

 moving sufficiently slow for a very nice adjustment ; with 

 these differences the instrument is the same as fig. 789. 



Price $55.00. 



Nachet's Achromatic Microscope. This instrument 

 (fig. 790) is constructed with a circular foot or base, 

 about four inches in diameter, loaded with lead ; upon 

 this is fitted a stout brass tube, with an oblong opening 

 in the front for the light to fall on the mirror, about three 

 inches high ; on the tube the stage-plate rests, haying a 

 circular opening in the centre, and over which the object 

 to be magnified is placed. 



