52 THE MICROSCOPE. [April, 



The instrument is of brass, with the exception of the base, 

 which is of cast-iron, neatly japanned. The base is of one piece 

 and very rigid, to which the bell-metal bar is attached by a joint, 

 allowing - the use of the instrument at any angle of inclination, 

 perpendicular and horizontal positions being indicated by stops. 



The coarse adjustment for focus is accomplished by rack and 

 pinion. 



The fine adjustment is of the same style as that of the American 

 Centennial stand. A concealed lever is acted upon by a microm- 

 eter screw, and moves the entire body, which is fitted to the 

 grooved bar, giving steadv and delicate movement. 



The plane and concave mirrors are hung in a plane with the 

 object, and may be swung over the stage for illuminating opaque 

 objects (instead of the bull's-eye condenser), having the object as 

 the centre. 



The stage is broad and firm, is only three (3) inches from the 

 table, and is provided with delicate spring-clips, which may be 

 removed if desired. 



The diaphragm is circular in form, with a series of different 

 size apertures. 



38. American Student stand, with 1 eyepiece (A or 

 B), 1 -inch objective, 19 ; 1-5 objective, 75 ; wal- 

 nut case, with lock and handle, .... $46.00 



39. American Student stand, with 1 eyepiece, and 

 walnut case, with lock and handle, . . . 30.00 



Zentmayer's American Student Stand. 



This stand is the same as No. 38, except that the coarse ad- 

 justment is accomplished by sliding the body-tube in a cloth - 

 lined outside tube, which gives an exceedingly smooth and deli- 

 cate movement. 



38B. American Student stand with one eyepiece (A 

 or B) ; S-10 in. objective of 19 ; 1-5 in. ob- 

 jective of 75 ; walnut case, with lock and 

 handle, ..... . . $38.00 



39B. American Student stand, with one eyepiece, 



walnut case, with lock and handle, . . 22.00 



extra eyepiece for Student stand, . . 5-°° 



Carmine. — A useful preparation is Grenadier's alcoholic 

 borax carmine, made by dissolving borax, 4 grams, in distilled 

 water, 100 c. c, adding carmine, 3 grams, and heating gently; 

 100 c. c. of 70 per cent, alcohol is then added, and the solution 

 filtered, if necessary, before use. The sections, after staining, are 

 tansferred to alcohol (70 per cent.) containing half to one per 

 cent, of hydrochloric acid (sp. gr. 1.16). 



