38 HOW TO SEE WITH THE MICROSCOPE. 



stage is three inches in diameter and extremely thin, 

 allowing, in connection with the swinging sub-stage 

 and mirror, not only the greatest obliquity of illumina- 

 tion, but the mirror and achromatic condenser will rise 

 above the stage when required, as in the case of sun- 

 light illumination, that of opaque objects, etc. 



The diameter of the sub-stage is the same as that of 

 the " Grand American;" the accessories of that stand 

 are therefore interchangeable. 



As to the general character of Mr. Zentmayer's work, 

 the author can affirm with confidence that it is not ex- 

 celled in any particular. The stand just described is 

 beautiful in design, is nicely proportioned, and in every 

 repect reliable and durable. It will stand all of the 

 tests named in the preceding pages. Those wishing a 

 first-class stand cannot fail to be satisfied with the Cen- 

 tennial. 



The swinging sub-stage carrying the mirror, etc., is a 

 most valuable improvement, and one that the observer 

 can hardly afford to be without; the mechanism, too, 

 by which this end is accomplished is of the strongest 

 and most workman-like order. 



Attention also is invited to the method of attachment 

 of the stage. The latter is solidly held in position, or 

 can in a moment be detached, and another stage substi- 

 tuted. 



It has occurred to the writer that the " principal 

 stage" mentioned might very well be dispensed with 

 the smaller stage being quite sufficient. Possibly a large 

 and plain stage might at times be found a convenience, 



