ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



83 



Bausch and Lomb's Duplex Substage.* — To meet the need for a 

 substage attachment which s-hall lie simpler than the complete Abbe 

 substage, and yet embrace its principal advantages, Mr. E. Bausch has 

 constructed a modification designated as above. As shown in fig. 4, two 

 arms are movable up and down upon a metal post rigidly fixed to the 

 stage. The upper arm carries an iris diaphragm which may be used in 

 the plane of the stage or below it ; the lower heavier arm carries the 

 Abbe condenser with an iris diaphragm attached below. In addition to 



Fig. 1. 



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the firmness afforded by the rigidly fixed supporting post, a metal guide 

 passes through the arm of each ring, the result of which is to render 

 i he substage accessories, when in position, absolutely free from any 

 appreciable lateral movements, and to keep them throughout all vertical 

 movements in the optical axis of the Microscope. 



The upper arm has a vertical movement sufficient to obtain the best 

 optical results from the iris diaphragm when this is used alone. The 

 lower arm, however, has a vertical movement the upper limit of which 

 brings the condenser into immersion contact with the object-slide ; from 



* Journ. App. Micr., July 1900, pp. 933-4 (1 fig.). 



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