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SUMMARY OF CURRENT RESEARCHES RELATING TO 



MICJEOSCOPY. 

 a. Instruments, Accessories, &c. 



Ahrens's Erecting Microscope. — In this instrument (fig. 28), by 

 Mr. C, D. Ahrens, the erecting prism is inserted below the body-tube, 

 and the latter is inclined at an angle of about 45°. 



The prism is similar to Nachet's erecting prism. 



"When the Microscope has a fine adjustment, the prism is mounted 

 on a piece of tube, as shown in the woodcut ; but when the fine 



Fig. 28. 



adjustment is omitted, as in the smaller forms, the prism is fixed 

 directly on the arm. 



For convenience of packing, the inclined body-tube slides ofi', and 

 a cap is fitted over the top of the prism-box. 



The advantages claimed by Mr. Ahrens for the instrument are 



