214 



THE AMEHICAN MONTHLY 



[Dec 



The attachment of the bed plate with the head post is 

 by two dressed circuhir surfaces and a bolt. Upon the 

 head post is mounted a screw which turns in threads cut 

 upon the edge of the circular plate attached to the bed 

 plate. By loosening the bolt and turning the crank upon 

 the end of the screw the bed plate may be made to ro- 

 tate upon its vertical axis. 



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The carriages are twelve inches long, grooved to fit 

 upon the steel rods, and are provided with pinions, cranks 

 and binding screws to make accurate adjustment. The 

 stand is provided with castors so adjusted that it may be 

 thrown on or off its legs with the foot. All the handles 

 are nickel-plated and the whole apparatus enameled black. 



The requisites of a good photo-micrographic apparatus 

 are rigidity, ease and accuracy of adjustment and adapt- 



