26ye 



PROJECTION MICROSCOPE 



\_CH.IXa 



glass surfaces be kept as clean as possible. The lenses of the lamp 

 condenser should be carefully wiped occasionally ; and the water bath 

 should be opened and the plane glass faces thoroughly cleaned. It 

 is desirable to soak them in the cleaning mixture for glass. There is 

 always a certain amount of deposit on the glass even though distilled 

 water is used. Every grade of opacity renders the image on the screen 

 less excellent. Cleanliness is one of the most important requirements 

 for successful micro-projection. 



Bach preparation should be wiped off before it is put in position 

 on the stage. Any particles of dust are painfully evident in the pro- 

 jected image. 



FIG. 214 A 



FIG. 214 A. The Combined Projection Lantern, Microscope and Mediascope of 

 Williams, Brown and Earle (cut loaned by Williams, Brown & Earle}. 



As shown in the figure an ordinary lantern slide objective, microscope and a 

 mediascope are mounted approximately parallel on a single cast iron frame. 



A, single arc lamp with a lamp condenser answers for all. It may be moved 

 opposite the piece of apparatus to be used and thus serve for givivg the proper illum- 

 ination. It is mechanically centered laterally for each by a click device. 



The mediascope, A. is a combination of achromatic lenses of large aperture 

 capable of projecting objects 30 mm. or more in diameter. The objective is made 

 adjustable in focus so that the screen may be filled with the image of objects which 

 vary considerably in size. 



