1844 



Journal of Applied Microscopy 



The density of a lantern slide should depend somewhat on the kind of light to 

 be used in the projection. If this is to be acetylene or oil, the slide should be 

 less dense than if the lime light or the electric arc light is to be used. Practice 

 only can give accurate information in this respect, however. The beginner 

 should practice with a negative from which a fine print has been made ; he 

 should have samples of the best work others have done with which to compare 

 his own. Such samples can be had of any dealer in lantern slides. The land- 

 scape slides made by Wilson of Aberdeen, and for sale by T. H. McAllister & 

 Co., 49 Nassau street. New York, are good. D. W. Dennis. 



Earlham College. 



The Technique of Biological Projection and Anesthesia 



of Animals. 



Copyrighted. 



IV. SOLAR PROJECTION APPARATUS AND ITS ADJUSTMENTS.— Continued. 



Having set the porte-lumiere in its place in the window, darkened the room 

 and arranged the screen, the microscope is adjusted as follows : Turn the handle 



Fig. :]. — Hydra fusca. Example of low power projection, using 1-inch 

 objective with porta lumiere. Distance to screen, 30 feet. 



(h) until the long axis of the mirror (m) points toward the sun. Rotate the mir- 

 ror screw (s) until the beam of sunlight is thrown into the condenser (c) and is 



