156 PRACTICAL PHOTO-MICEOGEAPHY. 



projected upon a screen in front of the class, and the professor 

 can point out to all at once, without a possibility of mistake, 

 the appearances and the parts he wishes to discuss. Further, 

 when the photo-micrographic negatives are to be used for this 

 purpose, the necessary magnification is so greatly reduced in all 

 cases that the original operation is very greatly simplified, and 

 in fact the results are probably better than when a considerable 

 original amplification is necessary in order that the points may 

 be seen. And on account of this smaller magnification the 

 surroundings of the critical object are better rendered. By 

 the process we now discuss the teacher shows things as, and 

 where, they are ; by a sketch he can only show them as he 

 thinks they are or ought to be. 



FIG. 36. LANTERN MICROSCOPE. 



"When practicable it is, perhaps, better to show the object 

 by a lantern microscope, or by a special arrangement of lantern 

 and the essential parts of a microscope. Here is figured an 

 arrangement of the kind alluded to (Fig. 36). The remarks 

 of this chapter will, in the main, apply to the use of this in- 

 strument as well as to the use of an ordinary optical lantern 

 furnished with a " photographic " projection lens, and used 

 with a photographic lantern slide. 



But it is easy to realize that the use of the lantern microscope 



