CH. VI] AVOIDANCE OF INVERSION; ERECT IMAGES 



173 



will be exactly like the object. It is believed that the following 

 directions will enable the worker to so arrange his specimen and the 

 apparatus that erect images may be produced without undue effort. 

 The simplest of all ways to get the image without inversion is to 

 arrange the slide on a piece of white paper so that the object is erect 

 and then to write with a very fine pen the letters a, k, on the cover- 

 glass of the specimen to be drawn (fig. 105). Now with the low 



FIG. 105. SLIDE OF SERIAL SECTIONS, SHOWING THE DEVELOPMENT OF THE 

 EYE WITH THE LETTERS a k, TO Am IN GETTING ERECT IMAGES LN DRAWING 

 WITH PROJECTION APPARATUS. 



(From Optic Projection). 



This slide is also to show how to mask preparations which are to be used in class 

 demonstration (Fig. 121). 



power (16 to 60 mm.) objective project the image of the specimen 

 and letters upon the drawing paper. One can then continue to 

 rearrange the slide until the letters are erect; the specimen will then 

 also be erect. 



278. Images to be traced in the photographic camera. These 

 images are wrong side up and the rights and lefts are reversed. This 

 can be corrected by drawing the picture on the tracing paper in the 

 inverted position and then inverting the tracing after it is finished; 

 or the specimen can be put in the inverted position, then the image 

 will be erect. 



Demonstrate this by putting the metric card in position and tracing 

 some of the larger lettlrs or figures on the tracing paper. Then 



