i34 



MAGNIFICATION BY THE MICROSCOPE 



[Ch. V 



dividers get the distance between any two lines of the image. This is 

 the so-called method of double vision in which the microscope image 

 is seen with one eye and the dividers with the other, the two images 

 appearing to be fused in a single visual field. 



§ 231. Measuring the spread of the dividers. — This should be 

 done on a steel scale divided to millimeters and ^ mm. 



Fig. 79. Real Image Formed by a Projection Microscope. 

 (From the Essays of George Adams). 



A B Mirror reflecting the parallel rays of the sun upon the condenser (C D). 



a b c d e f Parallel beams of light. 



C D The condenser. 



N The stage of the projection apparatus. 



E F The object. 



G II The proj cction objective. 



L M The screen upon which the real image is shown. 



/ K The real image of the object (E F). 



As 3- mm. cannot be seen plainly by the unaided eye, place one 

 arm of the dividers at a centimeter line, and with the tripod magnifier 

 count the number of spaces on the rule included between the points 

 of the dividers. The magnifier simply makes it easy to count the space 

 on the rule included between the points of the dividers — it does not, 

 of course, increase the number of spaces or change their value. 



As the distance between the points of the dividers gives the size of 



