664 



L.4BORATORY EXERCISES 



Table C 



Of the Achromatic Objectives with the Huyghenian Eyepieces at 250 mm. distance 



from the Drawing Board 



If the distance between eyepiece and drawing board = 250 mm. be altered, the 

 magnification of each combination will increase or decrease in proportion. The 

 distance should be read off the scale on the pillar by the aid of the special set square 

 supplied. 



Beside the Edinger apparatus there are a good many styles of photomicro- 

 graphic cameras, but the most recent t}"pe is an instrument known as the new 

 Spencer photomicrographic camera, which may be attached to the microscope with- 

 out disturbing the adjustments. It may be used on its tripod in any position from 

 horizontal to vertical which makes it available for carrying in any ordinary pho- 

 tography. This camera may be used with any microscope, or it may be removed 

 from its support and used for hand-camera purposes. 



LESSON 45 



TO THE INSTRUCTOR 



In connection with the use of the Edinger apparatus the following suggestions 

 as to drawing may be apropos. 



The erperience of most science teachers has revealed the fact that as a rule 

 beginners in attempting to give an accurate account of their own observations in 

 writing or drawing are in a large measure helpless for want of a definite aim or an 

 understanding of what is required of them and how to do it. 



While it is recognized that science teachers naturally differ in the method of 

 carrying out the detaUs of their work, yet it is believed that it will be helpful to the 

 pupil— an economy of his time and effort— if the features which characterize 

 scientific description and drawing in general, be clearly pointed out and impressed 

 at the beginning. It is believed that the following suggestions to pupils can be 

 indorsed by most teachers of Biology and that these suggestions will aid the ine.^- 

 perienced science pupil. 



