CHAPTER X. 



THE CONDENSER AND BULL'S-EYE. THEIR USE 

 AND ABUSE. 



IN some almost classical books on the Microscope, the Con- 

 denser, Achromatic or otherwise, is passed over with little more 

 than mere mention ; its construction is described en passant, 

 but it is easy to see that the writers placed little importance on, 

 even if they understood, its use. It is by no means a long 

 time since even the best microscopists were not wholly aware 

 of the full advantage to be gained by a proper use of the con- 

 denser, and the author is informed that Mr. E. M. Nelson 

 played a prominent part among the demonstrators of the 

 scientific application of what is now admitted on all hands to 

 be a matter almost as important as the objective itself. 



The condenser, as before stated, is not intended merely to 

 throw a blaze of light upon the object, and as it is necessary 

 that the photo-micrographer should thoroughly understand the 

 use of the condenser a diagram and some remarks are here 

 given, which, it is hoped, will elucidate the matter, and still 

 further remarks and diagrams will be found in a later chapter. 

 (See p. 83) 



FIG. 25. GENERAL OUTLINE OF ELEMENTS OF A CONDENSER. 



The substage condenser is made to collect the pencils of 

 light from the radiant R, and to focus these pencils on the 



