138 HO.W TO SEE WITH THE MICROSCOPE. 



In comparison with such as these, the high balsam 

 apertures have nothing to fear. As to working dis- 

 tance, a vast amount of misguided effort has been ex- 

 pended in the vain attempt of trying to compare one 

 kind of an objective with another; for instance, a wide- 

 angled air aperture with objectives of narrow air 

 angles. Hence, we have had nothing but muddle and 

 confusion. I repeat what I have before printed, that 

 any attempt of the kind is as futile in its very nature 

 as it would be to compare a " turnip with an orange." 

 It has, therefore, been my aim, however imperfectly I 

 may have succeeded, to lead my readers along one road 

 at a time, and this " objective" point has been steadily 

 held in view while writing this little book, and up to 

 the present writing, whether success has attended the 

 effort or not, I claim some credit for having essayed in 

 this direction. 



" Revenons a nos moutons." I repeat, then, that of 

 two superlative objectives having balsam angles ranging 

 from 82 to 100, the rule presented holds good, i. e., 

 that the higher aperture will have the shorter working 

 distance, or, in other parlance, the gain in aperture will 

 be accompanied by a sacrifice of working distance. 



Now, we all know what is lost with the decrease of 

 working distance. Let us, therefore, seek as to what is 

 gained by the increase of aperture. First, we gain a 

 wonderful increase in intensity of definition; an increase 

 in definition too, entirely unapproachable from any 

 other direction. In this particular these glasses stand 

 alone and defiant. Secondly, their immense power of 



