138 HOW TO SEE WITH THE MICROSCOPE. 



Iii 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. 



" He venous 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. 9 

 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 



