258 HOW TO SEE WITH THE MICROSCOPE. 



wide apertures. It is therefore high time that some 

 one kt assume the judicial." Any endeavor on the part 

 of anyone to teach the management of wide apertured 

 object-glasses must in the nature of things be incom- 

 plete, and at the best but approximative. Notably so 

 as to written instructions, no two objectives work 

 exactly alike, and appearances in the field will be mod- 

 ified by the individual corrections of the particular 

 glass employed. Of two objectives, one may be supe- 

 rior to the other. Hence the student not being a con- 

 noisseur becomes environed with doubts that the ex- 

 pert might easily cause to vanish by a little personal 

 interference. Object-glasses, too, wcrk differently over 

 different objects. The appearance of a dry mounted 

 object is characteristically at variance with the appear- 

 ances presented by balsam mounts, and here is our 

 reason for selecting in every instance the latter for the 

 instruction of the beginner. Neither is it possible for 

 the professional philologist by mere force of word pic- 

 turing to convey to the mind of the learner just what 

 may be desired. And even should the teacher be fortu- 

 nate enough to employ the most accurate descriptions 

 language can afford, then he has no assurance of being 

 perfectly understood by the pupil. The author being 

 no philologist, and having but a little command of 

 language desirous of using none other than the simplest 

 words, thus adapting this little book to the compre- 

 hension of all, can but essay his best and only hope for 

 partial success. 



A word or two further before we proceed with our 



