12 PREFACE. 



suggested to the author that a small work, giving in 

 detail the manipulations of the new objectives, with, 

 perhaps, some other items resulting from an experience 

 of over fifteen years as a microscopist, would not only 

 be acceptable, but would fill a place at present unoccu- 

 pied; and it is in response to this suggestion this little 

 book is presented, with the hope that it may prove of 

 some service to some of my brother microscopists. 



The book is entirely innocent of literary pretensions. 

 It has been my aim to express myself in the simplest 

 possible manner. The diction is at times redundant, 

 gossipy and commonplace, the dominant idea through- 

 out being to hold a good natured chat with my readers. 



During the past eight years the author has received 

 thousands of letters asking for information in the mat- 

 ter of microscope object glasses, and especially has his 

 experience been called on as to methods of manipulation 

 involved in the use of wide apertured objectives. In 

 the following pages he has endeavored to supply this in- 

 formation, introducing, it is believed, the first attempt 

 to teach the difficult art of collar adjustment, as will be 

 seen in the graduated series of lessons, which, imperfect 

 as they are, it is hoped will nevertheless be of value to 

 those commencing to use the four-system objectives. 



A.nd now, by way of apology, it remains to state that 

 circumstances entirely unlocked for, and entirely beyond 

 the author's control, have caused a delay in the publica- 

 tion, and many have suffered disappointment therefrom. 

 This delay, however, has furnished me with the oppor- 

 tunity to revise the MS., rendering it, I trust, more 



