10 PREFACE. 



one-tenth. This glass also occupied my leisure time for 

 a considerable interval. 



The performance of the one-tenth fully sustained the 

 high appreciation I had formed of the performance of 

 the duplex glasses. In some respects the work of the 

 one-tenth excelled that of the one-sixth. 



The article published in the Cincinnati Medical News 

 was therefore supplemented by several other communi- 

 cations written by me, giving my further experience 

 with the duplex objectives. 



Among the conclusions I had arrived at from the study 

 of the new four-system glasses were to be found em- 

 bodied ideas radically opposed to popular dogmas which 

 were at that date fully received and accepted by inicro- 

 scopists generally as settled matters of fact. For in- 

 stance, it was claimed for the duplex one-sixth and one- 

 tenth that either of these objectives would not only do 

 the work of, but excel the performance (under amplifi- 

 cations from 275 to 4,000 diameters) of any one-fiftieth 

 extant. Furthermore, it was claimed that the central 

 light work of the new wide apertured duplex objectives 

 would surpass that of the low angles. 



Referring to the resolution of the severest test objects, 

 it was the express purpose of the said contributions to 

 the Cincinnati Medical News to claim and insist on, as 

 a stubborn fact, that the work of the duplex one-sixth 

 or one-tenth excelled that of any glass extant, " be it a 

 one-fifth or a oue-fiftreth." 



These, as well as other statements so thoroughly hete- 

 rodox to established belief, met, as a matter of course, 



