SUPEELATIVE WIDE-ANGLED OBJECTIVE. 141 



view of perfecting himself in the manipulations of the 

 same, that he may in turn render his observations and 

 experience of value to those who devote their spare 

 time to investigations with the instrument? If these 

 are the ends in view to be accomplished, then I say, 

 " fight objectives," and furthermore that " E " need rot 

 be ashamed of his occupation. On the other hand, if 

 objectives are fought for other and baser purposes, that 

 is no afiair of mine. I cannot help it, and the objective 

 is not to blame. 



I claim, then, that the high balsam angles are indis- 

 pensable in the studies of the advanced investigator ; 

 they alone, " bother or no bother," are the ones for the 

 work. Let the reader keep constantly in mind that, in 

 the study of difficult and delicate structures, the slight- 

 est superiority of definition is of vital importance. A 

 first-class objective of high balsam angle will show, 

 clearly and accurately, details in an object, which, from 

 their extreme tenuity or transparency, would be totally 

 invisible when viewed under an objective having but air 

 angle. 



To sum up: We thus arrive at the conclusion that 

 objectives of high balsam angles, have, as compared 

 with others of less balsam angle, a shorter working dis- 

 tance, and in general are " inconvenient and bother- 

 some to use; nevertheless, that their use cannot be dis- 

 pensed with in the study of delicate and difficult struc- 

 tures, and it may be further stated that these are the 

 glasses suitable for the study of difficult diatoms, the 

 display of the Nobert nineteenth band, and the like. 



