50 American Quarterly Microscopical Journal. 



if this congress means to do a good work, it will do well 

 to adopt the millimeter as its standard for subdivisions. 



The time is ripe for it, and we must either assert ourselves 

 as ready to meet the demands of the time in which we live, or 

 be relegated to the age of conservatives. 



It is wonderful how science is progressing, and still more 

 wonderful it is when we think how few are doing the work. 



In all this large assembly, how few are really scientific 

 workers! And, yet, our science is advancing, and we, who, 

 from our numbers, hold the balance of power, can do nothing 

 better, it seems to me, than to meet or anticipate the wants of 

 the few, who add the treasures to our storehouse of knowledge. 



ANGULAR APERTURE DEFINED.* 



BY ROMYN HITCHCOCK. 



Even among those engaged in scientific pursuits we fre- 

 quently observe that there is a greater desire to come out best in 

 an argument than to arrive at the truth. This has well been 

 illustrated by the long-fought battle about angular aperture. 



In order to avoid any quibbling in the future about the 

 meaning of the term, I propose to this congress that it adopt a 

 definition, which, right or wrong, — if the right or wrong can, 

 ever be determined, — shall be adopted and used throughout 

 the country. I am fully aware that such action should be 

 taken after mature deliberation, and, in advocating any such 

 course, it is my duty to ask your careful attention to a number 

 of points, as follows: 



First. — What does angular aperture indicate ? Our definition 

 should be chosen to express some particular quality or qualities 

 of an objective, or else it must be merely an arbitrary one, 

 adopted to give a definite meaning to the term. The distinc- 

 tion between angular aperture and angle of field, made in my 

 paper before the New York Microscopical Society, and recently 

 published in the American Journal oj Microscopy, June, 1878, 

 governs my present use of the terms. 



♦Abstract of a paper read before the National Microscopical Congress, August isth, 1878. 



[The Editor deems it but right to say, that he is only led to devote so raHch space to this ab- 

 stract because of a deliberate effort, that has already been made, to misrepresent his motives in 

 presenting the resolutions which followed the reading of the paper. The subject cannot be of great 

 interest to scientific men generally, hence this apology.] 



