SOMETHING FURTHER ABOUT OBJECTIVES. 117 



and further, that no two of the five glasses will have 

 the same angular aperture. 



It's well enough to pause here and allow the approach 

 of a deluge of threadbare argument. Says one, "All 

 this proves nothing. It's quite possible that the glass 

 with the narrowest aperture may be the better corrected. 

 Let your own rule be here applied, and the quality of 

 the apertures tested; nothing short of a competitive 

 examination can be determinate." 



To this the writer says amen; but the reader is again 

 reminded that this is nothing more or less than u fiiit- 



O O 



ing objectives." This is the course, too, which the 

 author has pursued in the way of making competitive 

 examinations of objectives in his own interests, and in 

 behalf of those of his pupils, his friends, and his corre- 

 spondents. The result being, in nineteen cases out of 

 twenty, that the glass with the wider aperture proved in 

 every other respect the better glass a result, too, not 

 improbable in its nature, when it is borne in mind that 

 those of our opticians who have given great attention to 

 the development of aperture are no ways behind-hand 

 in their general professional attainments. 



Again, (to steer clear of cavil or controversy,) suppose 

 that of the five glasses before named, all having the 

 same working distance and amplification, the one with 

 the lower aperture being made by Mr. X., and the other 

 of wider angle being by Mr. Y., both objectives being, 

 too, equally well corrected. That such a condition of 

 things is possible no one will attempt to deny. Here 

 is :i condition to which the popular dogma can be 



