SOMETHING FURTHER ABOUT OBJECTIVES. 115 



tainly to be ameliorated if possible. It happens, too, 

 that the so-called "high powers," such as one-twenty- 

 fifths, one-fiftieths, and one seventy-fifths, cost in them- 

 selves more than the majority of observers could afford 

 to pay for an entire outfit, and thus have been accessi- 

 ble to only a favored few. The price of the fiftieth, as 

 furnished by eminent makers may be quoted at from 

 $250 to $300. I dare say that more than one of my 

 readers, earnest workers with the microscope have 

 yearned time and time again, as they have read of some 

 wonderful things accomplished with a twenty-filth or 

 one-fiftieth, for the means to enable them to pursue 

 similar investigations. Let all such hail with joy the 

 announcement that these costly glasses are no longer a 

 necessity, and that their work can be not only done, 

 but better and with greater ease accomplished, with 

 what are known as medium-power glasses of wide 

 apertures; that there is no longer, too, any necessity 

 of going abroad, or paying duties thereby; that a one- 

 sixth, or, at the furthest, a one-tenth, costing from $60 

 to $85, will (if properly selected) compete in perform- 

 ance with any one-fiftieth extant a fact, reader, worth 

 knowing. 



Another dogma in the popular mind has very general 

 acceptance to wit : that angular aperture can only be 

 obtained at the sacrifice of working 1 distance. The old 



O 



saying is, that " it's a poor rule that won't work both 

 ways;" hence it should obtain conversely, that with the 

 sacrifice of working distance, angular aperture ought to 

 be obtained ; but this is not always the case. For in- 



