degree of satisfaction and comfort derived from them. 



Caution. Unless a microscope, whether simple 

 or compound, is known to come from the hands of a 

 reliable maker, any claim as to magnifying power 

 should be accepted with reserve. In former years, 

 when the country was overrun with cheap foreign pro- 

 ductions, the most fanciful claims were made in this 

 direction. Avoid strolling or street venders who, as a 

 rule, not only make the most ridiculous claims as to 

 magnifying power, but charge much higher prices than 

 the same articles can be bought for from reliable 

 opticians and generally offer worthless articles or, at 

 best, of doubtful value. 



Some precaution should also be used in reference 

 to quality in purchasing a magnifier. As competition 

 causes a downward tendency in prices, it unfortunately 

 often involves a deterioration in quality. The ordinary 

 forms are mounted in vulcanite; black horn is 'often 

 palmed off as such, but is a poor substitute as it warps 

 and cracks. The surfaces of lenses, instead of being 

 perfectly polished, are often scratched and unfinished, 

 showing small pitholes or undulating surfaces. This 

 is common among cheap Coddington lenses and 

 naturally destroys the distinctness of the image. 



Magnifying Power. It is evident that a lens 

 magnifies an object equally in all directions ; this is 

 said to be in areas, and is the square of the linear, or 

 diameter, so that if an object is magnified four times 



24 



