185 



It is sometimes found that dealers offer the same 

 objectives of different quality at different prices. 

 Too great care cannot be observed in such cases, 

 as the very fact of the admission of a difference in 

 quality indicates that they are made by an unre- 

 liable maker. This mode of offering objectives 

 was in vogue many years ago when the principles 

 of optics and facilities for making were limited and 

 when a higher price was asked for those which 

 might be termed a happy combination. There is 

 no excuse however, at the present day, for any- 

 thing of this kind, because every conscientious 

 optician has his standard for every objective. 



In purchasing a microscope a beginner may be 

 easily misled by the enticing appearance of an 

 object, which may be due not so much to the in,- 

 strument as to the object itself and if the optical 

 parts are inferior, it will require but a short ex- 

 perience to become convinced of it usually as 

 soon as a comparison can be made with reliable 

 work. The investment in one of these objectives 

 is not only a source of disappointment, but usually 

 proves to be a pecuniary loss, as it is generally 

 followed by a fresh outlay in responsible work. 



It is of ordinary occurrence that such objectives 

 as have been spoken of are sent to the writer's 

 firm with the request to examine them and rectify 

 the faults ; but an examination almost invariably 

 proves that the cost of doing so is sonsiderably 



