208 HOW TO SEE WITH THE MICROSCOPE. 



chase a one-inch like those furnished by Mr. Gundlach 

 or the Messrs. Beck ; and for a high power select the 

 professional one-fourth of the Messrs. Spencer & Sons, 

 or its equivalent by any other maker. With these twa 

 glasses the physician can accomplish seven-tenths of any 

 and all work he may be professionally called on for. 

 Either one-inch named is a good reliable glass, giving, 

 when working with suitable oculars, very good shows- 

 indeed, and infinitely better than the imported French 

 triplet, while the cost is but very slightly enhanced. 

 We recommend a one-fourth similar to the Spencer pro- 

 fessional, because, having used one ourselves, we can 

 speak " by the card." One very strong reason is, that 

 the adjusting collar mechanism (although moving the 

 front lens) is very smooth and satisfactory in its work- 

 ing. A still more important reason is that these glasses 

 respond nicely to any movement of the collar, and they 

 are, too, well corrected throughout the range of their 

 aperture. The purchaser is thus thrown early in con- 

 tact with an adjusting objective, and hence by his daily 

 practice will he become more and more skilled in it& 

 use. 



The author desires the reader to make a special point 

 of this : Many there be who, having bought adjustable 

 objectives of poor quality, and having discovered "prac- 

 tically " that the position of the collar adjustment with 

 such glasses hardly affects in any way their efficiency of 

 performance, not only let them alone for the future, but 

 settle down strong in the faith that collar adjustment 

 don't amount to much, and that the " handling" of aD 



