Substage. This is an absolute necessity in a 

 modern microscope, except perhaps for students' use 

 in primary work. It should have a vertical adjustment 

 and preferably with rack and pinion. If possible select 

 the complete sub stage attachment. 



Substage Condenser. If means will permit, 

 purchase this, as it is in all work most convenient and 

 in some, bacteriology, etc., absolutely necessary. The 

 Abbe condenser is the cheapest form giving good 

 results and one with numerical aperture of 1.20 is 

 sufficient in all cases unless oil immersion objectives of 

 the greatest aperture are used. 



Objectives and Eyepieces. It is hoped that 

 the information given of the various qualities in an 

 objective will aid to make a suitable selection of the 

 optical parts. Since the stands have been classified as 

 of long and short standard tube lengths, the first quality 

 to look for is, after the stand has been selected, the 

 suitability of objective and eyepiece to it and to the 

 work. A variety of powers is obtained by a suitable 

 combination of eyepieces and objectives and while 

 a considerable increase in power can be obtained by 

 short focus eyepieces this is not advantageous. 



Eyepiece. Select the Huyghenian eyepiece and 

 no higher power than 3-4 inch. In catalogues many 

 outfits are made up of one eyepiece and two objectives, 

 but this is only for economy ; it is always advisable to 



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