always be toward the eye. In the case of two 

 plane convex lenses, they should be used with 

 their convex surfaces toward one another. 



In magnifiers containing several lenses, when 

 these are used together, the one of highest power 

 should be nearest the object. When reversed the 

 angular field is greater, but presents considerable 

 spherical and chromatic aberration, which it is 

 advantageous to limit. 



In simple dissecting microscopes like the 

 Barnes, in which the mirror is in a fixed position, 

 the microscope should be set squarely before the 

 source of light. Diffused light, such as daylight, 

 is always preferable to any artificial illumination. 



It should always be sought to modify the light 

 as much as possible and still have enough to see 

 easily as the eyes are much less fatigued. 



While in some classes of work it is perhaps un- 

 necessary to have the very best magnifiers, such 

 as the Aplantic or Hastings Triplets, the latter 

 can always be 'recommended when the means will 

 permit on account of the higher results and 

 greater degree of satisfaction and comfort derived 

 from them. 



Magnifying Power. - - Unless a microscope, 

 whether simple or compound, is known to come 

 from the hands of a reliable firm, any claim as to 

 magnifying power should be accepted with re- 

 serve. In former years, when the country was 



