53 



little heed to this standard, we believe that all of 

 the American firms follow it and if it has accom- 

 plished nothing with the foreign producers, it is at 

 any rate a mean between the standards of the 

 leading makers and with the publicity which the 

 matter has received, gives the user an opportunity 

 to use his intelligence to obtain the best results. 

 There are no optical advantages in the one or the 

 other. The short length is almost a necessity 

 however, in the Continental pattern of micro- 

 scopes as compactness is the special desideratum, 

 but while this subject will be given more extended 

 attention and optically considered farther on, it 

 might be here stated that when an objective, 

 except perhaps in the very low powers, is con- 

 structed to be used with a certain length of tube, 

 it should be used with this length only. This 

 statement cannot be made too prominent and will 

 bear repetition. 



Stage. --This being the plate or platform on 

 which the object is placed, it should be of a 

 strength to stand the weight of the finger under 

 considerable magnification. This depends upon 

 the material of which it is made and its thickness, 

 but since the material is virtually the same in all 

 instruments, we must depend upon the thickness 

 for rigidity. Absolute rigidity is practically impos- 

 sible when considerable force is exerted, as can 

 easily be determined in the best instruments and 



