232 HOW TO SEE WITH THE MICROSCOPE. 



Over the Kobert test plate the inch gave me the 9th 

 band, = 56 X lines in .001, Eng. inch. 



Working the two-thirds with the one-half inch ocular 

 and full length tube, and the inch with one-fourth inch 

 ocular and short tube, the amplifications were about 

 equal ; the inch in every instance affording the better 

 definition. 



According, then, to the inch manifest superiority in 

 point of defining power, its shorter working distance, 

 which in its most favorable aspect is 33 per cent, less 

 than that of the two-thirds, must receive due consider- 

 ation, this decrease, too, of working distance will be 

 accompanied by some loss of "penetrating power." 



A mueh mort important point, however, to the author 

 was to ascertain if the focal distance of the inch was 

 sufficient to allow its being worked over wet and uncov- 

 ered mounts without clouding from the evaporation. 

 To test this, we used the glass an entire evening in reg- 

 ular routine work over urinary deposits, and without 

 experiencing the least trouble from the source named ; 

 while on the other hand the general behavoir of the 

 objective while thus engaged in practical work was most 

 satisfactory. 



The reader is reminded that in comparing working 

 distances of long focus glasses, the same percentage of 

 weight does not obtain as would occur in comparisons 

 of object-glasses of nominally short focal lengths, and 

 giving high amplifications. 



A word or two concerning the standard " society 



