SOMETHING ABOUT AMERICAN STANDS, ETC. 19 



were no such things as wide-angled objectives, and, as 

 a matter of course, the work was principally done 

 with central or centrally disposed light. To this the 

 old and heavy stage offered no objection, for it was 

 quite possible, with the aid of achromatic condensers, 

 prisms, etc., to work with all the obliquity the objective 

 would respond to, using a stage two or three inches in 

 thickness. Luckily, there were those who would at 

 times "fight objectives," play with diatoms, etc., and 

 in response to their demands the optician increased his 

 angles and working force of the object-glasses. To meet 

 this in turn called for the construction of condensers of 

 greater angle; until finally it occurred that the aper- 

 ture of the objective had arrived at proportions to 

 which the condensers did not satisfactorily respond. 

 Something had to be done, and something was done, 

 for necessity is the " mother of invention." 



The simplest way is the best, and this was to reduce 

 the thickness of the stage. The "fighter" of objec 

 tives had discovered the fact that a stage, one-fifth of an 

 inch in thickness, was solid enough for any and all of 

 the delicate work required by the microscopist, while at 

 the same time he derived a great advantage in thus pro- 

 viding play for the aperture of his objectives. 



The writer remembers with pride that he " took a 

 hand" at this; he remembers, too, the unalloyed satis- 

 faction he experienced in seeing two heavy, lumbering, 

 and expensive stages, alone costing several hundred dol- 

 lars, removed from imported stands, and their place 

 substituted by plain, thin plates made by the local 



