552 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



tion of aerial or gaseous material, with the higher power of objectives, 

 without subjecting it to any previous manipulations, thus enabling 

 one to collect and immediately examine with any objective, " even a 

 -^ or perhaps a ^ inch." The apparatus consists of a rubber 

 bag (Fig. 97) with a tapering, hard rubber nozzle, into which is 

 inserted a perfectly tight fitting stopcock. A piece of soft rubber 

 tubing \ inch in diameter and about 2 feet long is furnished at one 

 end with a metal collar, to be inserted into the outer end of the brass 

 canule of the slide ; while the other is to be slipped over the nozzle 

 of the bag. The larger extremity of a small canule about li inch 

 long, is fixed by a binding screw into the upright B on the glass 

 slide, while its small end is inserted into the minute hole at the side 

 of the cell. The larger extremity is smoothly ground, to receive the 

 metal-finished end of the conducting tube. The slide has an ordinary 

 cell A (of rubber). 



The cell has its middle portion built up from the bottom by a 

 piece of glass, so as to bring it within the working distance of the 

 objective, allowing depth enough at the sides, which may be com- 

 pared to two. ditches, for the introduction of a canule of reasonable 



Fig. 97. 



calibre. This, the author says, is an important point, inasmuch as a 

 cell shallow enough for the adjustment of its bottom to the focus of 

 a first-class -|-inch objective, could have a depth of only about a 

 fortieth of an inch, and of course for higher powers less, altogether 

 too shallow to allow of the introduction of a canule of practicable 

 size. But, upon this plan, the cell may be built up ever so much, 

 even for adjustment of a ^-inch objective, while yet at its sides 

 will remain the same depth of ditches, or sulci, for the ingress of the 

 gas. 



The cover-glass may be cemented on, or laid on loosely. In the 

 former case the opposite side of the cell must be perforated to allow 



