738 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Prof. W. A. Eogers suggested a plan for overcoming this difficulty by 

 means of a cover-glass held in place by a wire ring, using a perforated 

 brass plate instead of the usual glass slip. While this may answer 

 for his expensive rulings, it clearly will not be convenient for ordinary 

 mountings ; but from his suggestions I have worked out the following 

 method. The object is fastened to the glass slip in the usual way, 

 and a cell built up around it by means of one or more tin rings. 

 When the cell is high enough so that the cover-glass laid on top will 

 not touch the object, a tin ring having a little larger hole is cemented 

 on, thus forming a ledge on which the cover-glass may rest, with room 

 above it for the wire ring, which holds it in so firmly that there is no 

 danger of its being jarred out. The tin cells are made as described at 

 the Elmira meeting last year, by punching rings from thick tinfoil, 

 and afterwards stringing the rough rings on a mandril that just fits 

 the hole, clamping them fast and turning them down until they are 

 just the right size outside. After considerable exjjeriment I have 

 adopted the following sizes in the various parts of this work, using a 

 5-8ths in. cover-glass. For the cell rings a No. 29 punch is used, 

 having a diameter of 0*543 of an inch. For the top rings the 

 punch is No. 22, with a diameter of • 505 of an inch. This cuts a 

 little larger than its inner diameter, and will just admit the 5-8ths 

 cover-glass. For the outer rim of both a No. 11 j)unch may be used, 

 0*751 of an inch in diameter, and making the rings large enough to 

 allow for turning down. The tinfoil for the upper ring should have 

 a thickness of about 0*032 of an inch. No. 21 of the Birmingham 

 wire gauge. Made with a gun-wad j^unch, the rings will have a bevel 

 on the inside, and being set with the smaller hole uppermost, the 

 bevel will help to hold the brass ring in place. The wire rings are 

 made from No. 24 spring brass wire, 0*022 of an inch in diameter. 

 These rings are easily made by winding a wire on a spindle about 

 0*4 of an inch in diameter, forming a sj)iral spring, every coil of 

 which, when cut open, makes a ring. The exact size of this spindle 

 is not important, for the. size of the spiral can be varied by putting 

 more or less strain on the wire, or by the rate at which the spindle is 

 revolved. The rings should be a trifle larger than the opening in the 

 cells, so that small pieces must be cut out to make them fit exactly 

 when sprung into place. They can then be taken out and the cover- 

 glass removed with the greatest ease. The cover-glasses should not 

 be more tlian 1-lOOth of an inch thick, and several thicknesses of 

 tinfoil may conveniently be used for the lower cells. The thinnest I 

 use is 0*005 of an inch. For objects requiring less than that I 

 simply turn a cement ring on the glass, and then put the top cell on 

 that. 



The advantages claimed for this method of mounting are many, 

 some of which I will mention. In the first place, no deposit will 

 collect on the under side of the cover-glass, or, if it does, the glass 

 can be cleaned or replaced by another. Next, there will be no running 

 in of cement, for there will be no partial vacuum, as is often the case 

 when colls arc hermetically sealed. If the object becomes dislodged, 

 as often haiipons when comparatively heavy pieces are mounted dry, 



