ENTOMOLOGICAL CONTRIBUTIONS. 187 



years, I have invariably been subjected to the serious annoyance of 

 being compelled to remove the entire contents of the case, clean the 

 glass and replace the corks with new cement. From some cause, 

 inexplicable to me, a gradual separation takes place of the cork with 

 its cement from the glass, first appearing at the angles of the cork, 

 and its progress indicated by an increasing number of iridescent 

 rings which form within until the center is reached, when, if not 

 previously detached, the insect falls with the cork, usually to its 

 injury and that of others beneath it. 



A number of years ago I happened to employ, in attaching a single 

 piece of cork in one of my cases, a cement originally made for other 

 purposes, consisting of six parts of resin, one of wax and one of Vene- 

 tian red. Several years thereafter, my attention was drawn to this 

 piece, by finding it as firmly united as when at first applied, and at 

 the present time (after the lapse of twelve years) it is without the 

 slightest indication of separation. Acting upon this hint, I have of 

 late used this cement in the restoration of a number of my cases, and 

 with the most satisfactory results. It is important that the cement, 

 when used, should be kept heated (by a spirit lamp or gas flame) to 

 as high a degree as it will bear without burning. An amount 

 sufficient to cover the bottom of the flat metal vessel containing it 

 to the depth of an eighth of an inch will suffice, and prevent the cork 

 from taking up more than its requisite quantity. It should occasion- 

 ally be stirred to prevent the precipitation of its heavier portions. 

 The cork may be conveniently dipped by the aid of a needle inserted 

 in a handle, when, as quickly as possible, it should be transferred to 

 the glass, for the degree of adhesion seems to depend upon the degree 

 of fluidity of the cement. From some experiments made by me, 

 after the corks had been attached as above, in heating the entire 

 glass to such a degree as thoroughly to melt the cement until it 

 spreads outward from beneath the weight of the cork, and then per- 

 mitted to cool the glass meanwhile held horizontally that the corks 

 might not be displaced the results appear to indicate that the above 

 cement, applied in this manner on glass properly cleaned, will prove 

 & permanent one ; it is scarcely necessary to state that this method is 

 not available where the glass has been bound as above. 



Preparatory to corking the glass for the specimens assigned to it, 

 the spaces required for them are to be ascertained by arranging them 

 in order on a cork surface or soft-wood board. On a sheet of paper 

 of the size of the glass, perpendicular lines, of the number of the rows 



