Collection and Mounting of Objects. 27 



ooze out in all directions ; then more warming is done, 

 and sometimes with success ; the thin glass is gently 

 pressed down over the object all which is detailed 

 in the works to which I have already referred. 



I have always used, instead of a lamp or hot-water 

 tin, a night-light for warming the slide ; and I have 

 found it necessary to pass the latter from end to end 

 over the flame, as unequal heating would make it 

 crack across. I sometimes found the air-bubbles 

 dispelled by a drop of spirit of turpentine, but its 

 introduction was generally accompanied by a great 

 spreading of the balsam, and considerable stickiness 

 about the whole affair; however, benzine, ether, or 

 spirit of turpentine itself can be used to clean the 

 slides that have suffered. The slides, when finished, 

 so far as the placing of the thin glass over the objects, 

 must be left to cool gradually, and then allowed to 

 harden for some days, if in a warm place so much the 

 better ; and after that the superfluous balsam can be 

 scraped away, and the slide cleaned with a rag soaked 

 in benzine or turpentine. I generally cover the 

 objects so prepared with green papers, similar to 

 those for the dry objects; sometimes, however, I 

 leave them plain, with a view to employing the tf Lie- 

 berkuhns" already described, which require light to 

 be transmitted around the object. For the same 

 reason I sometimes leave the paper which fastens on 

 the thin glass in "dry" mounting merely large enough 

 to answer the purpose, or make the aperture very 

 large, employing as broad a piece of thin glass as I 

 can find to cover the object. It is usual to write the. 



