10 



SOME HINTS ON THE PREPARATION AND 



fording the most satisfactory results in all sorts of mounts, but that 

 from which the spirits of turpentine has been expelled by heat, and 

 replaced by chloroform or pure benzole, answers a most excellent 

 purpose, whilst the many damar mediums are also good. But 

 following the plan upon which this article was begun, of giving 

 only those processes, which I habitually practice, and know to be 

 satisfactory, I shall confine myself to pure balsam alone. 

 The great secret in its successful use is to have it of just the proper 

 consistency, neither hard enough to resist the thrusting of a fly's 

 wing into a drop of it when placed upon the slide, or so limpid as 

 to spread and run when so placed. If too thick, a little chloroform 

 carefully stirred into the bottle containing the balsam, will reduce it 

 to proper consistency; if too thin, a covering of cotton cloth should 

 be placed over the mouth to exclude dust, and the bottle put in a 

 warm place for a day or two. My own plan is to put it when 

 found just right into collapsible tubes, from which the proper 

 amount can be squeezed out upon the slide, and in which it will re- 

 main of the same consistency until the last drop is used ; but most 

 persons will prefer to dip it from a wide mouthed bottle with a small 

 glass rod, and to such I would strongly 

 recommend the capped bottle, which I 

 have named under the head of non-es- 

 sentials, as it excludes all dust, allows the 

 rod to remain in the balsam when not in 

 use, and prevents any foreign particles from 

 falling into the latter, as must be the case 

 in all bottles closed with a cork. 



And now we have brought our work 

 down almost to the final operation. Our 

 specimens are soaking in oil of cloves 

 waiting to be mounted, our glass is clean 

 and bright, our balsam in its bottle, our 

 forceps and needles lying in their places 

 ready for instant use. What more do we 

 need ? Only a lamp or other convenient 

 method close at hand for warming the 

 3 some mode of centering the object 

 cover. The latter may be done by 

 sheet of white paper or card board, and 



Fig. 7. Capped Bottle 

 for Balsam. 



slide and cover ; an 

 before applying the 

 laying a slide on a 



