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1899J MICROSCOPICAL JOURNAL. 43 



quired but it must last for some time. Having now 

 lighted your lamp, proceed to prepare others in the same 

 way, or go on with other work for at least thirty minutes, 

 giving an occasional look to see all is going right. When 

 ready, take a cover glass in the forceps, place a very 

 small drop of balsam in the centre. Now put the cover 

 in position, not edge first in this case, but as flat as pos- 

 sible. By a judicious use of the spirit lamp the cover 

 will go down into its place. If any assistance is given 

 to it the touch must be very light indeed, as the forms are 

 very fragile. If the above operation is neatly done and 

 the right quantity of balsam used, there will be no ex- 

 cess of balsam, but a nice even bevel will be formed. 

 When this is the case, run a ring of cement round, and 

 finish in the usual way. The object of the above pro- 

 cess is two-fold : to get rid of the air contained in the 

 forms and let the balsam take its place, also to harden 

 the latter, thus saving any further drying. To mount 

 opaque objects in balsam, take a 3 X 1 in. slip, with a cell 

 of suitable size attached. See that all is clean, run a ring 

 of cement round the top. Now take a clean brush, dip 

 it in spirits of turpentine, and paint round the inside in 

 the extreme corner of jointure with slip. This is to ex- 

 pel all air. Drop in your balsam, which must in this case 

 be rather thin. Fill cell. Next put in your specimen, 

 which must have been previously soaking, either in 

 spirits of turpentine or benzole. Get rid of as much ex- 

 cess of this as possible. If the specimen has a concave 

 side, place it in the cell with the convex side downwards. 

 Turn it over in its cell. This will prevent any air from 

 getting imprisoned underneath. Examine under a low 

 power to see that all is right. Fill up your cell with more 

 balsam, so that the top is quite convex. Have ready a 

 cleaned cover, just a little smaller than the diameter of 

 the cell. Place it down edge first the edge farthest from 

 you. Grently lower it into position onto its bed of cement 



