40 THE AMERICAN MONTHLY [Feb 



finish a slide right off when mounted as described, but it is 

 better to let it stand for a short time. Cement will effectu- 

 ally seal up glycerine mounts, and may be used as de- 

 scribed to fasten tin cells to glass, or to turn cells of the 

 cement itself on 3 X 1 in. slips. The use of Gold size isonly 

 a nuisance from its tendency to run between the cover 

 and the object. The only remaining operation is to ap- 

 ply the finishing varnish, either white zinc or some other. 



Likely Failures.^ — 1. — Specimen leaving- the g-umnred pa- 

 per in the cell. — Cause : g-um not thick enough at bottom 

 of cell. 



2. — Zinc varnish running under cover. — Cause : the ring 

 of cement on top of cell imperfect. 



3. — Damp or condensation on under side of cover. — 

 Cause : object or cell not being well dried. 



Mounting in Canada Balsam or Canada Balsam and 

 Benzole.- — This covers the largest number of objects 

 one has to deal with. If proper care is taken in prepar- 

 ing specimens before they are placed in contact with the 

 balsam there is little fear of air bubbles, and in the case 

 of balsam and benzole they will go by themselves. Time 

 will cure them if they are not too large. 



Canada balsam may be used for mounting the majori- 

 ty of transparent objects, Avhether anatomical or botani- 

 cal, Foraminifera, Polycistina. Many of the Elytrons or 

 brilliant Coleoptera are much improved by being mount- 

 ed opaque in balsam, but no attempt must be made to 

 mount the wings of Lepidoptera opaque if their brilliancy 

 is to be retained. These are as a rule mounted dry. 



We will now suppose we have some sections prepared, 

 and in the oil of cloves. Some advise xylol for the former 

 as a final instead of the clove oil. There are two meth- 

 ods of balsam mounting — the quick and the slow. The 

 quick method is more often adopted with the balsam and 

 benzole. Canada balsam very often is rather thick. If 

 so, add a little spirits of turpentine, rinse the specimen 



