44 THE AMERICAN MONTHLY [Feb 



and apply gentle pressure to the edge (on each side at 

 once) by means of your needle points. If everything has 

 been done right, it may be set on one side for twelve 

 hours to harden the cement. Then clean it off with a 

 brush and sprits of turpentine or benzole. When all ex- 

 cess of balsam is removed and the slide is dry, finish with 

 another ring of cement. When that is dry, it may be 

 finally finished in the usual way, a piece of black paper 

 being fastened under the cell. Some recommend lining 

 the inner portion of the cell with varnish, but this is 

 likely to affect the specimen in time. 



Likely Failures. — 1. — Cloudiness round edges of sec- 

 tions. — Cause : not being thoroughly dehydrated by means 

 of the alcohol before going - into the oil of cloves. 



2. — Balsam drying up and leaving a small space or spaces 

 at edge of cover. — Cause : insufficient balsam used in 

 mounting. It can be filled up from the outside. 



3. — Section lifting cover glass. — Cause : sometimes hap- 

 pens with hard sections or fish scales. Use a wire clip un- 

 til balsam is set. 



4. — A bubble of air in the cell. — Cause : insufficient bal- 

 sam in cell before putting on cover. 



To Mount Insects and Insect Parts' With and With- 

 out Presure. — Mounting the different parts of insects to 

 show their structure, is very interesting. This may be 

 done in two ways : with presure, i. e., flattened out be- 

 tween the glasses ; or without, in a cell, keeping them as 

 near as possible in their original form. For a sample of 

 the former method, we take the Soldier Beetle to be 

 mounted entire. The same treatment will apply to many 

 insects or parts of same, but must not be taken to include 

 the more delicate specimens, as many of them reqjuire 

 very special treatment. Our specimen being ready pre- 

 pared, and in spirits and water, take it from the solution. 

 Place it in clean water, say from ten to fifteen minutes. 



Gently rinse it to get rid of any foreign bodies. If the 

 specimen has been in pure spirit, as is sometimes wrongly 



