224 Modern Microscopy 



A sufficient quantity of cement may then be added to finish 

 the mount, but if too much is applied at first it will over- 

 flow. 



The most suitable brush for ringing slides is a sable 

 ' rigger ' No. 2 in a metal holder ; it should be well washed 

 in methylated spirit after use. 



Cleaning off Failures. — During a course of microscopical 

 work many slides will be not worth keeping, but the slips 

 and covers are quite good, and they can be used again. 

 When a batch of failures has accumulated, make a strong 

 solution of Hudson's soap-powder in warm w^ter, and place 

 some of it in two jars. Warm the slide over a spirit-lamp, 

 and with a needle-point push off the cover into one of the 

 jars and put the slip into the other ; let them soak for an 

 hour or two, then wash away the soap solution with re- 

 peated changes of warm water, and finally pour away all 

 the water and add methylated spirit ; soak for a little while, 

 and then dry with a soft clean rag. 



Sometimes slips and covers have a dull, cloudy appear- 

 ance, which defies all attempts to remove it. When this 

 is the case, make up a solution of hydrochloric acid in 

 methylated spirit (about one part of acid in six of spirit), 

 and immerse the glasses for a few minutes. Wash away 

 the acid with methylated spirit, and dry with a soft rag. 



