72 HOW TO USE THE MICROSCOPE 



3. A short piece of solid glass rod for manipulat- 

 ing the balsam. 



4. A mounting table, consisting of a plate of 

 brass, usually about 4 inches by 3 inches, with four 

 legs a few inches high. This is used for heating 

 slides laid upon it. The heat is derived from a 

 spirit lamp placed beneath the table. A small brass 

 plate, resting upon a home-made wire support, will 

 serve. 



5. A supply of methylated spirit and turpentine. 



In drawing up this list of requisites I am assum- 

 ing that the worker already possesses sHps, cover- 

 glasses, spirit lamp, and other necessaries mentioned 

 in connection with opaque mounting, and I omit 

 details of reagents required in the preparation of 

 objects ; these will be mentioned in due course. 



Now, let it be understood that Canada balsam 

 is a resinous substance with which water is incom- 

 patible — -that is to say, balsam and water will not 

 blend. Therefore any object to be mounted in 

 balsam must be dehydrated : have every trace of 

 water extracted from it. Dehydration is effected 

 by soaking the object in methylated spirit. Another 

 point to be remembered is that before mounting an 

 object in balsam it must always have a final soaking 

 in turpentine, which blends with balsam and enables 

 it to permeate the object if it be permeable. 



If the worker desires to practise mounting in 

 balsam without going through the necessary stages 

 in the preparation of objects, he cannot do better 

 than communicate with Mr. R. G. Mason, 78, Fox- 

 bourne Road, Upper Tooting, S.W., who supplies 

 prepared objects at a very cheap figure. All that 



