300 



Proceedings of the Royal Physical Society. 



down on the hone to the required thinness. This part of the 

 process is the most difficult. The slides should be kept as 

 flat as possible, and looked at frequently with the micro- 

 scope, so that the first indication of disruption may be de- 

 tected. The proper thinness having been obtained, the 

 section should be at once covered with a glass cemented 

 with balsam; but considerable practice is required in this 

 part of the work, as the preparation, being very thin, is liable 

 to be broken into pieces by very slight overheating. The 

 superfluous Canada Balsam round the slice should be first 

 carefully scraped off with a sharp-pointed knife, and the slide 

 well washed in spirit of turpentine, using a camel-hair brush 

 to clean the section thoroughly. A little Canada Balsam 

 should then be dropped upon the centre of the section, and 

 a clean covering glass, heated a little, should be laid upon it 

 while yet warm and pressed down upon it, so as to force out 

 the air-bubbles if any remain. 



The slide on which the section still remains should not be 

 too hot, otherwise the gum will become soft and the prepara- 

 tion spoiled. Several preparations may be quite easily made 

 from one moulding, and when mounted labelled and laid 

 aside for future examination. 



Mineral particles, no matter how small, can be cut into 

 sections in the manner described. 



List of Articles used in the Process of Sectioning, 

 Moulding, etc. 



Porcelain crucibles 



Iron tripod stand, 9 x 9 in. 

 Cast-iron plate, | in. thick, £ 



long, and 7 in. wide. 

 Bunsen's burner or Spirit-Lamp, 



XT. 



nnd 



Tin moulds of various sizes (PI 



Fig. 1 ; 1, a). 

 Tin or iron crucible stands 



holders (PL XL, Fig. 3, h). 

 Large mounted needles. 

 Fine copper wire. 

 Fine wire gauze. 

 Common hone fitted with wood. 

 Water-of-Ayr stone. 

 Hard wood or iron presser (PL XL, 



Fig. 2). 



Ether, B.P 



(PL XL, Fig. 3 

 Porcelain dishes, 

 a). 



various sizes 

 various sizes (PI. 



XL, Fig. 4, 

 Glass rods. 

 Glass tubing. 

 Glass slips. 



Cover glasses, various sizes. 

 Small steel forceps. 

 Camel-hair brushes. 

 Bees-wax. 

 Resin. 



Finest gum copal. 

 Spirit of Turpentine. 

 Canada Balsam. 

 Sp. Gr. 0-735. 



