144 PREPARATION AND MOUNTING 



solution of carbonate of potash ; at the end of that time it 

 is possible to cut tolerably thin slices with a razor. These 

 slices are then placed in a watch-iilass with strong nitric 

 acid, covered, and gently heated ; they soon turn brownish, 

 then yellow, when the process must be arrested by dropping 

 the whole into a saucer of cold water, else the coal would 

 be dissolved. The slices thus treated appear of a darkish 

 amber colour, very transparent, and exhibit the structure, 

 when existing, most clearly. We have obtained longitudinal 

 and transverse sections of coniferous wood from various 

 coals in this way. The specimens are best preserved in 

 glycerine in cells ; we find that spirit renders them opaque, 

 and even Canada balsam has the same defect. Schultze 

 states that he has brought out the cellulose reaction with 

 iodine in coal treated with nitric acid and chlorate of 

 potash." Now and then in coal we meet with a half-formed 

 carbon-looking substance which is no more difficult to work 

 with than ordinary charcoal. From this it is an easy thing 

 to procure interesting slides. 



Cannel-coal is so close and firm in its structure as to be 

 much used instead of jet in the manufacture of ornaments : 

 it takes a beautiful polish, and consequently presents the 

 student with none but ordinary difficulties in getting sections 

 of it. Its formation is somewhat different from that of coal, 

 sometimes showing the transition very clearly. 



Fossil Wcod. This is very often brittle and requires 

 great care in cutting. There are, however, different kinds 

 of fossil wood, but to obtain anything like certainty and 

 perform much work a lathe is necessary. I know of no 

 method better than that given by Mr. Batterworth, and 

 shall therefore make use of his words. First, I will begin 

 with the cutting. To the framework of an ordinary foot- 

 lathe I attach an upright spindle (see engraving). On this 

 upright spindle I drive bv a band passing over " carry- 



? alleys" from the wheel below. On the top of this spindle 

 fix my cutting-disc, which is made from a very thin 

 piece of sheet iron, and is about six inches in diameter. 



