66 THE MEDALS OF CREATION. Cuap. IV. 
which will render it somewhat transparent, and it then 
should be examined by transmitted light. By this explora- 
tion we may detect structure, and ascertain if the specimen 
be worth the-trouble or expense of further preparation. 
Coal may be prepared for examination, by removing with 
a sharp knife a thin pellicle, or a minute scraping ; immerse 
it in a drop of oil of turpentine on a piece of glass ; then add 
a little Canada balsam, and hold the glass over the flame of 
a lamp till the balsam is spread evenly over the specimen. 
But without any preparation, the surface of coal recently 
broken may be successfully investigated. One of the most 
interesting examples of coniferous structure in coal that my 
cabinet contains, was discovered by my son in a piece lying 
on the fire, which had been cracked by the heat; and I 
have another fragment, showing the spiral vessels, and coni- 
ferous glands, which the Rev. J. B. Reade obtained under 
similar circumstances. But for choice specimens, the fol- 
lowing method is to be employed; and in many cases no 
other plan will succeed. Sections of teeth, bone, marble, &e. 
may be prepared by a like process. 
MODE OF PREPARING SLICES OF FOSSIL WOOD FOR 
MICROSCOPICAL EXAMINATION. 
“Tet a thin slice be cut off from the fossil wood, in a 
direction perpendicular to the length of its fibres—the slice 
thus obtained must be ground perfectly flat, and polished. 
The polished surface is then to be cemented to a piece of | 
plate glass (3 in. long and 1 in. wide) by Canada balsam— 
a thin layer of balsam must be applied to the polished sur- 
face of the slice, and also to one side of the glass—the slice 
and the glass are now to be laid on any thin plate of metal, 
and gradually heated over a slow fire, or a spirit lamp, to 
concentrate the balsam. The heat must not be so great as 
to throw the balsam into a state of ebullition ; for if air 
