DELVING INTO A PREHISTORIC RECORD 
usually impossible, in a hasty examination at the time, 
to decide which are valuable and which are not. Many 
details would be likely to escape attention and excellent 
material thus be lost. So the bulk of the material is 
brought home; some is carried in knapsacks, and some 
taken in automobiles from the mine or ravine to the 
laboratory for study. 
There the material is first organized roughly. Similar 
things are put together to await definite determination 
of their place in the plant kingdom. The impressions 
and casts are hammered and picked at until they show 
the best appearance. Then they are placed in trays for 
careful investigation. 
Fossil woods and coal balls require a more complicated 
treatment before they can be studied. They have to 
be sliced into thin sections for examination under the 
microscope. This cutting is done with a rotary saw whose 
edge is charged with coarse diamond powder. The 
technical name for this saw is a diamond saw. The 
diamond powder cuts the hardest rock as easily as one 
cuts a loaf of bread with a kitchen knife, only a little 
more slowly. Great care must be taken to cut the coal 
ball in the right direction. The first cut must necessarily 
be more or less of a guess, but after the structure of the 
ball becomes apparent, the cuts can be made exact. 
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