FERNS, FOSSILS AND FUEL 
where the plant impressions are embedded, is located. 
Such a layer was once a river bottom, or the surface of 
a mud-bank of a stream, upon which plant material had 
been washed. 
He visits coal mines and walks through the corridors 
and chambers, following the seam. The shale above is 
often plastered with plant impressions, or fossil remains 
may be observed in the coal itself, or the roots of plants 
can be seen in the fire-clay below the coal. He picks up 
pieces of fossilized wood in ravines into which they have 
rolled, sometimes from uplands a long distance away. 
He staggers home at the end of a day’s exploring, laden 
with rocks of all sizes and shapes. 
He also finds fossils in the drill cores brought up 
during the testing of deep layers of rock for coal or oil 
deposits. The diamond drill often goes down into the 
solid rock as deep as 4,000 feet, and cuts out a core 
which is brought to the surface. When the core, part 
of which is usually of shale, is split open, it frequently 
shows plant impressions. 
Plant fossils that have been so laboriously gathered in 
the field must be taken to the laboratory for thorough 
examination, classification, and interpretation. The paleo- 
botanist always carries away from the field many more 
specimens than he could possibly want to keep; for it is 
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