Pennsylvania Geology Final Report Volume 1 1981

22 GEOLOGICAL SURVEY OE PENNSYLVANIA.
Chapter III,
Geological Dimension..
The second fundamental element of geological thought is
the idea of space in its three dimensions of length, breadth
and thickness. Any transcendentally imagined fourth
dimension must appear to be absurd. Astronomy deals
with unimaginable and infinite distances, as its sister
science, geology, deals with unimaginable if not infinite
operations of time. In both cases the common mind is
subject to a thousand deceptions. Who can believe that
the moon when it rides in a clear night through the atmosphere
to all appearance no higher than balloons could
mount or an eagle soar, is in reality 240,000 miles distant
from the spectator, sixty times the radius of our globe. And
yet this distance is the smallest of the heavenly spaces.
The sun's mean distance from us is 92,000,000 of miles;
while the light of the nearest fixed star traveling at the
rate of 200,000 miles a minute does not reach us until after
a journey of eight days. Such ideas would seem to be useless
to the practical geologist. But no truth is useless; all
knowledge is practical either in its direct application to
facts or in its education of the finer qualities of the mind.
No man can rightly understand the descent of a coal bed or
ore vein from the surface into the depths of the underground
unless his imagination is disciplined to estimate properly
the dimensions of space, and by habituating himself to the
measurement of distances of all grades, long and short, he
acquires the power of calculating those lengths and breadths
and depths which are within the scope of mining opera-
tions.
To the practical astronomer our globe seems as small to
the surrounding solar system as a grain of sand compared
with the mass of a mountain. To the practical geologist