THE GEOLOGIST. 
31 
burial places. Such fossils are known as casts, where the rock 
has consolidated in their interiors; and as moulds or impressions 
where the external forms and ornamentation are indented in the 
clay or stone. There are many other processes of fossilization ; by 
some of which the most exquisite tissues have been retained, and 
in others even distinct evidences of colour have been conserved. 
On the slightest reflection it must be apparent that where, as is 
by no means uncommonly the case, an organic structure of much 
delicacy has been preserved in the soil, the process of preser- 
vation, must have been, at least in the first instance, if not posi- 
tively sudden, at least very rapid. Sometimes by an incrustation of 
the surface of the animal or plant soon after its death or its deposit 
in or upon the mud of the ancient seas, decomposition was for a 
time partially arrested, and the external parts thus saved from 
decay, while the internal have rotted away and left a cavity which 
may still remain, or which may have been filled up with sparry 
crystals, segregated from subterranean waters. At other times, as 
perhaps in the case of the chalk-flints, the inclosed organisms 
have been penetrated by the enveloping substance, the tenuity of 
which was often such as to have permitted its passage through 
the cracks and seams, and frequently even through the finest pores 
of the shells. So much then for " What is a fossil ? " 
Too many people stUl think Geology merely the art of collecting 
fossils and rocks and of getting names for them ; and himdreds of 
those who go into a quarry, come out again with little other diffe- 
rence than that of being dirtier and dustier on their exit than on 
their entrance. The possession of a shell or even a lot of fossils 
is not sufficient for science ; it may please the amateur or 
amuse the idle. FossUs are not to be hoarded as curiosities or 
rarities, but prized for their teachings. Go to the seaside and 
watch what takes place on shores which present the like conditions 
with the beds which have afforded your organic remains. Watch 
how the merry dancing waves, as they ebb away from the shore 
with playful dalliance, leave the impress of their last kisses on 
the sands ; watch how the rippled furrows are ridged and streaked 
by the breath of the gentle winds. See how the spray or the rain 
spatter out miniature craters, and the worms and crawling things 
make their tracks upon the sand ; dig out the annelide and the 
