THE GEOLOGIST. 



21 



burial places. Such fossils are Imown 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 structiu-e 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 dejDOsit 

 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 ha-ve 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 sheUs. So much then for " What is a fossil ? " 



Too many people still think Geology merely the art of collecting 

 fossils and rocks and of getting names for them ; and hundreds 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. Fossils 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 theii' tracks upon the sand 3 dig out the annelide and the 



