THE GEOLOGIST 



sliell-fisli from theii' oosy homes, and note their positions in the eailh; 

 observe the zones of various plants and living things, and how they 

 vaiy with the depth of tide or the kind of soil or sea-bed, and carry 

 back your experiences to the quariy, and then you will perceive 

 something, and as yet something only, of the value of a fossil. 



On our shores are three zones, of materials, animality, and 

 vegetation. The sea has sorted out the sand and mud from the 

 heavier fragments, — which the restless waves have tossed along the 

 strand and have rounded into boulders and pebbles, — and, between 

 the tidal marks, has left the sand, while the finer particles have 

 been carried into the region of, and below, low water. 



So too, nature presents her three zones of animal and vegetable 

 life ; and, as the briny currents have carried the still finer particles 

 of silt into yet low er depths and more profound abysses, so nature 

 in the deeper waters presents other zones of created beings, with 

 characters and habits equally suited to the varied conditions of their 

 existence. The researches of modem naturalists have shown that 

 not only are various forms of animals and vegetables circumscribed 

 in their geographical distribution, but that they are also limited in 

 their vertical range, or in other w^ords, are prescribed -wdthin a 

 certain depth of the sea, or a definite elevation of the land. Most 

 organic remains, from the very means and circumstances of their 

 preservation, are necessarily of marine origin, because terrestial 

 or subaerial influences are more essentially desti-uctive in their 

 ordinary action ; and it is more rarely in comparison to the sub- 

 marine operations, which are constantly at work, that those co-inci- 

 dences happen by which the relics of the land, or even of the 

 river or lake, are presen ed. 



Of actual depths of seas, the shell-fish or MoUusca, from the 

 limited range of their locomotive powers, must be, next to algse, 

 corals, bryozoa, and other Jia:ed fomis, the most certain and definite 

 in the evidence they afford ; and thus it vdW be perceived, what an 

 important bearing the study and knowledge of their habits, 

 regions, and ordinary limits of depths wiU have in determining from 

 the fossil species through their relations to their recent t}i)es, the 

 conditions under which the strata, in which they are embalmed, 

 were deposited, and the profundity of the pre-adamic seas or 

 estuaries. As by the modifications and adaptations which are pro- 



