THE GEOLOGIST. 
28 
vided for the necessities of the inhabitants of the lake, river, or 
land, we can now assort, by means of their organization and 
structure, the fresh water tribes from the terrestrial or the marine, so 
by the like evidence in any of the past great periods of Geology, 
we can also, in the like manner determine those three important 
classes of depositary rocks, by their fossU shells alone. 
Similai" inferences are ever to be drawn of ancient conditions, 
from every other department of Nature, — from birds and fish, 
mammalia or I'eptiles, insects or plants, — aU display alike the 
badges of their mundane offices while living ; and, changed into 
stone, their lifeless fragments appear self-recordant of the events 
and phases of their existences. Each, like a dimmed half-faded 
jihotogi-aph, seems tinged with the lights and shadows of the 
scenes in which its span of life was past. 
"When sUently we rest beneath warm and glowing skies, or 
in easy chair, by winter hearth and cheerful fire, how many a scene 
comes rolling through the mind — a vast panorama moving on 
and on — presenting still some fresh familiar scene. How many 
thousand yards of canvas, how many miles of bright and beautiful 
painting, are rolled up in that mysterious scroll, the memory. 
How fresh and vigorous, as we unroll it in our reveries, come forth 
the prominent faces and features, the endeared or hated spots of 
bye-gone days, and how time and forgetfulness have scumbled down 
most of the harsher details into a mysterious and delightful haze, 
through which those minor groups are faintly seen. How too, by 
instinctive perceptiveness from what we know, do we enter into the 
scenes coiled up within the stony forms of plants, and bones, and 
shells ; how curiously, piece by piece, do the fragments fit together, 
like the scattered tesseUse of a Roman pavement, displaying in the 
intervals of color, outline, and vacuity, enough to manifest the 
tracery of the ancient floor, while as a nail, a peg, a bit of stained 
mortar, or a coin, complete the associations ; — imagination — memory's 
sister, — re-buUds the luxurious viUa, and re-peoples it anew. 
So from slight and apparently insignificant incidents are the 
great pictures of Geology elaborated and designed — and so does 
imagination in her reveries, not untruthfully and with a feeling 
very like remembrance, wander through the phases of those 
wonderful ages which have passed for ever away. Thus does even 
