CONCLUSION. 
521 
CHAPTER XXV, 
CONCLUSION. 
In concluding this Report, we are naturally led to take a retrospective view of the condi¬ 
tion of the surface of this portion of our planet during the accumulation of these sedimentary 
deposits. We behold a wide expanse of ocean, which received these materials from adjoining 
land, and upon the bed of which flourished the myriads of living forms which were succes¬ 
sively imbedded in the strata, until finally the whole emerged a vast continent from beneath 
the sea. We find at one time the evidences of a quiet ocean, with clear waters, abounding in 
corals and shells ; and at another, a turbid condition in which all these forms ceased to exist. 
Long periods of repose were succeeded by disturbances which changed the whole scene, and 
then followed new creations and new materials of deposition. 
It is universally acknowledged among geologists, that these immense sedimentary deposits 
could only have accumulated beneath the waters of the ocean, during an incalculable period 
of time, long anterior to the present condition of the surface. Now in order to furnish mate¬ 
rials for such formations, we must conceive of the existence of continents where no vestige of 
them now remains ; from the abrasion and destruction of these, and from the transporting 
power of rivers and ocean currents, the materials composing them were reduced to the state 
of pebbles, sand, and finely comminuted mud, which were widely diffused and gradually or 
rapidly precipitated upon the ocean bed. The varying nature of the deposits proves to us 
that these elevated lands frequently changed their condition or outline, or that new sources 
of materials were opened to the destroying and transporting agencies. Sometimes, however, 
there is little variation for a long time : the same sources supplied the material; the same 
agents, with unchanging intensity, removed and distributed it widely over the bed of the ocean ; 
while, again, within a short period, its nature is entirely altered, or a new source brings in 
matter of a different kind to mingle with the hitherto uniform deposit. The disturbing forces 
that sometimes long slumbered, seem often to have broken out suddenly with renewed energy, 
changing the whole condition in a short space of time. 
[Geol. 4th Dist.] 66 
