260 FIRST FORMS OF VEGETATION. 
cal epoch to another, until at length we behold in 
the diatoms of our pools, rivers, and seas, the re- 
presentatives and exact counterparts of the races 
that lived and died in those ages of the world, 
compared with which the antiquity of recorded 
time is but as yesterday. Step by step, up from 
the lowest fossiliferous strata, when life was just 
feebly dawning, when the eye that gazed upon 
the dreary lifeless scenes which the earth then 
presented was more rudimentary than that of the 
mollusc, and the ear that listened to the wild 
ceaseless moaning of waves, the splintering of 
rocks, and the roar of volcanoes, was but a mere 
otolithic vesicle; through the old red sandstone, 
with its numerous strange and monstrous fishes ; 
the carboniferous strata, with their countless forms 
of gigantic vegetable life ; and the limestone rocks, 
the graves of whole hecatombs of madrepora,— 
through all these different geological deposits we 
can trace the presence of these little plants. En- 
dowed with the power of investing themselves, as 
if by a mysterious process of electrotype, with 
the silicious matter held in solution by the waters 
in which they abound, they are in truth indestruc- 
tible ; and of their remains, individually so minute 
that hundreds may be contained in a drop, and 
thousands packed together in a cubic inch, deep 
beds of marl, extensive chains of hills, huge lime- 
