paleontological geology 
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paleontological geology 
Antiquity of Lingula. As symbols of absolute changelessness, 
and as the certain embodiment of permanency among things num- 
dane, the adamantine rocks and the everlasting hills, popular 
fancy passes on to us Moderns many of the very old notions be¬ 
longing to the time when mankind itself was young. As applied 
to the rocks we now know that adamant is merely a relative 
term, and the span of its duration, as measured by geological 
time-units, is quite ephemeral. So, also, geologically speaking, 
the mountains eternal melt into the sea as does a pinch of sugar 
in a goblet of water. 
Turning directly to the relief features nearest us it is not the 
towering mountains which are the really permanent characters of 
the landscape but the restless brook at their foot. It may not be 
questioned that the lowly stream is the one wrinkle of Earth’s 
face that resists most resolutely all attempts at its removal. As 
the mobile river is an emblem of stability more lasting than that 
of the mountain rising from its banks, so active life passes on 
unscathed through ages that dwarf even the river’s long span. 
Certain innate advantages which life thus seems to present in its 
evolution through time permits it to form the basis of our geologi¬ 
cal chronology. 
Thus it is, that in order to establish something of a geological 
time-scale, which may be roughly measured in myriads of human 
years, it is the custom of the scientist to be guided in his reasoning 
by the amount of expressive change which past forms of life dis¬ 
play in their make up between any two levels. Although when 
m.easured by the time standards devised by man this organic change 
seems excessively slow — slower than the movement of the fixed 
stars. How great the elapse of the years is, which any ap¬ 
preciable change in the structures of ancient organic remains 
