THROUGH THE GEOLOGIST’S EYES 
has its root in that which preceded it. There were 
rude, half-defined fishesin the Silurian, and probably 
the beginning of amphibians in the Devonian, and 
some small mammalian forms in the Mesozoic time, 
and doubtless rude studies of the genus Homo in 
Tertiary times. Nature works up her higher forms 
like a human inventor from rude beginnings. Her 
first models barely suggest her later achievements. 
In the vegetable world it has been the same; from 
the first simple alge in the Cambrian seas up to the 
forests of our own times, the gradation is easily 
traced. Step by step has vegetable life mounted. 
The great majority of the plants and animals of 
one period fail to pass over into the next, just as our 
spring flowers fail to pass over into summer, and 
our summer flowers into fall. But the law of evolu- 
tion is at work, and life always rises on stepping- 
stones of its dead self to higher things. 
