Fossils. 
41 
still higher up in the series. The fossil figured on page 
203 is evidently a sea-shell, and therefore characterizes 
a marine formation. These fossils are never mixed. 
A single frond of any one of them is sufficient to decide 
the relative position of the beds containing them. 
We have already referred to fossils from the 
shales near Sydney. In case of the footprints, the 
fossils were preserved merely as impressions. Writing 
of similar impressions in New England, Winchell says: 
Fig, 10. — Microscopic structure of Granite. 
“ It is a solemn and impressive thought that the 
footprints of these dumb and senseless creatures have 
been preserved in all their perfection for thousands of 
ages, while so many of the works of man which date 
but a century back have been obliterated from the 
records of time. Kings and conquerors have marched 
at the head of armies, across continents, and piled up 
aggregates of bum an suffering and experience to the 
heavens, and all the physical traces of their march 
have totally disappeared, but the solitary biped which 
