WHAT FOSSILS ARE 45 
rate, he has set an example which is worthy of 
serious consideration. 
This chapter is to be devoted to fossils. I want 
to tell you what fossils are, say something about the 
rocks in which they are found, give you some idea 
of the story they tell, describe and picture some of 
them, and give you a few hints about collecting. 
A fossil, literally, is something-dug up, and the 
term applies to remains or impressions of animals 
and plants which are found in rocks, or naturally 
placed amongst clay, sand, or gravel. A fossil may 
be a petrified plant or animal, or an impression of 
such. A petrified tree-trunk is a fossil, and so is 
the impression in limestone or shale of a shell or a 
fern. The rocks have preserved burrows of worms, 
and even the footprints of birds, and these are also 
called. fossils. 
The fossils we find in the rocks to-day are only a 
slight indication of the number and variety of 
living creatures which occupied the world in past 
ages. The bodies of many creatures are too perish- 
able to become fossilized, except under very par- 
ticular circumstances. Creatures of the sea are more 
likely to be preserved in fossil form than land animals 
and plants, and for this reason the majority of fossils 
found are of the marine type. 
From fossils we can learn much about the story 
of Creation, and of the living inhabitants of the 
world from very remote times. Fossils also give us 
clues to the geography of the age in which the 
creatures they represent lived, and show us how 
there have been changes in geography. You know 
that chalk was formed under water ; if, therefore, 
