FOSSILS, AND HOW THEY ARE FORMED 13 
watched the leaves sailing to the ground to be 
covered by mud or sand at the next rain, or 
dropping into the water, where sooner or later 
they sink, as we may see them at the bottom 
of any quiet woodland spring. 
Impressions of leaves are among the early 
examples of color-printing, for they are fre- 
quently of a darker, or even different, tint from 
that of the surrounding rock, this being caused 
by the carbonization of vegetable matter or to 
its action on iron that may have been present 
in the soil or water. Besides complete miner- 
alization, or petrifaction, there are numerous 
cases of incomplete or semi-fossilization, where 
modern objects, still retaining their phosphate 
of lime and some animal matter even, are 
found buried in rock. This takes place when 
water containing carbonate of lime, silica, or 
sometimes iron, flows over beds of sand, ce- 
menting the grains into solid but not dense 
rock, and at the same time penetrating and 
uniting with it such things as chance to be bur- 
ied. In this way was formed the “ fossil man” 
of Guadeloupe, West Indies, a skeleton of a 
modern Carib lying in recent concretionary 
