1896.} Fossils and Fossilization. 905 
regions, and many fossils are in a more desirable condition, as 
specimens for study, when surface weathering has revealed 
them from the matrix and brought them into a clean and sig- 
nificant relief, as in the case of chain corals (Halysites catenu- 
latus) in the Niagara Limestone of western New York, or when 
the solvent of carbonated waters has left them accessible, in a 
friable and open ferruginous sand, as-in the weathered rinds 
and exteriors of the siliceous limestones of the Schoharie Grit 
of eastern New York. 
Fossils represent the hard parts of animals or such portions 
of their soft parts as have become replaced by mineral mate- 
rials. The fleshy organic elements of an animal undergo de- 
composition and disappear, even though enclosed in sediments 
of great thickness. Water-carrying oxygen finds its way 
around them and slowly introduces those putrefactive changes 
which result in disintegration and solution. But in this pro- 
cess, if it is prolonged, there is a substitution of earthy matter, 
and an infiltration of silt will assume the form of muscular 
bands, retain the outline of muscular scars and blood-vessels, 
while a more obscure course of substitution may slowly replace 
the chitinous, horny, or even fleshy, appendages with silica, 
iron pyrite, and other mineral species, preserving them with 
microscopic fidelity. Many forms of animal life, like the 
Medusee, Ctenophore, Holothurians and Worms, from their soft 
consistency, are necessarily almost excluded from a represen- 
tation amongst fossils, being, at the best, only indicated by 
impressions. The occasional and unusual preservation of the 
fleshy parts of extinct animals in ice can hardly be regarded 
as a contradiction of this universal rule. 
The various stages of the natural process by which organic 
beings become fossils‘ may be conveniently regarded as three 
—first, the placement of the object in its position preparatory to 
fossilization; second, its sepulture or burial, and third, the 
mineralogical or chemical changes by which it assumes its 
4The word “ fossil” receives a curious application by old writers, especially by’ 
the celebrated Werner, who used it to designate any mineral object extracted 
from the surface of the earth. Thus minerals become fossils, and he canal of 
** solid fossils,” and he divides them into * hard, semi-hard, soft, and very soft.” 
Also see Pinkerton’s Petrology. j 
63 
