; She Gata : ‘Se 
< . 4, -3 a 
1* ‘y 
_ 2 ’ 
4 ‘4 - i 4a 
’ - - ~ 
604 PALHONTOLOGICAL GEOLOGY. — [Book V. 
(coprolites) of fishes and reptiles are excellent fossils, and tell their 
tale as to the presence and food of vertebrate life in ancient waters. 
The little agglutinated cases of the caddis-worm remain as fossils in 
formations from which perchance most other traces of life may have 
passed away. Nay, the very handiwork of man, when preserved in 
any natural manner, is entitled to rank among fossils; as where his 
flint-implements have been dropped into the prehistoric gravels of 
river-valleys, or where his canoes have been buried in the silt of 
lake-bottoms. oT 
The term fossil, moreover, suffers no restriction as to the condition 
or state of preservation of any organism. In some rare instances the 
very flesh, skin, and hair of a mammal have been preserved for 
thousands of years, as in the case of the mammoths entombed within 
the frozen mud cliffs of Siberia. Generally all or most of the 
original animal matter has disappeared, and the organism has been 
more or less completely mineralized or petrified. It often happens 
that the whole organism has decayed, and a mere cast in amorphous 
mineral matter, as sand, clay, ironstone, silica, or limestone, remains ; 
yet all these variations must be comprised in the comprehensive term 
fossil. 
Two preliminary questions demand attention: in the first place 
how remains of plants and animals come to be entombed in rocks, 
and in the second how they have been preserved there so as now to 
be recognizable. 
i. Conditions for the entombment of organic remains.— 
If what takes place at the present day may fairly be taken as an 
indication of what has been the ordinary condition of things in the 
geological past, there must have been so many chances against the 
conservation of either animal or plant remains that their occurrence 
among: stratified formations should be regarded as exceptional, and 
as the result of various fortunate accidents. 
1. On land.—Let us consider, in the first place, what chances — 
exist for the preservation of remains of the present fauna and flora 
of a country. The surface of the land may be densely clothed with 
forest, and abundantly peopled with animal life. But the trees die 
and moulder into soil. The animals, too, disappear, generation after 
generation, and leave few perceptible traces of their existence. If 
we were not aware from authentic records that central and northern 
Europe was covered with vast forests at the beginning of our era, how 
could we know this fact? What has become of the herds of wild 
oxen, the bears, wolves, and other denizens of the lowlands of 
primeval Europe? How could we prove from the examination of 
the soil of any European country that those creatures though now 
extinct had once abounded there? We might search in vain for 
any such superficial traces, and should learn by so doing that the law 
of nature is everywhere “ dust to dust.” 
The conditions for the preservation of relics of terrestrial (includ- 
ing freshwater) plant and animal life must therefore be always local, 
4 
