INTRODUCTION. 



Objects much resembling fishes, shells, plants, and other 

 remains of living things, have been noticed in rocks from 

 time immemorial. So long ago as the fifth century, B.C., the 

 philosopher Pythagoras seems to have observed sea-shells 

 buried in the earth far away from the shores of the seas 

 then existing ; while Xenophanes of Colophon recorded the 

 discovery of fishes and other animals embedded in the hard 

 rock of the quarries near Syracuse. Herodotus afterwards 

 referred to sea-shells from the stone quarries in the hills 

 of Egypt and the Libyan desert. Other contemporary 

 philosophers and writers made similar observations, and 

 most of them appear to have reached the very natural 

 conclusion, that these petrified relics were originally buried 

 in the bed of the sea, which had hardened and become dry 

 land through the retreat of the waters. 



At this early period in the study of natural philosophy, 

 however, it was a common belief that animals could originate 

 from the mud or slime of lakes and rivers. There was 

 therefore another reasonable explanation of their occurrence 

 as petrifactions in stone which seemed simpler, because it 

 did not involve any startling theories as to great changes in 

 the relations of land and sea. If certain animals could be 

 generated in mud, it appeared quite probable that they should 

 sometimes remain concealed in their native element without 

 reaching the surface, and in that case they would become 

 hardened into stone itself. As Theophrastus remarked 

 concerning petrified fishes, they might have " either developed 

 from fresh spawn left behind in the earth, or gone astray 

 from rivers or the sea into cavities of the earth, where they 

 had become petrified." These bodies thus appeared to be 

 mere curiosities, and they were treated as such by Aristotle, 



