INTRODUCTION 



Objects much reseml)ling fishes, shells, plants, and other 

 remains of living things, have been noticed in rocks from 

 time immemorial. They are so abundant and conspicuous 

 in some of the countries round the Mediterranean, where 

 the Greek and Eoman civilisations flourished, that 

 they cann()t fail to have attracted the attention of the 

 earliest observers. Herodotus, for example, 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 

 ])etrified relics were originally l)uried in the bed of the sea, 

 whicli 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 whicli seemed simpler, l)ecause it 

 did not involve any startling theories as to great changes in 

 the relations of land and sea. If certain animals could l)e 

 generated in mud, it appeared quite probable that they should 

 sometimes remain c(mcealed in their native element without 

 rcacliing the surface, and in that case they would become 

 hardened into stone itself. As Theophrastus remarked 

 concerning ])etrified 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 l)ecome petrified." These bodies thus appeared to be 

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



