PLASTIC FORCE 233 



"heads" were no doubt the work of some practical 

 joker or fraudulent fossil-fm4er, yet the argument will 

 not be greatly affected, since-it is admitted that the fossil 

 forms often differ markedly from their living representa- 

 tives. The explanation of these differences had been 

 arrived at long before by Palissy, and is suggested by a 

 writer, bearing the illustrious name of Lister, who 

 says truly that these fossils must be either " terrigenous, 

 or, if otherwise, the animals they so exactly represent 

 have become extinct." Referring to this, Dr. Plot 

 remarks: "If it be said, that possibly these Species may 

 be now lost, I shall leave it to the Reader to judge, 

 whether it be likely that Providence, which took so 

 much care to secure the works of the Creation in Noah's 

 Flood, should either then, or since, have been so un- 

 mindful of some Shell-fish (and of no other Animals) as 

 to suffer any one Species to be lost." 



Since this was written we have learnt to accept the 

 doctrine of the extinction of species ; it has become a 

 commonplace amongst the educated, and has passed 

 into the language of our poets 



" So careful of the type she seems 1 But no 1 

 ' From scarped cliff and quarried stone,' 

 She cries, ' a thousand types are gone 1 

 I care for nothing; all shall go.' " 



After his exposition of the weak points in Steno's argu- 

 ment Dr. Plot proceeds to consider the alternative view, 

 that the formed stones are the result of some " plastic 

 force " ; and as later writers have made merry over this 

 expression, it will be merest justice to explain what Dr. 

 Plot meant by it. Whatever the plastic force of Theo- 

 phrastus may have been, that of Dr. Plot was certainly 

 what we now recognise as crystallisation. His words 



