12 



INTRODUCTION, 



this opinion, by showing that the planet must have been in a state of total or partial 

 fusion when it assumed its present shape. Such reasoners are led to suppose, that the 

 earliest accumulations occurred under conditions which forbade the possibility of any 

 ■vital organization ; and they are further strengthened in their creed, when on exa- 

 mining the innermost folds of the earth's covering which have been extruded, they 

 find in them no vestiges of life. They conclude therefore, that it was only after a long 

 time, and when the surface had to a certain extent been cooled down by succeeding 

 changes and the addition of fresh materials, that animals and vegetables were called into 

 existence. 



Other geologists contend, that as yet we gaze but dimly into the obscure vista of 

 these early periods ; and that even if organized beings did live when the first crystalline 

 rocks were formed, we cannot now hope to discover evident traces of their existence, 

 owing to the great metamorphoses which subsequent agencies have produced in these 

 masses, — metamorphoses which may be well supposed to have obliterated all traces of 

 primeval creation. 



Without here attempting to decide this question, I would merely observe, that the 

 term "Protozoic," as above interpreted, maybe used by the maintainers of either 

 doctrine. 



In conclusion, I repeat that my chief object is to develope the upper portion of this 

 vast series ; — its lower divisions belong to the task which has fortunately fallen to Pro- 

 fessor Sedgwick. 



