PHYSICAL HISTORY OF NEW HAMPSHIRE. 507 



to be discovered yet in the southern part of the state. Some of this 

 information will be obtained for our final geological map. If the reader 

 finds discrepancies, he may accept the conclusions last stated as the most 

 authoritative. 



This sketch is really an epitome of the geology of the state. It pre- 

 supposes the establishment of the entire geological column, the order of 

 the formations, and their geographical arrangement upon the map. If 

 correct, it assumes the solution of questions which have agitated geologi- 

 cal circles for forty years. We can only refer to the next volume for the 

 establishment of all these fundamental doctrines, and will state the sub- 

 ject as if they were thoroughly proved. 



It is not desirable to go further back in time than to the period of the 

 deposition of the first rock formation in the state. There are interesting 

 speculations respecting the history of our planet, for ages anterior to its 

 solidification. It may have formed part of a nebula comprising first 

 the entire solar system, and afterwards only the earth-mass. In later 

 times it is thought to have existed in the condition of igneous fluidity. 

 A long series of ages may have been occupied in the changes which 

 effected the formation of a solid crust, the falling of the steam and vapors 

 in the atmosphere to form a saline ocean, and the separation of elevated 

 and depressed areas from each other to allow of the erosion of rock and 

 deposition of material in the lower portions. During much of this time 

 the special area now known as New Hampshire could not be distin- 

 guished from the adjoining territory. It will therefore be best to con- 

 fine our studies to the time when dry land began to appear within our 

 borders, and then describe the successive eras of growth as truthfully as 

 possible. 



At this point it is important to state the terminology of our science. 

 Human history is divided into periods, according to the supremacy of 

 various nations or prominent ideas. Geological history is classified in 

 accordance with the succession of life, and the predominance of particu- 

 lar classes. Four groups are recognized, i. Eozoic, or the period of 

 the introduction or dawn of life. 2. Paleozoic, or the time when 

 ancient types of life predominated. 3. Mesozoic, or the time when the 

 middle types of life prevailed. 4. Cenozoic, the latest period, when all 

 will recognize the recent character of the organisms. 



