518 Revieios — Hitchcock's Geology of Neiv Hampshire. 



masses consist of various kinds of granitic, felspathic, and augitic 

 rocks. 



The third volume will probably be found of more interest than 

 the second, as under the head of " Surface Geology" there are two 

 important chapters on the Glacial period, and associated phenomena 

 of New Hampshire, which are perhaps as well shown there as in any 

 part of the earth. The first, by Mr. W. Upham, treats fully of 

 the observations made by him in the different districts, and includes 

 the " Lower Till " deposited during the Glacial period, and found 

 throughout the State. This is succeeded by the Upper Till, and the 

 Champlain period, which embraced the time occupied by the final 

 melting of the great ice-sheet, during which the abraded materials 

 contained in the ice-mass were washed away and deposited as 

 kames, kame-like plains, and valley or modified drift ; these were 

 followed by the recent or terrace period, during which deep and 

 wide channels were excavated in the Champlain deposits ; a table 

 is given showing the formations which have been described in the 

 chapter, arranged in the order of their deposition (p. 176). 



The general characters of the glacial drift are also further' de- 

 scribed by Mr. C. H. Hitchcock, who treats, amongst other points, 

 of the causes of the glacial cold, of interglacial deposits, and the 

 length of the Glacial period, concluding with his most recent 

 opinions on the order of events occurring in New Hampshire, in the 

 Glacial, Champlain, and subsequent periods. 



The Glacial period of the northern hemisphere has been a subject 

 of considerable attention among geologists and physicists, and various 

 theories have been suggested to account for the cause of the glacial 

 cold, but none have been universally accepted. Every additional 

 information tending to enlarge our knowledge of the origin, extent, 

 and movement of the ice-sheet, as fully indicated for New Hampshire 

 by Mr. Hitchcock, will be usefully consulted by those interested in 

 the subject. 



Part 4 contains a description by Mr. G. W. Hawes of the minerals 

 and rocks of the State, illustrated by eleven plates showing their 

 microscopic structure. Part 5 gives an account by Mr. Hitchcock of 

 the localities, modes of occurrence, and quantity of materials valu- 

 able for economic purposes, as metals and their ores, building- 

 materials, and natural fertilizers. 



The vast amount of information systematically arranged in these 

 volumes, on the physical features, agricultural character, geological 

 structure, and economical products, will be of great advantage 

 to those persons more directly interested in the natural resources 

 of the State. But the value of the descriptive portion is further 

 enhanced by the fine folio atlas which accompanies the work, con- 

 taining two topographical maps of the State, in the years 1784 and 

 1816; a lai'ge map showing the geological features and position of 

 the mines in the Ammonoosuk mining district, the details of which 

 are given in vol. ii. p. 272 ; a series of panoramic views and camera 

 profiles, illustrating the contours of many picturesque parts of the 

 country; five maps showing the position of the modified drift and 



