PREFACE. 



Nearly two years and a half have been occupied in the compilation and 

 printing of this volume. Material additions to our knowledge of the rocks, 

 consisting of two summers' field-work, have often corrected, improved, and 

 added to the statements already printed. This has been the most marked in 

 the White Mountain district. Mr. Huntington has performed an excellent 

 work, in his chapter upon the Coos and western Merrimack districts, particu- 

 larly in distinguishing the coarse granite belt and the fine-grained division of 

 the Bethlehem gneiss, the first being of practical consequence in determin- 

 ing the best places to work mica quarries. We have constantly endeavored 

 to state all facts in the briefest possible language ; and, in consequence of the 

 immense number of observations recorded, the last four chapters have been 

 much abbreviated. In spite of all our cfibrts, the subjects of Surface Geol- 

 ogy, Economics, Mineralogy, and Lithology are crowded out into a third 

 volume, nearly a hundred pages of which are already printed. Mr. Warren 

 Upham has undertaken the description of the Modified Drift ; and Mr. Geo. 

 W. Hawes will discuss Mineralogy and Lithology. Both these treatises will 

 be of rare value. We have undertaken the collection of several sets of speci- 

 mens illustrating our Lithology, each consisting of two hundred and fifty 

 varieties. These may be found at the college museum, at the state house, 

 and at the normal school. Other sets are on hand for exchange or sale. 



The study of the topography of the state has not ceased with the publica- 

 tion of Part L Our labors have been unexpectedly successful, so that we 

 shall present upon the geological map contour lines for every hundred feet 

 throughout the state. These lines will not interfere with the coloring repre- 

 senting the distribution of the formations, but will the rather aid in under- 

 standing their relations to mountains, plains, and valleys. We have also 



