140 A. Wan dice — Intrusive Rocks of 



Maine, and mentioned similar occurrences at Portsmouth, 

 New Hampshire ; G. P. Merrill 4 noted the Durham granite 

 in his i i Building Stones ' ' ; Dale 5 briefly referred to the 

 Berwick "black granite"; Powers 6 in 1914 had occasion 

 to visit Bald Head Cliffs while collecting material for his 

 paper on the inclusions in dikes. Recently the U. S. 

 Geological Survey began a systematic study of this 

 region and two papers 7 relating to the geology have 

 appeared. 



Acknowledgments. — In connection with this paper 

 acknowledgments are due to Professor R. A. Daly of 

 Harvard University under whose guidance the area was 

 studied; to Professors John E. Wolff and Charles 

 Palaclie, both of Harvard, for helpful aid in the micro- 

 scopic investigation; to Dr. L. Laforge and Dr. Frank 

 Katz of the IT. S. Geological Survey for suggestions 

 regarding the characteristics of the formations. 



Topography. 



The Portsmouth Basin lies within the tilted and dis- 

 sected Cretaceous peneplain of the Northern Appala- 

 chian Geological Province. The portion of this pene- 

 plain near the shore, spoken of as the coastal lowland, 

 to which the area under consideration properly belongs, 

 is a land surface of low relief and slight diversity. It 

 rises gently toward the interior and its few hills, 

 either monadnocks or morainal material left by the 

 Pleistocene glaciers, rarely attain an elevation of more 

 than 300 feet above sea level. Its valleys, except for 

 those of the short coastal streams, are relatively broad 

 and shallow depressions whose courses, determined 

 largely during post-Cretaceous time, were but slightly 

 affected by the glaciers of the Pleistocene period. The 

 shore line is marked by a succession of bold rocky head- 

 lands between which are marshes fronted by excellent 

 sand beaches. Wherever rivers enter the ocean they 

 generally afford good harbors, this being one result of 

 a recent drowning of the shore. 



4 G. P. Merrill, Stones for Building, 1897. 



5 T. N. Dale, U. S. Geol. Survey, Bull. 313, 1907. 



6 S. Powers, Jour, of Geol., vol. 23, 1915. 



7 U. S. Geol. Survey, Prof. Paper 108, 1917. 



