6 PROCEEDINGS OF THE ACADEMY OF [Jan., 



completely altered to a brown serpentine-like material sometimes 

 apparently mixed with felted masses of biotite and chlorite. This 

 may have been an orthorhombic pyroxene, as slight traces of it 

 remaining in the heart of a couple of the brown areas showed parallel 

 extinction, and it has none of the characteristics of olivine. In 

 addition to the usual magnetite, apatite is present as an accessory 

 mineral, but not at all plentifully. 



While the indurated shale is continuous along the sea coast for a 

 couple of miles south of Ogunquit, granite outcrops at a number of 

 places not far back from the shore, as at Pine Hill and further to the 

 west at Mt. Agamenticus. It is hornblendic at the outcrops noticed, 

 but I did not collect or further study any specimens. Some additional 

 collections of dyke rocks were, however, made just north of Ogunquit 

 on the road to Portland. Here, in widening the road, several outcrops 

 have been cut away, leaving fresh exposures. One such is located 

 on east side of road about one-eighth mile north of the car barn and 

 shows three different igneous rocks penetrating or in contact with 

 each other. Toward the south, there is first a gray, medium fine- 

 grained diabase, then a compact black basalt. A section of the 

 contact demonstrates that the basalt was a later flow than the 

 diabase. Next to it comes a coarse diabase porphyrite with feldspar 

 phenocrysts, sometimes exceeding an inch in length; and beyond this 

 another fine-grained diabase, and then indurated shale similar to that 

 described from the shore. 



On the west side of the road, one-eighth mile further toward the 

 north, is another good exposure of diabase porphyrite, in which the 

 phenocrysts are developed to an extent that they appear to make 

 up more than half the rock, in contact with basalt of later origin. 



For comparison, I give the following brief description of igneous 

 rocks at Pigeon Cove, Mass., where years ago I collected and studied 

 specimens from the dikes along a similar short section of the shore. 

 The end of Cape Ann consists of light gray hornblende granite, 

 quarried extensively for commercial purposes. Its feldspar is 

 almost exclusively microcline and the hornblende is generally accom- 

 panied by ])iotite. This granite is penetrated by many igneous 

 dikes, although these are not so numerous or varied in character as 

 those at Ogunquit. 



Near the extreme point of the cape, known as Andrew's Point, 

 below an unfinished square stone tower, is a dike of solvsbergite, 

 a uniformly crystalline mixture of jilagioclase with hornblende 

 allowing pleochroism from olive to indigo-blue, much finer grained in 



