548 OGILVIE 



the second is Dr. Bascom's, which has two outcrops on Ruther- 

 ford Island, and one on the east side of Linekin's Neck ; the third 

 is the longest of them and outcrops on Cabbage Island, on the 

 east and west coasts of Spruce Point, in the woods about a 

 quarter of a mile inland on Southport, twice respectively on the 

 east and west sides of the promontory of West Southport and 

 in Georgetown north of Five Islands; the northernmost dike 

 crosses Linekin Bay, being exposed on both coasts and on 

 Cabbage Island. These four dikes are closely related in their 

 petrographical characters, being porphyritic olivine diabases, 

 and in their chemical characters, falling into Class III of the 

 new system. 



Another large dike is found on the mainland running parallel 

 to the Sheepscot River with a strike of N. io° E. This differs 

 chemically and mineralogically from the others, being an acid, 

 very feldspathic diabase without olivine and non-porphyritic, 

 and falling into Class II of the new system. 



The remaining dikes are small, varying from a few inches to a 

 few feet in width. They are entirely variable in composition, and 

 variable also in direction. 



These three series were never found together so the age rela- 

 tions are unknown, but it is believed that there are two, possibly 

 three, types distinct in age, and that this classification holds for 

 other parts of the Maine coast. 



Placerose. II. 4. 3. 5. Diabase. Occurrence. — The rock which 

 falls into this subrang is the big dike with N. io° E. trend, 

 already mentioned (see Plate XXXI, Fig. 2). It has a maximum 

 width of about thirty feet, with a length of more than four miles, 

 during the greater part of which it is a conspicuous topographic 

 feature. In two localities it disappears for a short distance, 

 and in one place seems to be represented by three small dikes. 

 It grows narrower towards the south; at its northern end it 

 disappears suddenly. Its location can be seen on the map, 

 where it will be found running parallel to the trend of the 

 shore and a short distance inland. 



Megascopic Character.- — In the hand specimen the rock is a 

 dense black or gray black, fine-grained trap. A few needle- like 

 black crystals can be distinguished. In view of the apparent 



