108 
ences and preserving glacial striae almost as well as the mel- | 
aphyr and granite ; and they rarely weather brownish, or show 
in any marked degree peroxidation of the  ferruginous 
compounds. Finally, they are, as a rule, irregularly jointed, 
exhibiting only exceptionally a regular transverse or prismatic 
joint-strueture. The north-south dikes, on the other hand, are 
usually black on a fresh fracture and not conspicuously chloritic 4 
or epidotie ; they weather readily to brownish masses of rounded 
outline and later to a brown earth; and a well-developed cross 
or columnar jointing is often a conspicuous feature and never 
wholly wanting. 
Hast West Dikes of the Northern or Coastal Belt. 
Width 
No. Trend. Hade. in Remarks. 
feet. 
3| N. 759-809 E.] Vert.-N.109| 2.5-8.5 | Finely porphyritic. 
4 N. 75 B. 8. 159-209 3 Slightly porphyritic. 
0 N. 805 BN 8. 5° 3-5 Double dike; cut by 11. \ 
618.1807 B Vertical 8—4 Jogged or faulted in crossing 
beach. 
УЫ SOUP EN Vertical 15-20 Walls irregular and faulted. 
8 | 8, 829 E N. 25° 2.75-8 | Cross-jointed. 
9. | 8. S09 . Vertical 10 Probably divided or composite / 
toward the east. 
10 | S. 759-809 E. | Vert.-N. 150 4-5 Irregular in width and hade. 
iT | 8. 7692809 B. | N. 107 2.5 Encloses fragments of granite. 
12 8.75" E. Vertical 8.5-4.5 | Encloses fragments of granite 
апа syenite. 
18 S. 759-809 E. | Vert.-N.10° Very irregular at east end. 
14 | S. 759-809 E. | N. 109-209 Very irregular and broken. 
10 ЙАА Ba N. 59-109 —47 No satisfactory exposures. 
16 | S. 759-809 E. | Vertical 4 Quite irregular in trend and 
hade. 
17.79. S07 0. №. 109-15? | 4-5 Regular; probably a branch of 
18. 
18 | S. 759-80? Е. | N. 45° 8 Regular; unusually strong 
hade. 
19 S. 769-80? E. | N. 80? 8-9 Very irregular апа branching. 
) 
D 
The dikes of the coastal belt present many interesting and in- 
struetive features. Ав the map plainly shows, they form a 
well-defined belt coinciding with the immediate shore-line ; and 
