Cushing — Geology of Clinton County. 



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It is very difficult to get any trustworthy conception of the thickness of 

 the Potsdam as here exposed. The rock lies in a series of slight north and 

 south folds, with such a slight dip, that it is no easy matter to determine the 

 amount of pitch. The pitch is quite certainly to the north, and somewhat 

 in excess of the fall of the surface in the same direction. The floor on which 

 the rock was laid down also falls to the north, and at a greater rate than the 

 dip of the rock. 



Heavy basal conglomerates, such as those in Ellenburgh, make but little 

 show in Altona, very possibly because of the lack of exposures in the vicinity 

 of the crystallines, though this can not be the whole reason. Several outcrops 

 of small extent, but occurring within a few yards of anorthosite or gneiss, are 

 found on Rand hill, and are all of red, feldspathic, easily degraded type, with 

 no sign of conglomerates. Away from the crystallines the rock presents its 

 usual variations in color, size of grain, and degree of induration. 



Series V. The most impressive display of dikes to be seen in the county 

 is exhibited along the turnpike where it passes over the northeastern edge of 

 Rand hill. The anorthosite here is seamed with dikes, some of which are 

 very large and complex, branching repeatedly and covering considerable 

 territory. These vary so much from place to place that measurements five 

 yards apart would give wholly different results, but the complexity is well 

 illustrated by the following careful measurement of a portion of Dike No. 8, 

 made along the surface in a north and south direction. Commencing at the 



south is 



1. Anorthosite, 



2. Diabase, 8 ft. 1 in. 



3. Anorthosite, 11 " 9 " 



4. Diabase, " 9 " 



5. Anorthosite, 16 " 2 " 



f enclosing three small 



6. Diabase, 23 " 8 " ! horses of anortho- 



I 



l site. 



7. Anorthosite, 91 " 4 " 



8. Diabase, 1 " 10 " 



9. Anorthosite, 2 " " 



10. Diabase, 1 " 7 " 



11. Anorthosite, 15 " " 



12. Diabase, 4 " « 



13. Anorthosite, 



