274 



DIP AND STRIKE. 



evidence of shore action can be traced upon most of the groups of the lower silurian in 

 Vermont, and elsewhere, especially in the red sandstones about Burlington. These 

 shrinkage cracks in the Chazy are quite large and extensive. 



Divisional Planes. Cleavage planes are common in this rock. They are particularly noticeable in the 

 north part of the lake. Usually they dip at right angles to the strata, even ohscuring the strata, and they 

 are generally the most prominent marks of division. We measured the following divisional planes : 



On South Hero, at the middle of the west shore, the strata are nearly horizontal, and the cleavage seams 

 are perpendicular; and their deviation does not vary much from north and south. The same planes were 

 seen all over the island where this limestone occurs. 



South Hero, west part, cleavage seam; strike N. 13E.; dip 62W. 



South Hero, Merriam's Bay, cleavage seams; dip 25E., and the strata 8 northerly. 



Point au Eoche, N. Y., cleavage seams; dip 58E., and run N. 42E. 



In the west part of South Hero we measured several joints. The most common, and those that are 

 found wherever the rock occurs, run N. 60 W., and are perpendicular. Another set run N. 10 W. with 

 the same inclination. Perhaps the first observation given relates to joints rather than cleavage, but they 

 are as abundant as strata seams. 



At Isle La Motte the joints occur only at wide intervals; and those appear remarkably even and dis- 

 tinct, with a general east and west direction. 



DIP AND STRIKE OF THE STRATA. 



Locality. 



Larrabee's Point, 

 Larrabee's Point, south end, 

 Chimney Point, Addison, 

 Crown Point, N. Y., 

 Bridport, west part, 

 Addison, Snake Mountain, 

 Addison, Snake Mountain, 

 Waltham, 

 Panton, west part, 

 Panton, Adams' Ferry, 

 Vergennes, 



Ferrisburgh, west of Vergennes, 

 Ferrisburgh, center, 

 Ferrisburgh, Button Bay Island, 

 Ferrisburgh, do., 



Ferrisburgh, between do. and Scotch Bennet, 

 Ferrisburgh, Basin Harbor, 

 Ferrisburgh, west part, 

 Ferrisburgh, Island, 



Ferrisburgh, half mile north of Basin Harbor, 

 Ferrisburgh, a mile north of Basin Harbor, 

 Farrisburgh, northwest part, 

 Thompson's Point, 

 Butterfield's Island, 

 Charlotte, do., extreme end, 

 Charlotte, east of lake, 

 Valcour Island, N. Y., 

 South Hero, Merriam's Bay, 



Strike. Dip. 



E. and W., 12 N., 



E. andW., 9N., 



N.E. and S.W. 8 N.W., 



N.48E., 9NW., 



N.E. and S.W., Anticlinal, 



N. 46 E., 25 E., 



10-20 E., 



N. 35 E., 30 E., 



East of north, 15 E., 



N.10E., 15N.E., 



Nearly horizontal, 



50 W., 



N. 40 E., 30 E., 



N.40E., 18S.E., 



E.20S. 13 E., 



An arch, 

 Dip east, 

 15-20 E., 

 9 SB., 

 7E., 

 7E., 

 About N.E. and S.W., 12 S.E., 



do., 



East of north, 



8 SE., 

 9 S. of E., 

 Undulating, 

 Dip west, 



5E., 

 8N., 



Observer. 

 C. B. A. 

 C. H. H. 

 C. H. H. 

 C. H. H. 

 WING. 

 C. H. H. 

 C. B. A. 

 C. H. H. 

 C. H. H. 



C. H. H. and A. D. H. 

 C. H. H. 

 C. H. H. 

 C. H. H. 

 C. H. H. 

 Z. T. 

 Z. T. 

 C. H. H. 

 C. H. H. 

 C. H. H. 

 Z. T. 

 Z. T. 

 C. H. H. 

 Z. T. 

 Z. T. 

 Z. T. 



Prof. Emmons.* 

 C. H. H. 

 C. H. H. 



* Geology Second District, N. Y., page 281. 



