492 



STRIKE AND DIP. 



Very perfect rhomboidal joints arc not unfrcquent in the clay slate on a small scale. We copy Fig. 271 

 from Professor Adams' Report, showing a rather peculiar form from Dummerston. 



Fia. 271. 



Fio. 272. 



FIG. 273. 



Sometimes a succession of joints is seen very near to one another, along which there have been short 

 slides, not enough to break the slate entirely, but only to throw the pieces into what, in military move- 

 ments, is called an echellon form, of which we have given a sketch on page 559 of the Final Report on 

 Massachusetts. The specimen was found at Brace's quarry, in Guilford. At the same place striking 

 plications on a small scale sometimes occur, of which Figs. 272 and 273 are examples, copied from Professor 

 Adams' Report. One of them has in it small veins of white quartz; (Fig. 272) which were filled, probably, 

 by infiltration, the cracks having been made by the plication. 



STRIKE AND DIP. 



In the following observations no attempt was made to distinguish between cleavage and stratification. 

 But we have presented considerations above which show that in the ranges east of the Green Mountains, 

 the two are nearly or quite coincident ; and in the few observations of a different character as to the western 

 ranges, the difference appears to amount to only a few degrees. 



The strike, as is usual with geologists, is given from the magnetic meridian, that is, by the compass. To 

 convert it into angles made with the true meridian, it is only necessary to recollect that the declination of 

 the needle in Vermont varies from 9 W., in the southwest part of the State, to 11 W., in the north- 

 east part. 



RANGE ALONG CONNECTICUT RIVER FROM GUILFORD TO EAST BURKE. 



[The locality, strike and dip, and initials of the Observer are given.] 



Near State Line, Bernardston, Mass., strike N. 70 E., dip 19 S., C. H. H. Southwest part of Vernon, strike 

 N. 3 E., dip 63 E., C. H. H. Vernon, west part, strike N. 10 E., dip 70 E., C. H. H. Vernon, west part, strike 

 N. and S., dip 25 E., C. B. A. Vernon, north part, strike N. and S., dip 70 W., C. B. A. Vernon, north part, strike 

 N.45E., dip 50N.W., C. H. H. Guilford, south part, strike N.40E., dip 80S.E., C. B. A. Guilford, strike 

 N. 5 E., dip 50 E., C. B. A. Guilford, strike N. 32 E., dip 48 E., C. B. A. Guilford, near Algiers, strike N. 5 E., 

 dip 72 W., C. B. A. Guilford, New England Slate Co.'s quarry, strike N. 20 E., dip 77 W., C. H. H. Guilford, 

 west of do., strike N. 20 E., dip 80 W., C. H. H. Chesterfield, N. H., strike N. 23 E., dip 85 W., C. H. H. 

 Brattleboro, railroad depot, strike N.E. and S.W., dip 66 E., C. H. H. Brattleboro, west part of east village, dip 

 65 to 90 W., C. H. H. Brattleboro, near mouth of West River, strike east of north, dip 66 W., C. H. H. Brattle- 



