MEAN STEIKES. 479 







ALTERED MICA SCHISTS IN NORTHEASTERN VERMONT. 



Canaan, northeast corner, strike N. 44 E., dip 65-80 W. (46 W. true dip), C. H. H. Canaan, east part, strike 

 east of north, dip 25-69 E., C. H. H. West Stewartstown, N. H., strike east of north, dip 30 E., C. H. H. Canaan, 

 strike N. 50 E., dip 60 N. W., S. R. H. Canaan, west part, strike N. 40 E., dip 82 N.W., S. R. H. Morgan, east 

 part, dip northwesterly, S. R. H. Morgan, Four Corners, strike N.40E., dip 20N.W., S. R. H. Morgan, west 

 part, strike N. 32 E., dip 40 N.W., S. R. H. Lemmington, south line, dip 15 E., C. H. H. Brunswick, north line, 

 strike N. 35 E., dip 90, C. H. H. Brunswick, east part, strike N. and S., dip 25 W., C. B. A. Bloomfield, south- 

 east part, strike N. 30 E., dip 65 N.W., S. R. H. Columbia, N. H., strike east of north, dip 25 E., C. H. H. West 

 Guildhall, strike N. 55 E., dip 74 W., C.H.H. Granby, east part, strike N. 40 E., dip 80 S.E., S. R. H. Granby, 

 strike N. 55 E., dip 80 S.E., C. H. H. Granby, north of church, strike N. 80 E., dip 80 S., S. R. H. Granby, 

 strike N. 15 E., S. R. H. Victory, strike N. 60 W., dip 55 S.E., C. H. H. Victory, west part, strike N. 20 E., dip 

 45-50 E., S. R. H. East Burke, strike N. 20 E., dip 40 E., S. R. H. Tuckerman's Ravine, N. H., dip 28 westerly, 

 C. H. H. Top Mount Washington, N. H., dip 25 N.W., C. H. H. West base of Mount Washington, N. H., dip 

 30 N. (?), C. H. H. 



Mean N. 38 E. 11 N. 27 E. 



MODIFIED MICA SCHIST. 



This occurs mainly in the northeast part of the State. It may have been originally 

 calciferous, and the lime have been abstracted by metamorphism. 



Taking the mean strike of 165 observations in the above table for the calciferous mica 

 schist, where the direction is east of the magnetic north, we find it to be N. 31 E. Deduct- 

 ing 10 for variation, and it gives N. 21 E. by the true meridian. In the range of schist 

 in the northeast part of the State, the average strike is N. 28 E. of the true meridian. 

 In all these cases we have neglected the strikes that are west of the magnetic meridian, 

 which amount to thirty-one examples in the calciferous schist, and two in the other range; 

 because we can hardly doubt that they are the effect of local disturbance, as indeed are 

 probably some of the 165 cases we have used. To make this probable in the calciferous 

 range, if we divide the whole of the list above given into seven portions, in regular order 

 from south to north, the mean of the strikes will be as follows, east of true north : 



Number of examples. Sum of Strikes. Mean. Number of N. W. Strikes. 



1 26 815 20 1 



2 26 600 12 3 



3 22 444 10 6 



4 30 642 10 1 



5 16 723 34 3 



6 19 794 32 9 



7 26 1031 36 4 



From this table we learn that after getting nearly as far north as Montpclier, the strikes 

 veer a good deal to the northeast. It is also true that the greatest number of westerly 

 strikes are in the vicinity of large outbursts of granite, but this is not invariably the case. 



We ought to add that the axis of the whole calciferous formation ranges about N. 10 E. 

 This agrees with the average strikes in the southern half of the formation, but differs 

 considerably from their whole average. Towards the north part of the State the forma- 

 tion curves around more northeasterly, as all others do, to follow down the valley of the 

 St. Lawrence. 



