518 



CLEAVAGE AND STRATIFICATION. 



Locality. East Range. 



Section IV, 



Section V, 



Section VI, Vertical, 



Section VII, 



Section VIII, Anticlinal, 



Section IX, Anticlinal, 



Section X, 



Section Xa, 



Section XI, 



Section XII, 



Section XIII, 



Massachusetts Section, 



Middle Range. 



All dip east, 



Synclinal axis, 



All dip east at various angles, 



At least one synclinal, 

 At least one synclinal, 



West Range. 



All dip east. 

 All dip east. 



Synclinal, 

 All vertical, 



From Craftsbury to St. Albans, Synclinal, 



Fan-shaped stratification. 

 Synclinal. 



Fio. 276. 



There is one characteristic of the dip and strike of the strata not yet mentioned, and it 

 is difficult to do it justice. In certain districts the strata are exceedingly contorted, and 

 the average dip and strike are the ones that are recorded. There is not a square mile of 

 this rock in the State where there are not more or less of these irregularities. In a few 

 instances the difficulty of ascertaining the true position is so great that we have not 

 attempted it. 



As a general fact it may be stated that these disturbances are most marked among the 



.Green Mountains, or in the vicinity of the gneiss. We 

 give a single illustration of the true position of strata in 

 a region not at all distinguished for irregularity. Fig. 276 

 represents a surface of twelve square feet upon a ledge of 

 talco-micaceous schist exposed to view by a natural joint, 

 on the east border of the middle range near Proctorsville. 

 A, A, are two strata, two and a half inches wide, of quartz, 

 etc. The other strata are from one-sixteenth to one-fourth 

 of an inch in size, of talco-micaceous schist, aluminous 

 and plumbaginous slates, and a single narrow stratum 

 (vein?) of hyaline quartz. The strata are represented 

 upon the list of the dip and strike as perpendicular ; but 

 the inclinations of the strata in this figure, which are an 

 exact copy of the original, would seem to show quite a differ- 

 ent state of things. Yet the average dip of the strata of 

 that ledge must be nearly vertical, as recorded. 



This state of things suggests two important topics": First, do not these contortions prove 

 that the layers that have suffered this twisting are the strata themselves, and not the bed- 

 ding of cleavage or foliation ? For the beds between cleavage planes are rarely contorted. 

 The strata may be contorted while the cleavage planes cross them with perfect regularity. 

 In fact the cleavage does not appear to have been reduced until the strata had quietly set- 

 tled into their present positions, as a general thing. If cleavage results from pressure, 



Section near Proctorsville. 



