l84 STUDIES FOR STUDENTS 



all but remnants of the schist (see dotted, lines Figs, i and 2), 

 these lower parts would appear as ordinary synclines, with little 

 or no evidence of fanning. Indeed, in the case of a number of 

 the schist ridges in the Housatonic Valley, erosion has so far 

 advanced as to have left only the lower part of the synclines. 

 Thus one who studies two adjacent schist ridges cut to differ- 

 ent depths and overlooks the intermediate anticline of limestone, 

 which is difficult to discover because of the poor exposures, 

 might infer that one is an anticline and therefore is overlain by 

 the limestone, and that the other is a syncline and is therefore 

 underlain by the limestone. (See Fig. 2.) The conclusion 

 would thus be reached that there are two schist formations, one 

 ■of which is older than, and the other of which is younger than, 

 the limestone, whereas there is only a single schist formation, 

 and all ridges whether apparently anticlines or synclines, are 

 parts of synclines of the same type and all overlie the limestone. 



Positions of cleavage i?i anticlines and syncliries. — In another 

 place I have given the general law:^ "On opposite limbs of 

 a fold the cleavage usually dips in opposite directions. Upon 

 opposite sides of an anticline the cleavage usually diverges 

 downward, and on opposite sides of a syncline it usually con- 

 verges downward." No instance of this principle was given. 

 Since this was written it has been found that this principle is 

 well illustrated on Mount Barack MTeth above mentioned, upon 

 the southern part of Mount Washington in Massachusetts, and 

 upon all of the various synclines of Manhattan schist of Man- 

 hattan Island and of the area to the northward. In each of 

 these cases the areas are synclinal, and in all of them the cleav- 

 age on opposite sides of the ridges converges downward. Subor- 

 dinate anticlines of the Manhattan schist, in synclinoria which 

 illustrate the above principle, show the reverse principle, that is, 

 the cleavage diverges downward upon opposite sides of the 

 minor anticlines. This principle is also illustrated at the anti- 

 cline of Fordham gneiss a short distance south of Harlem 

 Bridge. In many of these cases the folds are monoclinal, and 



^Loc. cit., (A), pp. 649-650; (B), p. 474. 



