294 RESEARCH IN CHINA. 
more closely appressed. To a certain extent this is probably true; but 
inasmuch as the higher strata are even more intensely folded in the neigh- 
boring Han province than the lower strata are in the main range, there 
is good ground for the recognition of the increase in intensity northward. 
The stratigraphy of the folded rocks is, nevertheless, an important 
factor in the existing structure. The superficial zone, which yielded to 
compression, may be described as consisting of: (a) The relatively inco- 
herent K’ui-chéu series, which took no effective part, except as load; (6) 
the massive Wu-shan limestone, 4,000 feet, 1,200 meters, thick, a very 
stiff stratum; (c) the shaly Sin-t’an, 2,000 feet, 600 meters, thick, a layer 
of adjustment; (d) the partly slaty, but nevertheless stiff, Ki-sin-ling 
limestone, 4,500 feet, 1,350 meters thick; and (e) the underlying basement 
of metamorphic rocks. Except on the Yang-tzi the last does not come 
to the surface along our route, but of its presence at a depth of a few 
thousand feet there can be no doubt. 
This five-membered strut is unsymmetrical in vertical section. The 
lowest member, presumably also schistose and knitted by intrusives, prob- 
ably yielded to stress by shearing rather than by folding, and in so yield- 
ing may have induced broad dome-structures in the overlying strata, 
which were 12,000 feet, 3,600 meters, thick or more. ‘This total includes 
8,500 feet, 2,550 meters, of limestone, in two members, which are the ones 
that controlled, and of which the upper is the more competent. Assum- 
ing that the deformation was initiated by local doming over the lowest 
member as it rose in consequence of shortening, the two higher competent 
limestone members should fold in conformity of one to the other, their 
diverse movements being adjusted in the intermediate shale. We observe, 
as we might infer, that the types of folds which have resulted are very 
broad and shallow and also very narrow and deep. The whole strut, 
being very competent, could support a long arch; the upper and more 
competent limestone could independently carry the light load resting 
upon it (even though concurrent erosion be not considered) and could 
rise high as the chords of its long arches were shortened; in closer folds it 
therefore developed keels. The lower limestone, though relatively not so 
stiff as the upper, was competent to raise the weight of the Sin-t’an shale, 
plus whatever part of the weight of the still higher strata was not carried 
by the upper limestone, and thus it too developed broad arches in initial 
stages of folding, and high keels on closer compression. 
The tendency of the whole strut was to develop folds of great height, 
and thus to localize the horizontal movement in individual anticlines; and 
the resulting conditions were distinctly unfavorable to development of over- 
thrusts, of which only a few are known as local internal features of folds. 
