346 LMM OIE SS THONG SI GIOVEIN ICS 
folded districts may be taken as a type of such complex folding, 
That initial dip is not sufficient to explain the pitch of the folds 
in this region is shown by the following facts: A stratum or set 
of strata may rise at one end of a synclinal canoe. Beyond this 
for a distance the strata are removed by erosion, but farther on 
appear again plunging downward at the end of another canoe. 
Corresponding phenomena are observed in reference to anti- 
clines. 
In proportion as the major and minor thrusts approach each 
other in power, the canoes become shorter and broader. Where 
they are nearly equal the folds are domes and basins. Usually 
these domes and basins are associated with canoes, which may 
be in one or two directions in the same region. Where the two 
~sets of cross folds are about equally conspicuous the strikes and 
dips of the rocks vary constantly, their directions depending 
upon what part of the complex folds is under observation. 
Where the complex folds are also composite the canoes, 
domes, and basins are fluted or crenulated, being composed of 
secondary canoes, domes, and basins. Similarly, these may be 
composed of canoes, domes, and basins of the third order, and 
so on. 
OBSERVATIONS IN COMPLEXLY FOLDED DISTRICTS. 
From the relations of cross folds, as above explained, it is 
clear that where there are complex folds the axes of one set of 
folds and their pitch give the direction and dip of the cross fold 
at that point. Therefore to fully understand a district com- 
plexly folded it is necessary to make the following observations : 
(1) Determine the strike and dip of the strata at a given 
point. These give the resultant position of the strata as tilted 
by the forces of folding in both directions. 
(2) Determine the direction and pitch of the axes of the 
major folds. The first is the direction of dip and the second is 
the amount of the dip of the minor or cross folds. The average 
strike is, therefore, determined. 
(3) Determine the direction and pitch of the axes of the 
minor folds. The first is the direction of dip and the second the 
