OBSERVATIONS AND EXPERIMENTS ON JOINT PLANES 69 
is variable. Fig. 6 shows that many of the variable areas give 
averages to the south but the areas of greater constancy usually 
show averages to the north. The only really good area of strike 
joints in this district is at Forest Home. ‘There, out of 146 read- 
ings only two were to the south. It is fair to assume that on the 
northern limb of the Watkins anticline the tendency is to the north. 
From the axis of the Corbett Point syncline northward for about 
three miles the tendency is to the south. On the eastern side of the 
lake the readings are nearly all to the south from a point somewhat 
south of the axis of the syncline to a point about three-fourths of a 
mile north of Esty Glen (locality 43). On the western side the 
readings are more variable but the areas of more numerous and 
constant readings are strongly to the south. North of this is a 
region of variable joints on both sides of the lake. On the eastern 
side the three zeros represent one average of exactly zero and two 
averages of small fractions to the north. Just south of Shurger 
Point the readings are mostly to the south, north of Shurger Point 
they are variable with an average of about half a degree to the 
north. Just south of the anticlinal axis they are again nearly all 
to the south. Much the same thing occurs on the western side 
but there the northerly tendency predominates. Judging from the 
other folds a small change in the dip of the rocks, not sufficient to 
reverse the direction of dip or even to make the beds horizontal, 
might explain the behavior of the joints. Such a flexure might be 
local or a continuation of a fold dying out here. On the eastern 
side this turns the hades slightly to the north for a short distance 
but the general southerly tendency predominates. On the western 
side this flexure acts as if it merged with the main axis, either 
reversing the readings or making them variable from a point south 
of Crowbar Point to the main axis. Continued folding after the 
formation of the joints would also explain this irregularity. South 
of the axis of the fold the average hades to the north are so small 
that if the plane of the bedding instead of the horizontal were used 
as a datum plane the averages in most cases would be to the south. 
North of the axis of the Shurger Point fold the hades are 
unusually uniform and satisfactory. Along the shore north of 
Salmon Creek the cliffs are talus covered and falling where acces- 
