358 C. K. LEITH AND W. J. MEAD 
column, the Keewatin rocks of Lake Superior, are for the most 
part fresh basalts with minor quantities of sediments which cer- 
tainly have not been liquefied, notwithstanding the fact that they 
have been buried to maximum depths known to our observation. 
The great Laurentian batholiths of granite intruding the Keewatin 
and lower portions of the Huronian sediments have been regarded 
as the fused lower beds of the Huronian series fused by reason of 
depth of burial. And yet when these same Huronian sediments 
are followed out they are found in some adjacent areas to rest 
unconformably, with basal conglomerate, on an old basement of 
granite or Keewatin green schists with no signs of fusion. This 
depth has not been sufficient to cause fusion. The extreme of 
anamorphism shown is a schistose structure resulting from rock 
flowage in part of these rocks. It is known both by field and experi- 
mental observation that rock flowage producing schistosity does 
not require fusion. Adams" has shown experimentally that even 
to depths greater than 12 miles the weight of overlying rocks alone 
is not sufficient to close cavities—much less liquefy the rock. The 
only evidences for fusion are around the peripheries of intrusive 
igneous rocks. ‘These intrusions are, on the scale of the earth, 
relatively insignificant masses, which have worked their way 
upward from a much deeper zone, carrying up energy necessary 
for the fusion. 
In short, the metamorphic cycle within our zone of observation 
has usually not been completed. Since Keewatin time at least, the 
cycle has resulted in the gradual accumulation of sediments and 
their equivalent schists. Some small parts have been reconverted 
to igneous rocks around igneous intrusions. Whether beneath the 
Keewatin, sediments have been more largely converted into igneous 
rocks, we have no means of knowing. It may be that the span of 
time between the Keewatin and the present represents too small 
a part of the geological record from which to drawn inferences, 
but it is all we have as a basis of observation. 
2. Salts of the sea.—Certain salts split off from the cycle and 
remain in the ocean. ‘The salinity of the sea has been regarded as 
continuously increasing since the beginning of geological time. 
™ Journal of Geology, XX (1912), 97-118. 
