Cherts and Dolomites 37 
clouded crystalline quartz, with much red earthy material, 
probably iron hydroxide, which, being drawn out into long 
streaks, constitutes the wavy marking of the stone. The 
few particles left are also considerably drawn out and seem 
to be congregated at the apices of the bends. They are 
outlined by material similar to that constituting the streaks, 
which would appear to be long drawn out grains. Such 
evidences of dynamic action are, however, quite local and 
at some places would seem to be connected with the pre- 
sence of the trap sheets and might be therefore due to the 
force of their intrusion. 
The general appearance of these rocks under the micro- 
scope would seem to indicate that the secondary minerals 
at present constituting their bulk were not only supplied 
from the original materials of the grains, but deposited close 
to and around the points from which derived, long soaking 
in the percolating mineral waters producing all the different 
varieties of these rocks at present found. The extent to 
which the process has gone doubtless depended largely on 
the original constitution of the particles acted upon. These 
would seem mineralogically to have been largely made up 
of felspathic material accompanied in places by more basic 
silicates and just such as might have been derived from the 
disintegration of the Archean rocks upon whose water 
smoothed surface they rest. The great irregularity and 
indefiniteness of the distribution of the calcareous and 
dolomitic portions throughout the formation would also 
be accounted for on this supposition, and light would 
be thrown upon the formation of the curious spher- 
ical “bombs” which occur so frequently in the upper 
argillaceous division. In mauy places there will be seen to 
occur lenticules in the argillites around which the bedding 
is seen to bend conformably to their outline. Several 
specimens examined were found to effervesce more or less 
freely with acid, and the impression left after the study of 
a number of cases was that a process of dolomitization of 
the rock had gone on in spots, segregation of the earthy 
carbonates around a centre accounting for the more or less 
