150 The American Geologist. Mani,, i905 
Insoluble matter (sand and clay) 25 per cent to 60 per cent. 
Soluble and Volatile matter (mostly calcium carbonate) 40 
per cent to 75 per cent. 
The tests proved that in general the higher beds of 
marls were the richer in lime and that lower horizons rapidly 
decreased in this constituent to almost zero where the typical 
beds of the underlying clay shales are reached. 
Nearly all of these detailed examinations were made on 
the Mayo property at the mouth of Little Pembina river. 
On the north side of the Pembina river at this point the river 
bluffs are 400 feet high. A section of at least 350 feet of 
shales are exposed. A yellowish color of the uppermost 
beds as they occur here is not a constant character of the 
same beds throughout the whole district. This color is 
notable only where the immediate covering is drift, and 
therefore porous, or along much exposed bluffs. In recently 
exposed beds or where there is great thickness of shale cov- 
ering the color is drab or greenish gray as in the Little 
Pembina and Tongue river sections. It is clearly a case of 
bleaching or oxidation of the iron content with more or less 
leaching wherever water percolation is active. On the bench 
of land forming the inner margin of the "first mountain," 
drift lies directly upon the marl beds and here such bleach- 
ing has penetrated 15 to 20 feet. Seams where circulation 
is easiest are often red from iron stain while the interiors of 
larger blocks are still bluish. 
In all other respects samples of the gray cement rock 
of Tongue river are duplicated on the Pembina. They are 
undoubtedly the same beds and their relationship may be 
seen at a glance in the accompanying figure. 
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[Fig. 2. Cross section of the Pembina district from north to south show- 
ing the correlation of beds exposed in the chief river gorges.] 
So far as preliminary investigation may serve as indi- 
cation, one would be expected to prove as valuable as the 
