1920.] 
Speight.—Broken River Coal Area. 
101 
parallelism of the lowest beds to the greywacke surface, the marked irre¬ 
gularity in the direction, thickness, and character of the coal-seams of the 
middle series, and especially their cutting out suddenly and the replacement 
of the carbonaceous matter by sand or clay. These characters are exhibited 
also in other parts of the area. It would seem, therefore, that the most 
satisfactory explanation of the formation of the coal-measures is that they 
were deposited by a stream or streams flowing into the area from the north 
or north-east, and that the sea-bottom was gradually depressed till fairly- 
deep-water conditions extended over the area. 
This working hypothesis may be of value in considering the other parts 
of the area. 
Fig. 5.—Coal-beds on north side of Broken River, where they were worked originally. 
The seam, with evidence of working, cut out at a distance of about 3 chains 
from the face. [Photo, R. Speight. 
Broken River (fig. 5).—For some distance up-stream above the inflow of 
Alum Creek the slopes are covered with scrub and slip material, so that 
their stratigraphy cannot be made out exactly. There is no doubt, how¬ 
ever, that a considerable amount of material belonging to the horizon most 
prolific in coal has been removed by the erosive action of Broken River, so 
that the next locality, going up-stream, where coal of marketable value 
occurs lies about 30 chains west of Alum Creek and on the north side of the 
river. 
Here a series of sands, sandy clays, and fireclays with coal is exposed in 
the face of a cliff. The first mining operations were commenced here owing 
to a belief that the measures were less disturbed than on the south side of 
the river, and a main drive was put in for a distance of 10 chains just above 
the level of the river-bed and running N. 30° W., the strike of the measures 
being west-north-west. Additional drives, which were ultimately con¬ 
nected with the main drive, were put in from the face on the same seam. 
The chief seam here was about 7 ft. thick on the face of the cliff, with 
